JP4576818B2 - Zoom lens - Google Patents

Description

  The present invention relates to a zoom lens, and more particularly to a zoom lens suitable for a video camera or a digital still camera using a solid-state imaging device.

  In recent years, digital still cameras and video cameras that record subject images using solid-state imaging devices such as CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) are generally equipped with zoom lenses as photographing lenses. . The zoom lens has an advantage that the user can select an arbitrary focal length and perform photographing with a high degree of freedom. Here, the longest focal length of the lens is the telephoto end state, and the shortest focal length of the lens is the wide-angle end state.

  As such a zoom lens is generally mounted as a photographic lens in the above-described camera, a zoom ratio (a value obtained by dividing the focal length in the telephoto end state by the focal length in the wide-angle end state). A lens that increases the focal length in the telephoto end state and has a large focal length has become widespread. However, as the focal length in the telephoto end state increases, the overall length of the lens system also increases, resulting in inconvenience in the portability of the camera. Therefore, when the camera is carried, the portability is improved by moving the lens group constituting the zoom lens so that the distance between the lens groups is minimized and storing it in the camera body.

  In digital still cameras, portability is particularly important. Therefore, in order to reduce the size and weight of the camera body, the zoom lens as a photographing lens is also reduced in size and weight.

Conventionally, a zoom lens having the following configuration has been proposed (see, for example, Patent Document 1). In order from the object side, a so-called negative positive / positive three-group type including a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. This is a zoom lens. In this zoom lens, when the focal length state changes from the wide-angle end state to the telephoto end state, the first lens group moves nonlinearly so that the image plane position is constant, and the second lens group and the third lens group Are configured to move independently from the image plane side to the object side so that the distance between the lens groups becomes small.
Thus, the total length of the lens system can be shortened by increasing the movable lens group even if the zoom ratio is increased.
JP-A-5-173073

  In order to improve the portability of the camera, the thickness of the camera body when the lens is retracted by increasing the number of partial barrels constituting the zoom lens barrel and reducing the length of each partial barrel. It is conceivable to reduce. In this case, however, the diameter of the zoom lens barrel increases. For this reason, there is a problem in that the height and width of the camera body are increased, resulting in inconvenience in the portability of the camera.

  In order to avoid the inconvenience of portability, it is conceivable to shorten the overall length of the lens system. Methods for shortening the overall length of the lens system include, for example, a method of increasing the refractive power of each lens group and a method of increasing the number of movable lens groups. However, the former method has a problem that the stop accuracy required for each lens group becomes very high, or that a great performance deterioration is caused by a minute eccentricity. In addition, the latter method increases the number of lenses, which is contrary to the intention of the present invention to realize a small and lightweight zoom lens with a small number of lenses.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a small and lightweight high-performance zoom lens with a small number of lenses.

In order to solve the above problems, the present invention
In order from the object side, a first lens group having a negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power,
When the focal length state changes from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes. A zoom lens that increases and performs focusing by the third lens group,
The first lens group includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, at least one of which is an aspheric surface, and a positive lens having a convex surface facing the object side,
The second lens group includes, in order from the object side, an aperture stop, a positive lens having a convex surface facing the object side where at least one lens surface is an aspheric surface, a positive lens having a convex surface facing the object side, and an image surface side It consists of a cemented lens with a negative lens facing the concave surface and a positive lens with a biconvex shape,
The third lens group is composed of a single positive lens,
Provided is a zoom lens that satisfies the following conditional expression .
0 . 15 <D12 / (− f1) <0.50
0.35 <f2 / f3 ≦ 0.47346
However,
f1: Focal length of the first lens group D12: Air interval on the optical axis between the negative meniscus lens and the positive lens in the first lens group
f2: focal length of the second lens group
f3: focal length of the third lens group
The present invention also provides:
In order from the object side, the first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power,
When the focal length state changes from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes. A zoom lens that increases and performs focusing by the third lens group,
The first lens group includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side and at least one lens surface being an aspheric surface, and a positive lens having a convex surface facing the object side,
The second lens group includes, in order from the object side, an aperture stop, a positive lens having a convex surface facing the object side where at least one lens surface is an aspheric surface, a positive lens having a convex surface facing the object side, and an image surface side It consists of a cemented lens with a negative lens facing the concave surface and a positive lens with a biconvex shape,
The third lens group is composed of a single positive lens,
Provided is a zoom lens that satisfies the following conditional expression.
0.15 <D12 / (− f1) ≦ 0.18696
0.35 <f2 / f3 ≦ 0.47346
However,
f1: focal length of the first lens group
D12: an air space on the optical axis between the negative meniscus lens and the positive lens in the first lens group.
f2: focal length of the second lens group
f3: focal length of the third lens group

  According to the present invention, a small and lightweight high-performance zoom lens can be provided with a small number of lenses.

First, the configuration of the zoom lens according to the present invention will be described.
The zoom lens according to the present invention includes, 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 third lens group having a positive refractive power.
When the focal length state changes from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group increases. As described above, the first lens group and the second lens group move, and the third lens group performs focusing.

In the zoom lens according to the present invention, the first lens group includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side and at least one lens surface being an aspheric surface, and a positive meniscus having the convex surface facing the object side. It consists of a lens.
The second lens group includes, in order from the object side, an aperture stop, a positive lens having a convex surface facing the object side where at least one lens surface is aspheric, a positive lens and an image surface having a convex surface facing the object side It is composed of a cemented lens with a negative lens having a concave surface on the side, and a biconvex positive lens.
The third lens group is composed of a single positive lens.
Furthermore, the zoom lens according to the present invention is miniaturized by configuring each lens group as follows.

