JP2002090625A - Zoom lens and imaging device provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens constituted of few number of lenses, having a constitution capable of adopting rear focus, having stable image-forming performance over the entire zoom area and in the range from infinity to short distance, thinned overall by thinning respective lenses and is made inexpensive. SOLUTION: This zoom lens is constituted of a 1st negative lens group, a 2nd positive lens group and a 3rd positive lens group, starting from an object side, and the 3rd lens group is moved on an optical axis, so that a distance between the 3rd lens group and an image surface may be large, and consists of a single positive lens, so that the lenses satisfy conditions (1), (2), (3) and (4), where (1) |fW/f2R|<0.1, (2) 0.89<f3/fT<2.8, (3) 1.1<|β23T|<2, and (4) 1/β2T<0.25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens having a thin depth direction and an image pickup apparatus such as a video camera and a digital camera provided with the zoom lens.

[0002]

2. Description of the Related Art In recent years, digital cameras (electronic cameras) have attracted attention as next-generation cameras that can replace silver halide 35 mm film (so-called Leica) cameras.

[0003] These digital cameras are known in a wide range from high-functional ones for business use to portable popular types.

[0004] In the present invention, a portable video camera or digital camera, particularly a portable type, which is a bottleneck for realizing a video camera and a digital camera with high image quality and a small depth is an optical system,
In particular, it is to reduce the thickness of the zoom optical system from the most object side surface to the imaging surface.

Recently, it has been known to employ a collapsible lens barrel in which the optical system is protruded from the inside of the camera body at the time of photographing, while the optical system is housed inside the camera body when carrying.

[0006] However, the thickness of the optical system when the optical system is deposited differs greatly depending on the type of optical system and the filter used. A so-called positive-leading zoom lens, in which the most object-side lens group of the optical system has a positive refractive power, is particularly suitable for setting specifications such as the zoom ratio and the F-number high.
The thickness of each lens is large, the dead space becomes large, and the thickness cannot be made very small even when retracted (Japanese Patent Laid-Open No. 11-258507).

On the other hand, a negative-leading type second or third lens group zoom lens is advantageous when employing a retractable lens system.

The zoom lens described in Japanese Patent Application Laid-Open No. 11-52246 has a large number of constituent lenses in each group, and the lens closest to the object is a positive lens. It cannot be thin.

A currently known zoom lens, which is suitable for a camera using an electronic image pickup device, has good image forming performance such as a zoom ratio, an angle of view, and an F number, and can make the collapsed thickness the thinnest. JP-A-11-1942 as an example of an optical system
No. 74, JP-A-11-287953, JP-A-2000-
There is one described in each publication of No. 9997.

In these conventional examples, to make the first unit thinner, it is preferable to make the position of the entrance pupil shallower. However, for that purpose, the magnification of the second unit must be increased. But the second
If the load on the second group is increased by increasing the magnification of the group, the second group itself cannot be thinned, and it becomes difficult to correct aberrations.
The influence of manufacturing errors increases, which is not preferable.

Further, in order to achieve a reduction in thickness and size, it is necessary to reduce the size of the image sensor. However, in order to reduce the size of the image sensor with the same number of pixels, it is necessary to reduce the pixel pitch. It is necessary to cover with an optical system. In addition, it is not preferable because the influence of diffraction occurs.

[0012]

SUMMARY OF THE INVENTION The present invention has a small number of components and can adopt a rear focus, and is compact and simple, and has stable imaging performance over the entire zoom range and from infinity to short distance. It is an object of the present invention to provide an inexpensive zoom lens in which each lens is thinned and the thickness of each lens group is thinned to make the entire lens system thin, and an imaging device with a small depth provided with this zoom lens.

[0013]

A zoom lens according to the present invention comprises, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a positive refractive power. A lens system that moves the third lens group so as to increase the distance between the third lens group and the image plane when zooming from the wide-angle end to the telephoto end. The lens group consists of one positive lens, and the following conditions (1), (2),
(3) and (4) are satisfied. (1) | fW / f2R | <0.1 (2) 0.89 <f3 / fT <2.8 (3) 1.1 <| β23T | <2 (4) 1 / β2T <0.25 f2R is the focal length of the lens closest to the image in the second lens group, f3 is the focal length of the third lens group, β23T is the combined magnification of the second and third lens groups at the telephoto end,
β2T is the magnification of the second lens group at the telephoto end, fW is the focal length of the entire zoom lens system at the wide-angle end, and fT is the focal length of the entire zoom lens system at the telephoto end.

In an electronic imaging device such as a digital still camera, it is necessary to minimize the angle of a light beam incident on the electronic imaging device.

The zoom lens system according to the present invention is a zoom lens system comprising a second negative lens unit and a second positive lens unit.
The positive lens closest to the image side of the lens group is defined as a third lens group, and the third lens group is independently moved so that the angle of a light beam incident on the electronic image sensor becomes small. Further, the conditions (1), (2), (3) and (4) were satisfied so that the retracted thickness was reduced and the aberration from infinity to a short distance was improved.

The condition (1) is such that the focal length (refractive power) of the lens closest to the image side of the second lens group is restricted so as to reduce the collapsible thickness.

When the value exceeds the upper limit of 0.1 of the condition (1), it becomes difficult to reduce the thickness of the lens, and it is impossible to reduce the collapsed thickness.

In order to further reduce the collapsed thickness, to suppress the occurrence of chromatic aberration, and to be free from the effects of changes in temperature and humidity, the following condition (1-1) is used instead of condition (1).
It is desirable to satisfy 1). (1-1) | fW / f2R | <0.05

Condition (2) is provided to reduce the retracted thickness by limiting the amount of movement of the third lens unit.

In the zoom lens according to the present invention, the aberrations are favorably corrected by balancing the aberrations of the second lens unit and the third lens unit. 0 of the lower limit of the condition (2).
If it exceeds 89, the refracting power of the third lens group becomes strong,
It becomes difficult to correct coma and astigmatism generated in the lens group. When the value exceeds the upper limit of 2.8, the refractive power of the second lens group becomes strong, and it becomes difficult to correct spherical aberration.

In order to reduce the collapsed thickness,
It is preferable that the following condition (2-1) is satisfied instead of the condition (2). (2-1) 1.1 <f3 / fT <2

Condition (3) is a combination magnification β23T of the second lens unit and the third lens unit when focusing on infinity at the telephoto end.
Is defined. If the absolute value of β23T is as large as possible, the entrance pupil position at the wide-angle end can be made shallow, and the diameter of the first lens unit can be easily reduced.
The thickness of the lens group can be reduced. If the lower limit of 1.1 of the condition (3) is exceeded, it becomes difficult to reduce the thickness of the first lens unit. If the upper limit of 2 is exceeded, correction of spherical aberration, coma, astigmatism, and the like, will fail. It becomes difficult.

