JPH1048523A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small zoom lens having high variable power ratio and high optical performance over all variable power ranges and shortening the total length of lens in a two groups zoom lens by prescribing the exposition of each lens group, end satisfying prescribed conditions. SOLUTION: This zoom lens comprises, in order from the object side, a first group L1 of a positive refractive power and a second group L2 of a negative refractive power and power variation is performed by changing the interval between both lens groups L1, L2. The first group L1 has four lenses of a first positive lens whose convex surface confronts the object side, a second negative lens, a third lens having an aspherical surface and a fourth positive lens and the second group L2 has two lenses of a first positive lens having an aspherical surface and a second negative meniscus lens whose convex surface confronts the side of image plane. By representing the focal distance of ith group by fi, the focal distances of the whole system at the wide-angle end and the telescopic end by fw, fT and the ith radius of curvature by Ri, the conditions: 3<fT/f1<6, 3<|fT/f2|<9, 2.5<fT/fw<3.6, |R3/R4|<0.35 are satisfied.

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 short back focus comprising two lens groups suitable for a lens shutter camera, a video camera, and the like, and more particularly, to an aberration by appropriately setting a lens configuration of each lens group. The present invention relates to a zoom lens having a high zoom ratio of about 2.5 with a zoom ratio of about 2.5, which performs correction satisfactorily and reduces the overall length of the lens (the distance from the first lens surface to the image plane).

[0002]

2. Description of the Related Art Recently, an aspherical lens has been effectively used as a zoom lens for a lens shutter camera, a video camera, and the like, and the number of lenses has been reduced and the overall length of the lens has been shortened and simplified. Various zoom lenses have been proposed.

[0003] Among them, as a zoom lens for a lens shutter camera that does not require a long back focus,
The first group having a positive refractive power and the second group having a negative refractive power in order from the object side.
Many so-called two-unit zoom lenses that have two lens groups and have a relatively short overall lens length in which the magnification is changed by changing the distance between both lens groups have been proposed.

[0004] The present applicant has previously disclosed Japanese Patent Application Laid-Open No. 56-128911.
JP, JP-A-57-201213, JP-A-57-201213
JP-A-170816, JP-A-60-191216, JP-A-62-56917, and the like, in order from the object side, a first group having a positive refractive power and a second group having a negative refractive power.
A small so-called two-unit zoom lens, which includes one lens unit and changes the magnification by changing the distance between the two lens units, has been proposed.

In this publication, a two-unit zoom lens having high optical performance, which employs positive and negative refractive power arrangements in order from the object side, has a relatively short back focus and shortens the entire length of the lens. Have achieved.

[0006] For example, Japanese Patent Application Laid-Open No. Sho 56-128911
In the publication, the first group is composed of four lenses of positive, negative, positive and positive, and the second group is composed of two lenses of positive and negative, so as to simplify the entire lens system, and a compact zoom. Suggest a lens.

As another two-group zoom lens, Japanese Patent Laid-Open No.
In Japanese Patent Application Laid-Open No. 3-31224, the first unit includes four lenses of positive, negative, positive, and positive, and the second unit includes two positive and negative lenses, and each lens unit uses an aspheric surface. A small zoom lens with improved optical performance has been proposed.

In Japanese Patent Application Laid-Open No. Hei 4-161914, the first group is composed of four lenses of a positive lens, a negative lens, an aspheric lens and a positive lens, and the second group is composed of three lenses. A zoom lens using an aspheric surface for the lens group has been proposed.

Further, JP-A-62-90611, JP-A-62-113120, and JP-A-3-116110
In Japanese Patent Application Laid-Open Publication No. H11-264, a two-unit zoom lens having a zoom ratio of about 1.5, in which the first unit is composed of four lenses of positive, negative, negative, and positive, is proposed.

[0010]

SUMMARY OF THE INVENTION In the above-described two-unit zoom lens including the first lens unit having the positive refractive power and the second lens unit having the negative refractive power, the size of the entire lens system is reduced. In order to obtain a good optical performance over the entire zoom range, having a zoom ratio of about 2.5 times, the lens configuration of each lens group should be appropriately set, and the aspherical surface should have an appropriate shape for each lens group. Is very effective in correcting aberrations.