Next, the function of each lens group will be described.
The first lens group corrects fluctuations in image plane position due to zooming.
The second lens group is for enlarging the image of the subject, and the magnification ratio is increased by changing the distance between the first lens group and the second lens group from the wide-angle end state toward the telephoto end state. Change the focal length.
The third lens group is fixed during zooming, and focuses the subject image formed by the first lens group and the second lens group and adjusts the exit pupil position.

  Here, in the above-described camera using a solid-state imaging device such as a CCD, a microlens array is generally disposed immediately before the solid-state imaging device in order to increase the light receiving efficiency. For this reason, the zoom lens used in such a camera needs to keep the exit pupil position away from the element surface.

Therefore, the zoom lens according to the present invention is configured to satisfy the following conditional expression (1) under the above-described configuration.
(1) 0.15 <D12 / (− f1) <0.50
However,
f1: Focal length of the first lens group D12: Air interval on the optical axis between the negative meniscus lens and the positive lens in the first lens group

The conditional expression (1) is a conditional expression for defining an appropriate range of the air space on the optical axis between the negative meniscus lens and the positive lens in the first lens group.
When the upper limit of conditional expression (1) is exceeded, off-axis aberrations can be corrected satisfactorily. However, since the entire first lens group becomes thick, the entire lens system becomes large. Therefore, this case is contrary to the intention of the present invention.
On the other hand, if the lower limit value of conditional expression (1) is not reached, it is advantageous for downsizing of the entire lens system, but it is not preferable because off-axis aberrations deteriorate. In addition, the outer peripheral portion of the lens surface on the image side of the negative meniscus lens and the outer peripheral portion of the lens surface on the object side of the positive lens are too close. Therefore, since the light rays are irregularly reflected in the part that is too close, harmful light is generated.
In the zoom lens according to the present invention, it is desirable that the lower limit value of the conditional expression (1) is 0.16. In the zoom lens of the present invention, it is desirable that the upper limit value of conditional expression (1) is 0.30, more preferably 0.20.

According to a preferred aspect of the present invention, it is desirable that the zoom lens of the present invention satisfies the following conditional expression (2).
(2) 0.35 <f2 / f3 <0.55
However,
f2: focal length of the second lens group f3: focal length of the third lens group

The conditional expression (2) is a conditional expression for defining the refractive power distribution between the second lens group and the third lens group.
If the upper limit value of conditional expression (2) is exceeded, the focal length of the second lens group becomes large, and axial aberration can be corrected well. However, since the focal length of the first lens group is also increased, the lens system is increased in size. Therefore, in this case, the lens system cannot be downsized.
On the other hand, if the lower limit of conditional expression (2) is not reached, the refractive power of the second lens group will increase, and the on-axis aberration will deteriorate. In addition, the refractive power of the third lens group decreases, and the amount of movement of the third lens group during focusing increases. For this reason, it becomes impossible to achieve space saving when the lens system is stored in the camera body.

According to a preferred aspect of the present invention, it is desirable that the zoom lens of the present invention satisfies the following conditional expression (3).
(3) 0.135 <β3 × Y ₀ /fw<0.360
However,
β3: Image plane movement coefficient of the third lens group (ratio of the movement amount of the image plane to the movement amount of the third lens group)
Y ₀ : Maximum image height fw: Focal length of the entire zoom lens in the wide-angle end state

Conditional expression (3) defines the image plane movement coefficient of the third lens group (ratio of the movement amount of the image plane to the movement amount of the third lens group), and minimizes the change in performance from infinity to the shortest shooting distance. This is a conditional expression for limiting to the limit.
If the upper limit of conditional expression (3) is exceeded, the refractive power of the third lens group will become small. This is advantageous in correcting various aberrations, but is not preferable because the amount of movement of the third lens group during focusing increases.
On the other hand, if the lower limit value of conditional expression (3) is not reached, the refractive power of the third lens group becomes large. For this reason, the aberration generated by the third lens group alone becomes too large, and the performance at the shortest shooting distance is deteriorated.
In the zoom lens of the present invention, it is desirable that the upper limit value of conditional expression (3) is 0.250.

In order to further reduce the size of the zoom lens according to the present invention, the first lens unit includes a negative meniscus lens having a negative refractive power on the object side and a positive surface having a convex surface on the object side as described above. It consists of a lens.
For example, in the zoom lens disclosed in Patent Document 1, the first lens group is composed of three lenses of a negative lens, a negative lens, and a positive lens in order from the object side. It was unsuitable for shortening. On the other hand, since the zoom lens according to the present invention is composed of two lenses of a negative lens and a positive lens in order from the object side, the overall length of the lens system can be effectively shortened.

Further, according to a preferred aspect of the present invention, it is desirable that the zoom lens of the present invention satisfies the following conditional expressions (4) and (5) in order to further improve the performance.
(4) nd1> 1.75 and νd1> 44.0
(5) nd2> 1.78 and νd2 <25.0
However,
nd1: Refractive index for the d-line (λ = 587.6 nm) of the negative meniscus lens material in the first lens group νd1: Abbe number for the d-line (λ = 587.6 nm) of the negative meniscus lens material in the first lens group nd2: Refractive index for the positive lens material d-line (λ = 587.6 nm) in the first lens group νd2: Abbe number for the positive lens quality d-line (λ = 587.6 nm) in the first lens group

Conditional expression (4) and conditional expression (5) are conditional expressions for appropriately defining the optical material constituting the negative meniscus lens and the positive lens in the first lens group.
When the conditional expression (4) is not satisfied, it is difficult to correct the lateral chromatic aberration. Further, the Petzval sum is reduced, and field curvature occurs in the wide-angle end state.
Further, when the conditional expression (5) is not satisfied, it is difficult to correct the lateral chromatic aberration, and further off-axis aberrations are deteriorated, which is not preferable.

