JP5084312B2 - Imaging optical system and electronic imaging apparatus having the same - Google Patents

Description

  The present invention relates to an imaging optical system used for an imaging module, and an electronic imaging apparatus having the imaging optical system.

  In recent years, digital cameras have become widespread as next-generation cameras that replace silver salt 35 mm film cameras. Recently, digital cameras have become increasingly smaller and thinner. In addition, camera functions have been mounted on mobile phones that are becoming popular at the same time (hereinafter, camera functions are referred to as “imaging modules”). In order to mount an imaging module on a mobile phone, the zoom lens must be smaller and thinner than a digital camera. However, zoom lenses that are small enough to be installed in mobile phones are not well known.

Conventionally, the following two means A and B can be considered as representative means for reducing the size and thickness of a zoom lens. That is,
A. A retractable lens barrel is used to house the optical system in the thickness (depth) direction of the housing. The collapsible lens barrel is a lens barrel having a structure in which an optical system protrudes from the camera case during photographing and is housed in the camera case when carried.
B. A bending optical system is employed to accommodate the optical system in the width direction or height direction of the casing. This bending optical system is an optical system configured to bend the optical path (optical axis) of the optical system with a reflective optical element such as a mirror or a prism.

  The conventional example using the means A is described in, for example, the following Patent Document 1, and the conventional example using the means B is, for example, described in the following Patent Document 2. .

  In order to reduce the size and thickness of the zoom lens, correction of chromatic aberration is an important issue. As a solution to this problem, transparent media having effective dispersion characteristics or partial dispersion characteristics not found in conventional glass are known, for example, in Patent Document 3, Patent Document 4, and Patent Document 5 below.

  Furthermore, in an electronic imaging apparatus using an electronic imaging element, flare due to chromatic aberration of h-rays (404.66 nm) is likely to occur. For this reason, for example, the following Patent Document 6 is known as an explanation of the importance of correcting the chromatic aberration of the h-line.

  Further, there is no optical medium having a desired partial dispersion characteristic that can correct chromatic aberration in the vicinity of 400 nm. For this reason, for example, Patent Document 7 below is known as an object of capturing an image while intentionally lowering the transmittance of 400 nm and adjusting the color reproduction using the image processing function of the image capturing apparatus after the image capturing.

  In addition, since the partial dispersion characteristic on the short wavelength side of the optical material is particularly unsatisfactory, color flare that cannot be corrected by the optical system itself is corrected by image processing. Are known.

JP 2002-365545 A JP 2003-43354 A JP 2006-145823 A JP 2005-316047 A JP 2005-352265 A JP 2001-208964 A JP 2001-021805 A JP 2001-145117 A JP 2001-268583 A

  However, in the configuration using the means A described in Patent Document 1, the number of lenses constituting the optical system or the number of moving lens groups is still large, and it is difficult to reduce the size and thickness of the housing. .

  The configuration using the means B described in Patent Document 2 is easier to make the housing thinner than the case using the means A, but the amount of movement of the movable lens group at the time of zooming, The number of lenses constituting the system tends to increase. Therefore, it is not suitable for miniaturization in volume.

  Further, the optical media described in Patent Documents 3, 4, and 5 are highly dispersed and have a special partial dispersion ratio as compared with ordinary optical glass. Considering each example in view of this, application to the optical system is not necessarily the optimum application. As a result, the number of sheets has increased in the end, and this has not led to the miniaturization of the optical system.

  Further, Patent Documents 6, 7, 8, and 9 do not describe specific effective means for removing color flare in the optical system.

  The present invention has been made in view of the above-described conventional problems, and it is possible to obtain an imaging optical system in which various aberrations centering on chromatic aberration are favorably corrected, as well as the reduction in size and thickness of the optical system. An object of the imaging device is to sharpen an image and prevent occurrence of color blur.

In order to achieve the above object, an optical system according to the present invention is an imaging optical system having a positive lens group, a negative lens group, and a stop. In the orthogonal coordinate system in which the lens group includes a cemented lens formed by cementing a plurality of lenses, the horizontal axis is νd, and the vertical axis is θgF.
θgF = α × νd + β (where α = −0.00163)
When the straight line represented by is set, the area defined by the straight line when the range is the lower limit of the range of the following conditional expression (1) and the straight line when the upper limit is set, and the following conditional expression (2) In both of the fixed region and the fixed region, θgF and νd of at least one lens LA constituting the cemented lens are included , and
In an orthogonal coordinate system having a horizontal axis νd and a vertical axis θhg different from the orthogonal coordinate,
θhg = αhg × νd + βhg (where αhg = −0.00225)
When the straight line represented by is set, the area defined by the straight line when the range is the lower limit of the range of the following conditional expression (3 ′ ″) and the straight line when the upper limit is set, and the following conditional expression ( both the area of the defined area 2), θhg and νd of at least one of said lens LA constituting the cemented lens is included and is characterized in Rukoto.
0.3000 <β <0.6650 (1)
35 <νd <120 (2)
0.2500 <βhg ≦ 0.5722 (3 ′ ″)
Here, θgF is a partial dispersion ratio (ng−nF) / (nF−nC) , θhg is a partial dispersion ratio (nh−ng) / (nF−nC) , and νd is an Abbe number (nd−1) / (nF− nC), nd, nC, nF, ng and nh are the refractive indexes of the d-line, C-line, F-line, g-line and h-line , respectively.

  According to a preferred aspect of the present invention, when a lens having a negative paraxial focal length is a negative lens, the lens LA is preferably a negative lens.

According to a preferred aspect of the present invention, when a lens having a positive paraxial focal length is used as a positive lens, the counterpart lens LB to which the lens LA is joined is a positive lens and satisfies the following conditions: It is preferable to do this.
−0.40 ≦ θgF (LA) −θgF (LB) ≦ −0.05 (4)
Here, θgF (LA) is the partial dispersion ratio (ng−nF) / (nF−nC) of the lens LA, and θgF (LB) is the partial dispersion ratio (ng−nF) / of the mating lens LB to be joined. (NF-nC).

According to a preferred aspect of the present invention, when a lens having a positive paraxial focal length is used as a positive lens, the counterpart lens LB to which the lens LA is joined is a positive lens and satisfies the following conditions: It is preferable to do this.
−0.50 ≦ θhg (LA) −θhg (LB) ≦ −0.10 (5)
Here, .theta.hg (LA) is the partial dispersion ratio (nh-ng) / (nF-nC) of the lens LA, and .theta.hg (LB) is the partial dispersion ratio (nh-ng) / of the mating lens LB to be joined. (NF-nC).

According to a preferred aspect of the present invention, when a lens having a positive paraxial focal length is used as a positive lens, the counterpart lens LB to which the lens LA is joined is a positive lens and satisfies the following conditions: It is preferable to do this.
12 ≦ νd (LA) −νd (LB) (6)
Here, νd (LA) is the Abbe number (nd-1) / (nF-nC) of the lens LA, and νd (LB) is the Abbe number (nd-1) / (nF) of the mating lens LB to be joined. -NC).

  According to a preferred aspect of the present invention, it is preferable that the imaging optical system is a zoom lens, and the relative distance between the lens groups on the optical axis changes during zooming.

In addition, an electronic imaging device of the present invention is obtained by capturing an image formed through the imaging optical system with any one of the above-described imaging optical system of the present invention, an electronic imaging device, and the electronic imaging device. Image processing means for processing the obtained image data and outputting it as image data in which the shape of the image is changed. The imaging optical system is a zoom lens, and the zoom lens is focused on an object point at infinity. Sometimes the following condition is satisfied.
0.7 <y ₀₇ / (fw · tan ω _07w ) <0.99 (9)
Here, y ₀₇ is y ₀₇ = 0.7 · y, where y ₁₀ is the distance (maximum image height) from the center to the farthest point in the effective imaging plane (in the plane where imaging is possible) of the electronic imaging device. represented as _10, omega _07w angle relative to the central from the optical axis direction of an object point corresponding to an image point formed at a position of y ₀₇ on the imaging surface at the wide angle end, fw is the entire system at the wide-angle end of said zoom lens The focal length.

  According to the present invention, it is possible to obtain an imaging optical system in which the optical system is reduced in size and thickness, and various aberrations centered on chromatic aberration are favorably corrected. In addition, by using such an imaging optical system in an electronic imaging device, it is possible to sharpen an image and prevent color blurring.

  Prior to the description of the examples, the effects of the imaging optical system of the present embodiment will be described. A lens having a positive paraxial focal length is defined as a positive lens, and a lens having a negative paraxial focal length is defined as a negative lens.

  In the imaging optical system of the present embodiment, a cemented lens is used for the negative lens group on the object side of the stop. For this reason, particularly in a zoom lens, it is possible to easily suppress fluctuations in the on-axis and lateral chromatic aberration during zooming. Further, even if the number of lenses is small and the lens structure is thin, it is possible to sufficiently suppress the occurrence of color blur over the entire zoom range.

  Although the negative lens group on the object side tends to be thicker than the stop, in the imaging optical system of the present embodiment, the negative lens group on the object side can be made thinner than the stop. For this reason, in addition to making the distance from the surface top on the most object side to the entrance pupil shallow (short), there is also a synergistic effect that other lens groups on the object side than the stop can be made thinner.

In the imaging optical system of the present embodiment, in the orthogonal coordinate system in which the horizontal axis is νd and the vertical axis is θgF,
θgF = α × νd + β (where α = −0.00163)
When the straight line represented by is set, the area defined by the straight line when the range is the lower limit of the range of the following conditional expression (1) and the straight line when the upper limit is set, and the following conditional expression (2) Both the fixed region and θgF and νd of at least one lens LA constituting the cemented lens are included.
0.3000 <β <0.6650 (1)
35 <νd <120 (2)
Here, θgF is a partial dispersion ratio (ng−nF) / (nF−nC), νd is an Abbe number (nd−1) / (nF−nC), nd, nC, nF, and ng are d line and C line, respectively. , F-line and g-line refractive indexes.

The case where a glass material exceeding the upper limit value of conditional expression (1) is used will be described. When this glass material is used for a positive lens, the correction of lateral chromatic aberration due to the secondary spectrum, that is, the lateral chromatic aberration of the g-line when achromatic is performed with the F-line and the C-line, becomes insufficient. Therefore, it is difficult to ensure the sharpness of the peripheral portion of the image in the image obtained by imaging.
Further, when this glass material is used for a negative lens, correction of axial chromatic aberration due to the secondary spectrum, that is, g-axis axial chromatic aberration when the achromaticity is applied to the F-line and C-line, becomes insufficient. Therefore, it is difficult to ensure sharpness over the entire screen, particularly in an image obtained by imaging on the telephoto side.

The case where a glass material lower than the lower limit value of conditional expression (1) is used will be described. When this glass material is used for a positive lens, axial chromatic aberration due to secondary spectrum, that is, correction of axial chromatic aberration of g-line when achromatic is performed with F-line and C-line is not sufficient. Therefore, it is difficult to ensure sharpness over the entire screen, particularly in an image obtained by imaging on the telephoto side.
Further, when this glass material is used for a negative lens, the lateral chromatic aberration due to the secondary spectrum, that is, the g-line lateral chromatic aberration correction when the F-line and C-line are achromatic is not sufficient. Therefore, it is difficult to ensure the sharpness of the peripheral portion of the image in the image obtained by imaging.

A case where a glass material exceeding the upper limit value of conditional expression (2) is used will be described. When this glass material is used for a positive lens, it is difficult to erase the F line and C line.
Further, when this glass material is used for a negative lens, the effect of correcting Seidel's five aberrations is reduced even if the F-line and C-line can be achromatic.

A case where a glass material lower than the lower limit value of conditional expression (2) is used will be described. When this glass material is used for a positive lens, the effect of correcting Seidel's five aberrations is reduced even if the F-line and C-line can be achromatic.
In addition, when this glass material is used for a negative lens, it is difficult to erase the F line and the C line.

It is more preferable that the following conditional expression (1 ′) is satisfied instead of conditional expression (1).
0.3000 <β <0.6300 (1 ′)
Furthermore, it is more preferable that the following conditional expression (1 ″) is satisfied instead of conditional expression (1).
0.5000 <β <0.6250 (1 ″)

It is more preferable that the following conditional expression (2 ′) is satisfied instead of conditional expression (2).
63 <νd <120 (2 ′)
Furthermore, it is more preferable that the following conditional expression (2 ″) is satisfied instead of conditional expression (2).
75 <νd <120 (2 ″)

Further, in the imaging optical system of the present embodiment, the orthogonal coordinate having the horizontal axis νd and the vertical axis θhg is different from the orthogonal coordinate (orthogonal coordinate having the horizontal axis νd and the vertical axis θgF). In the coordinate system
θhg = αhg × νd + βhg (where αhg = −0.00225)
When the straight line represented by is set, the area defined by the straight line when the range is the lower limit of the range of the following conditional expression (3) and the straight line when the upper limit is set, and the following conditional expression (2) Both the fixed region and θhg and νd of at least one lens LA constituting the cemented lens are included.
0.2500 <βhg <0.6220 (3)
35 <νd <120 (2)
Here, .theta.hg is the partial dispersion ratio (nh-ng) / (nF-nC), and nh is the refractive index of the h-line.

The case where a glass material exceeding the upper limit value of conditional expression (3) is used will be described. When this glass material is used for a positive lens, the lateral chromatic aberration due to the secondary spectrum, that is, the lateral chromatic aberration correction of the h-line when achromatic with the F-line and C-line is not sufficient. Therefore, in an image obtained by imaging, purple color flare and color blur are likely to occur in the periphery of the image.
Further, when this glass material is used for a negative lens, the correction of axial chromatic aberration due to the secondary spectrum, that is, the axial chromatic aberration of the h-line when achromatization is performed with the F-line and the C-line becomes insufficient. Therefore, particularly in an image obtained by imaging on the telephoto side, purple color flare and color blur tend to occur over the entire screen.

A case where a glass material lower than the lower limit value of conditional expression (3) is used will be described. When this glass material is used for a positive lens, the axial chromatic aberration due to the secondary spectrum, that is, the axial chromatic aberration correction of the h line when the achromaticity is applied to the F line and the C line is not sufficient. Therefore, particularly in an image obtained by imaging on the telephoto side, purple color flare and color blur tend to occur over the entire screen.
Further, when this glass material is used for a negative lens, the correction of lateral chromatic aberration due to the secondary spectrum, that is, the lateral chromatic aberration correction of the h line when the F line and C line are achromatic is not sufficient. Therefore, in an image obtained by imaging, purple color flare and color blur are likely to occur in the periphery of the image.

It is more preferable that the following conditional expression (3 ′) is satisfied instead of conditional expression (3).
0.2500 <βhg <0.5730 (3 ′)
Furthermore, it is more preferable that the following conditional expression (3 ″) or (3 ′ ″) is satisfied instead of conditional expression (3).
0.4000 <βhg <0.5650 (3 ″)
0.2500 <βhg ≦ 0.5722 (3 ′ ″)

  Incidentally, the lens LA is preferably a negative lens. This lens LA is provided in a negative lens group closer to the object side than the stop. When the lens LA is a negative lens, it is easy to cancel axial chromatic aberration and lateral chromatic aberration generated by the negative lens group itself. As a result, it becomes easy to correct chromatic aberration occurring in the entire optical system.