Instead of the above condition (3), the following condition (3-
It is more desirable to satisfy 1). (3-1) 1.2 <| β23T | <1.8

Condition (4) is a condition for reducing the fluctuation of aberration due to focusing, and is a condition for suppressing the fluctuation of aberration to be small for photographing up to a magnification of 0.05. When the value exceeds the upper limit of 0.25 of the condition (4), it becomes difficult to correct spherical aberration, coma, astigmatism, and the like at the time of close-up shooting.

In order to obtain a good image in photographing at 0.1 times the short distance, it is desirable to satisfy the following condition (4-1) instead of condition (4). (4-1) 1 / β2T <0.1

In the lens system according to the present invention, the curvature of the second lens unit is made as small as possible in order to reduce the collapsed thickness, so that the refractive power of the second lens unit is weakened. This is supplemented by a lens group. Therefore, the third lens unit moves with respect to the movement of the second lens unit during zooming. The amount of movement of the second lens unit and the third lens unit from the wide-angle end to the telephoto end is determined by the following condition (5).
Is preferably satisfied. (5) 0.6 <Δ2 / Δ3 <3 where Δ2 and Δ3 are the amounts of movement of the second lens unit and the third lens unit from the wide-angle end to the telephoto end, respectively.

In condition (5), if the lower limit of 0.6 is exceeded, the refractive power of the second lens unit becomes weak, and it becomes difficult to correct aberrations. In addition, the overall length during shooting becomes longer, and it takes time to shift from the collapsed state to the shooting state, causing problems such as missing a photo opportunity. When the value exceeds the upper limit of 3 in the condition (5), the collapsed thickness becomes large.

In a camera using an electronic image pickup device, in the case of a three-plate camera in which three CCDs are arranged after a color separation prism to perform photographing, a light flux from an optical system is used because an interference film is used as the color separation prism. Tilting causes color shading. In order to avoid this, the inclination of the principal ray with respect to the optical axis needs to be within 5 degrees.

For this purpose, it is desirable that the zoom lens of the present invention having the above-described configuration satisfies the following condition (6). (6) DW / fW> 5 where DW is the distance from the aperture stop at the wide angle end to the image plane.

If the lower limit of 5 of the condition (6) is exceeded, color shading occurs because the inclination angle of the principal ray incident on the image pickup surface exceeds 5 degrees.

When the optical system has a single-lens reflex type finder, it is necessary to insert a half mirror or a quick return mirror between the lens and the image plane, and it is necessary to keep a distance between the lens and the image plane. For that purpose, the following condition (7) must be satisfied. (7) f2 / fW> 3.6 where f2 is the focal length of the second lens group.

When the lower limit of 3.6 to condition (7) is exceeded, it becomes impossible to arrange a single-lens reflex light splitting member, or it becomes necessary to increase the number of lenses in the second lens group, and the second lens group becomes thick. As a result, the overall length of the lens system becomes longer, and the collapsed thickness cannot be reduced. When a quick return mirror is provided, the overall length of the lens system becomes longer, but when the lens is collapsed, the quick return mirror is flipped up, so that the collapsed thickness can be reduced.

In the zoom lens of the present invention, it is desirable to use the third lens group for focusing. By extending the third lens group toward the object side, it is possible to focus on a subject at a short distance.

When the third lens group is moved for focusing, there is a problem of fluctuation of aberration due to movement of the lens.
In the case where an aspheric surface is provided in the third lens group to correct residual aberration in the first lens group and the second lens group, the correction balance is lost due to the movement of the third lens group for focusing. Therefore, when the third lens group is used for focusing, the first lens group and the second lens group preferably correct astigmatism satisfactorily over the entire zoom range, and the third lens group must be a spherical system. Is desirable.

It should be noted that satisfying conditional expression (2) is satisfied by the third condition.
This is also effective when the lens group is used as a focusing lens. If conditional expression (2) is satisfied, the movement of the third lens unit during focusing is restricted, and the collapsible thickness can be reduced.

If the lower limit of the condition (2) is exceeded, the amount of movement of the third lens unit at the telephoto end becomes large, and the mechanism for pointing the third lens unit becomes large, so that it is difficult to reduce the collapsed thickness. Become. In addition, the radial length of the third lens group becomes large. If the condition (2-1) is satisfied instead of the condition (2), the restriction at the wide-angle end becomes easier, and the collapsed thickness can be further reduced.

In the zoom lens according to the present invention, in order to make the collapsed thickness as small as possible, it is necessary to make the thickness of the second lens group as small as possible. For that, the second
It is necessary to reduce the number of lenses in the lens group or to reduce the curvature of the lens. However, since a refractive power is required for aberration correction, a certain degree of curvature is required. For that purpose, it is desirable to satisfy the following condition (8). (8) 0.3 <R2b / f2 <0.6 where R2b is the smallest radius of curvature of the convex surface in contact with air in the second lens group (in the case of an aspheric surface, the radius of curvature near the optical axis), and f2 is the second radius. This is the focal length of the lens group.

When the lower limit of 0.3 to condition (8) is exceeded, the second condition is satisfied.
The thickness of the lens group becomes too thick and the collapsed thickness becomes too thick. If the upper limit of 0.6 is exceeded, it becomes difficult to correct aberrations, especially spherical aberration.

In the zoom lens according to the present invention, the aperture stop is arranged on the object side of the second lens group, and the second lens group has a non-aperture lens closest to the image side, which is particularly effective for correcting off-axis aberrations. Preferably, a spherical surface is provided. By providing an aspherical surface on the lens closest to the image in the second lens group, coma can be satisfactorily corrected.

Generally, the glass material of a lens having an aspherical surface is:
Many have small Abbe numbers.

The lens provided with the aspheric surface can not only be reduced in thickness by satisfying the above condition (1), but also can suppress the occurrence of chromatic aberration by using a lens having a small Abbe number. In addition, it is hardly affected by changes in temperature and humidity.

Since the positive lens and the negative lens on the object side of the second lens group vary greatly in aberration due to the relative eccentricity of these lenses, it is preferable to join these positive and negative lenses. Further, in the lens group having such a configuration, since the front lens diameter is unlikely to be large, the aperture stop is integrated with the second lens group, that is, disposed on the object side of the second lens group. It is preferable to move the aperture stop and the aperture stop integrally because the mechanism is simple in structure and a dead space hardly occurs at the time of collapsing. Further, the F number at the wide-angle end and the telephoto end can be reduced.

In consideration of the above, the configuration of the second lens group is preferably a single lens-joint lens-single lens or a cemented lens-single lens. Here, when the focal length of the i-th single lens from the object side of the second lens group is f2i and the following conditional expression (9) is satisfied, the single lens is called a lens having a low refractive power. (9) | fW / f2i | <0.1

In the configuration of the second lens group, the single lens has a low refractive power and is close to a flat surface, and therefore has a small aberration correction capability. It is necessary to compensate for the insufficiency of the aberration correction by using an aspheric surface.