Further, according to a preferred aspect of the present invention, in order to further improve the performance of the zoom lens according to the present invention, it is desirable that the most object side positive lens in the second lens group has both aspherical lens surfaces. . In general, by introducing an aspherical surface to a lens group close to the aperture stop, it is possible to satisfactorily correct axial aberrations.
According to a preferred aspect of the present invention, in the zoom lens of the present invention, it is desirable that the position of the third lens group is fixed when the focal length state changes from the wide-angle end state to the telephoto end state.

Further, according to a preferred aspect of the present invention, the zoom lens of the present invention is designed to move the third lens group toward the object side from a long distance to minimize the change in performance during short-distance shooting. It is desirable to perform focusing on the distance and further satisfy the following conditional expressions (6) and (7).
(6) 0.2 <(rR + rF) / (rR−rF) ≦ 1.0
(7) nd3 <1.50 and νd3> 80.0
However,
rF: paraxial radius of curvature of the object side lens surface of the positive lens in the third lens group rR: paraxial radius of curvature of the image side lens surface of the positive lens in the third lens group nd3: material of the positive lens in the third lens group Refractive index νd3 with respect to d-line (λ = 587.6 nm): Abbe number with respect to d-line (λ = 587.6 nm) of the material of the positive lens in the third lens group

The conditional expression (6) is a conditional expression for satisfactorily correcting monochromatic aberration that occurs independently in the third lens group.
If the upper limit value of conditional expression (6) is exceeded, off-axis aberrations that occur independently in the third lens group cannot be corrected. Moreover, since distortion also increases, it is not preferable.
On the other hand, if the lower limit value of conditional expression (6) is not reached, off-axis aberrations that occur independently in the third lens group become too large, and the performance at the shortest shooting distance deteriorates.

The conditional expression (7) is a conditional expression for minimizing the deterioration of chromatic aberration.
When the conditional expression (7) is not satisfied, fluctuations in axial chromatic aberration and lateral chromatic aberration associated with focusing become large, and photographing performance at a short distance is deteriorated.

  In addition, the zoom lens according to the present invention includes a blur detection system that detects a blur of the lens system and a driving unit in order to prevent a shooting failure due to an image blur caused by a camera shake or the like that is likely to occur in a high-magnification zoom lens. By combining with a lens system, it can function as a so-called vibration-proof optical system. In this anti-vibration optical system, first, an image blur (fluctuation in image plane position) caused by the blur of the lens system is detected by the blur detection system. Then, the whole or a part of one of the lens groups constituting the lens system is driven by the driving means as a shift lens group. Image blur can be corrected by shifting the image by driving the shift lens group.

In the zoom lens according to each embodiment of the present invention described below, an aspheric lens is arranged in the first lens group. This makes it possible to satisfactorily correct off-axis aberration fluctuations that occur when the focal length changes from the wide-angle end state to the telephoto end state.
In the zoom lens according to each embodiment of the present invention described below, an aspherical lens is also disposed in the second lens group. Thereby, it is possible to satisfactorily correct the fluctuation of the axial aberration that occurs independently in the second lens group.

  In the zoom lens according to each embodiment of the present invention described below, the lens system is composed of three movable lens groups. However, the zoom lens of the present invention is not limited to this configuration, and other lens groups can be added between the lens groups constituting the lens system or adjacent to the image side or object side of the lens system.

Hereinafter, zoom lenses according to embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows the refractive power distribution of the zoom lens according to each embodiment of the present invention and the movement trajectory of each lens group when the focal length state changes from the wide-angle end state (W) to the telephoto end state (T). FIG.
As shown in FIG. 1, the zoom lens according to each embodiment of the present invention includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, The lens unit includes a third lens group G3 having a positive refractive power and a filter group FL including a low-pass filter and an infrared cut filter.
In the zoom lens according to each embodiment, the distance between the first lens group G1 and the second lens group G2 changes when the focal length state changes from the wide-angle end state to the telephoto end state (during zooming). The distance between the second lens group G2 and the third lens group G3 is increased, and the third lens group is fixed. Further, focusing is performed by the third lens group G3.

Here, the aspherical surface of the zoom lens according to each embodiment has a height in the direction perpendicular to the optical axis as y, and a distance along the optical axis from the tangential plane of the apex of the aspherical surface at the height y to the aspherical surface ( Sag amount) is S (y), the radius of curvature (vertex curvature radius) of the reference sphere is R, the conic constant is κ, and the fourth, sixth, eighth and tenth-order aspheric coefficients are C4, C6, C8 and C10, respectively. It is expressed by the following aspheric expression.
S (y) = (y ² / R) / {1+ (1−κ × y ² / R ² ) ^1/2 }
+ C4 × y ⁴ + C6 × y ⁶ + C8 × y ⁸ + C10 × y ¹⁰
In each embodiment, the secondary aspherical coefficient C2 is 0, and the radius of curvature R and the paraxial radius of curvature r of the reference spherical surface are the same. Further, in the (lens data) of each example, the aspherical surface is marked with * on the left side of the surface number.