The lens LA is cemented with another lens to constitute a cemented lens. When this other lens is the lens LB, the lens LB is a positive lens and preferably satisfies the following conditional expression (4).
−0.40 ≦ θgF (LA) −θgF (LB) ≦ −0.05 (4)
Here, θgF (LA) and θgF (LB) are partial dispersion ratios (ng−nF) / (nF−nC) of the lenses LA and LB, respectively.

  In this case, since a negative lens (lens LA) and a positive lens (lens LB) are combined, chromatic aberration can be corrected satisfactorily. In particular, when the above condition is satisfied with this combination, the effect of correcting chromatic aberration due to the secondary spectrum is increased. As a result, sharpness increases in an image obtained by imaging.

It is more desirable to satisfy (4 ′) instead of the conditional expression (4).
−0.40 ≦ θgF (LA) −θgF (LB) ≦ −0.10 (4 ′)
Furthermore, it is best to satisfy (4 ″) instead of the conditional expression (4).
−0.40 ≦ θgF (LA) −θgF (LB) ≦ −0.15 (4 ″)

The lens LB is a positive lens, and preferably satisfies the following conditional expression (5).
−0.50 ≦ θhg (LA) −θhg (LB) ≦ −0.10 (5)
Here, θhg (LA) and θhg (LB) are partial dispersion ratios (nh−ng) / (nF−nC) of the lenses LA and LB, respectively.

  In this case, since a negative lens (lens LA) and a positive lens (lens LB) are combined, chromatic aberration can be corrected satisfactorily. In particular, when the above condition is satisfied with this combination, color flare and color blur can be reduced in an image obtained by imaging.

It is more desirable to satisfy (5 ′) instead of the conditional expression (5).
−0.50 ≦ θhg (LA) −θhg (LB) ≦ −0.15 (5 ′)
Furthermore, it is best to satisfy (5 ″) instead of the conditional expression (5).
−0.50 ≦ θhg (LA) −θhg (LB) ≦ −0.20 (5 ″)

The lens LB is a positive lens, and preferably satisfies the following conditional expression (6).
12 ≦ νd (LA) −νd (LB) (6)
Here, νd (LA) and νd (LB) are the Abbe numbers (nd-1) / (nF-nC) of the lenses LA and LB, respectively.

  In this case, since a negative lens (lens LA) and a positive lens (lens LB) are combined, chromatic aberration can be corrected satisfactorily. In particular, when the above condition is satisfied with this combination, the C-line and F-line among the longitudinal chromatic aberration and the lateral chromatic aberration are easily erased.

It is more desirable to satisfy (6 ′) instead of the conditional expression (6).
22 ≦ νd (LA) −νd (LB) (6 ′)
Furthermore, it is best to satisfy (6 ″) instead of the conditional expression (6).
32 ≦ νd (LA) −νd (LB) (6 ″)

  When the cemented lens is composed of three or more lenses, the negative lens having the smallest θgF value among the negative lenses is defined as the lens LA, and the positive lens having the largest θgF value among the positive lenses is defined as the lens LB. And

  Here, the glass material means a lens material such as glass or resin. In addition, a lens appropriately selected from these glass materials is used for the cemented lens.

  The cemented lens includes a first lens and a second lens having a thin optical axis center thickness. The first lens is conditional expressions (1) and (2), or (3) and (2). Is preferably satisfied. By doing so, it is possible to expect further improvement of the correction effect of each aberration and further thinning of the lens group.

  The cemented lens is preferably a compound lens. The compound lens can be realized by closely curing a resin as a second lens on the surface of the first lens. Manufacturing accuracy can be improved by using a cemented lens as a compound lens. A compound lens manufacturing method includes molding. In the molding, there is a method in which a second lens material (for example, an energy curable transparent resin) is brought into contact with the first lens, and the second lens material is directly adhered to the first lens. This method is extremely effective for thinning the lens element. At the same time, this method makes it easy to make the cemented surface of the first lens and the second lens aspheric, and is particularly effective for correcting higher-order chromatic aberration.

The first lens may be an inorganic material such as glass. However, since the second lens to be joined is a resin, in consideration of the stability of optical performance against environmental changes, the first lens is more preferably a resin-based material like the second lens.

  When a cemented lens is used as a compound lens, glass may be adhered and cured as a second lens on the first lens surface. Glass is more advantageous than resin in terms of resistance such as light resistance and chemical resistance. In this case, as the characteristics of the second lens material, it is necessary that the melting point and the transition point are lower than those of the first lens material. A compound lens manufacturing method includes molding. In molding, there is a method in which the second lens material is brought into contact with the first lens, and the second lens material is brought into direct contact with the first lens. This method is extremely effective for thinning the lens element.

  An example of the energy curable transparent resin is an ultraviolet curable resin. In addition, whether the second lens is a resin or glass, the lens on the side serving as the base material may be subjected to a surface treatment such as coating in advance. Further, when the first lens is thinner, the first lens may be in close contact with the second lens.

  In addition, it is preferable to arrange a prism in the imaging optical system. This prism is used to bend the optical path of the optical system. In particular, when the imaging optical system is a zoom lens, the depth dimension of the optical system can be reduced (the entire length can be reduced). This prism is preferably arranged in the first positive lens group or negative lens group particularly from the object side.

By the way, suppose that an object at infinity is imaged by an optical system without distortion. In this case, since the image formed has no distortion,
f = y / tan ω (7)
Is established.
Here, y is the height of the image point from the optical axis, f is the focal length of the imaging system, and ω is the angle with respect to the optical axis in the object direction corresponding to the image point connected from the center on the imaging surface to the y position. It is.

On the other hand, if the optical system has barrel distortion,
f> y / tan ω (8)
It becomes. That is, if f and y are constant values, ω is a large value.

  Therefore, it is preferable to use an optical system that intentionally has a large barrel distortion, particularly at a focal length near the wide-angle end, for the electronic imaging device. In this case, it is possible to achieve a wider angle of view of the optical system as much as it is not necessary to correct distortion.

  However, the image of the object is formed on the electronic image pickup device in a state having barrel-shaped distortion. Therefore, in the electronic imaging device, image data obtained by the electronic imaging element is processed by image processing. In this processing, the image data (image shape) is changed so as to correct the barrel distortion.

  In this way, the finally obtained image data is image data having a shape substantially similar to the object. Therefore, an object image may be output to a CRT or printer based on the image data.

Therefore, it is preferable to use an imaging optical system that satisfies the following conditional expression (9) when focusing on an object point at infinity.
0.7 <y ₀₇ / (fw · tan ω _07w ) <0.99 (9)
Here, y ₀₇ is y ₀₇ = 0.7 · y ₁₀ when the distance to the point farthest from the center (maximum image height) was y ₁₀ at effective imaging plane of the electronic imaging device (imaging possible plane) Ω _07w is the angle with respect to the optical axis in the object direction corresponding to the image point connecting from the center on the imaging surface at the wide angle end to the position of y ₀₇ , and fw is the focal length of the entire system at the wide angle end of the zoom lens is there.

  Conditional expression (9) defines the degree of barrel distortion at the zoom wide-angle end. If conditional expression (9) is satisfied, it becomes possible to capture information with a wide angle of view without enlarging the optical system. Note that an image distorted in a barrel shape is photoelectrically converted by an image sensor to become image data distorted in a barrel shape.

  The image data distorted into a barrel shape is electrically processed by an image processing means, which is a signal processing system of an electronic imaging device, corresponding to a change in the shape of the image. In this way, even if the image data finally output from the image processing means is reproduced on the display device, the distortion is corrected and an image substantially similar to the subject shape is obtained.

  Here, when the value exceeds the upper limit value of conditional expression (9) and takes a value close to 1, an image in which distortion is optically corrected is obtained. Therefore, the correction performed by the image processing means can be small. However, it is difficult to widen the angle of view of the optical system while maintaining the miniaturization of the optical system.

  On the other hand, below the lower limit value of conditional expression (9), when image distortion due to distortion of the optical system is corrected by the image processing means, the stretching ratio in the radial direction of the peripheral portion of the angle of view becomes too high. As a result, in the image obtained by imaging, the sharpness degradation at the periphery of the image becomes conspicuous.

  Thus, by satisfying conditional expression (9), it is possible to reduce the size and widen the angle of the optical system (make the vertical angle of view of distortion more than 38 °).

It is more preferable that the following conditional expression (9 ′) is satisfied instead of conditional expression (9).
0.7 <y ₀₇ / (fw · tan ω _07w ) <0.97 (9 ′)
Furthermore, it is more preferable that the following conditional expression (9 ″) is satisfied instead of conditional expression (9).
0.75 <y ₀₇ / (fw · tan ω _07w ) <0.95 (9 ″)

In the imaging optical system of the present embodiment, θgF and νd of the lens LB are in an orthogonal coordinate system in which the horizontal axis is νd and the vertical axis is θgF.
θgF = α × νd + β (where α = −0.00163)
When the straight line represented by is set, the area defined by the straight line when it is the lower limit value and the straight line when it is the upper limit value of the range of the following conditional expression (10), and the following conditional expression (11) It should be included in both the fixed area and the fixed area.
0.6900 <β <0.9000 (10)
3 <νd <23 (11)

  In this case, it is particularly preferable to use a negative lens that satisfies the conditional expressions (1) and (2), and a positive lens that satisfies the conditional expressions (10) and (11). As a result, correction of axial / magnification chromatic aberration (on-axis / magnification of F-line and C-line) and secondary spectrum (g-line residual axial chromatic aberration when achromatized on F-line and C-line) ) Can be effectively corrected.

Alternatively, θgF and νd of the lens LB are in an orthogonal coordinate system in which the horizontal axis is νd and the vertical axis is θgF.
θgF = α × νd + β (where α = −0.00163)
When the straight line represented by is set, the region defined by the straight line when the range is the lower limit of the range of the following conditional expression (12) and the straight line when the upper limit is set, and the following conditional expression (13) It should be included in both the fixed area and the fixed area.
0.6900 <β <0.9000 (12)
23 <νd <120 (13)

  In this case, it is particularly preferable to use a negative lens that satisfies the conditional expressions (1) and (2) and a positive lens that satisfies the conditional expressions (12) and (13). As a result, correction of axial / magnification chromatic aberration (on-axis / magnification of F-line and C-line) and secondary spectrum (g-line residual axial chromatic aberration when achromatized on F-line and C-line) ) Can be effectively corrected.

Alternatively, θgF and νd of the lens LB are in an orthogonal coordinate system in which the horizontal axis is νd and the vertical axis is θgF.
θgF = α × νd + β (where α = −0.00163)
When the straight line represented by is set, the area defined by the straight line when the range is the lower limit value and the straight line when the upper limit value is in the range of the following conditional expression (14), and the following conditional expression (15) It should be included in both the fixed area and the fixed area.
0.4000 <β <0.6900 (14)
3 <νd <23 (15)

  In this case, it is particularly preferable to use a negative lens that satisfies the conditional expressions (1) and (2) and a positive lens that satisfies the conditional expressions (14) and (15). As a result, it is possible to effectively correct the secondary spectrum (the residual axial chromatic aberration of the g line when achromatic is applied to the F line and the C line).

The lens LA should satisfy the following conditional expression (16).
1.35 <nd <1.85 (16)
Here, nd is the refractive index of the medium of the lens LA.
If the condition (16) is satisfied, spherical aberration correction and astigmatism correction can be performed satisfactorily.

It is more preferable that the following conditional expression (16 ′) is satisfied instead of conditional expression (16).
1.40 <nd <1.81 (16 ′)
Furthermore, it is more preferable that the following conditional expression (16 ″) is satisfied instead of conditional expression (16).
1.45 <nd <1.77 (16 ")

  In the case where the most object side of the imaging optical system (particularly the zoom lens) is a positive lens group, the above cemented lens is preferably used for a negative lens group adjacent to the front and before the stop. On the other hand, in the case where the most object side of the imaging optical system (particularly the zoom lens) is a negative lens group, the above cemented lens is preferably used for the most negative lens group on the object side. That is, in any lens configuration, it is preferable to use the above cemented lens for the first negative lens group from the object side.

  The imaging optical system is a zoom lens, and it is preferable that the relative distance on the optical axis of each lens group changes during zooming. The cemented lens is preferably applied to such an imaging optical system (zoom lens).

Next, the imaging optical system of this embodiment will be described.
The imaging optical system of the present embodiment includes a three-group imaging optical system, a four-group imaging optical system, and a five-group imaging optical system. The refractive power arrangement in the three-group imaging optical system is one of the following.
There are the following four refractive power arrangements in the imaging optical system of the imaging optical system of the negative, (S), positive, and positive four groups.
Negative, (S), Positive, Positive, Positive Negative, (S), Positive, Negative, Positive Negative, Positive, (S), Negative, Positive Positive, Negative, (S), Positive, Positive The refractive power arrangement in the imaging optical system is the following two.
Positive, negative, (S), positive, positive, positive positive, negative, (S), positive, negative, positive (S) indicates the aperture stop. The aperture stop may or may not be independent of the lens group.

  The imaging optical system of the present embodiment has negative, positive, and positive lens groups in order from the object side, regardless of the number of groups. Therefore, the negative, positive, and positive configurations are common. Furthermore, when focusing on the aperture stop, (1) a configuration including two positive lens groups on the image side of the aperture stop, and (2) a negative lens group and a positive lens group on the object side of the aperture stop. It is divided into the composition equipped with. This is also common in that a negative lens group is provided on the object side of the aperture stop. Therefore, it can be said that the imaging optical system of the present embodiment has a basic configuration of negative / (S) / positive / positive or negative / positive / (S) / positive.

  In this basic configuration, the following lens LA is used for the negative lens group disposed on the object side of the stop.

  If another lens group is provided on the image side of the aperture stop, the other lens group is disposed between the two positive lens groups or between the stop and the positive lens group. Can be considered.

  The imaging optical system of the present embodiment has a configuration based on a three-group configuration of negative, positive, and positive. For example, a negative / positive / positive / positive configuration can be realized by disposing a positive lens group between two positive lens groups in a negative / positive / positive three-group configuration. The negative / positive / negative / positive configuration can be realized by disposing a negative lens group between two positive lens groups in a negative / positive / positive three-group configuration. The positive / negative / positive / positive configuration can be realized by arranging the positive lens unit closest to the object side in the negative / positive / positive three-group configuration.

Further, for example, an imaging optical system having a five-group configuration can be regarded as a modified optical system of an imaging optical system having a four-group configuration of positive, negative, positive, and positive. That is, the configuration of the four-group imaging optical system is defined as three groups on the object side (positive / negative / positive) and the final group (positive). Then, the imaging optical system having the five-group configuration can be regarded as a positive or negative lens group disposed between the three groups on the object side and the final group. Alternatively, in an arrangement of negative / positive / positive / positive and negative / positive / negative / positive, a positive lens group is arranged closest to the object side, thereby realizing an imaging optical system having a five-group structure.

In addition, regarding the negative / positive / negative / positive / four-group configuration, by adding a positive lens group closest to the object side, as a result, the refractive power arrangement has five groups of positive / negative / positive / negative / positive. The imaging optical system is configured. However, it is better to consider the above-mentioned positive / negative / positive / positive refractive power arrangement as the basic configuration in the five-group configuration of positive / negative / positive / negative / positive refractive power arrangement.

  When the basic configuration is negative, (S), positive, or positive, a cemented lens is disposed in a negative lens group that is closer to the object than the stop. A lens LA that satisfies the conditional expressions (1) and (2) is used for this cemented lens. The lens LA may be a lens satisfying (1 ') or (1 ") instead of (1) and satisfying (2') or (2") instead of (2).

