JP2014095841A - Imaging optical system, camera device, and mobile information terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging optical system which has a wide view angle of approximately 76 degrees and a large aperture with brightness of F2.8 and yet is sufficiently compact and provides excellent image forming performance despite use of an inner focusing system.SOLUTION: An imaging optical system includes a first lens group G1 which is located on the object side of an aperture stop S and has positive refractive power and a second lens group G2 which is located on the image side of the aperture stop S and has positive refractive power arranged along the optical axis. The second lens group G2 comprises a 2F lens group 2FG having positive refractive power and a 2R lens group 2RG having negative refractive power. Only the 2F lens group 2FG is moved along the optical axis for focusing. A magnification M2F of the 2F lens group 2FG when focused at infinity and a magnification M2R of the 2R lens group 2RG when focused at infinity satisfy a conditional expression: 1.00<(1-M2F)×M2R<3.00.

Description

  The present invention relates to an improvement of a single-focus imaging optical system used as an imaging optical system for various cameras including a so-called silver salt camera, and in particular, an imaging optical system suitable for cameras such as digital cameras and video cameras, and The present invention relates to a camera device and a portable information terminal device using such an imaging optical system.

In recent years, it is called a digital camera or an electronic camera, and a subject image is captured by a solid-state imaging device such as a CCD (charge coupled device) imaging device, and a still image (still image) or a moving image (movie image) of the subject is captured. The type of camera that obtains the image data and digitally records it in a nonvolatile semiconductor memory such as a flash memory has become common.
The market for such digital cameras is very large, and there are various demands for digital cameras by users. Among them, in particular, the category of compact and high-quality compact cameras equipped with high-performance single focus lenses has gained a certain amount of support from users, and expectations are high. In addition to high performance, in addition to high performance, the user demands a small F number, that is, a large aperture and a small size. In addition, in recent years, the autofocus speed is high and the operation sound is quiet. It is also required to be.
Here, in terms of high performance, it is necessary to have a resolution corresponding to at least an image sensor of 10 million to 20 million pixels. Furthermore, since the aperture is fully open, there is little coma flare, high contrast, no distortion of the point image to the periphery of the angle of view, no chromatic aberration, no unwanted coloring in areas with large luminance differences, little distortion and straight lines. It must be possible to describe as a straight line.

In terms of a large aperture, the F number of about 2.8 or less is desired because it is necessary to differentiate from a general compact camera equipped with a zoom lens.
In terms of miniaturization, it is necessary to keep the optical total length and the lens diameter small. Furthermore, in terms of miniaturization during non-photographing, a retractable type is a mechanism that shortens the overall lens length by shortening the air gap on the optical axis in the photographic optical system such as before and after the aperture and back focus during non-photographing. It is necessary to have.
In terms of improving the speed and quietness during autofocus, it is desirable to reduce the amount of movement required for focusing and to minimize the load on the driving source of the focusing mechanism, and to optimize the refractive power of the optical system of the focusing unit It is also necessary to reduce the size, reduce the weight of the driven parts, and simplify the driving method.
In addition, since there are many users who want a certain wide angle of view, the angle of view equivalent to 28 mm is equivalent to 28 mm with a focal length converted to a 35 mm silver salt camera (so-called Leica version), that is, a half angle of view of 38 degrees. The above is desirable.

Typical examples of focusing methods for wide-angle single-focus lenses include an overall extension method that moves the entire optical system, and an inner focus method that moves the rear and center of the optical system. It is also possible to combine floating systems that move the focusing unit while changing the upper interval. However, since the entire feeding system moves the entire optical system, the weight of the driven part is large, and it tends to be a disadvantageous problem for increasing the autofocus speed and quieting the operation sound. Also in the inner focus method, if the focus group includes an aperture mechanism or a shutter mechanism, the weight of the driven part increases, and the same problem as that of the entire extension tends to occur. In order to adopt the floating method, a mechanism for associating the movement ratios of at least two or more moving groups is required, and the load on the driving source may be increased.
As conventional examples of the inner focus type in a relatively wide-angle single focus lens, Patent Document 1 (Japanese Patent Publication No. 08-012325), Patent Document 2 (Japanese Patent Laid-Open No. 09-061708), and Patent Document 3 (Japanese Patent Laid-Open No. 11-2009). 030743), Patent Document 4 (JP 2003-043350 A), Patent Document 5 (JP 2006-349920 A), Patent Document 6 (JP 2008-020658 A), Patent Document 7 (JP 2009-116132), Patent Document 8 (Patent No. 3352264), Patent Document 9 (Patent No. 3261716), and the like.

  However, the optical systems disclosed in Patent Document 2, Patent Document 7, Patent Document 8, and Patent Document 9 are configured such that the aperture stop moves as a unit during focusing, and the aperture is relatively large and heavy during focusing. It is necessary to move the structure and the shutter structure, which is insufficient in terms of reducing the load on the drive source. Further, the optical systems disclosed in Patent Document 1, Patent Document 3, and Patent Document 6 perform a floating operation at the time of focusing, and require a mechanism for defining the moving ratio of two moving groups that move at the time of focusing. This is insufficient in terms of reducing the load on the drive source during focusing. The document of Patent Document 3 also describes an example in which the group behind the aperture stop is a focusing group alone. However, this is not the optimum focusing for the disclosed embodiment, and the four focusing groups are configured. large. Further, in the optical systems disclosed in Patent Document 4 and Patent Document 5, the front side or rear side group of the aperture stop is a single focusing group, but the total length of the optical system is long and the entire optical system is small. It's hard to say.

  The present invention has been made in view of the above-described circumstances, and has a wide angle lens having a high performance, a wide angle of view of about 76 °, and a large aperture of about F 2.8, and a driving source at the time of focusing. It is an object of the present invention to provide an inner focus type imaging optical system with a small load on the camera.

In order to achieve the above-described object, the imaging optical system according to claim 1
A first lens group having a positive refractive power located on the object side across the aperture stop, and a second lens group having a positive refractive power located on the image side, the second lens group being an object side In order from a second F lens group having a positive refractive power and a second R lens group having a negative refractive power, and during focusing, the first lens group, the aperture stop, and the second R lens The group is fixed, only the second F lens group moves in the optical axis direction, the magnification of the second F lens group at infinity focusing is M2F, and the magnification of the second R lens group at infinity focusing is As M2R, the following conditional expression (1):
1.00 <(1-M2F ² ) × M2R ² <3.00 (1)
It is characterized by satisfying.

According to the invention of claim 1,
A first lens group having a positive refractive power located on the object side across the aperture stop, and a second lens group having a positive refractive power located on the image side, the second lens group being an object side In order from a second F lens group having a positive refractive power and a second R lens group having a negative refractive power, and during focusing, the first lens group, the aperture stop, and the second R lens The group is fixed, only the second F lens group moves in the optical axis direction, the magnification of the second F lens group at infinity focusing is M2F, and the magnification of the second R lens group at infinity focusing is As M2R, the following conditional expression (1):
1.00 <(1-M2F ² ) × M2R ² <3.00 (1)
By satisfying the above, it is possible to ensure a very good image performance even when the inner focus type is sufficiently small, while having a wide field angle of about 76 ° and a large aperture of F2.8 or less. An imaging optical system can be provided.