In the above-described configuration, in the case of a cemented lens-single lens, if the surface closest to the object side is made aspherical, a single lens-joint lens-single lens can be replaced by a single lens -Joint lens-Imaging performance equivalent to that of a single lens can be obtained. In each case, the cemented lens is
It has a meniscus shape with the convex surface facing the object side. Also, if the cemented surface of the cemented lens is separated into two lenses arranged at a slight air gap, and the curvatures of the facing surfaces of both lenses are substantially equal, the same operation as the cemented lens can be obtained. Can be used as the lens component.

Next, in the zoom lens according to the present invention, the number of lenses in the first lens group is reduced to make it as thin as possible, the refractive power of each lens is reduced, and the number of lenses is reduced.
It is desirable that the aberration correction effect reduced by weakening the refractive power is compensated for by using an aspheric surface.

In the first lens group, when the focal length of the i-th single lens from the object side is f1i and the focal length of the first group is f1, if the following equation is satisfied, the lens is weak in refractive power. Called a single lens. (10) | f1 / f1i | <0.2 In order to make the first lens group thin, it is composed of two or three lenses. With a single lens with weak power, or a single lens with weak refractive power and a negative lens and a positive lens in order from the object side, or a single lens with weak refractive power and a negative lens and a single lens with weak refractive power in order from the object side In each case, it is preferable to provide an aspherical surface on a single lens having a low refractive power. In the case of using two lenses, it is preferable to use a negative lens and a positive lens and provide the negative lens with an aspheric surface.

When the first lens unit is composed of a single lens having a low refractive power, a negative lens and a positive lens,
By reducing the refractive power of the lens with the largest diameter on the object side, the thickness of the first lens group can be reduced, and the resulting lack of aberration correction can be compensated for by the aspherical surface.
Further, if the image side surface of the negative lens, which is the second lens of the first lens unit having this configuration, is made strongly concave and the positive lens, which is the third lens, is made a meniscus lens which is convex toward the object side, coma aberration and non-comaberation can be reduced. Astigmatism can be corrected well.

When the first lens unit is composed of a single lens having a low refractive power, a negative lens and a single lens having a low refractive power in order from the object side, the refractive power of the single lens having the lowest refractive power on the image side is determined. It is desirable to make it extremely weak and close to the plane-parallel plate, and to correct the aberrations caused thereby by providing an aspherical surface.

The case where the first lens group is composed of a positive lens, a negative lens, and a single lens having a low refractive power as described above will be described. When the first lens group is composed of three spherical lenses, a biconvex positive first lens, a negative second lens having a strong concave surface facing the image side, and a strong convex surface facing the object side In general, the third lens is a positive meniscus lens. However, since the third lens is a meniscus lens, the third lens becomes considerably thick in the optical axis direction. First
In order to make the lens group thinner, it is preferable that the refractive power of the third lens is weakened to reduce the thickness in the optical axis direction, and that the aberration generated thereby is corrected by the aspherical surface.

Therefore, when the first lens group is composed of three lenses, it is preferable that the first lens group is composed of a positive lens, a negative lens, and a single lens having a low refractive power in order from the object side. It is more desirable that the following condition (10-1) be satisfied: (10-1) | f1 / f1i | <0.13

Further, when the first lens group is composed of two lenses, it is preferable that the first lens group is composed of a negative lens and a positive lens, and the object side surface of the negative lens is made aspheric.

The aspherical single lens having a weak refracting power of the first lens group composed of a single lens having an aspheric surface and a weak refracting power and a negative lens and a positive lens is removed.
The negative lens and the positive lens may be composed of two lenses, and the aberration generated at that time may be corrected by setting the object-side surface of the negative lens to an aspheric surface.

As a result, the first lens group can be made thin, consisting of only two lenses, and can be made thinner.

The aspherical lens having a weak refractive power described above is
It is also possible to use a material whose refractive index changes with changes in temperature and humidity. Therefore, if plastic is used as the material, for example, mass production can be performed at low cost, and the cost can be reduced. In particular, when the camera has an autofocus function, parfocal deviation due to changes in temperature or humidity can be automatically corrected, and aberration fluctuation can be reduced.

If the following condition (11) is satisfied, the fluctuation of aberration due to the focus shift due to the temperature and humidity can be reduced to a level that does not cause a practical problem. (11) | fW / fp | <0.1 where fp is the focal length of the plastic lens, and fW is the focal length of the entire system at the wide-angle end.

It is more desirable to satisfy the following condition (11-1). (11-1) | fW / fp | <0.05

It is most desirable that the following condition (11-2) is satisfied: (11-2) | fW / fp | <0.02

By arranging the electronic image pickup device at the image position of the zoom lens of the present invention described above, the image pickup apparatus of the present invention can be constituted.

[0060]

Next, an embodiment of the present invention will be described.

First, an embodiment of the zoom lens of the present invention will be described based on an example having the following data. Example 1 f = 4.39 to 7.36 to 13.28, F-number = 2.75 to 3.14 to 4.10 2ω = 59.3 ° to 37.5 ° to 21.3 ° r ₁ = 31.2493 d ₁ = 1.9500 n ₁ = 1.84666 ν ₁ = 23.78 r ₂ = -65.0991 _{d 2 = 0.6808 r 3 = -444.0763} d 3 = 1.0000 n 2 = 1.77250 ν 2 = 49.60 r 4 = 3.9935 d 4 = 3.8998 r 5 = -137.8476 ( _{aspherical) d 5 = 1.8521 n 3 =} 1.80610 ν 3 = 40.92 _{r 6 = -51.1701 d 6 = D} 1 ( variable) r ₇ = ∞ _{(stop) d 7 = 1.0000 r 8 =} 7.7924 d 8 = 2.2000 n 4 = 1.58913 ν 4 = 61.14 r 9 = -22.1410 d 9 = 0.1000 r _{10 = 7.3555 d 10 = 2.9000 n} 5 = 1.51633 ν 5 = 64.14 r 11 = -7.3364 d 11 = 1.0000 n 6 = 1.83400 ν 6 = 37.16 r 12 = 7.7514 d 12 = 0.9000 r 13 = ∞ d 13 = 1.2000 n 7 = 1.58913 v ₇ = 61.14 r ₁₄ = -589.1299 (aspherical surface) d ₁₄ = D ₂ (variable) r ₁₅ = 15.609 d ₁₅ = 2.0000 n ₈ = 1.48749 v ₈ = 70.23 r ₁₆ = -17.1493 d ₁₆ = D ₃ ( Variable) r ₁₇ = ∞ d ₁₇ = 1.90 00 n ₉ = 1.54771 v ₉ = 62.84 r ₁₈ = ∞ d ₁₈ = 0.8000 r ₁₉ = ∞ d ₁₉ = 0.7500 n ₁₀ = 1.51633 v ₁₀ = 64.14 r ₂₀ = ∞ d ₂₀ = 1.15 r ₂₁ = ∞ (image) Aspheric surface coefficient (fifth _{surface) K = 0, A 2 =} 0, A 4 = 6.1115 × 10 -4, A 6 = 6.3032 × 10 -7 A 8 = 1.3229 × 10 -6, A 10 = 0 ( the fourteenth surface) K = 0, A ₂ = 0, A ₄ = 9.8979 × 10 ^-4 , A ₆ = 1.9313 × 10 ^-5 A ₈ = 4.2402 × 10 ^-7 , A ₁₀ = 0 When focused on infinity f 4.39 7.36 13.28 D ₁ 17.09115 7.30302 1.40000 D ₂ 4.72311 3.80530 3.35776 D ₃ 1.50000 6.53742 15.30673 When focused on an object distance of 100 mm f 4.39 7.36 13.28 D ₁ 17.09115 7.30302 1.40000 D ₂ 4.41989 3.23129 1.50000 D ₃ 1.80322 7.11143 17.16449 f2 = 12.05, f3 = 17.1, | /F2R|=0.0044, f3 / fT = 1.29 | β23T | = 1.64, 1 / β2T = 0.092, DW / fW = 5.04 f2 / fW = (2.74), R2b / f2 = 0.61, Δ2 / Δ3 = 0.9 | f1 / 13 | = 0.081, | fW / f24 | = 0.0044