  Here, focusing on the first positive lens group, the imaging optical system of the present embodiment has two features. First, the first feature is that the first positive lens group is composed of, in order from the object side, a positive lens component and a lens component having a cemented lens, and the most image side of the cemented lens is a negative lens. Is a point. A configuration having this feature will be described below.

  The negative lens group has one lens component. This lens component has a positive lens and a negative lens. The positive lens and the negative lens are preferably cemented. Here, the negative lens is preferably located on the object side. As described above, a lens LA that satisfies the conditional expressions (1) and (2) is used for this cemented lens. The lens LA may be a lens satisfying (1 ') or (1 ") instead of (1) and satisfying (2') or (2") instead of (2).

  The negative lens group may further include another lens component. This other lens component is arranged closer to the object side or the image side than the lens component having the positive lens and the negative lens. The negative lens group may include a prism. This prism is preferably arranged between another lens component and a lens component having a positive lens and a negative lens.

  The first positive lens group has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. Further, it is preferable that the most image side of the cemented lens is a negative lens.

  The first positive lens group further includes another lens component. This other lens component is a positive lens component, and is preferably disposed closer to the object side than the lens component having a cemented lens. Note that the first positive lens group preferably has a negative lens closest to the image side.

  As described above, when the lens components are arranged in order of the positive lens component and the lens component having the cemented lens from the object side, and the most image side of the cemented lens is a negative lens, the optical system can be easily downsized.

  The second positive lens group has one lens component. This lens component may be a single lens.

  Further, another lens group may be disposed between the first positive lens group and the second positive lens group. In this case, this another lens group has one lens component. In addition, this other lens group has a negative refracting power, so that it is easy to reduce the size of the optical system.

  Further, another positive lens group may be arranged on the object side of the negative lens group. In this case, another positive lens group has one lens component. This lens component has a positive lens and a negative lens. The positive lens and the negative lens may be joined, but may not be joined (each may be separated). When the positive lens and the negative lens are separately arranged, each of the positive lens and the negative lens can be regarded as one lens component. In this case, it can be said that another positive lens group is composed of two lens components.

  In addition, when another positive lens group includes two lens components, a prism can be disposed between the two lens components.

  Next, the second feature is that the first positive lens group has at least one of a meniscus lens component and a biconvex lens component. A configuration having this feature will be described below.

  The negative lens group has one lens component. This lens component has a positive lens and a negative lens. The positive lens and the negative lens are preferably cemented. As described above, a lens LA that satisfies the conditional expressions (1) and (2) is used for this cemented lens. The lens LA may be a lens satisfying (1 ') or (1 ") instead of (1) and satisfying (2') or (2") instead of (2).

  The negative lens group may further include another lens component. This other lens component is arranged closer to the object side or the image side than the lens component having the positive lens and the negative lens. The negative lens group may include a prism. This prism is preferably arranged between another lens component and a lens component having a positive lens and a negative lens.

  The first positive lens group has one lens component. This lens component is composed of a positive lens and a negative lens. The positive lens and the negative lens may be joined, but may not be joined (each may be separated). When the positive lens and the negative lens are separately arranged, each of the positive lens and the negative lens can be regarded as one lens component. In this case, it can be said that the first positive lens group is composed of two lens components.

When the positive lens and the negative lens are cemented, the cemented lens has a meniscus shape or a biconvex shape. Further, it is preferable that the most image side of the cemented lens is a negative lens. In addition, when the positive lens and the negative lens are separately arranged, it is preferable that both of the two lens components have a meniscus shape. The most image side is preferably a negative lens.

  The first positive lens group may further include another lens component. This other lens component has a meniscus shape or a biconvex shape. When the lens component having the cemented lens has a meniscus shape, the shape of another lens component is a biconvex shape. Further, when the positive lens and the negative lens are separately arranged, one of the two lens components may be regarded as another lens component. Note that the first positive lens group preferably has a negative lens closest to the image side.

  Further, it is preferable that the other lens component is disposed closer to the object side than the lens component having the cemented lens. This other lens component may be a single lens.

  Thus, if the first positive lens group has at least one meniscus lens component and biconvex lens component, the optical system can be easily miniaturized. In order to reduce the size of the optical system, it is particularly preferable that the first positive lens group includes the two lens components (a meniscus lens component and a biconvex lens component).

  The second positive lens group has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. Alternatively, this lens component may be a single lens.

  Further, another lens group may be disposed between the first positive lens group and the second positive lens group. In this case, this another lens group has one lens component. In addition, this other lens group has a negative refracting power, so that it is easy to reduce the size of the optical system.

  Further, another positive lens group may be arranged on the object side of the negative lens group. In this case, another positive lens group has one lens component. This lens component has a positive lens and a negative lens. The positive lens and the negative lens may be joined, but may not be joined (each may be separated). When the positive lens and the negative lens are separately arranged, each of the positive lens and the negative lens can be regarded as one lens component. In this case, it can be said that another positive lens group is composed of two lens components.

  In addition, when another positive lens group includes two lens components, a prism may be provided. This prism is preferably arranged between two lens components.

  Next, when the basic configuration is negative / positive / (S) / positive, a negative lens group is disposed on the object side of the stop, and a cemented lens is disposed in the negative lens group. A lens LA that satisfies the conditional expressions (1) and (2) is used for this cemented lens. The lens LA may be a lens satisfying (1 ') or (1 ") instead of (1) and satisfying (2') or (2") instead of (2).

  The negative lens group has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. In any case, it is preferable that the negative lens is located on the object side. A lens LA that satisfies the conditional expressions (1) and (2) is used for this cemented lens. The lens LA may be a lens satisfying (1 ') or (1 ") instead of (1) and satisfying (2') or (2") instead of (2).

  The negative lens group may further include another lens component. This other lens component is composed of a cemented lens of a positive lens and a negative lens. The other lens component is preferably arranged on the image side of the lens component having the cemented lens. The negative lens group may include a prism. This prism is preferably arranged between two lens components.

  The first positive lens group has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens.

  The second positive lens group has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. Further, it is preferable that the most image side of the cemented lens is a negative lens.

  The second positive lens group preferably has a negative lens closest to the image side. The lens component of the second positive lens group has a biconvex shape.

  Further, a negative lens group may be disposed between the stop and the second positive lens group. In this case, it has one lens component. This lens component has a positive lens and a negative lens. The positive lens and the negative lens may be joined, but may not be joined (each may be separated). This another lens group can also have a positive refractive power.

  Further, in the case of negative / positive / negative / positive refractive power arrangement, it corresponds to a configuration in which a negative lens group is arranged between two positive lens groups having negative, positive, and positive configurations as a source. On the other hand, when the negative / positive / positive / positive refractive power arrangement is a basic configuration, this corresponds to the arrangement of a positive lens group (between two positive lens groups). In the case of a negative lens group, the optical system can be easily miniaturized, but in the case of a positive lens group, aberration correction is easy.

  By the way, in the positive / negative / positive / positive configuration, another lens group may be arranged between the second and third positive lens groups. On the other hand, in the negative / positive / negative / positive common configuration, two positive lens groups (second and third positive lens groups) are arranged on the image side of the first negative lens group. . Then, the second negative lens group can be regarded as another lens group disposed between the second and third positive lens groups. Therefore, this second negative lens group can also have a positive refractive power (for example, negative / positive / positive / positive in the 4-group configuration and positive / negative / positive / positive / positive in the 5-group configuration). If the second negative lens group has a negative refractive power, the optical system can be easily miniaturized, but if it has a positive refractive power, aberration correction is easy.

  In the basic configuration described so far, when the most object side lens group includes a prism, the position of the most object side lens group is fixed at the time of zooming from the wide-angle end to the telephoto end. When a lens group other than the most object side lens group includes a prism, the most object side lens group moves monotonously along the optical axis toward the object side during zooming from the wide-angle end to the telephoto end. When the imaging optical system does not include a prism, the lens unit closest to the object moves along a locus convex to the image side during zooming from the wide-angle end to the telephoto end.

  The first positive lens unit in the basic configuration moves monotonously to the object side during zooming from the wide angle end to the telephoto end.

  Then, it demonstrates for every group structure. First, an imaging optical system having a three-group configuration will be described. The imaging optical system having a three-group configuration includes, in order from the object side, a negative first lens group G1, an aperture stop, a positive second lens group G2, and a positive third lens group G3.

  The negative first lens group G1 has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the negative lens and the positive lens are arranged in this order from the object side.

  In addition, a lens LA that satisfies the conditional expressions (1) and (2) is used as the negative lens of the cemented lens in this lens component. The lens LA may be a lens satisfying (1 ') or (1 ") instead of (1) and satisfying (2') or (2") instead of (2).

  The positive second lens group G2 has two lens components. Of the two lens components, one lens component is a positive lens component. The other lens component is composed of a cemented lens of a positive lens and a negative lens. Further, it is preferable that one lens component is located closer to the object side than the other lens component. The most image side of the positive second lens group G2 is preferably a negative lens.

  Here, one lens component is composed of one positive lens. This one lens component may be a positive single lens. Moreover, it is preferable that the cemented lens in the other lens component is configured in the order of a positive lens and a negative lens from the object side.

  Thus, the positive second lens group G2 has a lens component arranged in the order of a positive lens component (one lens component) and a lens component having the cemented lens (the other lens component). The most image side is a negative lens.

  Alternatively, it is preferable that one lens component has a biconvex shape and the other lens component has a meniscus shape that is convex toward the object side. One lens component is preferably located closer to the object side than the other lens component. The most image side of the cemented lens is a negative lens.

  The positive third lens group G3 has one lens component. This lens component is composed of one positive lens. This lens component may be a positive single lens.

  Next, a four-group imaging optical system will be described. There are four types of four-group imaging optical systems. The first type of imaging optical system includes, in order from the object side, a positive first lens group G1, a negative second lens group G2, an aperture stop, a positive third lens group G3, and a positive fourth lens group. Consists of G4.

  The positive first lens group G1 has one lens component or two lens components. When there is one lens component, this lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the positive lens and the negative lens are arranged in this order from the object side.

  When there are two lens components, one of the two lens components is a negative lens component. The other lens component is a positive lens component. Further, it is preferable that one lens component is located closer to the object side than the other lens component.

  Here, one lens component is composed of one negative lens. This one lens component may be a negative single lens. The other lens component is composed of one positive lens. This one lens component may be a positive single lens.

  When there are two lens components, the positive first lens group G1 may further include a prism. The prism is disposed between the two lens components. This prism is used to bend the optical path. One lens component may be bonded to the prism or integrated with the prism (so that one surface of the prism is a negative lens).

  The negative second lens group G2 has one lens component or two lens components. When the prism is arranged in the positive first lens group G1, the negative second lens group G2 has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the negative lens and the positive lens are arranged in this order from the object side.

  When no prism is arranged in the positive first lens group G1, the negative second lens group G2 has two lens components. Of the two lens components, one lens component is composed of a cemented lens of a positive lens and a negative lens. The other lens component is a positive lens component. Then, in order from the object side, one lens component and the other lens component are arranged in this order.

  Here, it is preferable that the cemented lens in one lens component is configured in the order of the negative lens and the positive lens from the object side. The other lens component is composed of one positive lens. The other lens component may be a positive single lens.

  A lens LA that satisfies the conditions (1) and (2) is used as the negative lens of the cemented lens. The lens LA may be a lens that satisfies (1 ') or (1 ") instead of (1) and (2') or (2") instead of (2).

  The positive third lens group G3 has two lens components. Of the two lens components, one lens component is a positive lens component. The other lens component is composed of a cemented lens of a positive lens and a negative lens. Further, it is preferable that one lens component is located closer to the object side than the other lens component. The most image side of the positive third lens group G3 is preferably a negative lens.

  Here, one lens component is composed of one positive lens. This one lens component may be a positive single lens. Moreover, it is preferable that the cemented lens in the other lens component is configured in the order of a positive lens and a negative lens from the object side.

  Thus, the positive third lens group G3 has a lens component arranged in the order of a positive lens component (one lens component) and a lens component having the cemented lens (the other lens component). The most image side is a negative lens.

  Alternatively, it is preferable that one lens component has a biconvex shape and the other lens component has a meniscus shape that is convex toward the object side. One lens component is preferably located closer to the object side than the other lens component. The most image side of the cemented lens is a negative lens.

  The positive fourth lens group G4 has one lens component. This lens component is composed of one positive lens. This lens component may be a positive single lens.

  The second type of imaging optical system includes, in order from the object side, a negative first lens group G1, an aperture stop, a positive second lens group G2, a negative third lens group G3, and a positive fourth lens group. It consists of four lens groups, G4.

  The negative first lens group G1 has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the negative lens and the positive lens are arranged in this order from the object side.

  In addition, a lens LA that satisfies the conditional expressions (1) and (2) is used as the negative lens of the cemented lens in this lens component. The lens LA may be a lens satisfying (1 ') or (1 ") instead of (1) and satisfying (2') or (2") instead of (2).

  The positive second lens group G2 has two lens components. Of the two lens components, one lens component is a positive lens component. The other lens component is composed of a cemented lens of a positive lens and a negative lens. Further, it is preferable that one lens component is located closer to the object side than the other lens component. The most image side of the positive second lens group G2 is preferably a negative lens.

  Here, one lens component is composed of one positive lens. This one lens component may be a positive single lens. Moreover, it is preferable that the cemented lens in the other lens component is configured in the order of a positive lens and a negative lens from the object side.

  Thus, the positive second lens group G2 has a lens component arranged in the order of a positive lens component (one lens component) and a lens component having the cemented lens (the other lens component). The most image side is a negative lens.

  Alternatively, it is preferable that one lens component has a biconvex shape and the other lens component has a meniscus shape that is convex toward the object side. One lens component is preferably located closer to the object side than the other lens component. The most image side of the cemented lens is a negative lens.

  The negative third lens group G3 has one lens component. This lens component may be composed of a single lens. The refractive power of the negative third lens group G3 may be positive. This facilitates aberration correction. However, if the refractive power is negative, the optical system can be easily downsized.

  The positive fourth lens group G4 has one lens component. This lens component is composed of one positive lens. This lens component may be a positive single lens.

  The third type of imaging optical system differs in the position of the aperture stop compared to the second type of imaging optical system. That is, the third type of imaging optical system includes, in order from the object side, a negative first lens group G1, a positive second lens group G2, an aperture stop, a negative third lens group G3, and a positive fourth lens group. It consists of four lens groups, the lens group G4.

  The negative first lens group G1 has two lens components. One lens component and the other lens component are both composed of a cemented lens of a positive lens and a negative lens. Further, it is preferable that the cemented lens in one lens component is configured in the order of the negative lens and the positive lens from the object side. Moreover, it is preferable that the cemented lens in the other lens component is configured in the order of a positive lens and a negative lens from the object side.

  The negative first lens group G1 has a prism. The prism is disposed between the two lens components. This prism is used to bend the optical path.

  A lens LA that satisfies the conditional expressions (1) and (2) is used as the negative lens of the cemented lens in one lens component. The lens LA may be a lens satisfying (1 ') or (1 ") instead of (1) and satisfying (2') or (2") instead of (2).

  The positive second lens group G2 has one positive lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the positive lens and the negative lens are arranged in this order from the object side.

  The negative third lens group G3 has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the negative lens and the positive lens are arranged in this order from the object side.

  The refractive power of the negative third lens group G3 may be positive. This facilitates aberration correction. However, if the refractive power is negative, the optical system can be easily downsized.