FIG. 1 is a cross-sectional view along the optical axis showing the configuration of an imaging optical system according to a first embodiment of the present invention, (a) is a cross-sectional view at the time of focusing on an object at infinity; (B) is a sectional view at the time of focusing on a short-distance object (photographing magnification: 0.1 times). FIG. 2 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration characteristics when the object distance of the imaging optical system according to the first embodiment of the present invention shown in FIG. . Each aberration of spherical aberration, astigmatism, distortion aberration and coma aberration when the object distance of the imaging optical system according to the first embodiment of the present invention shown in FIG. It is an aberration curve diagram showing the characteristics. It is 2nd Embodiment of this invention, Comprising: It is sectional drawing along the optical axis which shows the structure of the imaging optical system which concerns on Example 2, (a) is sectional drawing at the time of infinity focusing, b) is a cross-sectional view when focusing on a short distance (photographing magnification 0.1 times). FIG. 5A is an aberration curve diagram illustrating spherical aberration, astigmatism, distortion aberration, and coma aberration characteristics when the object distance of the imaging optical system according to the second embodiment of the present invention illustrated in FIG. . Each aberration of spherical aberration, astigmatism, distortion aberration and coma aberration when the object distance of the imaging optical system according to the second embodiment of the present invention shown in FIG. It is an aberration curve diagram showing the characteristics. FIG. 10 is a cross-sectional view along the optical axis showing the configuration of the imaging optical system according to Example 3, which is the third embodiment of the present invention, and (a) is a cross-sectional view at the time of focusing on infinity; b) is a cross-sectional view when focusing on a short distance (photographing magnification 0.1 times). FIG. 10A is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration and coma aberration characteristics when the object distance of the imaging optical system according to Example 3 of the present invention shown in FIG. . Each aberration of spherical aberration, astigmatism, distortion aberration and coma aberration when the object distance of the imaging optical system according to the third embodiment of the present invention shown in FIG. It is an aberration curve diagram showing the characteristics. FIG. 9 is a cross-sectional view along the optical axis showing the configuration of the imaging optical system according to Example 4 according to a fourth embodiment of the present invention, (a) is a cross-sectional view at the time of focusing on infinity; b) is a cross-sectional view when focusing on a short distance (photographing magnification 0.1 times). FIG. 10A is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration, and coma aberration characteristics when the object distance of the imaging optical system according to the fourth embodiment of the present invention shown in FIG. . Each aberration of spherical aberration, astigmatism, distortion aberration, and coma aberration when the object distance of the imaging optical system according to the fourth embodiment of the present invention shown in FIG. It is an aberration curve diagram showing the characteristics. FIG. 10 is a cross-sectional view along the optical axis showing the configuration of the imaging optical system according to Example 5 according to a fifth embodiment of the present invention, (a) is a cross-sectional view at the time of focusing on infinity; b) is a cross-sectional view when focusing on a short distance (photographing magnification 0.1 times). FIG. 13A is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration and coma aberration characteristics when the object distance of the imaging optical system according to the fifth embodiment of the present invention shown in FIG. . Each aberration of spherical aberration, astigmatism, distortion aberration and coma aberration when the object distance of the image pickup optical system according to the fifth embodiment of the present invention shown in FIG. It is an aberration curve diagram showing the characteristics.

In the aberration curve diagram, the solid line represents sagittal and the broken line represents meridional. Further, the thin line is the d line, and the thick line is an aberration curve diagram with respect to the g line.
It is the perspective view seen from the to-be-photographed object side which shows typically the external appearance structure of the digital camera as a camera apparatus which concerns on the 6th Embodiment of this invention. It is the perspective view seen from the photographer side which shows typically the external appearance structure of the digital camera of FIG. It is a block diagram which shows typically the function structure of the digital camera of FIG.

Hereinafter, based on an embodiment of the present invention, an imaging optical system, a camera device, and a portable information terminal device according to the present invention will be described in detail with reference to the drawings. Before describing specific examples (numerical examples), first, a fundamental embodiment of the present invention will be described.
Currently, there is a strong need for higher quality, smaller size, wider angle, and larger aperture for digital cameras, and it is necessary to develop to meet these demands. In addition, in recent years, in addition to this, there has been an increasing need for high-speed autofocus operation and quiet operation noise, and an optical design that satisfies both of these needs is required.
In general, coma aberration, astigmatism, curvature of field, and especially distortion are likely to increase as the angle of view increases, and coma aberration and especially spherical aberration increases as the aperture increases. In order to correct this aberration, the optical system tends to become longer. For faster autofocus operation and quieter operation noise, the amount of movement of the focus group required for focusing must be small to some extent, light weight, and in addition, the drive mechanism is simple and the load to drive reduction is small. An inner focus method that uses a part of the optical system as a focus group is desirable. However, if the inner focus method is used in a wide-angle and large-diameter optical system, fluctuations in spherical aberration, curvature of field, and distortion due to focusing are suppressed. Or balance.

The present invention has been found that the following problems can be solved by correcting the aberrations and increasing the length of the optical system by adopting the following configuration.
The first lens group having a positive refractive power located on the object side with the aperture stop interposed therebetween and the second lens group having a positive refractive power located on the image side, the second lens group having a positive refraction. And a second R lens group having negative refracting power, and the first lens group, aperture stop and second R lens group are fixed during focusing, and the second F lens group Is moved in the optical axis direction, the magnification of the second F lens group at infinity focusing is M2F, and the magnification of the second R lens group at infinity focusing is M2R, the following conditional expression (1):
1.00 <(1-M2F ² ) × M2R ² <3.00 (1)
Is satisfied (corresponding to claim 1).

  First, in the imaging optical system according to each embodiment of the present invention, a first lens group having a positive refractive power and a second lens group having a positive refractive power are arranged with an aperture stop interposed therebetween. Although the principal point position is near the center of the optical system, and it is not strict, the refractive power arrangement has symmetry, and the difficulty of correcting coma aberration, chromatic aberration of magnification, and distortion is reduced. Further, in the second lens group having positive refractive power, the second F lens group having negative refractive power is disposed behind the second F lens group having positive refractive power, which is the focusing group, so that the second F It is possible to increase the image plane position movement amount per unit movement amount of the lens group and reduce the movement amount necessary for focusing to some extent. Conditional expression (1) expresses the paraxial image plane position movement amount per unit movement amount of the second F lens group, and defines an appropriate range of magnification of the second F lens group and the second R lens group. If the lower limit value of conditional expression (1) is not reached, the amount of movement required during focusing increases, the autofocus speed may decrease, and the optical system may become longer in order to secure the movement space for the focus group. . In addition, the amount of movement required during focusing is increased as compared with the entire payout method, and one of the merits of the inner focus method is lost. On the other hand, if the upper limit value of conditional expression (1) is exceeded, the amount of movement required during focusing is reduced, which is advantageous for speeding up autofocusing, but excessive accuracy may be required for the stop position of the focus group. .