(First embodiment)
FIG. 2 is a diagram showing a configuration of the zoom lens according to the first embodiment of the present invention.
As shown in FIG. 2, in the zoom lens according to the present embodiment, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a convex surface facing the object side, and a positive meniscus having a convex surface facing the object side. It comprises a lens L12.
The second lens group G2, in order from the object side, is a negative lens composed of an aperture stop S, a biconvex positive lens L21, a biconvex positive lens L22, and a biconcave negative lens L23. And a biconvex positive lens L24.

The third lens group G3 is composed of a single biconvex positive lens L31.
Further, the filter group FL includes a low-pass filter, an infrared cut filter, and the like.
Further, as described above, the aperture stop S is disposed closer to the object side than the lens closest to the object side of the second lens group G2, and the second lens group G2 is used during zooming from the wide-angle end state to the telephoto end state. And move together.

Table 1 below lists values of specifications of the zoom lens according to the first example of the present invention.
In (Overall Specifications), f is the focal length, F.NO is the F number, and 2ω is the angle of view.
In (lens data), the surface number indicates the order of the lens surfaces from the object side along the direction in which the light beam travels, and the refractive index and the Abbe number indicate values for the d-line (λ = 587.6 nm), respectively. . Further, the radius of curvature of 0.0000 indicates a plane, and the refractive index of air of 1.0000 is omitted. Bf indicates back focus.

Here, in general, “mm” is used as a unit of the focal length f, the radius of curvature r, and other lengths listed in all the specification values of the following embodiments. However, since the optical system can obtain the same optical performance even when proportionally enlarged or reduced, the unit is not limited to “mm”.
In addition, the same code | symbol as a present Example is used also in the specification value of all the following Examples.

[Table 1]
(Overall specifications)
Wide-angle end state Intermediate focal length state Telephoto end state
f = 8.00 to 13.00 to 22.80
F.NO = 2.93 to 3.71 to 5.24
2ω = 64.42 to 40.31 to 23.27

(Lens data)
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 255.9490 1.30 1.77377 47.18
* 2 6.8464 2.90
3 12.2345 1.50 1.84666 23.78
4 25.1050 (d4)
5 0.0000 1.00 (Aperture stop S)
* 6 7.9062 2.00 1.69350 53.22
* 7 -190.2272 0.10
8 10.9070 2.30 1.80610 40.94
9 -15.8830 0.80 1.79504 28.55
10 5.0295 0.80
11 86.7490 1.15 1.75500 52.32
12 -36.7195 (d12)
13 20.3334 1.85 1.49700 81.61
14 -45.0032 (d14)
15 0.0000 2.18 1.54437 70.51
16 0.0000 0.50
17 0.0000 0.50 1.51633 64.14
18 0.0000 (Bf)

(Aspheric data)
The second lens surface, the sixth lens surface, and the seventh lens surface are aspheric surfaces, and the respective aspheric data (values of the radius of curvature R of the reference sphere, the conic constant κ, and the aspheric constants C4 to C10) are as follows. To
[Second side]
R κ C4 C6
6.8464 +0.3373 + 5.8876 × 10 ^-6 2.8432 × 10 ^-6
C8 C10
-1.4098 × 10 ^-7 2.5952 × 10 ^-9
[Sixth page]
R κ C4 C6
7.9062 +0.1369 -2.3439 × 10 ^-5 9.7848 × 10 ^-6
C8 C10
-3.3829 × 10 ^-7 -8.2323 × 10 ^-9
[Seventh side]
R κ C4 C6
-190.2272 -9.0000 -3.8573 × 10 ^-5 1.7911 × 10 ^-5
C8 C10
-1.1897 × 10 ^-6 1.7262 × 10 ^-8

(Variable interval data)
During zooming, the on-axis air distance d4 between the first lens group G1 and the second lens group G2 and the on-axis air distance d12 between the second lens group G2 and the third lens group G3 change, and the third lens group. The axial air distance d14 between G3 and the filter group FL does not change. Therefore, values in the wide-angle end state, the intermediate focal length state, and the telephoto end state at these variable intervals are described below.

Wide-angle end state Intermediate focal length state Telephoto end state
f 7.9953 13.0021 22.8028
d4 15.4439 7.2724 1.6758
d12 8.3544 13.5794 23.8144
d14 1.2308 1.2308 1.2308

(Values for conditional expressions)
f1 = -15.73160
f2 = 13.30033
f3 = 28.44741
fw = 7.99527
Y ₀ = 4.70000
β3 = 0.34176
D12 = 2.90000
nd1 = 1.77377
νd1 = 47.18
nd2 = 1.84666
νd2 = 23.78
rF = 20.33343
rR = -45.00317
nd3 = 1.49700
νd3 = 81.61
(1) D12 / (− f1) = 0.18434
(2) f2 / f3 = 0.46754
(3) β3 × Y ₀ /fw=0.20090
(4) nd1 = 1.77377
νd1 = 47.18
(5) nd2 = 1.84666
νd2 = 23.78
(6) (rR + rF) / (rR-rF) = 0.37758
(7) nd3 = 1.49700
νd3 = 81.61

  3, 4 and 5 are graphs showing various aberrations with respect to the d-line (λ = 587.6 nm) and the g-line (λ = 435.8 nm) of the zoom lens according to Example 1 of the present invention. FIG. 6 is a diagram illustrating various aberrations when focusing on infinity in a state (f = 8.00 mm), an intermediate focal length state (f = 13.00 mm), and a telephoto end state (f = 22.20 mm).