  The positive fourth lens group G4 has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the positive lens and the negative lens are arranged in this order from the object side. Thus, it is preferable that the most image side of the cemented lens is a negative lens. The most image side of the positive fourth lens group G4 is preferably a negative lens. The cemented lens has a biconvex shape.

  The fourth type imaging optical system includes, in order from the object side, a negative first lens group G1, an aperture stop, a positive second lens group G2, a positive third lens group G3, and a positive fourth lens group. It consists of four lens groups, G4.

  The negative first lens group G1 has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the negative lens and the positive lens are arranged in this order from the object side.

  A lens LA that satisfies the conditional expressions (1) and (2) is used as the negative lens of the cemented lens. The lens LA may be a lens satisfying (1 ') or (1 ") instead of (1) and satisfying (2') or (2") instead of (2).

  The positive second lens group G2 has one lens component. Of the two lens components, one lens component is a positive lens component. The other lens component is a negative lens component. At this time, it is preferable that one lens component is positioned closer to the object side than the other lens component.

  One lens component is composed of one positive lens. This one lens component may be a positive single lens. The other lens component is composed of one negative lens. The other lens component may be a negative single lens.

  Here, both the one lens component and the other lens component have a meniscus shape that is convex toward the object side. The most image side of the positive second lens group G2 is a negative lens.

  The positive third lens group G3 has one lens component. This lens component is composed of one positive lens. This lens component may be a positive single lens.

  The refractive power of the positive third lens group G3 may be negative. In this way, it is easy to miniaturize the optical system. However, if the refractive power is positive, aberration correction is easy.

  The positive fourth lens group G4 has one lens component. This lens component is composed of one positive lens. This lens component may be a positive single lens.

  Next, an imaging optical system having a five-group configuration will be described. This imaging optical system includes, in order from the object side, a positive first lens group G1, a negative second lens group G2, an aperture stop, a positive third lens group, a positive or negative fourth lens group G4, and a positive Consists of a fifth lens group G5.

  The positive first lens group G1 has one lens component or two lens components. When there is one lens component, this lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the positive lens and the negative lens are arranged in this order from the object side.

  When there are two lens components, one of the two lens components is a negative lens component. The other lens component is a positive lens component. Further, it is preferable that one lens component is located closer to the object side than the other lens component.

  Here, one lens component is composed of one negative lens. This one lens component may be a negative single lens. The other lens component is composed of one positive lens. This one lens component may be a positive single lens.

  When there are two lens components, the positive first lens group G1 may further include a prism. The prism is disposed between the two lens components. This prism is used to bend the optical path. One lens component may be bonded to the prism or integrated with the prism (so that one surface of the prism is a negative lens).

  The negative second lens group G2 has one lens component or two lens components. When there is one lens component, this lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the negative lens and the positive lens are arranged in this order from the object side.

  When there are two lens components, one of the two lens components is a negative lens component. The other lens component is composed of a cemented lens of a positive lens and a negative lens.

  Here, one lens component is composed of one negative lens. This one lens component may be a negative single lens. Further, it is preferable that the cemented lens in the other lens component is configured in the order of the negative lens and the positive lens from the object side.

  When there are two lens components, the negative first lens group G1 may further include a prism. The prism is disposed between the two lens components. This prism is used to bend the optical path. One lens component may be bonded to the prism or integrated with the prism (so that one surface of the prism is a negative lens).

  A lens LA that satisfies the conditional expressions (1) and (2) is used as the negative lens of the cemented lens. The lens LA may be a lens satisfying (1 ') or (1 ") instead of (1) and satisfying (2') or (2") instead of (2).

  The positive third lens group G3 has one lens component or two lens components. When a prism is arranged in the positive first lens group G1, the positive third lens group G3 has one lens component. This lens component is composed of a cemented lens of a positive lens and a negative lens. The cemented lens is preferably configured so that the positive lens and the negative lens are arranged in this order from the object side.

  When no prism is disposed in the positive first lens group G1, the positive third lens group G3 has two lens components. Of the two lens components, one lens component is a positive lens component. The other lens component is composed of a cemented lens of a positive lens and a negative lens. At this time, it is preferable that one lens component is positioned closer to the object side than the other lens component.

  Here, one lens component is composed of one positive lens. This one lens component may be a positive single lens. Moreover, it is preferable that the cemented lens in the other lens component is configured in the order of a positive lens and a negative lens from the object side.

  Further, in any one lens component and two lens components, it is preferable that one lens component has a biconvex shape. Further, it is preferable that the most image side of the cemented lens is a negative lens. The most image side of the positive third lens group G3 is preferably a negative lens.

  When the positive third lens group G3 has two lens components, the positive third lens group G3 has a positive lens component (one lens component) and a lens component having a cemented lens (the other lens component). It is preferable that a negative lens is provided on the most image side of the cemented lens.

  Alternatively, it is preferable that one lens component has a biconvex shape and the other lens component has a meniscus shape that is convex toward the object side. One lens component is preferably located closer to the object side than the other lens component. The most image side of the cemented lens is a negative lens.

  The positive or negative fourth lens group G4 has one lens component. This lens component is composed of one positive lens or one negative lens. This lens component may be a positive single lens or a negative single lens.

  Here, the positive or negative fourth lens group G4 has a negative refracting power, so that the optical system can be easily downsized. However, the positive or negative fourth lens group G4 is more easily corrected for aberrations with a positive refractive power.

  The positive fifth lens group G5 has one lens component. This lens component is composed of one positive lens. This lens component may be a positive single lens.

  In the above description, an optical system having a four-group configuration in which the refractive power arrangement is negative, positive, negative, and positive is exemplified as the imaging optical system. In this configuration, if a lens group having a positive refractive power is disposed closest to the object side, it is advantageous for increasing the magnification when a zoom lens is used. In that case, the second positive lens group when the positive lens is arranged on the object side moves only to the object side when zooming from the wide-angle end to the telephoto end.

  As described above, if the distortion generated in the imaging optical system is corrected by the image processing function of the electronic imaging apparatus, other aberrations can be corrected satisfactorily.

  In each of the imaging optical systems described so far, it is preferable that the lens satisfying the conditional expressions (1) and (2) is a negative lens. The negative lens is preferably a lens that satisfies (1 ') or (1 ") instead of (1) and satisfies (2') or (2") instead of (2).

  Each imaging optical system described so far is a zoom lens. In such a zoom lens, it is preferable that the zoom lens is an optical system in which the relative distance between the lens groups changes during zooming.

  However, in each imaging optical system, when the most object-side lens group includes a prism, the position of the most object-side lens group is fixed when zooming from the wide-angle end to the telephoto end. preferable. Further, when there is no lens group including a prism, the lens group closest to the object draws a convex locus on the image side along the optical axis at the time of zooming from the wide-angle end to the telephoto end. When there is a lens group on the object side of the prism, the lens group draws a locus that monotonously moves toward the object side.

  In addition, with the zooming from the wide-angle end to the telephoto end, the third lens group G3 is in the object side when the first lens group G1 is positive, and the second lens group G2 is in the object side when the first lens group G1 is negative. Move monotonously.

  Note that the refractive power of one lens can be borne by a plurality of lenses. Therefore, in each lens group described above, for example, one lens can be replaced with two lenses. However, from the viewpoint of size reduction and thickness reduction, it is preferable that the number of lenses to be replaced is two. Although the replacement may be performed in each lens group, it is preferable that the number of lens groups to be replaced is small from the viewpoint of miniaturization and thinning.

When the lens LA is used as the cemented lens, the lens LA is cemented with the lens LB. At this time, the center thickness of the optical axis of the lens LB is preferably thinner than that of the lens LA. The optical axis center thickness tB of the lens LB preferably satisfies the following conditional expression (17).
0.1 <tB <1.4 (17)

  By satisfying the above conditions, it is possible to reduce the size of the optical system. Further, when the lens LA is obtained by molding, stable molding can be performed.

It is more preferable that the following conditional expression (17 ′) is satisfied instead of conditional expression (17).
0.1 <tB <1.1 (17 ')
Furthermore, it is even better if the following conditional expression (17 ″) is satisfied instead of conditional expression (17).
0.1 <tB <0.95 (17 ")

  In addition, it is preferable that at least one surface of the lens LB is an aspherical surface.

  Incidentally, the chromatic aberration due to the secondary spectrum includes axial chromatic aberration (chromatic aberration at the focal position) and lateral chromatic aberration. Of these, the above conditions and configuration are very effective for correcting axial chromatic aberration. On the other hand, with respect to lateral chromatic aberration due to the secondary spectrum, aberrations are likely to occur. However, high-order component aberrations related to image height, such as lateral chromatic aberration, can be improved by other means. As an example, there is a means for improving aberration by image processing.

  Here, it is assumed that the image pickup optical system, the electronic image pickup device, and the image processing unit are mounted on the electronic image pickup apparatus. The image processing unit can process the image data and output it as image data having a changed shape. An image of a subject is captured using such an electronic imaging device. Image data obtained by imaging is color-separated by an image processing unit, and becomes image data for each color. Subsequently, after changing the shape (the size of the image of the subject) for each image data, these image data are synthesized. As a result, it is possible to prevent sharpness degradation and color blurring at the periphery of the image due to lateral chromatic aberration. This method is particularly effective for an electronic imaging apparatus having an electronic imaging element provided with a color separation mosaic filter. In the case where the electronic imaging apparatus has a plurality of (for each color) electronic imaging elements, it is not necessary to perform color separation on the obtained image data.

  The imaging optical system of the present invention can achieve both downsizing and thinning of the imaging optical system by satisfying or having the conditional expressions and structural features described above individually. Good aberration correction can be realized. In addition, the imaging optical system of the present invention can be provided with (satisfied with) the above conditional expressions and structural features in combination. In this case, the imaging optical system can be further reduced in size and thickness, or better aberration correction and a wider angle of the optical system can be achieved.

  In addition, the electronic imaging apparatus having the imaging optical system of the present invention is provided with such an imaging optical system, so that it is possible to sharpen the image and prevent color blur in the captured image.

Next, examples of the present invention will be described. Examples 6 and 8 are reference examples. A zoom lens according to Example 1 of the present invention will be described. FIGS. 1A and 1B are cross-sectional views along the optical axis showing the optical configuration of the zoom lens according to the first embodiment of the present invention when focusing on an object point at infinity. FIG. 1A is a wide-angle end, and FIG. (C) is a sectional view at the telephoto end.

  FIG. 2 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when the zoom lens according to Example 1 is focused on an object point at infinity. a) shows the wide-angle end, (b) shows the intermediate focal length state, and (c) shows the state at the telephoto end. FIY represents the image height. The symbols in the aberration diagrams are the same in the examples described later.

  As shown in FIG. 1, the zoom lens according to the first exemplary embodiment includes, in order from the object side, a first lens group G1, an aperture stop S, a second lens group G2, and a third lens group G3. .

  The first lens group G1 includes a cemented lens of a negative biconcave lens L1 and a positive meniscus lens L2 having a convex surface directed toward the object side, and has a negative refracting power as a whole. The negative biconcave lens L1 corresponds to the lens LA, and the positive meniscus lens L2 having a convex surface facing the object side corresponds to the lens LB.

  The second lens group G2 includes a positive biconvex lens L3, a cemented lens including a positive meniscus lens L4 having a convex surface facing the object side and a negative meniscus lens L5 having a convex surface facing the object side, and is positively refracted as a whole. Have power.

  The third lens group G3 includes a positive meniscus lens L6 having a convex surface directed toward the image side, and has a positive refracting power as a whole.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 once moves to the image side, then the moving direction reverses and moves to the object side, and the second lens group G2 is integrated with the aperture stop S. The third lens group G3 is moved to the object side, and once moved to the image side, the moving direction is reversed and moved to the object side.

  The aspherical surfaces include both surfaces of the negative biconcave lens L1 in the first lens group G1, both surfaces of the positive meniscus lens L2 having a convex surface facing the object side, both surfaces of the positive biconvex lens L3 in the second lens group G2, and the third lens group. It is provided on the image side surface of the positive meniscus lens L6 having a convex surface facing the image side in G3.

  Next, a zoom lens according to embodiment 2 of the present invention will be described. FIGS. 3A and 3B are cross-sectional views along the optical axis showing the optical configuration of the zoom lens according to the second embodiment of the present invention when focusing on an object point at infinity, where FIG. 3A is a wide-angle end, and FIG. (C) is a sectional view at the telephoto end.

  4A and 4B are diagrams showing spherical aberration, astigmatism, distortion aberration, and chromatic aberration of magnification when the zoom lens according to Example 2 is focused on an object point at infinity, where FIG. 4A is a wide angle end, and FIG. 4B is an intermediate focus. The distance state, (c) shows the state at the telephoto end.

  As shown in FIG. 3, the zoom lens according to the second embodiment includes, in order from the object side, the first lens group G1, the aperture stop S, the second lens group G2, the third lens group G3, and the fourth lens group. G4.

  The first lens group G1 includes a cemented lens of a negative biconcave lens L1 and a positive meniscus lens L2 having a convex surface directed toward the object side, and has a negative refracting power as a whole. The negative biconcave lens L1 corresponds to the lens LA, and the positive meniscus lens L2 having a convex surface facing the object side corresponds to the lens LB.

  The second lens group G2 includes a positive meniscus lens L3 having a convex surface directed toward the object side and a negative meniscus lens L4 having a convex surface directed toward the object side, and has a positive refractive power as a whole.

  The third lens group G3 includes a positive meniscus lens L5 having a convex surface directed toward the image side, and has a positive refractive power as a whole.

  The fourth lens group G4 includes a positive meniscus lens L6 having a convex surface directed toward the image side, and has a positive refracting power as a whole.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 once moves to the image side, then the moving direction reverses and moves to the object side, and the second lens group G2 is integrated with the aperture stop S. Accordingly, the third lens group G3 moves to the image side, and the fourth lens group G4 moves to the image side.

  The aspherical surface includes both surfaces of a negative biconcave lens L1 in the first lens group G1, both surfaces of a positive meniscus lens L2 having a convex surface facing the object side, and a positive meniscus lens L3 having a convex surface facing the object side in the second lens group G2. Of the positive meniscus lens L5 having a convex surface facing the image side in the third lens group G3, and on the object side surface of the positive meniscus lens L6 having a convex surface facing the image side in the fourth lens group G4. ing.

  Next, a zoom lens according to embodiment 3 of the present invention will be described. FIGS. 5A and 5B are cross-sectional views along the optical axis showing an optical configuration when focusing on an object point at infinity of a zoom lens according to Example 3 of the present invention, where FIG. 5A is a wide-angle end, and FIG. (C) is a sectional view at the telephoto end.

  6A and 6B are diagrams illustrating spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to Example 3 is focused on an object point at infinity, in which FIG. 6A is a wide-angle end, and FIG. 6B is an intermediate focus. The distance state, (c) shows the state at the telephoto end.

  As shown in FIG. 5, the zoom lens according to the third exemplary embodiment includes, in order from the object side, the first lens group G1, the aperture stop S, the second lens group G2, the third lens group G3, and the fourth lens group. G4.

  The first lens group G1 includes a cemented lens of a negative biconcave lens L1 and a positive meniscus lens L2 having a convex surface directed toward the object side, and has a negative refracting power as a whole. The negative biconcave lens L1 corresponds to the lens LA, and the positive meniscus lens L2 having a convex surface facing the object side corresponds to the lens LB.

  The second lens group G2 includes a positive biconvex lens L3, a cemented lens including a positive meniscus lens L4 having a convex surface facing the object side and a negative meniscus lens L5 having a convex surface facing the object side, and is positively refracted as a whole. Have power.