According to the configuration of the imaging optical system according to each embodiment of the present invention, as described above, it is possible to obtain a large effect on aberration correction, and a wide angle of about 38 degrees half field angle, F number. It is possible to adopt an inner focus method that maintains high image performance even under severe conditions of a large aperture of about 8.
In order to achieve better performance, it is desirable to satisfy the following conditional expression (1A).
1.00 <(1-M2F ² ) × M2R ² <2.00 (1A)
In order to achieve higher performance, let f be the focal length of the entire system, and F2F be the focal length of the second F lens group. The following conditional expression (2):
0.40 <f / f2F <1.50 (2)
Is preferably satisfied (corresponding to claim 2).
Conditional expression (2) defines an appropriate range of the focal length of the second F lens group with respect to the focal length of the entire system. If the lower limit value of conditional expression (2) is not reached, it is necessary to increase the positive power of the first lens group, and the symmetry of the refractive power arrangement of the optical system is greatly lost. In particular, coma aberration, chromatic aberration of magnification, The degree of difficulty in correcting distortion and the like increases, and there is a risk that the entire optical system will become longer in order to correct it. If the upper limit value of conditional expression (2) is exceeded, the exchange of aberration correction between the second F lens group and the second R lens group becomes excessive, and there is a risk that the image performance degradation due to manufacturing errors will increase.

In order to achieve better performance, it is desirable to satisfy the following conditional expression (2A), where f2R is the focal length of the second R lens group.
0.50 <f / f2F <1.40 (2A)
For higher performance, the focal length of the second R lens group is f2R, and the following conditional expression (3):
0.20 <f / | f2R | <1.30 (3)
Is satisfied (corresponding to claim 3).
Conditional expression (3) defines an appropriate range of the focal length f2R of the second R lens group with respect to the focal length f of the entire system. If the lower limit of conditional expression (3) is not reached, the image plane position fluctuation amount per unit movement amount of the second F lens group that is the focus group becomes too small, and the speed during autofocus may be reduced. If the upper limit of conditional expression (3) is exceeded, the amount of image plane position fluctuation per unit movement amount of the second F lens group, which is the focus group, becomes large, which is advantageous for improving the speed during autofocusing. Excessive accuracy may be required for the stop position of the group. Also, it approaches the telephoto type and is advantageous for downsizing the entire optical system, but there is an excessive exchange of aberration correction between the second F lens group and the second R lens group, and there is a risk that image performance deterioration due to manufacturing errors will increase. There is.

In order to achieve better performance, it is desirable to satisfy the following conditional expression (3A).
0.35 <f / | f2R | <1.15 (3A)
In order to achieve higher performance, the focal length of the first lens group is f1, and the following conditional expression (4):
0.15 <f / f1 <1.00 (4)
Is satisfied (corresponding to claim 4).
Conditional expression (4) defines an appropriate range of the focal length f1 of the first lens group with respect to the focal length of the entire system. If the lower limit value of the conditional expression (4) is not reached, it is necessary to increase the positive power of the second F lens group, and the symmetry of the refractive power arrangement is greatly lost. In particular, coma aberration, chromatic aberration of magnification, distortion aberration, etc. The degree of difficulty of correction increases, and there is a possibility that the entire optical system becomes longer in order to correct it. If the upper limit value of conditional expression (4) is exceeded, the symmetry of the optical power arrangement of the optical system is greatly lost, and the difficulty of correcting coma aberration, chromatic aberration of magnification, distortion, etc. increases. In order to correct this, the entire optical system may be lengthened.

In order to perform better aberration correction, the following conditional expression (4A) should be satisfied.
0.30 <f / f1 <0.85 (4A)
In order to achieve higher performance, the following conditional expression (5) is established as the distance on the optical axis from the final surface of the first lens group to the aperture stop at the time of focusing on infinity:
0.00 <Ls / f <0.10 (5)
Is satisfied (corresponding to claim 5).
Conditional expression (5) defines an appropriate range of the distance on the optical axis between the first lens unit and the aperture stop with respect to the focal length f of the entire system. If the lower limit of conditional expression (5) is not reached, the upper light beam passing through the second lens group becomes too high, and the second lens group may become large in diameter. If the upper limit value of conditional expression (5) is exceeded, the lower ray passing through the first lens group becomes too low, and the first lens group may become large in diameter.
In order to achieve higher performance, the following conditional expression (6) is established as the distance on the optical axis from the front of the first lens group to the final surface of the second R lens group when focusing on infinity:
0.85 <TL / f <1.95 (6)
Is preferably satisfied (corresponding to claim 6).

Conditional expression (6) defines an appropriate range of the total lens length when focusing on infinity with respect to the focal length of the entire system. If the lower limit of conditional expression (6) is not reached, the symmetry of the refractive power arrangement is greatly lost, and in particular, the difficulty of correcting coma aberration, chromatic aberration of magnification, distortion, etc. is increased. There is a risk that the entire optical system may become longer. In addition, in order to increase the refractive power of each surface, it is necessary to use an expensive high refractive index glass material, which leads to high costs or excessive exchange of aberrations, resulting in increased image performance degradation due to manufacturing errors. There is a fear. When the upper limit value of conditional expression (6) is exceeded, it is necessary to dispose a lens at a position far from the entrance pupil or exit pupil, which may increase the diameter.
In order to perform better aberration correction, the following conditional expression (6A) should be satisfied.
1.00 <TL / f <1.80 (6A)
In order to achieve higher performance, the most image surface side element of the first lens group is a cemented lens of an unordered positive lens and a negative lens, and the most object side element of the second F lens group is unordered across the aperture stop. The positive lens and the negative lens may be a cemented lens (corresponding to claim 7).

By arranging the positive and negative cemented lenses with the aperture stop interposed therebetween, it is possible to effectively correct the axial chromatic aberration while maintaining the symmetry of the refractive power arrangement to some extent. In addition, it is a lens element that is close to the stop and greatly corrects spherical aberration, so it tends to cause image performance deterioration due to manufacturing errors, but it can suppress image performance deterioration by suppressing manufacturing errors to some extent as a cemented lens. Become.
In order to achieve higher performance, it is only necessary to have a positive lens having a convex surface on the image surface side in the second F lens group and a negative lens having a concave surface on the object side in the second R lens group. Corresponds to item 8).
By having a positive lens having a convex surface on the image plane side in the second F lens group and having a negative lens having a concave surface on the object side in the second R lens group, the two lenses are paired, In particular, it is effective for correcting curvature of field. In addition, there is an effect of suppressing the amount of variation in spherical aberration and field curvature due to focusing, or balancing the amount of variation in spherical aberration and field curvature.
Next, specific examples based on the above-described embodiment of the present invention will be described in detail. Examples 1 to 5 described below are examples of specific configurations based on specific numerical examples of the imaging optical system according to the present invention. After that, an embodiment of a camera device and a portable information terminal device using an imaging optical system as shown in Examples 1 to 5 will be described.