Example 2 f = 4.39 to 7.36 to 13.28, F number = 2.74 to 3.08 to 3.83 2ω = 59.3 ° to 37.5 ° to 21.3 ° r ₁ = 50.0880 d ₁ = 2.3000 n ₁ = 1.84666 ν ₁ = 23.78 r ₂ = -35.1849 d ₂ = 0.2000 r ₃ = -65.7634 d ₃ = 1.0000 n ₂ = 1.72916 ν ₂ = 54.68 r ₄ = 4.4610 d ₄ = 3.1218 r ₅ = 13.0318 (aspherical surface) d ₅ = 1.1000 n ₃ = 1.49241 ν ₃ = 57.66 r ₆ = 19.9534 d ₆ = D ₁ (variable) r ₇ = ∞ (aperture) d ₇ = 1.0000 r ₈ = 14.3782 (aspherical surface) d ₈ = 1.0000 n ₄ = 1.49241 ν ₄ = 57.66 r ₉ = 19.8421 d _{9 = 0.1000 r 10 = 5.4400 d} 10 = 2.5000 n 5 = 1.51633 ν 5 = 64.14 r 11 = -52.8689 d 11 = 1.0000 n 6 = 1.78470 ν 6 = 26.29 r 12 = 14.9521 d 12 = 0.8000 r 13 = -987.0956 d _{13 = 1.2000 n 7 = 1.49241 ν} 7 = 57.66 r 14 = 982.9308 ( aspherical) d ₁₄ = D _{2 (variable) r 15 = 15.7957 d 15 =} 1.8000 n 8 = 1.48749 ν 8 = 70.23 r 16 = -17.0241 d 16 = D ₃ (Variable) r ₁₇ = ∞ d ₁₇ = 1.9000 n ₉ = 1.54771 v ₉ = 62.84 r ₁₈ = ∞ d ₁₈ = 0.8000 r ₁₉ = ∞ d ₁₉ = 0.7500 n ₁₀ = 1.51633 v ₁₀ = 64.14 r ₂₀ = ∞ d ₂₀ = 1.15 r ₂₁ = ∞ (image) Aspheric coefficient (fifth surface) K = 0, A ₂ = 0, A ₄ = 8.6004 × 10 ⁻⁴ , A ₆ = −1.3646 × 10 ⁻⁵ A ₈ = 1.6576 × 10 ^{− 6} , A ₁₀ = 0 (eighth surface) K = 0, A ₂ = 0, A ₄ = −2.8930 × 10 ⁻⁵ , A ₆ = 6.0475 × 10 ⁻⁶ A ₈ = −1.4072 × 10 ⁻⁷ , A ₁₀ = 0 (14th surface) K = 0, A ₂ = 0, A ₄ = 1.6825 × 10 ^-3 , A ₆ = 1.0800 × 10 ^-5 A ₈ = 3.9927 × 10 ^-6 , A ₁₀ = 0 Infinity focusing Hour f 4.39 7.36 13.28 D ₁ 18.29793 7.99696 1.40000 D ₂ 3.72779 2.79199 3.65481 D ₃ 6.49849 10.56281 18.38607 Focusing on object distance 100 mm f 4.39 7.36 13.28 D ₁ 18.29793 7.99696 1.40000 D ₂ 3.52350 2.27425 1.50000 D ₃ 6.70278 11.08055 20.540 , F3 = 17.12, | fW / f2R | = 0.0044, f3 / f = 1.29 | β23T | = 1.46, 1 / β2T = 0.22, DW / fW = 5.52 f2 / fW = 3.90, R2b / f2 = 0.32, Δ2 / Δ3 = 0.99 | f1 / f13 | = 0.125, | fW / f21 | = 0.044 | fW / f24 | = 0.0044 | fW / fp | = 0.061 (first group image side lens), 0.044 (second group object side lens), 0.0044 (second group image side lens)