  The third lens group G3 includes a negative biconcave lens L6, and has a negative refracting power as a whole.

  The fourth lens group G4 includes a positive biconvex lens L7, and has a positive refractive power as a whole.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 once moves to the image side, then the moving direction reverses and moves to the object side, and the second lens group G2 is integrated with the aperture stop S. The third lens group G3 temporarily moves to the image side, then the moving direction reverses and moves to the object side, and the fourth lens group G4 moves to the image side.

  The aspherical surfaces are the object-side surface of the negative biconcave lens L1 in the first lens group G1, the image-side surface of the positive meniscus lens L2 with the convex surface facing the object side, and the positive biconvex lens L3 in the second lens group G2. Object side surface of positive meniscus lens L4 having convex surfaces facing both sides, object side, object side surface of negative biconcave lens L6 in third lens group G3, object side of positive biconvex lens L7 in fourth lens group G4 It is provided on the surface.

  Next, a zoom lens according to embodiment 4 of the present invention will be described. FIGS. 7A and 7B are cross-sectional views along the optical axis showing the optical configuration when focusing on an object point at infinity of a zoom lens according to Example 4 of the present invention, where FIG. 7A is a wide angle end, and FIG. (C) is a sectional view at the telephoto end.

  8A and 8B are diagrams showing spherical aberration, astigmatism, distortion aberration, and chromatic aberration of magnification when the zoom lens according to Example 4 is focused on an object point at infinity, where FIG. 8A is a wide angle end, and FIG. 8B is an intermediate focus. The distance state, (c) shows the state at the telephoto end.

  As shown in FIG. 7, the zoom lens of Example 4 includes, in order from the object side, the first lens group G1, the second lens group G2, the aperture stop S, the third lens group G3, and the fourth lens group. G4.

  The first lens group G1 includes a cemented lens of a negative biconcave lens L1 and a positive meniscus lens L2 having a convex surface facing the object side, a prism L3, and a cemented lens of a positive biconvex lens L4 and a negative biconcave lens L5. It has a negative refractive power as a whole. The negative biconcave lens L1 in the first lens group G1 corresponds to the lens LA, and the positive meniscus lens L2 with the convex surface facing the object side corresponds to the lens LB.

  The second lens group G2 includes a biconvex lens L6 and a negative meniscus lens L7 having a convex surface directed toward the image side, and has a positive refractive power as a whole.

  The third lens group G3 includes a cemented lens which is formed by a negative biconcave lens L8 and a positive meniscus lens L9 having a convex surface directed toward the object side, and has a negative refracting power as a whole.

  The fourth lens group G4 includes a positive biconvex lens L10 and a negative meniscus lens L11 having a convex surface directed toward the image side, and has a positive refracting power as a whole.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 is moved to the object side, the aperture stop S is fixed, and the third lens group G3 is moved to the image side. Then, the fourth lens group G4 moves to the image side.

  The aspherical surface is an image side surface of a positive meniscus lens L2 having a convex surface facing the object side in the first lens group G1, an object side surface of the positive biconvex lens L6 in the second lens group G2, and a fourth lens group G4. It is provided on the object side surface of the middle positive biconvex lens L10.

  Next, a zoom lens according to embodiment 5 of the present invention will be described. 9A and 9B are cross-sectional views along the optical axis showing the optical configuration of the zoom lens according to Example 5 of the present invention when focusing on an object point at infinity, where FIG. 9A is a wide-angle end, and FIG. (C) is a sectional view at the telephoto end.

  10A and 10B are diagrams showing spherical aberration, astigmatism, distortion aberration, and chromatic aberration of magnification when the zoom lens according to Example 5 is focused on an object point at infinity, where FIG. 10A is a wide-angle end, and FIG. 10B is an intermediate focus. The distance state, (c) shows the state at the telephoto end.

  As shown in FIG. 9, the zoom lens of Example 5 includes, in order from the object side, a first lens group G1, a second lens group G2, an aperture stop S, a third lens group G3, and a fourth lens group. G4.

  The first lens group G1 includes a cemented lens of a positive biconvex lens L1 and a negative biconcave lens L2, and has a positive refractive power as a whole.

  The second lens group G2 includes a cemented lens of a negative meniscus lens L3 having a convex surface facing the object side and a positive meniscus lens L4 having a convex surface facing the object side, and a positive meniscus lens L5 having a convex surface facing the object side. And has a negative refractive power as a whole. The negative biconcave lens L3 corresponds to the lens LA, and the positive meniscus lens L4 having a convex surface facing the object side corresponds to the lens LB.

  The third lens group G3 includes a positive biconvex lens L6, a cemented lens of a positive meniscus lens L7 having a convex surface facing the object side, and a negative meniscus lens L8 having a convex surface facing the object side. Has refractive power.

  The fourth lens group G4 includes a positive meniscus lens L9 having a convex surface directed toward the object side, and has a positive refracting power as a whole.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 once moves to the image side, then the moving direction reverses and moves to the object side, and the second lens group G2 moves to the image side. The third lens group G3 moves to the object side integrally with the aperture stop S, and the fourth lens group G4 once moves to the object side and then reverses the moving direction to move to the image side. Note that the position of the second lens group at the telephoto end is closer to the object side than the position in the intermediate focal length state, but there is almost no difference.

  The aspherical surface has an image side surface of the negative biconcave lens L2 in the first lens group G1, an image side surface of the positive meniscus lens L4 with the convex surface facing the object side in the second lens group G2, and a convex surface on the object side. Both surfaces of the positive meniscus lens L5 facing, the object-side surface of the positive biconvex lens L6 in the third lens group G3, the image-side surface of the negative meniscus lens L8 with the convex surface facing the object side, and in the fourth lens group G4 It is provided on the object side surface of a positive meniscus lens L9 having a convex surface facing the object side.

  Next, a zoom lens according to embodiment 6 of the present invention will be described. 11A and 11B are cross-sectional views along the optical axis showing the optical configuration of the zoom lens according to Example 6 of the present invention when focusing on an object point at infinity. FIG. 11A is a wide angle end, and FIG. 11B is an intermediate focal length state. (C) is a sectional view at the telephoto end.

  12A and 12B are diagrams showing spherical aberration, astigmatism, distortion aberration, and chromatic aberration of magnification when the zoom lens according to Example 6 is focused on an object point at infinity, where FIG. 12A is a wide angle end, and FIG. 12B is an intermediate focus. The distance state, (c) shows the state at the telephoto end.

  As shown in FIG. 11, the zoom lens of Example 6 includes, in order from the object side, a first lens group G1, a second lens group G2, an aperture stop S, a third lens group G3, and a fourth lens group. G4 and the fifth lens group G5 are included.

  The first lens group G1 includes a cemented lens of a biconvex lens L1 and a negative meniscus lens L2 having a convex surface directed toward the image side, and has a positive refractive power as a whole.

  The second lens group G2 is a cemented lens of a negative meniscus lens L3 having a convex surface facing the object side, a prism L4, a negative meniscus lens L5 having a convex surface facing the object side, and a positive meniscus lens L6 having a convex surface facing the object side. It has a negative refractive power as a whole. The negative meniscus lens L5 with the convex surface facing the object side corresponds to the lens LA, and the positive meniscus lens L6 with the convex surface facing the object side corresponds to the lens LB.

  The third lens group G3 includes a positive biconvex lens L7, a cemented lens including a positive meniscus lens L8 having a convex surface directed toward the object side and a negative meniscus lens L9 having a convex surface directed toward the object side, and is positively refracted as a whole. Have power.

  The fourth lens group G4 includes a positive meniscus lens L10 having a convex surface directed toward the object side, and has a positive refracting power as a whole.

  The fifth lens group G5 includes a positive meniscus lens L11 having a convex surface directed toward the object side, and has a positive refracting power as a whole.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side, the second lens group G2 is fixed, and the third lens group G3 is integrated with the aperture stop S toward the object side. The fourth lens group G4 moves to the object side, and the fifth lens group G5 is fixed.

  The aspherical surface is an image side surface of the negative meniscus lens L2 having a convex surface facing the image side in the first lens group G1, and an image side surface of the negative meniscus lens L3 having a convex surface facing the object side in the second lens group G2. Surface, the image side surface of the positive meniscus lens L6 with the convex surface facing the object side, the object side surface of the positive biconvex lens L7 in the third lens group G3, and the positive surface with the convex surface facing the object side of the fifth lens group G5 It is provided on the image side surface of the meniscus lens L11.

  Next, a zoom lens according to embodiment 7 of the present invention will be described. FIGS. 13A and 13B are cross-sectional views along the optical axis showing the optical configuration when focusing on an object point at infinity of a zoom lens according to Example 7 of the present invention. FIG. 13A is a wide-angle end, and FIG. (C) is a sectional view at the telephoto end.

  14A and 14B are diagrams showing spherical aberration, astigmatism, distortion aberration, and chromatic aberration of magnification when the zoom lens according to Example 7 is focused on an object point at infinity, where FIG. 14A is a wide angle end, and FIG. 14B is an intermediate focus. The distance state, (c) shows the state at the telephoto end.

  As shown in FIG. 13, the zoom lens according to the seventh exemplary embodiment includes, in order from the object side, the first lens group G1, the second lens group G2, the aperture stop S, the third lens group G3, and the fourth lens group. G4 and the fifth lens group G5 are included.

  The first lens group G1 includes a negative meniscus lens L1, a prism L2, and a positive biconvex lens L3 having a convex surface directed toward the object side, and has a positive refractive power as a whole.

  The second lens group G2 includes a cemented lens of a biconcave lens L4 and a positive meniscus lens L5 having a convex surface directed toward the object side, and has a negative refracting power as a whole. The biconcave lens L4 corresponds to the lens LA, and the positive meniscus lens L5 with the convex surface facing the object side corresponds to the lens LB.

  The third lens group G3 includes a cemented lens which is formed by a positive biconvex lens L6 and a negative meniscus lens L7 having a convex surface directed toward the image side, and has a positive refracting power as a whole.

  The fourth lens group G4 includes a negative meniscus lens L8 having a convex surface directed toward the object side, and has a negative refracting power as a whole.

  The fifth lens group G5 includes a positive meniscus lens L9 having a convex surface directed toward the object side, and has a positive refracting power as a whole.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 is moved to the image side, the aperture stop S is fixed, and the third lens group G3 is moved to the object side. Then, the fourth lens group G4 moves to the object side, and the fifth lens group G5 once moves to the object side, then the moving direction is reversed and moves to the image side.

  The aspherical surfaces are the image side surface of the negative meniscus lens L1 having a convex surface facing the object side in the first lens group G1, the object side surface of the positive biconvex lens L3, and the negative biconcave lens L4 in the second lens group G2. Object-side surface, image-side surface of positive meniscus lens L5 having a convex surface facing the object side, object-side surface of positive biconvex lens L6 in third lens group G3, and convex surface on the object side in fifth lens group G5 Is provided on the object side surface of the positive meniscus lens L9.

  Next, a zoom lens according to embodiment 8 of the present invention will be described. 15A and 15B are cross-sectional views along the optical axis showing the optical configuration of the zoom lens according to Example 8 of the present invention when focusing on an object point at infinity, where FIG. 15A is a wide angle end, and FIG. 15B is an intermediate focal length state. (C) is a sectional view at the telephoto end.

  FIG. 16 is a diagram illustrating spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to Example 8 is focused on an object point at infinity, where (a) is a wide angle end and (b) is an intermediate focus. The distance state, (c) shows the state at the telephoto end.

  As shown in FIG. 15, the zoom lens of Example 8 includes, in order from the object side, the first lens group G1, the aperture stop S, the second lens group G2, the third lens group G3, and the fourth lens group. G4.

  The first lens group G1 includes a cemented lens of a negative biconcave lens L1 and a positive meniscus lens L2 having a convex surface directed toward the object side, and has a negative refracting power as a whole. The negative biconcave lens L1 corresponds to the lens LA, and the positive meniscus lens L2 corresponds to the lens LB.

  The second lens group G2 includes a positive biconvex lens L3, and a cemented lens of a positive biconvex lens L4 and a negative biconcave lens L5, and has a positive refractive power as a whole.

  The third lens group G3 includes a negative biconcave lens L6, and has a negative refracting power as a whole.

  The fourth lens group G4 includes a positive biconvex lens L7, and has a positive refractive power as a whole.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 once moves to the image side, then the moving direction reverses and moves to the object side, and the second lens group G2 is integrated with the aperture stop S. The third lens group G3 temporarily moves to the image side, and then the moving direction reverses and moves to the object side, and the fourth lens group G4 moves to the image side.

  The aspherical surfaces are the object-side surface of the negative biconcave lens L1 in the first lens group G1, the image-side surface of the positive meniscus lens L2 with the convex surface facing the object side, and the positive biconvex lens L3 in the second lens group G2. Both surfaces are provided on the object side surface of the positive biconvex lens L4, the object side surface of the negative biconcave lens L6 in the third lens group G3, and the object side surface of the positive biconvex lens L7 in the fourth lens group G4. .

  Next, a zoom lens according to embodiment 9 of the present invention will be described. FIGS. 17A and 17B are cross-sectional views along the optical axis showing the optical configuration of the zoom lens according to Example 9 of the present invention when focusing on an object point at infinity, where FIG. 17A is a wide-angle end, and FIG. (C) is a sectional view at the telephoto end.

  18A and 18B are diagrams illustrating spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to Example 9 is focused on an object point at infinity, in which FIG. 18A is a wide angle end, and FIG. 18B is an intermediate focus. The distance state, (c) shows the state at the telephoto end.

  As shown in FIG. 17, the zoom lens according to the ninth embodiment includes, in order from the object side, the first lens group G1, the second lens group G2, the aperture stop S, the third lens group G3, and the fourth lens group. G4.

  The first lens group G1 includes a negative meniscus lens L1, a prism L2, and a positive biconvex lens L3 having a convex surface directed toward the object side, and has a positive refractive power as a whole.

  The second lens group G2 includes a cemented lens which includes a negative biconcave lens L4 and a positive meniscus lens L5 having a convex surface directed toward the object side, and has a negative refracting power as a whole. The negative biconcave lens L4 corresponds to the lens LA, and the positive meniscus lens L5 having a convex surface facing the object side corresponds to the lens LB.

  The third lens group G3 includes a positive biconvex lens L6, a cemented lens of a positive biconvex lens L7 and a negative biconcave lens L8, and has a positive refractive power as a whole.

  The fourth lens group G4 includes a positive meniscus lens L9 having a convex surface directed toward the object side, and has a positive refracting power as a whole.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 is moved to the image side, the aperture stop S is fixed, and the third lens group G3 is moved to the object side. Then, the fourth lens group G4 moves to the image side.

  The aspherical surfaces are the image side surface of the negative meniscus lens L1 having a convex surface facing the object side in the first lens group G1, the object side surface of the positive biconvex lens L3, and the negative biconcave lens L4 in the second lens group G2. An object side surface, an image side surface of a positive meniscus lens L5 having a convex surface facing the object side, an object side surface of a positive biconvex lens L6 in the third lens group G3, and a convex surface on the object side in the fourth lens group G4 Is provided on the object side surface of the positive meniscus lens L9.

  Next, numerical data of optical members constituting the zoom lens of each of the above embodiments will be listed. In the numerical data of each embodiment, r1, r2,... Are the curvature radii of the lens surfaces, d1, d2,... Are the thickness or air spacing of each lens, and nd1, nd2,. Are the Abbe number of each lens, Fno. Is the F number, f is the focal length of the entire system, and D0 is the distance from the object to the first surface. Further, asp indicates an aspheric surface, and STO indicates an aperture.