In the first to fifth embodiments showing the imaging optical system according to the present invention, the configuration of the imaging optical system and specific numerical examples thereof are shown.
By constructing the imaging optical system as in the present invention, it has a wide angle of view of about 76 ° and a large aperture of about F2.8 or less, but it is sufficiently small, even if it is an inner focus type. It is clear from the examples that good image performance can be secured, and it can be seen that the present invention has good performance.
The meanings of the symbols in Examples 1 to 5 are as follows.

f: Focal length of the entire system Fno: F number ω: Half angle of view Y ′: Maximum image height R: Curvature radius D: Surface spacing Nd: Refractive index at d-line νd: Abbe number K: Aspherical conical constant A ₄ : 4th order aspheric coefficient A ₆ : 6th order aspheric coefficient A ₈ : 8th order aspheric coefficient A ₁₀ : 10th order aspheric coefficient However, the aspheric surface used here is the reciprocal of the paraxial radius of curvature. When the paraxial curvature is C and the height from the optical axis is H, the amount of displacement in the optical axis direction from the surface apex is A _2i , and the aspherical surface is defined by the following equation.

実施例１〜実施例５の各実施例においては、最も像面側の第２Ｒレンズ群の最も像面側のレンズ面と像面との間にある平行平板Ｆは、ローパスフィルタおよび赤外カットフィルタ等のフィルタ類または、例えばＣＣＤ撮像素子等の撮像素子を保護する保護ガラス等である。

In each of Examples 1 to 5, the parallel plate F between the image surface side lens surface of the second R lens group closest to the image surface and the image surface includes a low-pass filter and an infrared cut. Filters such as a filter, or protective glass for protecting an image sensor such as a CCD image sensor.

FIG. 1 is a first embodiment of the present invention, and shows the configuration of an imaging optical system according to Example 1 with a longitudinal section along the optical axis. FIG. FIG. 1B is a cross-sectional view when an object is in focus, and FIG.
In FIGS. 1A and 1B showing the lens group arrangement of Example 1, the left side in the drawing is the object (subject) side.
An imaging optical system 1 shown in FIGS. 1A and 1B includes a first lens group G1 having a positive refractive power located on the object side across the aperture stop S and a positive refractive power located on the image side. And a second lens group G2. The second lens group G2 includes a second F lens group 2FG having a positive refractive power and a second R lens group 2RG having a negative refractive power in order from the object side to the image side. The aperture stop S is disposed between the first lens group G1 and the second F lens group 2FG of the second lens group G2.
The first lens group G1 includes a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4.
The second lens group G2 includes a fifth lens L5, a sixth lens L6, and a seventh lens L7 that constitute the second F lens group 2FG, and an eighth lens L8 that constitutes the second R lens group 2RG.

At the time of focusing, only the second F lens group 2FG is supported by a support frame or the like and is movable in the optical axis direction, and the first lens group G1, the aperture stop S, and the second R lens group 2RG are fixed. .
1A and 1B show the surface numbers of the optical surfaces.
The first lens group G1 includes, in order from the object side to the image side, a first lens (negative lens) L1 including a negative meniscus lens having a convex surface directed toward the object side, and a negative meniscus lens having a concave surface directed toward the object side. The second lens (negative lens) L2 is an aspherical lens that forms aspherical surfaces on both sides, and a biconvex lens with a convex surface having a larger curvature than the object-side surface on the image side. A third lens (positive lens) L3 and a fourth lens L4 made of a negative meniscus lens having a concave surface facing the object side are arranged. The two lenses, the third lens L3 and the fourth lens L4, are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The second F lens 2FG in the second lens group G2 is a fifth lens (positive lens) composed of a biconvex lens having a convex surface having a larger curvature than the image side surface in order from the object side to the image side. ) L5, a sixth lens (negative lens) L6 composed of a biconcave lens having a concave surface with a larger curvature than the object side surface on the image side, and a positive meniscus lens having a convex surface on the image side, and an aspheric surface on the image side surface And a seventh lens (positive lens) L7 made of an aspherical lens. The two lenses, the fifth lens L5 and the sixth lens L6, are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses.

The second R lens group 2RG in the second lens group G2 is a negative meniscus lens having a concave surface directed toward the object side, and an eighth lens (negative lens) formed of an aspheric lens having an aspheric surface formed on the object side surface. ) L8 is arranged.
In this case, in focusing from the infinite focus state shown in FIG. 1A to the short distance shown in FIG. 1B, the second F lens group 2FG is moved to the object side along the optical axis. To do.
The optical characteristics of each optical element in Example 1 are as shown in Table 1 below.

In Table 1, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspheric surface, and the glass name in the “glass type” column is the name of the manufacturer of the glass material. Abbreviated as “HOYA” (HOYA Corporation), “OHARA” (Ohara Corporation) and “SCHOTT” (Shot Japan Corporation).
That is, in Table 1, the optical surfaces of the third surface, the fourth surface, the thirteenth surface, and the fourteenth surface marked with “*” are aspheric surfaces, and the parameters of each aspheric surface in the equation (7) are It is as follows.
Aspherical surface (surface with * symbol added to the surface number)
Third side
K = 0.0, A ₄ = 2.74129E-04, A ₆ = -9.74928E-06, A ₈ = 1.52109E-07
4th page
K = 0.0, A ₄ = 3.01050E-04, A ₆ = -9.60030E-06, A ₈ = 2.07820E-07
13th page
K = 0.0, A ₄ = 6.00043E-04, A ₆ = 1.46158E-06, A ₈ = 1.10658E-07
14th page
K = 0.0, A ₄ = 5.73394E-04, A ₆ = -5.25213E-06, A ₈ = 1.19735E-07
In the first embodiment, the focal length f of the entire optical system, the variable distance DA between the aperture stop S and the second F lens group 2FG at the time of focusing on infinity, and the variable between the seventh lens L7 and the eighth lens L8. The distance DB, the variable distance DC between the aperture stop S and the second F lens 2FG, and the variable distance between the seventh lens L7 and the eighth lens L8 at the time of focusing at a short distance (imaging magnification 0.1 times) DD is changed as shown in the following Table 2 along with focusing.

  Values corresponding to the conditional expressions (1) to (6) in the first embodiment are as shown in the following Table 3, which respectively satisfy the conditional expressions (1) to (6).

FIGS. 2 and 3 are graphs showing spherical aberration, astigmatism, distortion, and coma aberration in Example 1 when focusing on infinity and focusing at close distance (imaging magnification of 0.1 times), respectively. Show.
In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional.
Moreover, g in each aberration diagram of spherical aberration, astigmatism, and coma represents the g-line. The broken line on the spherical aberration diagram indicates the deviation from the sine condition on the d-line. The same applies to the aberration diagrams of the other examples.