Example 3 f = 4.33 to 8.67 to 13.10, F-number = 2.86 to 3.80 to 4.87 2ω = 60 ° to 32.2 ° to 21.6 ° r ₁ = 34.5719 d ₁ = 2.0000 n ₁ = 1.52540 ν ₁ = 56.25 r ₂ = 39.2868 (aspherical surface) d ₂ = 1.3000 r ₃ = -20.0546 d ₃ = 1.0000 n ₂ = 1.63854 v ₂ = 55.38 r ₄ = 5.2000 d ₄ = 3.5745 r ₅ = 9.3216 d ₅ = 1.4617 n ₃ = 1.80518 v ₃ = 25.42 r ₆ = 14.0641 d ₆ = D ₁ (variable) r ₇ = ∞ (aperture) d ₇ = 0 r ₈ = 4.4179 (aspherical surface) d ₈ = 0.8000 n ₄ = 1.52540 ν ₄ = 56.25 r ₉ = 4.0737 d ₉ = 0.6355 r ₁₀ = 5.5000 d ₁₀ = 2.0000 n ₅ = 1.77250 v ₅ = 49.60 r ₁₁ = -12.8000 d ₁₁ = 0.8000 n ₆ = 1.80809 v ₆ = 22.76 r ₁₂ = 23.4461 d ₁₂ = 1.4502 r ₁₃ = 6.0905 (aspheric surface) _{) d 13 = 1.0000 n 7 =} 1.52540 ν 7 = 56.25 r 14 = 5.0127 d 14 = D 2 ( _{variable) r 15 = -94.6826 d 15 =} 1.4000 n 8 = 1.51633 ν 8 = 64.14 r 16 = -14.1789 d 16 = D ₃ (variable) r ₁₇ = ∞ d ₁₇ = 0.8000 n ₉ = 1.51633 v ₉ = 64.14 r ₁₈ = ∞ d ₁₈ = 1.3600 n ₁₀ = 1.54771 v ₁₀ = 62.84 r ₁₉ = ₁₉ d ₁₉ = 0.8000 r ₂₀ = ∞ d ₂₀ = 0.7500 n ₁₁ = 1.51633 ν ₁₁ = 94.14 r ₂₁ = ∞ d ₂₁ = 1.2000 r ₂₂ = ∞ (image) Aspheric coefficient (second surface) K = 0, A ₂ = 0, A ₄ = -6.2517 × 10 ^-4 , A ₆ = 2.2895 × 10 ⁻⁶ A ₈ = 4.3661 × 10 ⁻⁸ , A ₁₀ = 0 (eighth surface) K = 0, A ₂ = 0, A ₄ = −5.3350 × 10 ⁻⁵ , A ₆ = 4.1213 × 10 ^{− 7} A ₈ = -8.8818 × 10 ^-7 , A ₁₀ = 0 (13th surface) K = 0, A ₂ = 0, A ₄ = -2.2384 × 10 ^-3 A ₆ = -6.4370 × 10 ^-5 , A ₈ = -3.74747 × 10 ^-7 A ₁₀ = 0 at infinity focusing f 4.33 8.67 13.10 D ₁ 13.81397 4.20997 1.28197 D ₂ 2.20675 4.44595 9.13211 D ₃ 1.59012 4.52960 6.08009 f 4.33 8.67 13.10 D ₁ 13.81397 4.20997 1.28197 D ₂ 1.70301 3.0306 _{3 2.09386 5.94491 8.80712 f2 = 9.81,} f3 = 32.11, | fW / f2R | = 0.055, f /FT=2.45|β23T|=1.41, 1 / β2T = −0.488, DW / fW = (3.98) f2 / fW = (2.27), R2b / f2 = 0.45, Δ2 / Δ3 = 2.54 | f1 / f11 | = 0.19 , │fW / f21│ = 0.0087 │fW / f24│ = 0.55 │fW / fp│ = 0.0091 (first-group object-side lens), 0.0087 (second-group object-side lens), 0.055 (second-group image-side lens)

Example 4 f = 4.39 to 7.36 to 13.28, F number = 2.78 to 3.28 to 4.35 2ω = 59.3 ° to 37.5 ° to 21.3 ° r ₁ = 7.2293 d ₁ = 1.5000 n ₁ = 1.52540 ν ₁ = 56.25 r ₂ = 5.8997 _{(aspherical) d 2 = 1.4000 r 3 =} 72.0533 d 3 = 1.0000 n 2 = 1.72916 ν 2 = 54.68 r 4 = 3.7137 d 4 = 1.8000 r 5 = 5.3208 d 5 = 1.5235 n 3 = 1.78470 ν 3 = 26.29 r ₆ = 7.3093 d ₆ = D ₁ (variable) r ₇ = ∞ (aperture) d ₇ = 1.0000 r ₈ = 4.6247 (aspheric surface) d ₈ = 2.5000 n ₄ = 1.69350 v ₄ = 53.21 r ₉ = -13.2200 d _{9 = 1.0000 n 5 = 1.78470 ν 5} = 26.29 r 10 = 9.8161 d 10 = 0.6000 r 11 = 8.9607 ( _{aspherical) d 11 = 1.0589 n 6 =} 1.52540 ν 6 = 56.25 r 12 = 9.9956 d 12 = D 2 ( variable) _{r 13 = 10.8186 d 13 = 1.7000} n 7 = 1.48749 ν 7 = 70.23 r 14 = -34.4570 d 14 = D 3 ( _{variable) r 15 = ∞ d 15 =} 1.9000 n 8 = 1.54771 ν 8 = 62.84 r 16 = ∞ d ₁₆ = 0.8000 r _{1 7 = ∞ d 17 = 0.7500 n} 9 = 1.51633 ν 9 = 64.14 r 18 = ∞ d 18 = 1.15 r 19 = ∞ ( image) aspherical coefficients (second _{surface) K = 0, A 2 =} 0, A 4 = _{^{-3.2448 × 10 -4 A 6 = -5.7220}} × 10 -5, A 8 = -2.5069 × 10 -7 A 10 = 0 ( eighth _{surface) K = 0, A 2 =} 0, A 4 = 2.6425 × 10 - ⁴ , A ₆ = -1.1410 × 10 ^-5 A ₈ = 1.6780 × 10 ^-6 , A ₁₀ = 0 (11th surface) K = 0, A ₂ = 0, A ₄ = -4.3533 × 10 ^-3 A ₆ = -9.7990 × 10 ^-5 , A ₈ = -4.1447 × 10 ^-5 A ₁₀ = 0 when focused on infinity f 4.39 7.36 13.28 D ₁ 12.05238 5.51069 1.40000 D ₂ 3.80706 3.23467 3.30769 D ₃ 2.45821 6.38167 13.60995 When the object distance is 100 mm In focus f 4.39 7.36 13.28 D ₁ 12.05238 5.51069 1.40000 D ₂ 3.53882 2.65713 1.50000 D ₃ 2.72645 6.95921 15.41765 f2 = 10.27, f3 = 17.1, | fW / f2R | = 0.036, f3 / fT = 1.29 | β23T | = 1.73, 1 / β2T = 0.035, DW / fW = (4.26) f2 / fW = (2.34) R2b / f2 = 0.45, Δ2 / Δ3 = 0.96 | f1 / f11 | = 0.075, | fW / f23 | = 0.036 | fW / fp | = 0.044 (first group object side lens), 0.036 (second unit image side lens)