The aspherical shape is expressed by the following equation when the optical axis direction is z, the direction orthogonal to the optical axis is y, the conical coefficient is K, and the aspherical coefficients are A4, A6, A8, and A10. .
z = (y ² / r) / [1+ {1− (1 + K) (y / r) ² } ^1/2 ]
+ A4y ⁴ + A6y ⁶ + A8y ⁸ + A10y ¹⁰
E represents a power of 10. The symbols of these specification values are common to the numerical data of the examples described later.

Example 1
Unit mm
Surface data Surface number rd nd νd
1 * -62.9785 0.9000 1.52542 55.78
2 * 6.2220 0.5000 1.63494 23.22
3 * 9.3781 Variable
4 (Aperture) ∞ 0.
5 * 4.3728 1.4527 1.80139 45.46
6 * -22.6777 0.1000
7 11.4978 1.0000 1.80518 25.42
8 11.4978 0.5000 1.80810 22.76
9 2.8708 Variable
10 -25.8411 2.2417 1.52542 55.78
11 * -5.4142 variable
12 ∞ 0.4000 1.54771 62.84
13 ∞ 0.2000
14 ∞ 0.5000 1.51633 64.14
15 ∞ Variable
Image plane ∞

Aspherical coefficient first surface K = 115.8250, A4 = -1.0211E-03, A6 = 4.6492E-05, A8 = -1.0362E-06, A10 = 1.2514E-08
2nd surface K = -6.1725, A4 = -5.1068E-04, A6 = 6.0529E-05, A8 = -1.2283E-06
3rd surface K = -9.2729, A4 = -5.2138E-04, A6 = 3.7887E-05, A8 = -9.8473E-07, A10 = 1.2720E-08
5th surface K = -2.2655, A4 = 1.8497E-03, A6 = -1.7322E-04, A8 = 1.1012E-06, A10 = -3.7091E-06
6th surface K = -6.4910, A4 = 2.7022E-05, A6 = -1.5210E-04, A8 = -1.8174E-05, A10 = -8.0149E-07
11th surface K = -1.9637, A4 = -2.9213E-04, A6 = -1.0810E-05, A8 = 3.8863E-07, A10 = -7.5271E-09

Zoom data
Wide angle Medium telephoto focal length 6.37584 10.57824 18.33837
F number 3.1264 4.1941 5.8030
d3 13.16409 7.34139 2.33000
d9 2.70221 7.30761 13.65861
d11 3.80230 3.13340 3.68000
d15 0.39947 0.39947 0.39947

[Glass Material Refractive Index Table] ... Refractive index list by wavelength of medium used in this example lens 587.56 656.27 486.13 435.84 404.66
L2 1.634937 1.627308 1.654649 1.672358 1.688773
LPF 1.547710 1.545046 1.553762 1.558427 1.562262
L1 1.525420 1.522680 1.532100 1.537007 1.540993
L3 1.801390 1.796100 1.813730 1.823569 1.831860
CG 1.516330 1.513855 1.521905 1.526213 1.529768
L5 1.808095 1.798009 1.833513 1.855902 1.876580
L4 1.805181 1.796106 1.827775 1.847283 1.864939
L6 1.525420 1.522680 1.532100 1.537050 1.540699

(Example 2)
Unit mm
Surface data Surface number rd nd νd
1 * -58.9431 0.8000 1.58313 59.38
2 * 8.1380 0.6828 1.63494 23.22
3 * 13.7667 Variable
4 (Aperture) ∞ -0.3000
5 * 4.4724 1.5596 1.83481 42.71
6 * 130.3653 0.1000
7 8.5524 1.3755 1.92286 18.90
8 3.2419 Variable
9 * -38.1669 2.0346 1.80610 40.92
10 * -9.5137 variable
11 * -31.0170 1.0000 1.52542 55.78
12 -14.0000 0.1300
13 ∞ 0.5000 1.54771 62.84
14 ∞ 0.2000
15 ∞ 0.5000 1.51633 64.14
16 ∞ variable

Aspherical coefficient first surface K = 0, A4 = -5.8885E-04, A6 = 1.4288E-05, A8 = -1.7633E-07, A10 = 1.0171E-09
2nd surface K = -8.8482, A4 = 1.2303E-05, A6 = 8.2901E-06, A8 = -2.2270E-07, A10 = 0.0000E + 00
Third surface K = -10.3478, A4 = -4.0540E-04, A6 = 1.2052E-05, A8 = -1.5322E-07, A10 = 1.0250E-09
5th surface K = -1.5713, A4 = 1.8734E-03, A6 = 1.3210E-04, A8 = -1.3012E-05, A10 = 3.2830E-06
6th surface K = 0, A4 = 1.2278E-03, A6 = 2.2014E-04, A8 = -3.1910E-05, A10 = 7.1101E-06
9th page K = -118.8738
10th surface K = -2.0132, A4 = 1.5398E-04, A6 = -1.1684E-05, A8 = 1.3701E-07, A10 = 1.0039E-09
11th surface K = 11.1220, A4 = -1.2538E-03, A6 = 1.1705E-05, A8 = 2.0163E-07

Zoom data
Wide angle Medium telephoto focal length 7.59604 12.60933 21.87623
F number 2.9488 3.9735 5.6645
d3 13.85724 7.45744 2.50000
d8 4.02077 9.33886 16.71742
d10 3.53942 2.65010 2.20000
d16 0.39978 0.39978 0.39978

[Glass Material Refractive Index Table] ... Refractive index list by wavelength of medium used in this example lens 587.56 656.27 486.13 435.84 404.66
L2 1.634937 1.627308 1.654649 1.672358 1.688773
LPF 1.547710 1.545046 1.553762 1.558427 1.562262
L1 1.583126 1.580139 1.589960 1.594676 1.598296
CG 1.516330 1.513855 1.521905 1.526213 1.529768
L5 1.806098 1.800248 1.819945 1.831173 1.840781
L3 1.834807 1.828975 1.848520 1.859547 1.868911
L4 1.922860 1.909158 1.957996 1.989713 2.019763
L6 1.525420 1.522680 1.532100 1.537050 1.540699

(Example 3)
Unit mm
Surface data Surface number rd nd νd
1 * -12.9570 0.8000 1.52542 55.78
2 10.4409 0.7032 1.63494 23.22
3 * 22.2162 variable
4 (Aperture) ∞ 0.3000
5 * 8.6298 * 1.8448 1.83481 42.71
6 * -26.5988 0.0791
7 * 7.1432 1.7812 1.83481 42.71
8 -239.3124 0.4000 1.80810 23.80
9 3.9396 Variable
10 * -42.3355 0.5000 1.52542 55.78
11 19.6055 Variable
12 * 64.2346 1.3800 1.83481 42.71
13 -9.6000 Variable
14 ∞ 0.5000 1.54771 62.84
15 ∞ 0.5000
16 ∞ 0.5000 1.51633 64.14
17 ∞ Variable
Image plane ∞

Aspherical coefficient first surface K = -3.9537, A4 = 0.0000E + 00, A6 = 2.4737E-06, A8 = -3.9226E-08
3rd surface K = -0.9087, A4 = 7.1688E-05, A6 = 3.7777E-06, A8 = -4.9770E-08
5th surface K = -1.9337, A4 = -3.4869E-04, A6 = -2.2526E-05, A8 = -5.7283E-08
6th surface K = -5.9352, A4 = -3.7375E-04, A6 = -6.1314E-06, A8 = -1.7507E-07
7th surface K = 0.2051, A4 = 8.5095E-05, A6 = 1.8765E-05, A8 = 4.8202E-07, A10 = 1.0705E-08
10th surface K = 43.0913, A4 = -2.6920E-04, A6 = -1.0679E-05, A8 = 1.0544E-06
12th surface K = 0, A4 = -4.1294E-04, A6 = 3.6637E-06, A8 = 0.0000E + 00

Zoom data
Wide angle Medium telephoto focal length 6.42001 11.01031 18.48951
F number 1.8685 2.4621 3.4244
d3 14.46707 7.07125 2.86615
d9 2.20000 6.43367 10.48474
d11 2.41629 2.29056 3.84331
d13 3.12835 2.29609 1.60000
d17 0.50016 0.50016 0.50016

[Glass Material Refractive Index Table] ... Refractive index list by wavelength of medium used in this example lens 587.56 656.27 486.13 435.84 404.66
L2 1.634937 1.627308 1.654649 1.672358 1.688773
L5 1.808097 1.798451 1.832401 1.853497 1.872497
LPF 1.547710 1.545046 1.553762 1.558427 1.562262
L1 1.525420 1.522680 1.532100 1.536263 1.539251
CG 1.516330 1.513855 1.521905 1.526213 1.529768
L3, L4, L7 1.834807 1.828975 1.848520 1.859547 1.868911
L6 1.525420 1.522680 1.532100 1.537050 1.540699

Example 4
Unit mm
Surface data Surface number rd nd νd
1 -148.2378 0.8000 1.61800 63.33
2 10.5000 0.9000 1.70000 20.50
3 * 12.5375 2.7000
4 ∞ 12.5000 1.80610 40.92
5 ∞ 0.2000
6 86.3959 2.8000 1.81600 46.62
7 -15.5225 0.7000 1.51742 52.43
8 20.9252 Variable
9 * 16.7269 3.5000 1.74320 49.34
10 -13.1850 0.7000 1.84666 23.78
11 -43.9733 Variable
12 (Aperture) ∞ Variable
13 -14.1403 0.7000 1.51823 58.90
14 9.5058 1.2000 1.80610 40.92
15 24.0964 Variable
16 * 12.9283 4.0000 1.74320 49.34
17 -7.9831 0.7000 1.84666 23.78
18 -16.7658 Variable
19 ∞ 1.4400 1.54771 62.84
20 ∞ 0.8000
21 ∞ 0.6000 1.51633 64.14
22 ∞ Variable
Image plane ∞

Aspherical coefficient third surface K = -0.1161, A4 = -1.4293E-06, A6 = -1.4339E-07, A8 = 0.0000E + 00
9th surface K = 0.5819, A4 = -2.6544E-05, A6 = -7.4893E-08, A8 = 0.0000E + 00
16th surface K = 0.1991, A4 = -2.1271E-04, A6 = -2.7865E-07, A8 = 0.0000E + 00

Zoom data
Wide angle Medium telephoto focal length 6.00532 10.39581 17.99608
F number 2.8644 3.2972 3.8315
d8 14.63665 7.78825 0.79919
d11 1.59938 8.44544 15.43690
d12 1.39901 5.38884 9.49803
d15 6.49016 4.75048 3.00021
d18 5.80409 3.55313 1.19508
d22 1.35981 1.35981 1.35981

[Glass Material Refractive Index Table] ... Refractive index list by wavelength of medium used in this example lens 587.56 656.27 486.13 435.83 404.66
L2 1.699997 1.690560 1.724703 1.747239 1.768350
LPF 1.547710 1.545046 1.553762 1.558428 1.562261
L1 1.618000 1.615036 1.624794 1.629870 1.633987
CG 1.516330 1.513855 1.521905 1.526214 1.529768
L3, L9 1.806098 1.800248 1.819945 1.831174 1.840781
L4 1.816000 1.810749 1.828252 1.837997 1.846185
L6, L10 1.743198 1.738653 1.753716 1.762047 1.769040
L5 1.517417 1.514444 1.524313 1.529804 1.534439
L8 1.518229 1.515556 1.524354 1.529155 1.533151
L7, L11 1.846660 1.836491 1.872096 1.894187 1.914278

(Example 5)
Unit mm
Surface data Surface number rd nd νd
1 18.0638 2.5625 1.61800 63.33
2 -411.3935 0.2000 1.62740 22.28
3 * 58.2672 Variable
4 64.3728 0.8000 1.88300 40.76
5 6.0538 0.7000 1.75000 17.50
6 * 6.7548 1.5257
7 * 10.0815 1.3190 2.04005 23.47
8 * 15.0800 variable
9 (Aperture) ∞ 0.5000
10 * 6.0765 2.2489 1.69350 53.21
11 -30.6535 0.2000
12 9.2885 1.5027 1.83481 42.71
13 25.0625 0.5000 1.80810 22.76
14 * 4.1256 Variable
15 * 10.1052 2.0000 1.80610 40.92
16 93.7214 Variable
17 ∞ 0.5556 1.51633 64.14
18 ∞ variable
Image plane ∞

Aspherical coefficient third surface K = 0, A4 = -5.1871E-06, A6 = 1.9740E-08, A8 = 0.0000E + 00
6th surface K = 0.1870, A4 = -2.4759E-04, A6 = 1.8899E-05, A8 = 3.0471E-08
7th surface K = 2.0742, A4 = -8.3788E-04, A6 = 4.8720E-06, A8 = -6.5300E-08
8th surface K = -14.8045, A4 = -1.5356E-04, A6 = -1.3062E-05, A8 = 4.1097E-07
10th surface K = -0.5350, A4 = -1.7116E-04, A6 = -1.7013E-05, A8 = 5.8607E-07
14th surface K = 0.2799, A4 = -4.6846E-05, A6 = -4.5493E-05, A8 = 7.6143E-06, A10 = -1.2652E-06
15th surface K = -1.3007, A4 = 1.7097E-04, A6 = 6.9200E-06, A8 = -5.3822E-08

Zoom data
Wide angle Medium telephoto focal length 6.78044 11.59644 19.79961
F number 2.0605 2.4114 2.7434
d3 0.89943 3.00074 11.93912
d8 12.40988 3.16832 1.19961
d14 2.37320 3.97492 7.94905
d16 3.06856 3.97526 2.00707
d18 1.35022 1.35022 1.35022

[Glass Material Refractive Index Table] ... Refractive index list by wavelength of medium used in this example lens 587.56 656.27 486.13 435.84 404.66
L2 1.627395 1.619588 1.647747 1.666234 1.683516
L4 1.749996 1.738343 1.781194 1.810388 1.838277
L5 2.040052 2.027333 2.071650 2.098501 2.122228
L3 1.882997 1.876560 1.898221 1.908740 1.916880
CG 1.516330 1.513855 1.521905 1.526213 1.529768
L9 1.806098 1.800248 1.819945 1.831173 1.840781
L7 1.834807 1.828975 1.848520 1.859547 1.868911
L6 1.693501 1.689548 1.702582 1.709715 1.715662
L8 1.808095 1.798009 1.833513 1.855902 1.876580
L1 1.618000 1.615036 1.624794 1.630103 1.634506

(Example 6)
Unit mm
Surface data Surface number rd nd νd
1 65.3278 4.5000 1.61800 63.33
2 -99.2330 0.7000 1.80810 22.76
3 * -139.3664 variable
4 1.563E + 04 0.8000 1.69350 53.21
5 * 11.1871 3.1000
6 ∞ 13.6000 1.77250 49.60
7 ∞ 0.3000
8 472.5189 0.8000 1.43389 95.15
9 14.9256 0.9000 1.74910 18.01
10 * 20.2831 Variable
11 (Aperture) ∞ 0.5000
12 * 14.6231 2.7000 1.83481 42.71
13 -757.3457 0.1500
14 8.1833 2.7000 1.75500 52.32
15 28.3224 0.5000 1.80810 24.00
16 5.8490 Variable
17 15.4383 2.0000 1.69680 55.53
18 41.0361 Variable
19 15.9428 2.0000 1.69350 53.21
20 * 33.1358 1.4000
21 ∞ 1.2000 1.51633 64.14
22 ∞ Variable
Image plane ∞