FIG. 4 is a second embodiment of the present invention, and shows the configuration of the imaging optical system according to Example 2 with a longitudinal section along the optical axis. FIG. FIG. 4B is a cross-sectional view when an object is in focus, and FIG.
In FIGS. 4A and 4B showing the lens group arrangement of the second embodiment, the left side is the object (subject) side.
The imaging optical system 2 shown in FIGS. 4A and 4B includes a first lens group G1 having a positive refractive power located on the object side across the aperture stop S and a positive refractive power located on the image side. And a second lens group G2. The second lens group G2 includes a second F lens group 2FG having a positive refractive power and a second R lens group 2RG having a negative refractive power in order from the object side to the image side. The aperture stop S is disposed between the first lens group G1 and the second F lens group 2FG of the second lens group G2.
The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3.
The second lens group G2 includes a fourth lens L4, a fifth lens L5, and a sixth lens L6 that constitute the second F lens group 2FG, and a seventh lens L7 that constitutes the second R lens group 2RG.

At the time of focusing, only the second F lens group 2FG is supported by a support frame or the like and is movable in the optical axis direction, and the first lens group G1, the aperture stop S, and the second R lens group 2RG are fixed. .
4A and 4B show the surface numbers of the optical surfaces.
The first lens group G1 is a biconcave lens in which a concave surface having a curvature larger than that of the image side surface is sequentially directed from the object side to the image side, and an aspheric surface is formed on both surfaces thereof. A first lens (negative lens) L1 composed of an aspheric lens, a second lens (positive lens) L2 composed of a biconvex lens with a convex surface having a larger curvature than the object-side surface on the image side surface, and a concave surface directed toward the object side A third lens (negative lens) L3 made of a negative meniscus lens is disposed. The two lenses, the second lens L2 and the third lens L3, are closely bonded to each other and joined together to form a cemented lens composed of two lenses.
The second F lens 2FG in the second lens group G2 is a fourth lens (positive lens) composed of a biconvex lens with a convex surface having a larger curvature than the object side surface in order from the object side to the image side. ) A fifth lens (negative lens) L5 composed of L4 and a biconcave lens having a concave surface having a larger curvature than the image side surface on the object side, and a positive meniscus lens having a convex surface on the image side, and an aspheric surface on the image side surface And a sixth lens (positive lens) L6 made of an aspheric lens. The two lenses, the fourth lens L4 and the fifth lens L5, are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses.

The second R lens group 2RG of the second lens group G2 is a negative meniscus lens having a concave surface directed toward the object side, and a seventh lens (negative lens) formed of an aspheric lens having an aspheric surface formed on the object side surface. ) L7.
In this case, in focusing from the infinite focus state shown in FIG. 4A to the short distance shown in FIG. 4B, the second F lens group 2FG is moved to the object side along the optical axis. To do.
The optical characteristics of the optical elements in Example 2 are as shown in Table 4 below.

In Table 4, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspheric surface, and after the glass name in the “glass type” column is the name of the manufacturer of the glass material. Abbreviated as “HOYA” (HOYA Corporation) and “OHARA” (Ohara Corporation).
That is, in Table 4, the optical surfaces of the first surface, the second surface, the eleventh surface, and the twelfth surface marked with “*” are aspheric surfaces, and the parameters of each aspheric surface in Equation (7) are as follows: It is as follows.
○ Aspherical surface (Surface number with * symbol)
First side
K = 0.0, A ₄ = 3.75453E-05, A ₆ = -4.80873E-07, A ₈ = -9.61857E-10
Second side
K = 0.0, A ₄ = 2.07887E-04, A ₆ = -1.89335E-07, A ₈ = 2.15144E-08
11th page
K = 0.0, A ₄ = 5.47412E-04, A ₆ = 3.52660E-06, A ₈ = 1.47153E-08
12th page
K = 0.0, A ₄ = 5.13350E-04, A ₆ = -1.68836E-06, A ₈ = 2.27834E-08
In Example 2, the focal length f of the entire optical system, the variable distance DA between the aperture stop S and the second F lens group 2FG at the time of focusing on infinity, and between the sixth lens L6 and the seventh lens L7. Variable distance DB, and a variable distance DC between the aperture stop S and the second F lens 2FG at the time of focusing at a short distance (imaging magnification 0.1 times), and between the sixth lens L6 and the seventh lens L7. The variable interval DD is changed as shown in Table 5 along with focusing.

  The values corresponding to the conditional expressions (1) to (6) in Example 2 described above are as shown in the following Table 6 and satisfy the conditional expressions (1) to (6), respectively.

FIGS. 5 and 6 are graphs showing spherical aberration, astigmatism, distortion, and coma aberration, respectively, at the time of focusing on infinity and focusing on a short distance (imaging magnification of 0.1 times) in Example 2. FIG. Show.
In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional.
Moreover, g in each aberration diagram of spherical aberration, astigmatism, and coma represents the g-line. The broken line on the spherical aberration diagram indicates the deviation from the sine condition on the d-line. The same applies to the aberration diagrams of the other examples.

FIG. 7 shows the configuration of the imaging optical system according to the third embodiment of the present invention and Example 3 with a longitudinal section along the optical axis, and FIG. FIG. 7B is a cross-sectional view when an object is focused, and FIG. 7B is a cross-sectional view when a short-range object is focused (imaging magnification is 0.1 times).
In FIGS. 7A and 7B showing the lens group arrangement of Example 3, the left side in the drawing is the object (subject) side.
The imaging optical system 3 shown in FIGS. 7A and 7B includes a first lens group G1 having a positive refractive power located on the object side across the aperture stop S, and a positive refractive power located on the image side. And a second lens group G2. The second lens group G2 includes a second F lens group 2FG having a positive refractive power and a second R lens group 2RG having a negative refractive power in order from the object side to the image side. The aperture stop S is disposed between the first lens group G1 and the second F lens group 2FG of the second lens group G2.
The first lens group G1 includes a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4.
The second lens group G2 includes a fifth lens L5, a sixth lens L6, and a seventh lens L7 that constitute the second F lens group 2FG, and an eighth lens L8 that constitutes the second R lens group 2RG.

At the time of focusing, only the second F lens group 2FG is supported by a support frame or the like and is movable in the optical axis direction, and the first lens group G1, the aperture stop S, and the second R lens group 2RG are fixed. .
7A and 7B show the surface numbers of the optical surfaces.
The first lens group G1 includes, in order from the object side to the image side, a first lens (negative lens) L1 including a negative meniscus lens having a convex surface directed toward the object side, and a negative meniscus lens having a concave surface directed toward the object side. A second lens (negative lens) L2 made of an aspheric lens forming an aspheric surface on the image surface side, and a biconvex lens having a convex surface having a larger curvature than the object side surface on the image side. A third lens (positive lens) L3 and a fourth lens L4 made of a negative meniscus lens having a concave surface facing the object side. The two lenses, the third lens L3 and the fourth lens L4, are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The second F lens 2FG in the second lens group G2 is a fifth lens (positive lens) composed of a biconvex lens having a convex surface having a larger curvature than the object side surface in order from the object side to the image side. ) L5, a sixth lens (negative lens) L6 composed of a biconcave lens having a concave surface having a larger curvature than the image side surface on the object side, and a positive meniscus lens having a convex surface on the image side, and an aspheric surface on the image side surface And a seventh lens (positive lens) L7 made of an aspherical lens.