In each aberration diagram, FNO is an F number, Y is an image height, and A is a half angle of view corresponding to each image height. The spherical aberration diagram shows the F-number value corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum image height, and the coma diagram shows the value of each half field angle.
In the spherical aberration diagram, the solid line indicates spherical aberration, and the broken line indicates sine condition (sine condition). In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane.
In addition, in the various aberration diagrams of each example described below, the same reference numerals as those in this example are used.

  From the various aberration diagrams, it can be seen that the zoom lens according to the present embodiment corrects various aberrations well and has excellent imaging performance in each focal length state from the wide-angle end state to the telephoto end state.

(Second embodiment)
FIG. 6 is a diagram showing a configuration of a zoom lens according to Example 2 of the present invention.
As shown in FIG. 6, in the zoom lens according to the present embodiment, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a convex surface facing the object side, and a positive meniscus having a convex surface facing the object side. It comprises a lens L12.
The second lens group G2, in order from the object side, is a negative lens composed of an aperture stop S, a biconvex positive lens L21, a biconvex positive lens L22, and a biconcave negative lens L23. And a biconvex positive lens L24.

The third lens group G3 is composed of a single biconvex positive lens L31.
Further, the filter group FL includes a low-pass filter, an infrared cut filter, and the like.
Further, as described above, the aperture stop S is disposed closer to the object side than the lens closest to the object side of the second lens group G2, and the second lens group G2 is used during zooming from the wide-angle end state to the telephoto end state. And move together.
Table 2 below provides values of specifications of the zoom lens according to the second example of the present invention.

[Table 2]
(Overall specifications)
Wide-angle end state Intermediate focal length state Telephoto end state
f = 8.00 to 13.00 to 22.80
F.NO = 2.88 to 3.64 to 5.15
2ω = 63.91 to 40.23 to 23.23

(Lens data)
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 333.3333 1.30 1.79668 45.34
* 2 6.6007 2.88
3 12.8507 1.50 1.80809 22.76
4 35.7031 (d4)
5 0.0000 1.00 (Aperture stop S)
* 6 7.2942 2.00 1.58313 59.44
7 -51.3859 0.10
8 11.2293 2.35 1.79952 42.24
9 -15.6250 0.80 1.79504 28.39
10 5.1369 0.78
11 100.4143 1.14 1.80 100 34.96
12 -35.6618 (d12)
13 17.5915 1.69 1.49700 81.61
14 -150.0002 (d14)
15 0.0000 2.76 1.54437 70.51
16 0.0000 0.50
17 0.0000 0.50 1.51633 64.14
18 0.0000 (Bf)

(Aspheric data)
The second lens surface and the sixth lens surface are aspheric surfaces, and the respective aspheric surface data (values of the radius of curvature R, the conic constant κ, and the aspheric constants C4 to C10 of the reference surface) are described below.
[Second side]
R κ C4 C6
6.6007 +1.2718 -4.3902 × 10 ^-4 -7.8327 × 10 ^-6
C8 C10
7.0030 × 10 ^-8 -1.4141 × 10 ^-8
[Sixth page]
R κ C4 C6
7.2942 +0.3913 -1.0998 × 10 ^-4 -1.8908 × 10 ^-6
C8 C10
1.9723 × 10 ^-7 -8.2937 × 10 ^-9

(Variable interval data)
During zooming, the on-axis air distance d4 between the first lens group G1 and the second lens group G2 and the on-axis air distance d12 between the second lens group G2 and the third lens group G3 change, and the third lens group. The axial air distance d14 between G3 and the filter group FL does not change. Therefore, values in the wide-angle end state, the intermediate focal length state, and the telephoto end state at these variable intervals are described below.

Wide-angle end state Intermediate focal length state Telephoto end state
f 7.9980 13.0000 22.7999
d4 15.3585 7.1766 1.5532
d12 8.6034 13.9441 24.4077
d14 1.1493 1.1493 1.1493

(Values for conditional expressions)
f1 = -15.42004
f2 = 13.47566
f3 = 31.78646
fw = 7.99800
Y ₀ = 4.70000
β3 = 0.33008
D12 = 2.88300
nd1 = 1.79668
νd1 = 45.34
nd2 = 1.80809
νd2 = 22.76
rF = 17.59151
rR = -150.00021
nd3 = 1.49700
νd3 = 81.61
(1) D12 / (− f1) = 0.18696
(2) f2 / f3 = 0.42394
(3) β3 × Y ₀ /fw=0.19397
(4) nd1 = 1.79668
νd1 = 45.34
(5) nd2 = 1.80809
νd2 = 2.76
(6) (rR + rF) / (rR-rF) = 0.70097
(7) nd3 = 1.49700
νd3 = 81.61

7, 8 and 9 are graphs showing various aberrations with respect to d-line (λ = 587.6 nm) and g-line (λ = 435.8 nm) of the zoom lens according to Example 2 of the present invention. FIG. 6 is a diagram illustrating various aberrations when focusing on infinity in a state (f = 8.00 mm), an intermediate focal length state (f = 13.00 mm), and a telephoto end state (f = 22.20 mm).
From the various aberration diagrams, it can be seen that the zoom lens according to the present embodiment corrects various aberrations well and has excellent imaging performance in each focal length state from the wide-angle end state to the telephoto end state.