Example 5 f = 4.41 to 8.82 to 13.28, F number = 2.73 to 3.71 to 4.49 2ω = 59.1 ° to 31.6 ° to 21.3 ° r ₁ = -104.2415 (aspherical surface) d ₁ = 1.2000 n ₁ = 1.69350 ν _{1 = 53.21 r 2 = 5.3000 d} 2 = 3.3438 r 3 = 8.0044 d 3 = 1.7417 n 2 = 1.80809 ν 2 = 22.76 r 4 = 9.9324 d 4 = D 1 ( variable) r ₅ = ∞ (stop) d ₅ = 0.2000 _{r 6 = 12.0603 d 6 = 1.4500} n 3 = 1.69350 ν 3 = 53.21 r 7 = -518.8844 d 7 = 0.6334 r 8 = 5.9602 d 8 = 2.2477 n 4 = 1.74100 ν 4 = 52.64 r 9 = 35.0000 d 9 = 1.0000 n _{5 = 1.84666 ν 5 = 23.78 r} 10 = 6.0288 d 10 = 0.9627 r 11 = 8.4031 d 11 = 0.8000 n 6 = 1.52540 ν 6 = 56.25 r 12 = 8.0498 d 12 = D 2 ( variable) r ₁₃ = 58.0569 d ₁₃ = 2.0662 n ₇ = 1.51633 v ₇ = 64.14 r ₁₄ = -10.8016 d ₁₄ = D ₃ (variable) r ₁₅ = ∞ d ₁₅ = 0.8000 n ₈ = 1.51633 v ₈ = 64.14 r ₁₆ = ∞ d ₁₆ = 1.3600 n ₉ = 1.54771 ν ₉ = 62.84 _{17 = ∞ d 17 = 0.8000 r} 18 = ∞ d 18 = 0.7500 n 10 = 1.51633 ν 10 = 64.14 r 19 = ∞ d 19 = 1.2000 r 20 = ∞ ( image) aspheric coefficients (first surface) K = 0, A ₂ = 0, A ₄ = 5.2742 × 10 ^-4 , A ₆ = -1.0626 × 10 ^-5 A ₈ = 1.6927 × 10 ^-7 , A ₁₀ = 0 (Twelfth surface) K = 0, A ₂ = 0, A ₄ = 2.3060 × 10 ^-3 , A ₆ = 8.1827 × 10 ^-6 A ₈ = 8.0844 × 10 ^-6 , A ₁₀ = 0 when focused at infinity f 4.41 8.82 13.28 D ₁ 13.91370 5.06449 1.40646 D ₂ 1.11092 4.87076 9.20261 D ₃ 2.51043 5.58000 10.30000 When focused on an object point distance of 100 mm f 4.41 8.82 13.28 D ₁ 13.91370 5.06449 1.40646 D ₂ 0.81599 3.95939 7.45519 D ₃ 2.80537 6.49136 12.04742 f2 = 10.7, f3 = 17.82, | fW / f2R | = 0.0028, f3 / fT = 1.34 | β23T | = 1.442, 1 / β2T = −0.137, DW / fW = (4.07) f2 / fW = (2.43), R2b / f2 = 0.56, Δ2 / Δ3 = 2.04 | fW / f24 | = 0.0027 | f /Fp|=0.0027 (second unit image side lens)

Example 6 f = 4.39 to 7.36 to 13.28, F number = 2.78 to 3.28 to 4.37 2ω = 59.3 ° to 37.5 ° to 21.3 ° r ₁ = 8.3849 d ₁ = 1.7928 n ₁ = 1.58423 ν ₁ = 30.49 r ₂ = 9.8428 (aspheric surface) d ₂ = 0.6000 r ₃ = 28.0540 d ₃ = 1.0000 n ₂ = 1.72916 ν ₂ = 54.68 r ₄ = 3.5362 d ₄ = 3.0222 r ₅ = 12.88838 (aspheric surface) d ₅ = 1.2000 n ₃ = 1.58423 ν ₃ = 30.49 r ₆ = 18.5909 d ₆ = D ₁ (variable) r ₇ = ∞ (aperture) d ₇ = 1.0000 r ₈ = 26.1792 (aspherical surface) d ₈ = 1.2000 n ₄ = 1.52540 ν ₄ = 56.25 r ₉ = 51.3543 d ₉ = 0.1000 r ₁₀ = 4.6180 d ₁₀ = 3.5500 n ₅ = 1.58913 ν ₅ = 61.14 r ₁₁ = -7.4000 d ₁₁ = 1.0000 n ₆ = 1.83400 ν ₆ = 37.16 r ₁₂ = 25.0466 d ₁₂ = 0.6000 r ₁₃ =- _{16.5805 d 13 = 1.0589 n 7 =} 1.52540 ν 7 = 56.25 r 14 = -24.7585 ( aspherical) d ₁₄ = D _{2 (variable) r 15 = 7.9289 d 15 =} 1.8000 n 8 = 1.48749 ν 8 = 70.23 r 16 = 39.2941 d ₁₆ D _{3 (variable) r 17 = ∞ d 17 =} 1.9000 n 9 = 1.54771 ν 9 = 62.84 r 18 = ∞ d 18 = 0.8000 r 19 = ∞ d 19 = 0.7500 n 10 = 1.51633 ν 10 = 64.14 r 20 = ∞ d ₂₀ = 1.15 r ₂₁ = ∞ (image) Aspheric coefficient (second surface) K = 0, A ₂ = 0, A ₄ = −5.6589 × 10 ⁻⁵ A ₆ = −3.9492 × 10 ⁻⁵ , A ₈ = 6.8699 × 10 ^-7 A ₁₀ = 0 (Fifth surface) K = 0, A ₂ = 0, A ₄ = 1.3917 × 10 ^-3 , A ₆ = -7.5570 × 10 ^-5 A ₈ = 7.7507 × 10 ^-6 , A ₁₀ = 0 (eighth _{surface) K = 0, A 2 =} 0, A 4 = -8.7478 × 10 -5, A 6 = 1.2731 × 10 -5 A 8 = 9.8692 × 10 -7, A 10 = 0 ( the 14) K = 0, A ₂ = 0, A ₄ = 3.1309 × 10 ^-3 , A ₆ = 1.0134 × 10 ^-4 A ₈ = 1.5628 × 10 ^-5 , A ₁₀ = 0 When focused on infinity f 4.39 7.36 13.28 D ₁ 13.24697 5.96984 1.40000 D ₂ 2.77930 2.08223 3.25837 D ₃ 3.44990 7.46635 14.81779 Focused on object distance 100 mm f 4.39 7.36 13.28 D ₁ 13.24697 5.96984 1.40000 D ₂ 2.51945 1. 50000 1.50000 D ₃ 3.70974 8.04858 16.57617 f2 = 11.72, f3 = 20.0, | fW / f2R | = 0.044, f3 / fT = 1.51 | β23T | = 1.70, 1 / β2T = 0.00, DW / fW = (4.82) f2 / fW = (2.67), R2b / f2 = 0.39, Δ2 / Δ3 = 1.04 | f1 / f11 | = 0.117, | f1 / f13 | = 0.117 | fW / f21 | = 0.044, | fW / f24 | = 0.044 | fW / fp | = 0.066 (first group object side lens), 0.066 (first group image side lens), 0.044 (second group object side lens), 0.044 (second group image side lens)

[0067] However r _1, r _2, ··· the radius of curvature of each lens surface, d _1, d _2, ··· wall thickness and spacing of each lens, n _1, n _2, ··· is Refractive index of each lens, ν ₁ , ν
₂ , ... are Abbe numbers of each lens. Note that f, r ₁ , r
_{2, ···, d 1, d} 2 ··· units of length, such as is in mm.

Embodiment 1 of the zoom lens according to the present invention is shown in FIG.
And a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power, from the wide-angle end to the telephoto end. At the time of zooming, all the lens groups G1, G2, G3 and the aperture stop S move on the optical axis as shown. The third lens group G3 moves so that the distance from the image plane I increases.

The first lens group G1 comprises three lenses. That is, in order from the object side, a positive lens, a negative lens, and a single lens having a low refractive power are formed, and the object-side surface (r ₅ ) of the single lens having a low refractive power is an aspheric surface. The second lens group G2 includes a single lens, a cemented lens, and a single lens. The single lens closest to the image is a lens having a shape close to a plane and having a low refractive power, and the image-side surface (r ₁₄ ) of this lens is It is an aspheric surface. The third lens group is a biconvex lens.