The two lenses, the fifth lens L5 and the sixth lens L6, are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses.
The second R lens group 2RG in the second lens group G2 is a negative meniscus lens having a concave surface directed toward the object side, and an eighth lens (negative lens) formed of an aspheric lens having an aspheric surface formed on the object side surface. ) L8 is arranged.
In this case, in focusing from the infinitely focused state shown in FIG. 7A to the short distance shown in FIG. 7B, the second F lens group 2FG is moved to the object side along the optical axis. To do.
The optical characteristics of the optical elements in Example 3 are as shown in Table 7 below.

In Table 7, the surface number indicated by “* (asterisk)” in the surface number is an aspherical surface, and the glass name in the “glass type” column is the name of the manufacturer of the glass material. Abbreviated as “HOYA” (HOYA Corporation) and “OHARA” (Ohara Corporation).
That is, in Table 7, the optical surfaces of the fourth surface, the thirteenth surface, and the fourteenth surface marked with “*” are aspheric surfaces, and the parameters of each aspheric surface in the equation (7) are as follows. It is.
○ Aspherical surface (Surface number with * symbol)
4th page
K = 0.0, A ₄ = 9.22225E-05, A ₆ = 5.61904E-07, A ₈ = 6.98506E-08
13th page
K = 0.0, A ₄ = 4.94833E-04, A ₆ = 2.71456E-06, A ₈ = 1.97550E-08
14th page
K = 0.0, A ₄ = 3.32941E-04, A ₆ = -2.71717E-06, A ₈ = 5.72391E-08
In Example 3, the focal length f of the entire optical system, the variable distance DA between the aperture stop S and the second F lens group 2FG at the time of focusing on infinity, and between the seventh lens L7 and the eighth lens L8. Variable distance DB, and a variable distance DC between the aperture stop S and the second F lens 2FG at the time of focusing at a short distance (imaging magnification 0.1 times), and between the seventh lens L7 and the eighth lens L8. The variable interval DD is changed as shown in Table 8 along with focusing.

  The values corresponding to the conditional expressions (1) to (6) in Example 3 described above are as shown in Table 9 below, and satisfy the conditional expressions (1) to (6), respectively.

FIGS. 8 and 9 are graphs showing spherical aberration, astigmatism, distortion, and coma aberration in Example 3, respectively, when focused at infinity and when focused at close distance (imaging magnification 0.1 times). Show.
In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional.
Moreover, g in each aberration diagram of spherical aberration, astigmatism, and coma represents the g-line. The broken line on the spherical aberration diagram indicates the deviation from the sine condition on the d-line. The same applies to the aberration diagrams of the other examples.

FIG. 10 is a fourth embodiment of the present invention, and shows the configuration of the imaging optical system according to Example 4 with a longitudinal section along the optical axis. FIG. FIG. 10B is a cross-sectional view when an object is focused, and FIG.
In FIGS. 10A and 10B showing the lens group arrangement of Example 4, the left side in the figure is the object (subject) side.
The imaging optical system 4 shown in FIGS. 10A and 10B includes a first lens group G1 having a positive refractive power located on the object side across the aperture stop S, and a positive refractive power located on the image side. And a second lens group G2. The second lens group G2 includes a second F lens group 2FG having a positive refractive power and a second R lens group 2RG having a negative refractive power in order from the object side to the image side. The aperture stop S is disposed between the first lens group G1 and the second F lens group 2FG of the second lens group G2.
The first lens group G1 includes a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4.

The second lens group G2 includes a fifth lens L5, a sixth lens L6, and a seventh lens L7 that constitute the second F lens group 2FG, and an eighth lens L8 that constitutes the second R lens group 2RG.
At the time of focusing, only the second F lens group 2FG is supported by a support frame or the like and is movable in the optical axis direction, and the first lens group G1, the aperture stop S, and the second R lens group 2RG are fixed. .
10A and 10B show the surface numbers of the optical surfaces.
The first lens group G1 includes, in order from the object side to the image side, a first lens (negative lens) L1 including a negative meniscus lens having a convex surface directed toward the object side, and a positive meniscus lens having a convex surface directed toward the object side. A second lens (positive lens) L2 made of an aspheric lens forming an aspheric surface on the image surface side, and a third lens (negative lens) made of a negative meniscus lens having a convex surface facing the object side. L3 and a fourth lens (positive lens) L4 made of a biconvex lens having a convex surface having a larger curvature than the image-side surface are disposed on the object side. The two lenses, the third lens L3 and the fourth lens L4, are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.

The second F lens 2FG in the second lens group G2 is a fifth lens (negative lens) composed of a biconcave lens having a concave surface having a larger curvature than the image side surface in order from the object side to the image side. ) L5, a sixth lens (positive lens) L6 composed of a biconvex lens having a convex surface having a larger curvature than the object side surface on the image side, and a biconvex lens having a convex surface having a larger curvature than the object side surface on the image side And a seventh lens (positive lens) L7 made of an aspherical lens having an aspherical surface on the image side surface. The two lenses, the fifth lens L5 and the sixth lens L6, are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses.
The second R lens group 2RG of the second lens group G2 is a biconcave lens having a concave surface having a larger curvature than the image side surface on the object side, and an aspheric lens having an aspheric surface formed on the object side surface. An eighth lens (negative lens) L8 is arranged.
In this case, in focusing from the infinite focus state shown in FIG. 10A to the short distance shown in FIG. 10B, the second F lens group 2FG is moved along the optical axis toward the object side. To do.
The optical characteristics of the optical elements in Example 4 are as shown in Table 10 below.

In Table 10, the surface number indicated by “* (asterisk)” in the surface number is an aspherical surface, and the glass name in the “glass type” column is the name of the manufacturer of the glass material. Abbreviated as “HOYA” (HOYA Corporation) and “OHARA” (Ohara Corporation).
That is, in Table 10, the optical surfaces of the fourth surface, the thirteenth surface, and the fourteenth surface marked with “*” are aspheric surfaces, and the parameters of each aspheric surface in Expression (7) are as follows. It is.
○ Aspherical surface (Surface number with * symbol)
4th page
K = 0.0, A ₄ = 3.37534E-05, A ₆ = -1.53994E-08, A ₈ = 1.59227E-09
13th page
K = 0.0, A ₄ = 1.96922E-04, A ₆ = -4.90024E-07, A ₈ = 4.34311E-09
14th page
K = 0.0, A ₄ = 8.13517E-05, A ₆ = -9.69858E-07, A ₈ = 2.09115E-09
In Example 4, the focal length f of the entire optical system, the variable distance DA between the aperture stop S and the second F lens group 2FG at the time of focusing on infinity, and between the seventh lens L7 and the eighth lens L8. Variable distance DB, and a variable distance DC between the aperture stop S and the second F lens 2FG at the time of focusing at a short distance (imaging magnification 0.1 times), and between the seventh lens L7 and the eighth lens L8. The variable interval DD is changed as shown in Table 11 along with focusing.