(Third embodiment)
FIG. 10 is a diagram showing a configuration of a zoom lens according to Example 3 of the present invention.
As shown in FIG. 10, in the zoom lens according to the present embodiment, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a convex surface facing the object side, and a positive meniscus having a convex surface facing the object side. It comprises a lens L12.
The second lens group G2 includes, in order from the object side, a biconvex positive lens L21, and a negative cemented lens L22 formed by bonding a biconvex positive lens L22 and a biconcave negative lens L23. And a biconvex positive lens L24.

The third lens group G3 is composed of a single biconvex positive lens L31.
Further, the filter group FL includes a low-pass filter, an infrared cut filter, and the like.
Further, as described above, the aperture stop S is disposed closer to the object side than the lens closest to the object side of the second lens group G2, and the second lens group G2 is used during zooming from the wide-angle end state to the telephoto end state. And move together.
Table 3 below lists values of specifications of the zoom lens according to the third example of the present invention.

[Table 3]
(Overall specifications)
Wide-angle end state Intermediate focal length state Telephoto end state
f = 7.99 to 13.21 to 22.79
F.NO = 2.88 to 3.68 to 5.15
2ω = 64.47 to 39.70 to 23.30

(Lens data)
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 206.9525 1.30 1.79668 45.34
* 2 7.0042 2.95
3 12.4059 1.50 1.80809 22.76
4 27.2136 (d4)
5 0.0000 1.00 (Aperture stop S)
* 6 8.0139 2.00 1.69350 53.22
* 7 -142.8571 0.10
8 10.8539 2.33 1.80610 40.94
9 -15.6429 0.80 1.79504 28.55
10 5.0013 0.78
11 67.8614 1.14 1.75500 52.32
12 -42.9847 (d12)
13 20.7086 1.83 1.49700 81.61
14 -41.8291 (d14)
15 0.0000 2.76 1.54437 70.51
16 0.0000 0.50
17 0.0000 0.50 1.51633 64.14
18 0.0000 (Bf)

(Aspheric data)
The second lens surface, the sixth lens surface, and the seventh lens surface are aspheric surfaces, and the respective aspheric data (values of the radius of curvature R of the reference surface, the conic constant κ, and the aspheric constants C4 to C10) are obtained. Described below.
[Second side]
R κ C4 C6
6.8464 +0.3373 + 5.8876 × 10 ^-6 2.8432 × 10 ^-6
C8 C10
-1.4098 × 10 ^-7 2.5952 × 10 ^-9

[Sixth page]
R κ C4 C6
7.9062 +0.1369 -2.3439 × 10 ^-5 9.7848 × 10 ^-6
C8 C10
-3.3829 × 10 ^-7 -8.2323 × 10 ^-9

[Seventh side]
R κ C4 C6
-190.2272 -9.0000 -3.8573 × 10 ^-5 1.7911 × 10 ^-5
C8 C10
-1.1897 × 10 ^-6 1.7262 × 10 ^-8

(Variable interval data)
During zooming, the on-axis air distance d4 between the first lens group G1 and the second lens group G2 and the on-axis air distance d12 between the second lens group G2 and the third lens group G3 change, and the third lens group. The axial air distance d14 between G3 and the filter group FL does not change. Therefore, values in the wide-angle end state, the intermediate focal length state, and the telephoto end state at these variable intervals are described below.

Wide-angle end state Intermediate focal length state Telephoto end state
f 7.9949 13.2114 22.7861
d4 15.4867 7.0635 1.6388
d12 8.3835 13.8140 23.7815
d14 0.8785 0.8785 0.8785

(Values for conditional expressions)
f1 = -15.77883
f2 = 13.32490
f3 = 28.14385
fw = 7.99494
Y ₀ = 4.70000
β3 = 0.34195
D12 = 2.94500
nd1 = 1.79668
νd1 = 45.34
nd2 = 1.80809
νd2 = 22.76
rF = 20.70861
rR = -41.82913
nd3 = 1.49700
νd3 = 81.61
(1) D12 / (− f1) = 0.18664
(2) f2 / f3 = 0.47346
(3) β3 × Y ₀ /fw=0.21001
(4) nd1 = 1.79668
νd1 = 45.34
(5) nd2 = 1.80809
νd2 = 2.76
(6) (rR + rF) / (rR-rF) = 0.33772
(7) nd3 = 1.49700
νd3 = 81.61

11, 12 and 13 are graphs showing various aberrations with respect to d-line (λ = 587.6 nm) and g-line (λ = 435.8 nm) of the zoom lens according to Example 3 of the present invention. FIG. 10 is a diagram showing various aberrations when focusing on infinity in a state (f = 7.9 mm), an intermediate focal length state (f = 13.21 mm), and a telephoto end state (f = 22.79 mm).
From the various aberration diagrams, it can be seen that the zoom lens according to the present embodiment corrects various aberrations well and has excellent imaging performance in each focal length state from the wide-angle end state to the telephoto end state.

[Fourth embodiment]
FIG. 14 is a diagram showing a configuration of a zoom lens according to Example 4 of the present invention.
As shown in FIG. 14, in the zoom lens according to the present embodiment, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a convex surface facing the object side, and a positive meniscus having a convex surface facing the object side. It comprises a lens L12.
The second lens group G2, in order from the object side, includes a biconvex positive lens L21, a negative cemented lens formed by bonding a biconvex positive lens L22 and a biconcave negative lens L23, and It is composed of a biconvex positive lens L24.