Aspherical coefficient third surface K = 2.5591, A4 = 3.3082E-06, A6 = -1.2445E-08, A8 = 0.0000E + 00
5th surface K = -0.0260, A4 = -1.4735E-05, A6 = 9.2686E-07, A8 = 0.0000E + 00
10th surface K = 0.1098, A4 = -4.3198E-05, A6 = -1.2444E-07, A8 = 0.0000E + 00
12th surface K = 0, A4 = -3.6784E-05, A6 = 2.7642E-07, A8 = -9.3527E-09
20th surface K = -0.1766, A4 = 2.0397E-05, A6 = 7.2338E-06, A8 = 0.0000E + 00

Zoom data
Wide angle Medium telephoto focal length 6.19748 13.86333 31.00007
F number 2.8000 3.7907 4.9791
d3 0.79948 13.61553 21.10507
d10 23.86378 12.91453 1.80057
d16 4.05251 13.70605 10.01991
d18 6.75188 8.04945 22.84758
d22 1.50059 1.50059 1.50059

[Glass Material Refractive Index Table] ... Refractive index list by wavelength of medium used in this example lens 587.56 656.27 486.13 435.83 404.66
L6 1.749096 1.737741 1.779330 1.807446 1.834165
L9 1.808097 1.798524 1.832190 1.853078 1.871855
L5 1.433890 1.432475 1.437035 1.439355 1.441210
CG 1.516330 1.513855 1.521905 1.526214 1.529768
L7 1.834807 1.828975 1.848520 1.859548 1.868911
L4 1.772499 1.767798 1.783374 1.791972 1.799174
L3, L11 1.693501 1.689548 1.702582 1.709715 1.715662
L10 1.696797 1.692974 1.705522 1.712340 1.718005
L2 1.808095 1.798009 1.833513 1.855904 1.876580
L1 1.618000 1.615036 1.624794 1.630103 1.634506
L8 1.754999 1.750624 1.765055 1.772956 1.779544

(Example 7)
Unit mm
Surface data Surface number rd nd νd
1 28.6603 0.9000 1.84666 23.78
2 * 10.5002 3.0000
3 ∞ 12.0000 1.80610 40.92
4 ∞ 0.2000
5 * 32.1236 2.4000 1.80610 40.92
6 -27.2234 Variable
7 * -17.5310 0.6000 1.69350 53.18
8 16.1122 0.6000 1.80000 17.30
9 * 34.3995 Variable
10 (Aperture) ∞ Variable
11 * 10.9350 4.0000 1.83481 42.71
12 -7.4017 0.6000 1.80810 22.76
13 -26.5473 Variable
14 10.9560 1.0000 1.84666 23.78
15 5.8771 Variable
16 * 12.5362 2.0000 1.49700 81.54
17 31.9270 Variable
18 ∞ 1.5000 1.54771 62.84
19 ∞ 0.8000
20 ∞ 0.7500 1.51633 64.14
21 ∞ Variable
Image plane ∞

Aspheric coefficient K = -0.3499, A4 = 1.2776E-05, A6 = 2.8239E-07, A8 = 0.0000E + 00
5th surface K = -0.3428, A4 = 2.8408E-06, A6 = 1.1795E-07, A8 = 0.0000E + 00
7th surface K = -0.2794, A4 = -1.2407E-04, A6 = 3.0845E-06, A8 = 0.0000E + 00
9th surface K = -0.1625, A4 = -1.6863E-04, A6 = 4.4868E-06, A8 = 0.0000E + 00
11th surface K = 0.0563, A4 = -2.3176E-04, A6 = -1.8609E-09, A8 = 0.0000E + 00
16th surface K = -1.5326, A4 = 1.3085E-04, A6 = 3.1037E-06, A8 = 0.0000E + 00

Zoom data
Wide angle Medium telephoto focal length 6.00668 10.39857 17.99302
F number 2.8002 3.3565 4.7748
d6 0.99746 8.01926 11.55591
d9 11.94945 4.92767 1.39096
d10 8.72015 6.22992 1.19364
d13 2.29144 1.63036 0.80191
d15 1.49943 4.57525 11.18987
d17 2.67739 2.75193 2.00294
d21 1.36041 1.36041 1.36041

[Glass Material Refractive Index Table] ... Refractive index list by wavelength of medium used in this example lens 587.56 656.27 486.13 435.83 404.66
LPF 1.547710 1.545046 1.553762 1.558428 1.562261
L5 1.800000 1.787370 1.833600 1.866890 1.899621
L4 1.693500 1.689551 1.702591 1.709312 1.714733
CG 1.516330 1.513855 1.521905 1.526214 1.529768
L9 1.496999 1.495136 1.501231 1.504507 1.507205
L2 1.806098 1.800248 1.819945 1.831174 1.840781
L3 1.806098 1.800248 1.819945 1.831174 1.840781
L6 1.834807 1.828975 1.848520 1.859548 1.868911
L7 1.808095 1.798009 1.833513 1.855904 1.876580
L1, L8 1.846660 1.836488 1.872096 1.894189 1.914294

(Example 8)
Unit mm
Surface data Surface number rd nd νd
1 * -13.2566 0.8000 1.49700 75.30
2 13.1877 0.4237 1.63494 23.22
3 * 20.8972 Variable
4 (Aperture) ∞ 0.3000
5 * 8.6234 1.8201 1.83481 42.71
6 * -28.1231 0.0791
7 * 7.0624 1.7619 1.83481 42.71
8 -462.1726 0.4000 1.80810 24.00
9 3.9333 Variable
10 * -34.2928 0.5000 1.52542 55.78
11 22.6658 Variable
12 * 63.7715 1.3800 1.83481 42.71
13 -9.6000 Variable
14 ∞ 0.5000 1.54771 62.84
15 ∞ 0.5000
16 ∞ 0.5000 1.51633 64.14
17 ∞ Variable
Image plane ∞

Aspheric coefficient K = -2.8817, A4 = 0.0000E + 00, A6 = 3.6881E-06, A8 = -5.5124E-08
3rd surface K = -2.9323, A4 = 3.6856E-05, A6 = 5.0066E-06, A8 = -5.9251E-08
5th surface K = -1.8270, A4 = -3.4535E-04, A6 = -2.1823E-05, A8 = -7.8527E-08
6th surface K = -5.3587, A4 = -3.7600E-04, A6 = -4.8554E-06, A8 = -2.1415E-07
7th surface K = 0.1274, A4 = 8.3040E-05, A6 = 1.9928E-05, A8 = 5.0707E-07, A10 = 8.1677E-09
10th surface K = 57.7596, A4 = -1.7412E-04, A6 = -4.6146E-06, A8 = 1.1872E-06
12th surface K = 0, A4 = -4.1049E-04, A6 = 3.1634E-06, A8 = 0.0000E + 00

Zoom data
Wide angle Medium telephoto focal length 6.42002 11.01032 18.48954
F number 1.8604 2.4534 3.4040
d3 14.77955 7.26463 2.92947
d9 2.20000 6.46215 10.54460
d11 2.38783 2.27230 3.76136
d13 3.16783 2.30230 1.60000
d17 0.50018 0.50018 0.50018

[Glass Material Refractive Index Table] ... Refractive index list by wavelength of medium used in this example lens 587.56 656.27 486.13 435.83 404.66
L2 1.634937 1.627308 1.654649 1.672362 1.688770
L5 1.808097 1.798524 1.832190 1.853078 1.871855
LPF 1.547710 1.545046 1.553762 1.558428 1.562261
L1 1.496999 1.494960 1.501560 1.505134 1.508110
CG 1.516330 1.513855 1.521905 1.526214 1.529768
L3, L4, L7 1.834807 1.828975 1.848520 1.859548 1.868911
L6 1.525420 1.522680 1.532100 1.537051 1.540699

Example 9
Unit mm
Surface data Surface number rd nd νd
1 26.0703 1.0000 1.84666 23.78
2 * 10.0493 2.8000
3 ∞ 12.0000 1.80610 40.92
4 ∞ 0.3000
5 * 55.1285 2.8000 1.80610 40.92
6 -19.7344 Variable
7 * -12.9630 0.8000 1.48000 63.71
8 11.2890 0.9000 1.73000 18.00
9 * 15.5279 Variable
10 (Aperture) ∞ Variable
11 * 8.5684 2.7000 1.69350 53.21
12 -36.3621 0.1500
13 12.0725 2.0000 1.75000 38.01
14 -32.7527 0.5000 1.64000 23.00
15 5.0941 Variable
16 * 11.1680 2.0000 1.48749 70.23
17 24.6117 Variable
18 ∞ 1.5000 1.54771 62.84
19 ∞ 0.8000
20 ∞ 0.7500 1.51633 64.14
21 ∞ Variable
Image plane ∞

Aspherical coefficient second surface K = -0.2445, A4 = 3.3441E-05, A6 = 1.0596E-06, A8 = 0.0000E + 00
5th surface K = 0.0958, A4 = 7.8476E-06, A6 = 2.0218E-07, A8 = 0.0000E + 00
7th surface K = 0.1315, A4 = 1.9730E-04, A6 = -1.3581E-06, A8 = 0.0000E + 00
9th surface K = 0.0129, A4 = 3.6466E-05, A6 = 6.2332E-07, A8 = 0.0000E + 00
11th surface K = 0, A4 = -2.6709E-04, A6 = -1.4355E-06, A8 = 0.0000E + 00
16th surface K = -1.6203, A4 = 6.2499E-05, A6 = 7.4331E-06, A8 = 0.0000E + 00

Zoom data
Wide angle Medium telephoto focal length 5.99916 10.40019 17.99974
F number 2.8002 3.5217 4.6109
d6 1.00012 6.67324 11.24575
d9 11.64484 5.97198 1.39922
d10 8.14167 4.80552 1.19987
d15 1.50041 6.45956 11.33780
d17 4.89563 3.27180 2.00002
d21 1.36013 1.36013 1.36013

[Glass Material Refractive Index Table] ... Refractive index list by wavelength of medium used in this example lens 587.56 656.27 486.13 435.84 404.66
L8 1.639997 1.632239 1.660062 1.678108 1.694848
L5 1.729996 1.718951 1.759502 1.787050 1.813326
L7 1.749998 1.744194 1.763923 1.775332 1.785128
LPF 1.547710 1.545046 1.553762 1.558427 1.562261
L4 1.479999 1.477699 1.485233 1.489189 1.492420
CG 1.516330 1.513855 1.521905 1.526213 1.529768
L9 1.487490 1.485344 1.492285 1.495963 1.498983
L2 1.806098 1.800248 1.819945 1.831173 1.840781
L3 1.806098 1.800248 1.819945 1.831173 1.840781
L6 1.693501 1.689548 1.702582 1.709715 1.715662
L1 1.846660 1.836488 1.872096 1.894186 1.914294

Next, the values of parameters in each example are listed.
Example 1 Example 2 Example 3 Example 4 Example 5
fw 6.3695 7.59604 6.42001 6.00532 6.78044
y ₁₀ 3.84 4.74 3.6 3.32 3.8
nd (LA) 1.52542 1.58313 1.52542 1.618 1.883
νd (LA) 55.78 59.38 55.78 63.33 40.76
θgF (LA) 0.5209 0.4802 0.4419 0.5201 0.4856
β (LA) 0.6118 0.577 0.5328 0.6233 0.552
θhg (LA) 0.4231 0.3686 0.3172 0.422 0.3758
βhg (LA) 0.5486 0.5022 0.4427 0.5645 0.4675
nd (LB) 1.63494 1.63494 1.63494 1.7 1.75
νd (LB) 23.22 23.22 23.22 20.5 17.5
θgF (LB) 0.6477 0.6477 0.6477 0.66 0.6813
β (LB) 0.6855 0.6855 0.6855 0.6935 0.7098
θhg (LB) 0.6004 0.6004 0.6004 0.6183 0.6508
y ₀₇ 2.688 3.318 2.52 2.324 2.66
tanω ₀₇ 0.43442 0.44307 0.41862 0.4062 0.41837
tB 0.5 0.6828 0.7032 0.9 0.7

Example 6 Example 7 Example 8 Example 9
fw 6.19748 6.00668 6.42002 5.99916
y ₁₀ 3.6 3.32 3.6 3.32
nd (LA) 1.43389 1.6935 1.497 1.48
νd (LA) 95.15 53.18 75.3 63.71
θgF (LA) 0.5087 0.5154 0.5416 0.5251
β (LA) 0.6638 0.6021 0.6643 0.629
θhg (LA) 0.4068 0.4157 0.4508 0.4289
βhg (LA) 0.6209 0.5354 0.6203 0.5722
nd (LB) 1.7491 1.8 1.63494 1.73
νd (LB) 18.01 17.3 23.22 18
θgF (LB) 0.734 0.7201 0.6477 0.6793
β (LB) 0.7634 0.7483 0.6855 0.7087
θhg (LB) 0.734 0.708 0.6004 0.648
y ₀₇ 2.52 2.324 2.52 2.324
tanω ₀₇ 0.42856 0.40543 0.4189 0.41095
tB 0.9 0.6 0.4237 0.9

Next, the values of the conditional expressions in each example are listed. () Indicates that the condition is not satisfied.
Example 1 Example 2 Example 3 Example 4 Example 5
(1) β (LA) 0.6118 0.577 0.5328 0.6233 0.552
(2) νd (LA) 55.78 59.38 55.78 63.33 40.76
(3) βhg (LA) 0.5486 0.5022 0.4427 0.5645 0.4675
(4) θgF (LA) -θgF (LB) -0.1268 -0.1675 -0.2058 -0.1399 -0.1957
(5) θhg (LA) -θhg (LB) -0.1773 -0.2318 -0.2832 -0.1963 -0.275
(6) νd (LA) -νd (LB) 32.56 36.16 32.56 42.83 23.26
(9) y ₀₇ / (fw ・ tanω ₀₇ ) 0.9714 0.9859 0.9377 0.9527 0.9377
(10) β (LB) (0.6855) (0.6855) (0.6855) 0.6935 0.7098
(11) νd (LB) (23.22) (23.22) (23.22) 20.5 17.5
(12) β (LB) (0.6855) (0.6855) (0.6855) 0.6935 0.7098
(13) νd (LB) 23.22 23.22 23.22 (20.5) (17.5)
(14) β (LB) 0.6855 0.6855 0.6855 (0.6935) (0.7098)
(15) νd (LB) (23.22) (23.22) (23.22) 20.5 17.5
(16) nd (LA) 1.52542 1.58313 1.52542 1.618 (1.883)
(17) tB 0.5 0.6828 0.7032 0.9 0.7

Example 6 Example 7 Example 8 Example 9
(1) β (LA) 0.6638 0.6021 0.6643 0.629
(2) νd (LA) 95.15 53.18 75.3 63.71
(3) βhg (LA) 0.6209 0.5354 0.6203 0.5722
(4) θgF (LA) -θgF (LB) -0.2253 -0.2047 -0.1061 -0.1542
(5) θhg (LA) -θhg (LB) -0.3272 -0.2923 -0.1496 -0.2191
(6) νd (LA) -νd (LB) 77.14 35.88 52.08 45.71
(9) y ₀₇ / (fw ・ tanω ₀₇ ) 0.9488 0.9543 0.9370 0.9427
(10) β (LB) 0.7634 0.7483 (0.6855) 0.7087
(11) νd (LB) 18.01 17.3 (23.22) 18
(12) β (LB) 0.7634 0.7483 (0.6855) 0.7087
(13) νd (LB) (18.01) (17.3) 23.22 (18)
(14) β (LB) (0.7634) (0.7483) 0.6855 (0.7087)
(15) νd (LB) 18.01 17.3 (23.22) 18
(16) nd (LA) 1.43389 1.6935 1.497 1.48
(17) tB 0.9 0.6 0.4237 0.9

(Example 10)
The imaging optical system of the present invention as described above is a photographing apparatus for photographing an image of an object with an electronic image sensor such as a CCD or a CMOS, especially a digital camera, a video camera, a personal computer or an example of an information processing apparatus, a telephone. It can be used for portable terminals, especially mobile phones that are convenient to carry. The embodiment is illustrated below.