On the other hand, Japanese Unexamined Patent Publication No. Sho 63-31122 discloses
The zoom lens proposed in Japanese Patent Publication No. 4 has a zoom ratio of about 2, and the overall lens length tends to be relatively long. Further, the zoom lens proposed in Japanese Patent Application Laid-Open No. 4-161914 has an aspherical lens made of a plastic material to make it easy to manufacture, but the zoom ratio is not always enough, such as about 2. In addition, the distance from the first lens surface to the final lens surface is long at the telephoto end, which is not suitable for a compact camera in which the lens barrel is collapsed when the camera is carried.

According to the present invention, in a so-called two-unit zoom lens system, by appropriately setting the lens configuration of each lens unit and effectively using an aspherical lens, a zoom ratio of 2.times.
It is an object of the present invention to provide a small zoom lens having high optical performance over the entire zoom range with a high zoom ratio of about 5 and shortening the entire length of the lens.

[0013]

The zoom lens of the present invention roughly includes two inventions, a first invention and a second invention. Hereinafter, the first invention and the second invention are collectively referred to as the present invention.

First, the zoom lens according to the first invention is:
(1-1) A zoom lens having two lens groups, a first group having a positive refractive power and a second group having a negative refractive power, in order from the object side, and performing zooming by changing the distance between the two lens groups. The first group includes a positive eleventh lens with a convex surface facing the object side, and a negative twelfth lens.
The second group includes a lens, a negative thirteenth lens having an aspherical surface, and a positive fourteenth lens. The second group includes a positive twenty-first lens having an aspherical surface and a meniscus shape having a convex surface facing the image surface side. , The focal length of the i-th lens unit is fi, the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and fT, respectively, and the i-th lens in order from the object side. When the curvature radius of the surface is Ri, 3 <fT / f1 <6 (1a) 3 <| fT / f2 | <9 (2a) 2.5 <fT / fw <3.6 (3a) | R3 / R4 | <0.35 (4a) .

In particular, the focal length of the twelfth lens is f1
When 2 is satisfied, the following condition is satisfied: 1 <(fT / f12) ² <10 (5a)

The zoom lens according to the second aspect of the present invention includes (1-
2) A zoom lens having two lens groups, a first group having a positive refractive power and a second group having a negative refractive power, in order from the object side, and performing zooming by changing the distance between both lens groups. The first group includes a positive eleventh lens having a convex surface facing the object side, a negative twelfth lens, a negative thirteenth lens having an aspheric surface, and a positive fourteenth lens.
The second group includes two lenses, a positive twenty-first lens having an aspheric surface and a negative twenty-second meniscus lens having a convex surface facing the image surface side. When the focal length of the i-th group is fi, the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and fT, and the refractive index and Abbe number of the material of the thirteenth lens are N13 and ν13, respectively, 3 <fT / f1 <6 (3b) 3 <| fT / f2 | <9 (2b) 2.5 <fT / fw <3.6 (1b) (3b) 1.60 <N13 (4b1) ν13 <40 (4b2) The following condition is satisfied. .

In particular, when the focal length of the thirteenth lens is f1
When 3, it is characterized that the following condition is satisfied: 0.01 <(fT / f13) ² <2 (5b)

[0018]

1 to 5 are sectional views of a lens at a wide angle end according to Numerical Examples 1 to 5 of the present invention.

In the drawing, L1 denotes a first group having a positive refractive power, and L2 denotes a second group having a negative refractive power. The distance between the two lens groups is reduced, and both lens groups are moved toward the object side as shown by arrows. Moving the zoom from the wide-angle end to the telephoto end.

An aperture SP is disposed on the image plane side of the first lens unit in the present invention, and moves together with the first lens unit with zooming. IP is an image plane.

In the present embodiment, by adopting such a zoom system and the lens configuration as described above, the overall length of the lens is shortened, especially at the wide-angle end, and the zoom ratio is increased to 2.5. Aberration fluctuation due to degree and zooming is corrected well, and high optical performance is obtained over the entire zooming range.

Next, the features of the lens configuration of the two-unit zoom lens of the present invention will be described.

In the two-unit zoom lens of the present invention, the first
Since the imaging performance of the group is enlarged while being corrected by the second group, it is desired that the first group has a lens configuration that can satisfactorily correct aberrations. Therefore, the first group basically has a triplet lens composed of three lenses, that is, a positive lens, a negative lens, and a positive lens that can favorably correct aberration as a single focus lens. Then, the negative second lens of the triplet lens is divided into two lenses, a negative spherical lens and a negative aspheric lens, and four lens configurations of positive, negative, negative and positive lenses capable of excellently correcting aberrations as a whole are provided. I have to.