The third lens group G3 includes a single biconvex positive lens L31.
Further, the filter group FL includes a low-pass filter, an infrared cut filter, and the like.
Further, as described above, the aperture stop S is disposed closer to the object side than the lens closest to the object side of the second lens group G2, and the second lens group G2 is used during zooming from the wide-angle end state to the telephoto end state. And move together.
Table 4 below provides values of specifications of the zoom lens according to Example 4 of the present invention.

[Table 4]
(Overall specifications)
Wide-angle end state Intermediate focal length state Telephoto end state
f = 7.99 to 13.00 to 22.80
F.NO = 2.88 to 3.64 to 5.15
2ω = 64.47 to 40.35 to 23.24

(Lens data)
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 293.1907 1.30 1.79668 45.34
* 2 6.9230 2.89
3 12.7118 1.50 1.80809 22.76
4 30.8030 (d4)
5 0.0000 1.00 (Aperture stop S)
* 6 8.0126 2.00 1.69350 53.22
* 7 -142.8571 0.10
8 11.2302 2.23 1.80610 40.94
9 -15.6250 0.80 1.79504 28.39
10 5.1420 0.77
11 81.4284 1.14 1.75500 52.32
12 -38.8813 (d12)
13 16.7732 1.83 1.49700 81.61
14 -96.2608 (d14)
15 0.0000 2.76 1.54437 70.51
16 0.0000 0.50
17 0.0000 0.50 1.51633 64.14
18 0.0000 (Bf)

(Aspheric data)
The second lens surface, the sixth lens surface, and the seventh lens surface are aspheric surfaces, and the respective aspheric data (values of the radius of curvature R of the reference surface, the conic constant κ, and the aspheric constants C4 to C10) are obtained. Described below.
[Second side]
R κ C4 C6
6.9230 +1.2846 -3.6067 × 10 ^-4 -6.1263 × 10 ^-6
C8 C10
2.4817 × 10 ^-8 -8.5788 × 10 ^-9

[Sixth page]
R κ C4 C6
8.0126 +0.2963 -1.0507 × 10 ^-4 1.5144 × 10 ^-5
C8 C10
-1.5264 × 10 ^-6 3.3783 × 10 ^-8

[Seventh side]
R κ C4 C6
-142.8571 10.3603 -7.4392 × 10 ^-5 2.0053 × 10 ^-5
C8 C10
-2.2748 × 10 ^-6 6.2845 × 10 ^-8

(Variable interval data)
During zooming, the on-axis air distance d4 between the first lens group G1 and the second lens group G2 and the on-axis air distance d12 between the second lens group G2 and the third lens group G3 change, and the third lens group. The axial air distance d14 between G3 and the filter group FL does not change. Therefore, values in the wide-angle end state, the intermediate focal length state, and the telephoto end state at these variable intervals are described below.

Wide-angle end state Intermediate focal length state Telephoto end state
f 7.9949 12.9999 22.7999
d4 15.4943 7.2571 1.6014
d12 8.5549 13.9116 24.4002
d14 1.0880 1.0880 1.0880

(Values for conditional expressions)
f1 = -15.77655
f2 = 13.53049
f3 = 28.89616
fw = 7.99494
Y ₀ = 4.70000
β3 = 0.35787
D12 = 2.88975
nd1 = 1.79668
νd1 = 45.34
nd2 = 1.80809
νd2 = 22.76
rF = 16.77325
rR = -96.26082
nd3 = 1.49700
νd3 = 81.61
(1) D12 / (− f1) = 0.18317
(2) f2 / f3 = 0.46825
(3) β3 × Y ₀ /fw=0.21037
(4) nd1 = 1.79668
νd1 = 45.34
(5) nd2 = 1.80809
νd2 = 2.76
(6) (rR + rF) / (rR-rF) = 0.70322
(7) nd3 = 1.49700
νd3 = 81.61

15, 16, and 17 are graphs showing various aberrations with respect to d-line (λ = 587.6 nm) and g-line (λ = 435.8 nm) of the zoom lens according to Example 4 of the present invention. FIG. 6 is a diagram showing various aberrations when focusing on infinity in a state (f = 7.9 mm), an intermediate focal length state (f = 13.00 mm), and a telephoto end state (f = 22.80 mm).
From the various aberration diagrams, it can be seen that the zoom lens according to the present embodiment corrects various aberrations well and has excellent imaging performance in each focal length state from the wide-angle end state to the telephoto end state.

  As described above, according to each of the above embodiments, it is possible to realize a zoom lens having a high zoom ratio with a small number of lenses, excellent lens storage, small size and light weight and excellent imaging performance.