  FIGS. 19 to 21 are conceptual diagrams of structures in which the imaging optical system according to the present invention is incorporated in the photographing optical system 41 of a digital camera. 19 is a front perspective view showing the appearance of the digital camera 40, FIG. 20 is a rear perspective view thereof, and FIG. 21 is a cross-sectional view showing an optical configuration of the digital camera 40.

  In this example, the digital camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter 45, a flash 46, a liquid crystal display monitor 47, and the like. Then, when the photographer presses the shutter 45 disposed on the upper part of the camera 40, photographing is performed through the photographing optical system 41, for example, the zoom lens 48 of the first embodiment in conjunction therewith.

  The object image formed by the photographing optical system 41 is formed on the image pickup surface of the CCD 49. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the image processing means 51. Further, the image processing means 51 is provided with a memory or the like, and can record a captured electronic image. This memory may be provided separately from the image processing means 51, or may be configured to perform recording and writing electronically using a flexible disk, memory card, MO, or the like.

  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The finder objective optical system 53 includes a cover lens 54, a first prism 10, an aperture stop 2, a second prism 20, and a focusing lens 66. An object image is formed on the imaging surface 67 by the finder objective optical system 53. This object image is formed on the field frame 57 of the Porro prism 55 which is an image erecting member. Behind the Porro prism 55, an eyepiece optical system 59 for guiding an erect image to the observer eyeball E is disposed.

  According to the digital camera 40 configured as described above, an electronic imaging device having a compact and thin zoom lens in which the number of components of the photographing optical system 41 is reduced can be realized. The present invention is not limited to the above-described retractable digital camera, but can also be applied to a folding digital camera that employs a bending optical system.

  Next, a personal computer which is an example of an information processing apparatus in which the imaging optical system of the present invention is incorporated as an objective optical system is shown in FIGS. 22 is a front perspective view of the personal computer 300 with the cover open, FIG. 23 is a sectional view of the photographing optical system 303 of the personal computer 300, and FIG. 24 is a side view of FIG. As shown in FIGS. 22 to 24, the personal computer 300 includes a keyboard 301, information processing means and recording means, a monitor 302, and a photographing optical system 303.

Here, the keyboard 301 is for an operator to input information from the outside. The information processing means and recording means are not shown. The monitor 302 is for displaying information to the operator. The photographing optical system 303 is for photographing an image of the operator himself or a surrounding area. The monitor 302 may be a liquid crystal display element, a CRT display, or the like. Examples of the liquid crystal display element include a transmissive liquid crystal display element that illuminates from the back with a backlight (not shown), and a reflective liquid crystal display element that reflects and displays light from the front. In the drawing, the photographing optical system 303 is built in the upper right of the monitor 302.
This may be anywhere around 02 or around the keyboard 301.

  The photographing optical system 303 includes, on the photographing optical path 304, the objective optical system 100 including, for example, the zoom lens according to the first embodiment, and the electronic imaging element chip 162 that receives an image. These are built in the personal computer 300.

A cover glass 102 for protecting the objective optical system 100 is disposed at the tip of the mirror frame.
The object image received by the electronic image sensor chip 162 is input to the processing means of the personal computer 300 via the terminal 166. Finally, the object image is displayed on the monitor 302 as an electronic image. FIG. 22 shows an image 305 taken by the operator as an example. The image 305 can also be displayed on a communication partner's personal computer from a remote location via the processing means. The Internet and telephone are used for image transmission to remote places.

  Next, FIG. 25 shows a telephone which is an example of an information processing apparatus in which the imaging optical system of the present invention is incorporated as a photographing optical system, particularly a portable telephone which is convenient to carry. 25A is a front view of the mobile phone 400, FIG. 25B is a side view, and FIG. 25C is a cross-sectional view of the photographing optical system 405. As shown in FIGS. 25A to 25C, the mobile phone 400 includes a microphone unit 401, a speaker unit 402, an input dial 403, a monitor 404, a photographing optical system 405, an antenna 406, and processing. Means.

  Here, the microphone unit 401 is for inputting an operator's voice as information. The speaker unit 402 is for outputting the voice of the other party. An input dial 403 is used by an operator to input information. The monitor 404 is for displaying information such as a photographed image of the operator himself or the other party, a telephone number, and the like. The antenna 406 is for transmitting and receiving communication radio waves. The processing means (not shown) is for processing image information, communication information, input signals, and the like.

  Here, the monitor 404 is a liquid crystal display element. Further, in the drawing, the arrangement positions of the respective components, in particular, are not limited thereto. The photographing optical system 405 includes the objective optical system 100 disposed on the photographing optical path 407 and an electronic image sensor chip 162 that receives an object image. As the objective optical system 100, for example, the zoom lens of Example 1 is used. These are built in the mobile phone 400.

A cover glass 102 for protecting the objective optical system 100 is disposed at the tip of the mirror frame.
The object image received by the electronic imaging element chip 162 is input to an image processing unit (not shown) via the terminal 166. Finally, the object image is displayed as an electronic image on the monitor 404, the monitor of the communication partner, or both. The processing means includes a signal processing function. When transmitting an image to a communication partner, this function converts information on the object image received by the electronic image sensor chip 162 into a signal that can be transmitted.

  The present invention can take various modifications without departing from the spirit of the present invention.

(A) of the zoom lens according to Example 1 of the present invention is a cross-sectional view along the optical axis showing an optical configuration at the time of focusing on an object point at infinity at the wide-angle end, (b) at the middle, and (c) at the telephoto end. is there. FIG. 2 is a diagram illustrating spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to Example 1 is focused on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, and (c). Indicates the state at the telephoto end. (A) of the zoom lens according to Example 2 of the present invention is a cross-sectional view along the optical axis showing an optical configuration at the time of focusing on an object point at infinity at the wide-angle end, (b) at the middle, and (c) at the telephoto end. is there. FIG. 6 is a diagram illustrating spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to Example 2 is focused on an object point at infinity, where (a) is a wide-angle end, (b) is a middle, and (c). Indicates the state at the telephoto end. (A) of the zoom lens according to Example 3 of the present invention is a cross-sectional view along the optical axis showing an optical configuration at the time of focusing on an object point at infinity at the wide-angle end, (b) at the middle, and (c) at the telephoto end. is there. FIG. 6 is a diagram illustrating spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to Example 3 is focused on an object point at infinity, (a) is a wide-angle end, (b) is an intermediate, (c) Indicates the state at the telephoto end. (A) of the zoom lens according to Example 4 of the present invention is a cross-sectional view along the optical axis showing an optical configuration at the time of focusing on an object point at infinity at the wide-angle end, (b) at the middle, and (c) at the telephoto end. is there. FIG. 10 is a diagram illustrating spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to Example 4 is focused on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, and (c). Indicates the state at the telephoto end. (A) of the zoom lens according to Example 5 of the present invention is a cross-sectional view along the optical axis showing the optical configuration at the time of focusing on an object point at infinity at the wide-angle end, (b) at the middle, and (c) at the telephoto end. is there. FIG. 10 is a diagram illustrating spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to Example 5 is focused on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, and (c). Indicates the state at the telephoto end. (A) of the zoom lens according to Example 6 of the present invention is a cross-sectional view along the optical axis showing an optical configuration at the time of focusing on an object point at infinity at the wide-angle end, (b) at the middle, and (c) at the telephoto end. is there. FIG. 8 is a diagram illustrating spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to Example 6 is focused on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, and (c). Indicates the state at the telephoto end. (A) of the zoom lens according to Example 7 of the present invention is a cross-sectional view along the optical axis showing an optical configuration at the time of focusing on an object point at infinity at the wide-angle end, (b) at the middle, and (c) at the telephoto end. is there. FIG. 10 is a diagram showing spherical aberration, astigmatism, distortion aberration, and chromatic aberration of magnification when the zoom lens according to Example 7 is focused on an object point at infinity, where (a) is the wide-angle end, (b) is the middle, and (c). Indicates the state at the telephoto end. (A) of the zoom lens according to Example 8 of the present invention is a cross-sectional view along the optical axis showing an optical configuration at the time of focusing on an object point at infinity at the wide-angle end, (b) at the middle, and (c) at the telephoto end. is there. FIG. 10 is a diagram illustrating spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to Example 8 is focused on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, and (c). Indicates the state at the telephoto end. (A) of the zoom lens according to Example 9 of the present invention is a cross-sectional view along the optical axis showing an optical configuration at the time of focusing on an object point at infinity at the wide-angle end, (b) at the middle, and (c) at the telephoto end. is there. FIG. 10 is a diagram illustrating spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to Example 9 is focused on an object point at infinity, where (a) is a wide-angle end, (b) is an intermediate, and (c). Indicates the state at the telephoto end. It is a front perspective view which shows the external appearance of the digital camera 40 incorporating the zoom optical system by this invention. 2 is a rear perspective view of the digital camera 40. FIG. 2 is a cross-sectional view showing an optical configuration of a digital camera 40. FIG. 1 is a front perspective view of a state in which a cover of a personal computer 300 which is an example of an information processing apparatus in which a zoom optical system of the present invention is built as an objective optical system is opened. FIG. 2 is a cross-sectional view of a photographing optical system 303 of a personal computer 300. FIG. 2 is a side view of a personal computer 300. FIG. 1A and 1B are views showing a mobile phone as an example of an information processing apparatus in which the zoom optical system of the present invention is built in as a photographing optical system, where FIG. 1A is a front view of the mobile phone 400, FIG. FIG. 4 is a sectional view of the photographing optical system 405.

Explanation of symbols

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group L1 to L11 Each lens LPF Low pass filter CG Cover glass I Imaging surface E Observer's eye 40 Digital camera 41 Shooting optics System 42 Optical path for photographing 43 Viewfinder optical system 44 Optical path for viewfinder 45 Shutter 46 Flash 47 LCD monitor 48 Zoom lens 49 CCD
DESCRIPTION OF SYMBOLS 50 Image pick-up surface 51 Processing means 53 Finder objective optical system 55 Porro prism 57 Field frame 59 Eyepiece optical system 66 Focusing lens 67 Imaging surface 100 Objective optical system 102 Cover glass 162 Electronic image pick-up element chip | tip 166 Terminal 300 Personal computer 301 Keyboard 302 Monitor 303 Imaging Optical System 304 Imaging Optical Path 305 Image 400 Mobile Phone 401 Microphone Unit 402 Speaker Unit 403 Input Dial 404 Monitor 405 Imaging Optical System 406 Antenna 407 Imaging Optical Path

Claims (7)

In an imaging optical system having a positive lens group, a negative lens group, and a diaphragm,
The negative lens group is disposed closer to the object side than the diaphragm,
The negative lens group has a cemented lens formed by cementing a plurality of lenses,
In an orthogonal coordinate system in which the horizontal axis is νd and the vertical axis is θgF,
θgF = α × νd + β (where α = −0.00163)
When the straight line represented by is set, the area defined by the straight line when the range is the lower limit of the range of the following conditional expression (1) and the straight line when the upper limit is set, and the following conditional expression (2) In both of the fixed region and the fixed region, θgF and νd of at least one lens LA constituting the cemented lens are included , and
In an orthogonal coordinate system having a horizontal axis νd and a vertical axis θhg different from the orthogonal coordinate,
θhg = αhg × νd + βhg (where αhg = −0.00225)
When the straight line represented by is set, the area defined by the straight line when the range is the lower limit of the range of the following conditional expression (3 ′ ″) and the straight line when the upper limit is set, and the following conditional expression ( both the area of the region defined by 2), at least one of said lens imaging optical system, wherein Rukoto contains θhg and νd of LA constituting the cemented lens.
0.3000 <β <0.6650 (1)
35 <νd <120 (2)
0.2500 <βhg ≦ 0.5722 (3 ′ ″)
Here, θgF is a partial dispersion ratio (ng−nF) / (nF−nC) , θhg is a partial dispersion ratio (nh−ng) / (nF−nC) , and νd is an Abbe number (nd−1) / (nF− nC), nd, nC, nF, ng and nh are the refractive indexes of the d-line, C-line, F-line, g-line and h-line , respectively. 2. The imaging optical system according to claim 1, wherein when a lens having a negative paraxial focal length is a negative lens, the lens LA is a negative lens. 3. When a lens having a positive paraxial focal length is used as a positive lens, the counterpart lens LB to which the lens LA is joined is a positive lens, and satisfies the following conditions. The imaging optical system described in 1.
−0.40 ≦ θgF (LA) −θgF (LB) ≦ −0.05 (4)
Here, θgF (LA) is the partial dispersion ratio (ng−nF) / (nF−nC) of the lens LA, and θgF (LB) is the partial dispersion ratio (ng−nF) / of the mating lens LB to be joined. (NF-nC). 4. When a lens having a positive paraxial focal length is used as a positive lens, the counterpart lens LB to which the lens LA is cemented is a positive lens, and satisfies the following conditions: The imaging optical system according to any one of the above.
−0.50 ≦ θhg (LA) −θhg (LB) ≦ −0.10 (5)
Here, .theta.hg (LA) is the partial dispersion ratio (nh-ng) / (nF-nC) of the lens LA, and .theta.hg (LB) is the partial dispersion ratio (nh-ng) / of the mating lens LB to be joined. (NF-nC). 5. When a lens having a positive paraxial focal length is used as a positive lens, the counterpart lens LB to which the lens LA is cemented is a positive lens and satisfies the following conditions: The imaging optical system described in 1.
 12 ≦ νd (LA) −νd (LB) (6)
Here, νd (LA) is the Abbe number (nd-1) / (nF-nC) of the lens LA, and νd (LB) is the Abbe number (nd-1) / (nF) of the mating lens LB to be joined. -NC). The image forming optical system according to claim 1, wherein the image forming optical system is a zoom lens, and a relative distance between the lens groups on the optical axis changes during zooming. Optical system. The imaging optical system according to any one of claims 1 to 6, an electronic imaging device, and image data obtained by imaging an image formed through the imaging optical system with the electronic imaging device. Image processing means for processing and outputting as image data in which the shape of the image is changed, and the imaging optical system is a zoom lens, and when the zoom lens is focused on an object point at infinity, the following conditional expression An electronic imaging device characterized by satisfying
0.7 <y ₀₇ / (Fw · tanω _07w ) <0.99 (9)
Where y ₀₇ Is the distance (maximum image height) from the center to the farthest point in the effective imaging plane (in the plane where imaging is possible) of the electronic imaging device. _Ten When y ₀₇ = 0.7 · y _Ten Expressed as ω _07w Is y from the center on the imaging surface at the wide-angle end. ₀₇ The angle fw with respect to the optical axis in the object direction corresponding to the image point connected to the position fw is the focal length of the entire system at the wide-angle end of the zoom lens.

Images