In the zoom lens of the first embodiment, as described above, the most image side lens of the first lens group G1 and the most image side lens of the second lens group G2 are aspherical lenses, and the refractive power of these lenses And the thickness of the lens was reduced to reduce the retracted thickness.

The second embodiment has a configuration as shown in FIG. 2, and includes a first negative lens unit G1, a second positive lens unit G2, and a third positive lens unit G3.

The second embodiment has a configuration similar to that of the first embodiment, but differs from the first embodiment in that the most object-side surface (r ₈ ) of the second lens unit G2 is also aspherical.

In the zoom lens according to the second embodiment, the image-side lens of the first lens group G1 and the image-side lens of the second lens group G2 are aspherical lenses, and the object-side lens of the second lens group G2. Were made aspherical lenses, the refractive power of these lenses was reduced, and the optical system material was made of plastic. Further, the distance between the third lens group G3 and the image plane I is increased so that the quick return mirror can be disposed.

The third embodiment is a zoom lens as shown in FIG. 3 and has a similar configuration to the first and second embodiments.

In the third embodiment, the image-side surface (r ₂ ) of the lens closest to the object in the first lens group G1 and the second lens group G2
The surface closest to the object (r ₈ ) and the surface closest to the object of the lens closest to the image in the second lens group (r ₁₃ ) are aspherical surfaces.
That is, the lens closest to the object side in the first lens group G1, the second lens
The lens closest to the object and the lens closest to the image in the lens group G2 are aspherical lenses, and these are plastic lenses.

Embodiment 4 is similar to Embodiments 1 and 2 as shown in FIG.
This is a configuration similar to the zoom lens of No. 3.

In the fourth embodiment, the first lens group G1 comprises a positive lens, a negative lens and a positive lens, and the second lens group G2
Comprises a cemented lens of a biconvex lens and a biconcave lens and a negative meniscus lens, and the third lens group G3 comprises one positive lens. That is, the configuration of the second lens group G2 is the same as that of the first to third embodiments.
3 is different.

In the fourth embodiment, the surface (r ₂ ), which is the image-side surface of the lens closest to the object in the first lens group G1, and the image-side surface of the lens closest to the object in the second lens group G2 (R ₈ )
And the object-side surface (r ₁₁ ) of the lens closest to the image in the second lens group G2 is an aspheric surface. As described above, in the fourth embodiment, the plastic aspherical lens closest to the object side in the second lens group G2 in the third embodiment is eliminated, and the aberration correction is performed by making the object side surface of the cemented lens aspherical. As a result, the second lens group G2 was made thinner, and the collapsed thickness was made thinner.

The fifth embodiment differs from the other first to fourth embodiments in that the first lens group G1 comprises two lenses, a negative lens and a positive lens, as shown in FIG.

In the fifth embodiment, the first lens group G1
The object-side surface of the object-side lens (r ₁ ) And the second lens group
The image-side surface (r) of the most image-side lens of G2₁₂) Is aspheric
is there.

In the fifth embodiment, the first lens group G1 is made up of two lenses, a negative lens and a positive lens, so that the first lens group G1 is made thin to reduce the collapsed thickness.

The sixth embodiment is a zoom lens having the same configuration as that of the first embodiment and the like, having the configuration shown in FIG.

[0083] Example 6 is the most image side surface of the object side of the lens (r ₂₎ and the object side surface of the most image side of the lens and (r _5), the second lens group of the first lens group G1 The object-side surface (r ₈ ) of the lens closest to the object and the image-side surface (r ₁₄ ) of the lens closest to the image in G2 are aspherical.

The zoom lens of the sixth embodiment has an inexpensive lens system by arranging plastic aspheric lenses on the object side and the image side of the first lens group G1 and on the object side and the image side of the second lens group G2. .

The aberrations of the zoom lens of Embodiment 1 at the wide-angle end, the intermediate focal length, and the telephoto end when focused on infinity are:
As shown in FIG. 7, FIG. 8, and FIG. 9, respectively, the aberration is satisfactorily corrected.

The aberrations of the zoom lenses of the second to sixth embodiments are also corrected well as in the first embodiment.

Also, in FIGS. 1 to 6, S denotes a brightness stop, F1 and F2 denote filters such as an infrared cut filter and a low-pass filter, and I denotes an image plane.

The shape of the aspherical surface used in each embodiment is represented by the following equation, where the direction of light on the optical axis is the x-axis and the direction orthogonal to the optical axis is the y-axis. .

X = (y ² / r) / [1+ ｛1- (1+
^{K) (y / r) 2} } 1/2] + A 2 y 2 + A 4 y 4 + A 6 y 6 + A
₈ y ⁸ + ... where r is the radius of curvature of the reference sphere, K is the conic coefficient,
A ₂ , A ₄ , A ₆ , A ₈ ,... Are aspherical coefficients.

FIGS. 10 to 12 are conceptual views of a digital camera which is an embodiment of the image pickup apparatus of the present invention. FIG. 10 is a front perspective view showing the appearance of the digital camera 10, FIG. 11 is a rear perspective view of the same, and FIG. The digital camera 10 shown in FIG.
A shutter button including a shooting optical system 11 having a shooting optical path 12, a viewfinder optical system 13 having a viewfinder optical path 14, a shutter button 15, a flash 16, and a liquid crystal display monitor 17, and disposed above the camera 10. When the button 15 is pressed, the photographing is performed in conjunction with the photographing optical system 11, for example, the zoom lens according to the first embodiment of the present invention shown in FIG. An object image formed by the photographing optical system 11 is formed on an imaging surface of an electronic imaging device (CCD) 19 via filters F1 and F2 such as a low-pass filter and an infrared cut filter. This C
The object image received by the CD 19 passes through the processing unit 21,
The image is displayed as an electronic image on a liquid crystal display monitor 17 provided on the back of the camera. Further, a recording unit 22 is connected to the processing unit 21 so that a captured electronic image can be recorded. The recording means 22 may be provided separately from the processing means 21, or may be configured to perform recording and writing electronically using a floppy (registered trademark) disk, a memory card, an MO, or the like. Further, instead of the CCD 19, a silver halide camera in which a silver halide film is arranged may be configured.

Further, a finder objective optical system 23 is arranged on the finder optical path 14. The object image formed by the finder objective optical system 23 is
It is formed on a field frame 27 of a Porro prism 25 which is an image erecting member. Behind the porro prism 25, an eyepiece optical system 29 that guides the erect image into the observer's eyeball E is disposed. Note that cover members 20 are arranged on the incident side of the photographing optical system 11 and the objective optical system 23 for the viewfinder, and on the exit side of the eyepiece optical system 29, respectively.

The digital camera 10 configured as described above
Since the photographing optical system 11 is a zoom lens having a wide angle of view, a high zoom ratio, good aberration, good brightness, and a large back focus on which filters and the like can be arranged, high performance and low cost can be realized. That is, as described above, the photographing optical system shown in FIG. 12 is the zoom lens according to the first embodiment of the present invention, and includes the first lens group G1, the second lens group G2, and the third lens group G3. S is the aperture stop, F1, F2
Is a filter.