In particular, when the zoom ratio is increased, the variation of the spherical aberration increases from the wide-angle end to the telephoto end, and it becomes difficult to correct this in a well-balanced manner. Therefore, in this embodiment,
The fluctuation of the spherical aberration at this time is favorably corrected by applying an aspheric surface to the negative thirteenth lens on which the on-axis light beam is relatively widened and incident.

Particularly, the first lens unit has a positive meniscus eleventh lens having a convex surface facing the object side, a negative twelfth lens having a concave surface facing the object side, and a negative thirteenth lens having a concave surface facing the object side.
4 of the lens and the positive fourteenth lens with both lens surfaces convex
By using one lens, spherical aberration, coma aberration, chromatic aberration and the like are mainly satisfactorily corrected.

In the two-unit zoom lens, the second unit is located close to the image plane, and the outside diameter of the lens becomes large because an off-axis light beam enters a high position on the lens surface. For this reason, the amount of occurrence of aberration increases, and when the second group is constituted by a large number of lenses, the size of the lens system increases.

Therefore, in the present invention, the second group is composed of two lenses of a predetermined shape, one of which is an aspherical lens to correct various aberrations at the wide-angle end and the telephoto end with good balance. . In particular, off-axis aberrations are constituted by two lenses: a positive meniscus twenty-first lens having an aspheric surface with a convex surface facing the image surface, and a negative meniscus twenty-second lens with a convex surface facing the image surface. Is corrected favorably.

In the compact zoom lens according to the present invention, the first lens unit having a positive refractive power and the second lens unit having a negative refractive power are arranged in order from the object side.
In a small zoom lens having two lens groups and performing zooming by changing the distance between both lens groups, the first group is a positive first lens group.
It has four lenses, one lens, a negative twelfth lens, a negative thirteenth lens composed of an aspherical lens, and a positive fourteenth lens. The second group has a positive 21st lens composed of an aspherical lens and a negative lens. The basic configuration is a lens configuration having two lenses of the 22nd lens.

The first lens configuration that satisfies the above-mentioned conditional expressions (1a) to (4a) in the lens configuration of the basic configuration is defined as a first invention. In order to further improve the optical performance, conditional expression (5) is adopted.
a) is satisfied. In the lens configuration of the basic configuration, a lens that satisfies the conditional expressions (1b) to (4b) is defined as a second invention. In order to further improve the optical performance, the conditional expression (5b) is satisfied. I have.

Next, the technical meaning of each conditional expression according to the first and second aspects of the invention will be described.

The conditional expressions (1a) and (1b) relate to the ratio between the focal length fT of the entire system at the telephoto end and the focal length f1 of the first lens group, and mainly balance the miniaturization of the first lens group and the optical performance. This is for planning. When the value exceeds the upper limit, the amount of fluctuation of the spherical aberration generated from the first lens unit increases from the wide-angle end to the telephoto end, and it becomes difficult to satisfactorily correct this. If the value exceeds the lower limit, the size of the first lens unit increases, which is not good.

In order to obtain higher optical performance in the first and second aspects of the present invention, it is preferable to set the upper limit of conditional expressions (1a) and (1b) to 5.0. In order to further reduce the size of the first lens unit, it is preferable to set the lower limit of conditional expressions (1a) and (1b) to 3.5.

The conditional expressions (2a) and (2b) relate to the ratio between the focal length fT of the entire system at the telephoto end and the focal length f2 of the second lens unit, and mainly balance the miniaturization of the second lens unit and the optical performance. This is for planning. If the value exceeds the upper limit, distortion particularly at the wide-angle end deteriorates, and it becomes difficult to satisfactorily correct the distortion. If the lower limit value is exceeded, the size of the second lens unit becomes large, the amount of movement of the second lens unit during zooming increases, and the total optical length at the telephoto end increases.

In order to obtain higher optical performance in the first and second aspects of the present invention, it is preferable to set the upper limit of conditional expressions (2a) and (2b) to 6.0. In order to further reduce the size of the second lens unit and shorten the overall optical length at the telephoto end, it is preferable to set the lower limit of conditional expressions (2a) and (2b) to 3.5.