It is a figure which shows the refractive power distribution of the zoom lens which concerns on each Example of this invention, and the movement locus | trajectory of each lens group when a focal distance state changes from a wide-angle end state (W) to a telephoto end state (T). . It is a figure which shows the structure of the zoom lens which concerns on 1st Example of this invention. FIG. 7 is a diagram illustrating various aberrations when the zoom lens according to Example 1 of the present invention is in focus at infinity in the wide-angle end state (f = 8.00 mm). FIG. 6 is a diagram illustrating various aberrations when the zoom lens according to Example 1 of the present invention is focused at infinity in the intermediate focal length state (f = 13.00 mm). FIG. 6 is a diagram illustrating various aberrations when the zoom lens according to Example 1 of the present invention is focused at infinity in the telephoto end state (f = 22.80 mm). It is a figure which shows the structure of the zoom lens which concerns on 2nd Example of this invention. FIG. 10 is a diagram illustrating various aberrations when the zoom lens according to Example 2 of the present invention is in focus at infinity in the wide-angle end state (f = 8.00 mm). FIG. 10 is a diagram illustrating various aberrations when the zoom lens according to Example 2 of the present invention is in focus at infinity in the intermediate focal length state (f = 13.00 mm). FIG. 12 is a diagram illustrating various aberrations at the time of focusing on infinity in the telephoto end state (f = 22.280 mm) of the zoom lens according to Example 2 of the present invention. It is a figure which shows the structure of the zoom lens which concerns on 3rd Example of this invention. FIG. 12 is a diagram illustrating various aberrations when the zoom lens according to Example 3 of the present invention is in focus at infinity in the wide-angle end state (f = 7.9 mm). FIG. 10 is a diagram illustrating various aberrations when the zoom lens according to Example 3 of the present invention is focused at infinity in the intermediate focal length state (f = 13.21 mm). FIG. 10 is a diagram illustrating various aberrations when the zoom lens according to Example 3 of the present invention is in focus at infinity in the telephoto end state (f = 22.79 mm). It is a figure which shows the structure of the zoom lens which concerns on 4th Example of this invention. FIG. 10 is various aberration diagrams at the time of focusing on infinity in the wide-angle end state (f = 7.9mm) of the zoom lens according to Example 4 of the present invention. FIG. 10 is a diagram illustrating various aberrations when the zoom lens according to Example 4 of the present invention is in focus at infinity in the intermediate focal length state (f = 13.00 mm). FIG. 10 is a diagram illustrating various aberrations at the time of focusing on infinity in the telephoto end state (f = 22.280 mm) of the zoom lens according to Example 4 of the present invention.

Explanation of symbols

G1 First lens group G2 Second lens group G3 Third lens group FL Filter group S Aperture stop I Image surface

Claims (6)

In order from the object side, a first lens group having a negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power,
When the focal length state changes from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes. A zoom lens that increases and performs focusing by the third lens group,
The first lens group includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side and at least one lens surface being an aspheric surface, and a positive lens having a convex surface facing the object side,
The second lens group includes, in order from the object side, an aperture stop, a positive lens having a convex surface facing the object side where at least one lens surface is an aspheric surface, a positive lens having a convex surface facing the object side, and an image surface side It consists of a cemented lens with a negative lens facing the concave surface and a positive lens with a biconvex shape,
The third lens group is composed of a single positive lens,
A zoom lens satisfying the following conditional expression:
0.15 <D12 / (− f1) <0.50
0.35 <f2 / f3 ≦ 0.47346
However,
f1: Focal length of the first lens group D12: Air interval on the optical axis between the negative meniscus lens and the positive lens in the first lens group
f2: focal length of the second lens group
f3: focal length of the third lens group In order from the object side, the first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power,
When the focal length state changes from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes. A zoom lens that increases and performs focusing by the third lens group,
The first lens group includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side and at least one lens surface being an aspheric surface, and a positive lens having a convex surface facing the object side,
The second lens group includes, in order from the object side, an aperture stop, a positive lens having a convex surface facing the object side where at least one lens surface is an aspheric surface, a positive lens having a convex surface facing the object side, and an image surface side It consists of a cemented lens with a negative lens facing the concave surface and a positive lens with a biconvex shape,
The third lens group is composed of a single positive lens,
A zoom lens satisfying the following conditional expression:
0.15 <D12 / (− f1) ≦ 0.18696
0.35 <f2 / f3 ≦ 0.47346
However,
f1: focal length of the first lens group
D12: an air space on the optical axis between the negative meniscus lens and the positive lens in the first lens group.
f2: focal length of the second lens group
f3: focal length of the third lens group The zoom lens according to claim 1 or claim 2, characterized by satisfying the following conditional expression.
nd1> 1.75 and νd1> 44.0
nd2> 1.78 and νd2 <25.0
However,
nd1: Refractive index νd1: d-line (λ = 587.6 nm) of the negative meniscus lens material in the first lens group with respect to the d-line (λ = 587.6 nm) of the negative meniscus lens material in the first lens group. ) Abbe number nd2: refractive index νd2 for the positive lens material d-line (λ = 587.6 nm) in the first lens group: d-line (λ = 587) for the positive lens material in the first lens group Abbe number for .6nm) Wherein the positive lens on the most object side in the second lens group, the zoom lens according to any one of claims 1 to 3, characterized in that both sides of the lens surface is aspheric. When changing the focal length state from the wide-angle end to the telephoto end, the zoom lens as claimed in any one of claims 4 to the position of the third lens group is equal to or is a fixed . Focusing from a long distance to a short distance by moving the third lens group to the object side,
The zoom lens according to any one of claims 1 to 5 , further satisfying the following conditional expression.
0.2 <(rR + rF) / (rR−rF) ≦ 1.0
nd3 <1.50 and νd3> 80.0
However,
rF: paraxial radius of curvature of the object side lens surface of the positive lens in the third lens group rR: paraxial radius of curvature of the image side lens surface of the positive lens in the third lens group nd3: third lens group Refractive index νd3 with respect to d-line (λ = 587.6 nm) of the material of the positive lens at: the Abbe number with respect to d-line (λ = 587.6 nm) of the material of the positive lens in the third lens group

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