  Values corresponding to the conditional expressions (1) to (6) in the above-described fourth embodiment are as shown in the following Table 12, which respectively satisfy the conditional expressions (1) to (6).

FIGS. 11 and 12 are graphs showing spherical aberration, astigmatism, distortion, and coma aberration, respectively, when focusing on infinity and focusing at close distance (imaging magnification of 0.1) in Example 4. FIGS. Show.
In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional.
Moreover, g in each aberration diagram of spherical aberration, astigmatism, and coma represents the g-line. The broken line on the spherical aberration diagram indicates the deviation from the sine condition on the d-line. The same applies to the aberration diagrams of the other examples.

FIG. 13 is a fifth embodiment of the present invention, and shows the configuration of an imaging optical system according to Example 5 with a longitudinal section along the optical axis. FIG. FIG. 13B is a cross-sectional view when an object is in focus, and FIG.
In FIGS. 13A and 13B showing the lens group arrangement of Example 5, the left side in the drawing is the object (subject) side.
The imaging optical system 1 shown in FIGS. 13A and 13B includes a first lens group G1 having a positive refractive power located on the object side across the aperture stop S and a positive refractive power located on the image side. And a second lens group G2. The second lens group G2 includes a second F lens group 2FG having a positive refractive power and a second R lens group 2RG having a negative refractive power in order from the object side to the image side. The aperture stop S is disposed between the first lens group G1 and the second F lens group 2FG of the second lens group G2.
The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3.
The second lens group G2 includes a fourth lens L4, a fifth lens L5, and a sixth lens L6 that constitute the second F lens group 2FG, and a seventh lens L7 that constitutes the second R lens group 2RG. .

At the time of focusing, only the second F lens group 2FG is supported by a support frame or the like and is movable in the optical axis direction, and the first lens group G1, the aperture stop S, and the second R lens group 2RG are fixed. .
FIGS. 13A and 13B show the surface numbers of the respective optical surfaces.
The first lens group G1 is a negative meniscus lens having a convex surface directed toward the object side in order from the object side to the image side, and is a first aspheric lens that forms an aspheric surface on the image surface side. A lens (negative lens) L1, a second lens (negative lens) L2 made of a negative meniscus lens having a convex surface facing the object side, and a biconvex lens having a convex surface having a larger curvature than the image side surface facing the object side. A third lens (positive lens) L3 is disposed. The two lenses, the second lens L2 and the third lens L3, are closely bonded to each other and joined together to form a cemented lens composed of two lenses.
The second F lens 2FG in the second lens group G2 is a fourth lens (negative lens) composed of a biconcave lens having a concave surface having a larger curvature than the image side surface in order from the object side to the image side. ) L4, a fifth lens (positive lens) L5 composed of a biconvex lens having a convex surface having a larger curvature than the object side surface on the image side, and a biconvex lens having a convex surface having a larger curvature than the object side surface on the image side And a sixth lens (positive lens) L6 made of an aspherical lens having an aspherical surface formed on the image side surface. The two lenses, the fourth lens L4 and the fifth lens L5, are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses.

The second R lens group 2RG of the second lens group G2 is a negative meniscus lens having a concave surface directed toward the object side, and a seventh lens (negative lens) formed of an aspheric lens having an aspheric surface formed on the object side surface. ) L7.
In this case, in focusing from the infinite focus state shown in FIG. 13A to the short distance shown in FIG. 13B, the second F lens group 2FG is moved to the object side along the optical axis. Is done by.
The optical characteristics of the optical elements in Example 5 are as shown in Table 13 below.

In Table 13, the surface number indicated by “* (asterisk)” in the surface number is an aspherical surface, and the glass name in the “glass type” column is the name of the manufacturer of the glass material. Abbreviated as “HOYA” (HOYA Corporation) and “OHARA” (Ohara Corporation).
That is, in Table 13, the optical surfaces of the second surface, the eleventh surface, and the twelfth surface marked with “*” are aspheric surfaces, and the parameters of each aspheric surface in the equation (7) are as follows. It is.
○ Aspherical surface (Surface number with * symbol)
Second side
K = 0.0, A ₄ = 6.90372E-05, A ₆ = 7.25045E-08, A ₈ = 3.13977E-09
11th page
K = 0.0, A ₄ = 6.60256E-05, A ₆ = 5.15015E-07, A ₈ = -2.52597E-09
12th page
K = 0.0, A ₄ = 2.02086E-04, A ₆ = -2.99066E-07, A ₈ = 6.38673E-09
In Example 5, the focal length f of the entire optical system, the variable distance DA between the aperture stop S and the second F lens group 2FG at the time of focusing on infinity, and between the sixth lens L6 and the seventh lens L7. Variable distance DB, and a variable distance DC between the aperture stop S and the second F lens 2FG at the time of focusing at a short distance (imaging magnification 0.1 times), and between the sixth lens L6 and the seventh lens L7. The variable interval DD is changed as shown in Table 14 along with focusing.

  The values corresponding to the conditional expressions (1) to (6) in Example 5 described above are as shown in Table 15 below, and satisfy the conditional expressions (1) to (6), respectively.

FIGS. 14 and 15 show aberration diagrams of spherical aberration, astigmatism, distortion aberration, and coma aberration in Example 5 when focused at infinity and when focused at close distance (imaging magnification 0.1 times), respectively. Show.
In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional.
Moreover, g in each aberration diagram of spherical aberration, astigmatism, and coma represents the g-line. The broken line on the spherical aberration diagram indicates the deviation from the sine condition on the d-line. The same applies to the aberration diagrams of the other examples.
[Sixth Embodiment]
Next, a digital camera as a camera apparatus according to the sixth embodiment of the present invention configured by employing the imaging optical system according to the first to fifth embodiments of the present invention described above. Will be described with reference to FIGS. FIG. 16 is a perspective view schematically showing the external appearance of the digital camera viewed from the front side that is the object side, that is, the subject side, and FIG. 17 is a schematic external view of the digital camera viewed from the back side that is the photographer side. FIG. 18 is a schematic block diagram showing a functional configuration of a digital camera. Here, the camera apparatus has been described by taking a digital camera as an example, but the imaging optical system according to the present invention may be employed in a silver salt film camera that uses a silver salt film as a conventional image recording medium.