FIGS. 10 to 12 show a digital camera as an example of the image pickup apparatus of the present invention. As another example, there is a video camera equipped with the zoom lens of the present invention. Further, the imaging device of the present invention can be used as an image input unit attached to an information processing device such as a personal computer or an image input unit attached to a telephone, particularly a communication device such as a mobile phone.

As described above, the zoom lens according to the present invention is a zoom lens that can achieve the object of the present invention, in addition to those described in the claims and those described in the following items.

(1) In the lens system according to claim 1 or 2, the second lens group includes, in order from the object side, a single lens, a cemented lens, and a single lens;
A zoom lens, wherein the single lens closest to the object has an aspherical surface.

(2) The lens system described in (1) above, wherein the cemented lens in the second group has a meniscus shape with the convex surface facing the object side, and satisfies the following condition. Zoom lens. | FW / f21 | <0.1 where f21 is the focal length of the single lens closest to the object side in the second group.

(3) In the lens system according to claim 1 or 2, the second lens group is composed of a cemented lens and a single lens in order from the object side, and A zoom lens having an aspheric surface.

(4) In the lens system according to claim 1 or 2, the first lens group includes, in order from the object side, a single lens having an aspheric surface, a single lens having a negative refractive power, and an object. A zoom lens comprising a positive meniscus lens having a convex surface facing the side, and satisfying the following conditional expression. | F1 / f11 | <0.2 where f11 is the focal length of the lens closest to the object in the first lens group, and f1 is the focal length of the first lens group.

(5) In the lens system according to claim 1 or 2, the first lens group includes, in order from the object side, a biconvex single lens and a negative concave surface having a strong concave surface facing the image side. A zoom lens comprising a single lens having a refractive power and a single lens having an aspheric surface, wherein the zoom lens satisfies the following conditional expression. | F1 / f13 | <0.2 where f13 is the focal length of the lens closest to the image in the first unit.

(6) In the lens system according to claim 1 or 2, the first lens group includes a single lens having an aspheric surface and a single lens having a negative refractive power with a strong concave surface facing the image side. A zoom lens comprising a lens and a single lens having an aspheric surface, wherein the zoom lens satisfies the following conditional expression. | F1 / f11 | <0.2 | f1 / f13 | <0.2

(7) The lens system according to claim 1 or 2, wherein the first lens unit has an aspherical surface, a lens having a negative refractive power having a strong concave surface facing the image side, and a lens having a negative refractive power. A zoom lens comprising a meniscus lens having a convex surface facing the lens.

(8) The above (2), (4), (5),
A zoom lens according to the item (6) or (7), wherein the following condition (9) is satisfied. (9) | fW / fp | <0.05 where fp is the focal length of the plastic lens, and fW is the focal length of the entire system at the wide-angle end.

(9) A zoom lens according to claim 1 or 2, wherein the third lens group is moved toward the object side to focus on a short-distance object.

(10) Claim 1 or 2 of the claims
A zoom lens, wherein the lens closest to the image in the second lens group has an aspherical surface.

[0105]

According to the present invention, it is possible to realize a zoom lens having a thin collapsible thickness, excellent storability, high magnification and high imaging performance even in rear focus. The provision of the zoom lens of the present invention makes it possible to reduce the thickness of a video camera or a digital camera.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zoom lens according to a first embodiment of the present invention;

FIG. 2 is a sectional view of a zoom lens according to a second embodiment of the present invention;

FIG. 3 is a sectional view of a zoom lens according to a third embodiment of the present invention;

FIG. 4 is a sectional view of a zoom lens according to a fourth embodiment of the present invention;

FIG. 5 is a sectional view of a zoom lens according to a fifth embodiment of the present invention;

FIG. 6 is a sectional view of a zoom lens according to a sixth embodiment of the present invention;

FIG. 7 is an aberration diagram at a wide-angle end when focusing on infinity according to the first embodiment.

FIG. 8 is an aberration diagram at an intermediate focal length when focusing on infinity according to the first embodiment.

FIG. 9 is an aberration diagram at a telephoto end when focusing on infinity according to the first embodiment.

FIG. 10 is a front perspective view of the imaging device of the present invention.

FIG. 11 is a rear perspective view of the imaging device.

FIG. 12 is a cross-sectional view of the imaging device.

Continued on the front page F-term (reference) 2H054 AA01 2H087 KA03 MA14 PA06 PA07 PA18 PB07 PB08 QA02 QA03 QA06 QA07 QA12 QA14 QA19 QA21 QA22 QA25 QA32 QA34 QA41 QA42 QA46 RA05 RA12 RA13 SB16 SA14 SA16 SA16 SA16 5C022 AB43 AB66 AC32 AC42 AC52 AC54 AC78

Claims (3)

[Claims] 1. A first lens having a negative refractive power in order from the object side.
A lens group, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the third lens group and the image plane Is a lens system that moves the third lens group so that the distance between the lenses becomes large. The third lens group is composed of one positive lens.
A zoom lens that satisfies (2), (3) and (4). (1) | fW / f2R | <0.1 (2) 0.89 <f3 / fT <2.8 (3) 1.1 <| β23T | <2 (4) 1 / β2T <0.25 f2R is the focal length of the lens closest to the image in the second lens group, f3 is the focal length of the third lens group, β23T is the combined magnification of the second and third lens groups at the telephoto end,
β2T is the magnification of the second lens group at the telephoto end, fW is the focal length of the entire zoom lens system at the wide-angle end, and fT is the focal length of the entire zoom lens system at the telephoto end. 2. Conditions (1), (2), (3) and (4) are replaced by the following conditions (1-1), (2-1), (3-1),
The zoom lens according to claim 1, which satisfies (4-1). (1-1) | fW / f2R | <0.05 (2-1) 1.1 <f3 / fT <2 (3-1) 1.2 <| β23T | <1.8 (4-1) 1 /Β2T<0.1 3. A zoom lens comprising a zoom lens and an image pickup means, wherein the zoom lens has a negative refractive power in order from the object side.
A lens group, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the third lens group and the image plane Is a lens system that moves the third lens group so that the distance between the lenses becomes large. The third lens group is composed of one positive lens.
An imaging device that satisfies (2), (3), and (4). (1) | fW / f2R | <0.1 (2) 0.89 <f3 / fT <2.8 (3) 1.1 <| β23T | <2 (4) 1 / β2T <0.25 f2R is the focal length of the lens closest to the image in the second lens group, f3 is the focal length of the third lens group, β23T is the magnification of the combination of the second and third lens groups at the telephoto end, and β2T is the focal length at the telephoto end. Magnification of the second lens group, fW
Is the focal length of the entire zoom lens system at the wide-angle end, and fT is the focal length of the entire zoom lens system at the telephoto end.