In addition, an information device such as a so-called PDA (personal data assistant) or a portable information terminal device such as a cellular phone in which a camera function is incorporated is widely used. Although such an information device has a slightly different appearance, it includes substantially the same functions and configuration as a digital camera, and may be employed as an imaging optical system in such an information device.
As shown in FIGS. 16 to 18, the digital camera includes a photographing lens 1, an optical viewfinder 2, a strobe (flashlight) 3, a shutter button 4, a camera body 5, a power switch 6, a liquid crystal monitor 7, an operation button 8, a memory. A card slot 9 and the like are provided. Further, as shown in FIG. 18, the digital camera includes a central processing unit (CPU) 11, an image processing device 12, a light receiving element 13, a signal processing device 14, a semiconductor memory 15 and a communication card 16.
The digital camera includes a photographing lens 1 as an imaging optical system and a light receiving element 13 configured as an image sensor using a CMOS (complementary metal oxide semiconductor) imaging element or a CCD (charge coupled device) imaging element. The light receiving element 13 reads an optical image of a subject (object) formed by the photographing lens 1. As the photographing lens 1, the imaging optical system according to the present invention as described in the first to fifth embodiments is used (corresponding to claim 9 or claim 11).

The output of the light receiving element 13 is processed by a signal processing device 14 controlled by the central processing unit 11 and converted into digital image information. That is, such a digital camera includes means for converting a captured image (subject image) into digital image information, which substantially controls the light receiving element 13, the signal processing device 14, and these. And a central processing unit (CPU) 11 or the like.
The image information digitized by the signal processing device 14 is subjected to predetermined image processing in the image processing device 12 which is also controlled by the central processing unit 11 and then recorded in the semiconductor memory 15 such as a nonvolatile memory. In this case, the semiconductor memory 15 may be a memory card loaded in the memory card slot 9 or a semiconductor memory built in the camera body (onboard). The liquid crystal monitor 7 can display an image being shot, and can display an image recorded in the semiconductor memory 15. The image recorded in the semiconductor memory 15 can also be transmitted to the outside via a communication card 16 or the like loaded in a communication card slot (not shown).
When the camera is carried, the objective surface of the photographic lens 1 is covered with a lens barrier (not shown). When the user operates the power switch 6 to turn on the power, the lens barrier is opened and the objective surface is The structure is exposed.

In many cases, focusing is performed by half-pressing the shutter button 4. Focusing in the imaging optical system according to the present invention (imaging optical system defined in claims 1 to 8 or shown in the first to fifth embodiments described above) is a part of the plurality of optical systems. This can be done by moving the 2F lens group 2FG or moving the light receiving element. When the shutter button 4 is further pushed down to the fully depressed state, photographing is performed, and then the processing as described above is performed.
When the image recorded in the semiconductor memory 15 is displayed on the liquid crystal monitor 7 or transmitted to the outside via the communication card 16 or the like, the operation button 8 is operated in a predetermined manner. The semiconductor memory 15 and the communication card 16 are used by being loaded into dedicated or general-purpose slots such as the memory card slot 9 and the communication card slot.
As described above, the digital camera (imaging device) or the portable information terminal device as described above includes the photographic lens 1 configured using the imaging optical system as shown in the first to fifth embodiments. It can be used as an imaging optical system. Accordingly, while the angle of view is a wide angle of view of 76 degrees or more, the F number is a large aperture of about 2.8 or less, and the number of pixels is 10 to 20 million pixels or more. A small camera (imaging device) with high image quality using a light receiving element or a portable information terminal device can be realized.
Also, it can be applied as a zoom photographing lens of a silver salt camera and a projection lens of a projector.

G1 first lens group (positive)
G2 Second lens group (positive)
2FG 2F lens group 2RG 2R lens group L1, L2, L3, L4, L5, L6, L7, L8 First lens, second lens, third lens, fourth lens, fifth lens, sixth lens, first lens 7 lenses, 8th lens S Aperture stop F Parallel plate 1 Shooting lens 2 Optical viewfinder 3 Strobe (flash light)
4 Shutter button 5 Camera body 6 Power switch 7 LCD monitor 8 Operation button 11 Central processing unit (CPU)
DESCRIPTION OF SYMBOLS 12 Image processing apparatus 13 Light receiving element 14 Signal processing apparatus 15 Semiconductor memory 16 Communication card etc.

Japanese Patent Publication No. 08-012325 JP 09-061708 A Japanese Patent Laid-Open No. 11-030743 JP 2003-043350 A JP 2006-349920 A JP 2008-020658 A JP 2009-116132 A Japanese Patent No. 3352264 Japanese Patent No. 3261716

Claims (11)

A first lens group having a positive refractive power located on the object side across the aperture stop, and a second lens group having a positive refractive power located on the image side, the second lens group being an object side In order from a second F lens group having a positive refractive power and a second R lens group having a negative refractive power, and during focusing, the first lens group, the aperture stop, and the second R lens An imaging optical system, wherein the group is fixed, and only the second F lens group moves in the optical axis direction, and satisfies the following conditional expression (1).
1.00 <(1-M2F ² ) × M2R ² <3.00 (1)
However, M2F represents the magnification when the second F lens group is focused at infinity, and M2R represents the magnification when the second R lens group is focused at infinity. The imaging optical system according to claim 1, wherein the following conditional expression (2) is satisfied.
0.40 <f / f2F <1.50 (2)
Here, f represents the focal length of the entire system, and f2F represents the focal length of the second F lens group. The imaging optical system according to claim 1 or 2, wherein the following conditional expression (3) is satisfied.
0.20 <f / | f2R | <1.30 (3)
Here, f represents the focal length of the entire system, and f2R represents the focal length of the second R lens group. The imaging optical system according to any one of claims 1 to 3, wherein the following conditional expression (4) is satisfied.
0.15 <f / f1 <1.00 (4)
However, f represents the focal length of the entire system, and f1 represents the focal length of the first lens group. 5. The imaging optical system according to claim 1, wherein the imaging optical system satisfies the following conditional expression (5): 6.
0.00 <Ls / f <0.10 (5)
Here, f represents the focal length of the entire system, and Ls represents the distance on the optical axis from the final surface of the first lens group to the aperture stop when focusing on infinity. 6. The imaging optical system according to claim 1, wherein the following conditional expression (6) is satisfied.
0.85 <TL / f <1.95 (6)
However, f represents the focal length of the entire system, and TL represents the distance on the optical axis from the first surface of the first lens group to the final surface of the second R lens group when focusing on infinity.   7. The imaging optical system according to claim 1, wherein an element on the most image plane side of the first lens group sandwiching the aperture stop is a cemented lens of a positive lens and a negative lens in any order. An imaging optical system, wherein the most object side element of the second F lens group is a cemented lens of a positive lens and a negative lens out of order.   8. The imaging optical system according to claim 1, further comprising: a positive lens having a convex surface on the image surface side in the second F lens group, and a concave surface on the object side in the second R lens group. An imaging optical system comprising a negative lens having   A camera apparatus comprising the imaging optical system according to claim 1.   The camera device according to claim 9, wherein the camera device has a function of using a captured image as digital information.   A portable information terminal device comprising the imaging optical system according to claim 1.

Images