The conditional expressions (3a) and (3b) define the ratio of the focal lengths fT and fw between the telephoto end and the wide-angle end, that is, the zoom ratio. Exceeding the upper limit is not preferable because it is difficult to obtain good optical performance with a simple lens configuration. If the lower limit value is exceeded, the zoom lens having a high zoom ratio, which is the object of the present invention, is out of the intended purpose, which is not good.

Conditional expression (4a) relates to the ratio of the radius of curvature of the lens surface on the object side to the image surface side of the twelfth lens, and is mainly used to set a lens shape for favorably correcting various aberrations at the wide-angle end. Things. Exceeding the upper limit is not preferable because distortion occurring in the first lens group at the wide-angle end increases.

In order to obtain higher optical performance in the first invention, it is preferable to set the upper limit of conditional expression (4a) to 0.5.

Conditional expression (5a) relates to the ratio of the focal lengths fT and f12 of the twelfth lens to the telephoto end, mainly for suppressing the variation of axial chromatic aberration from the wide-angle end to the telephoto end. When the value exceeds the upper limit, the refractive power of the twelfth lens becomes relatively strong, and the axial chromatic aberration particularly at the telephoto end tends to deteriorate. If the lower limit value is exceeded, the refractive power of the twelfth lens becomes relatively weak, and in particular, axial chromatic aberration at the wide-angle end tends to worsen, which is not good.

In the first invention, it is preferable to set the upper limit of conditional expression (5a) to 8.0 in order to further correct axial chromatic aberration particularly in the entire zoom range. The lower limit is preferably set to 2.0.

Conditional expression (4b1) defines the refractive index of the glass material of the thirteenth lens. If the lower limit value is exceeded, the image surface characteristic tends to deteriorate, and it is difficult to satisfactorily correct this. Is not preferred.

Conditional expression (4b2) defines the Abbe number of the glass material of the thirteenth lens. Exceeding the upper limit of the conditional expression (4b2) makes it difficult to correct axial chromatic aberration especially at the wide-angle end, which is not preferable.

Conditional expression (5b) represents the relationship between the focal length at the telephoto end and the first focal length.
The ratio between the focal lengths fT and f13 of the three lenses is intended to favorably correct spherical aberration and chromatic aberration mainly in the entire zoom range. If the focal length of the thirteenth lens becomes relatively short beyond the upper limit, the amount of change in spherical aberration increases, especially at zooming, and it becomes difficult to correct axial chromatic aberration at the telephoto end. In addition, thirteenth
If the focal length of the lens is relatively large, it becomes difficult to correct axial chromatic aberration particularly at the wide-angle end, which is not good.

In order to obtain better optical performance in the second aspect, it is preferable to set the upper limit of conditional expression (5b) to 1.5. The lower limit is preferably set to 0.1.

In the first and second aspects of the present invention, an aspherical surface is effectively used to satisfactorily correct various aberrations. To satisfactorily correct aberrations in the entire zoom range, it is desirable that each lens group itself has some degree of aberration correction.

In the first and second inventions, at least one aspheric surface is used for each lens group. For the first group having a positive refractive power, an aspherical surface having a shape in which the negative refractive power becomes stronger toward the periphery of the lens is used, and thereby spherical aberration is particularly well corrected. For the second group having a negative refractive power, an aspherical surface having a shape in which the positive refractive power becomes stronger toward the periphery of the lens is used, so that coma and distortion at the wide-angle end are particularly well corrected. .

The first and second inventions realize a compact zoom lens having high optical performance by having the above-described structure. In the numerical examples according to the first and second aspects of the present invention, the stop SP is disposed between the first and second units. However, in order to further reduce the size, a twelfth lens and a thirteenth lens are used. May be arranged at the air intervals.

For focusing from an object at infinity to an object at a close distance, it is preferable to move the first lens unit to the object side along the optical axis because the amount of extension is relatively small.

On the other hand, when the zoom ratio is increased, the focus sensitivity particularly in focusing at the telephoto end increases. For this reason, in order to increase the focusing control accuracy, it is preferable that the first lens unit is moved out at the same time as the first lens unit is moved out, so that the second lens unit is moved out smaller than the first lens unit. Therefore, the focus sensitivity in focusing can be suppressed well. . In order to obtain higher optical performance for the first invention and the second invention,
It is desirable to satisfy at least one of the following conditions.

(A-1) When the refractive indices of the materials of the twenty-first lens and the twenty-second lens are N21 and N22, respectively, and the focal length of the twenty-first lens is f21, N21 <1.6. (6c) 0.7 <fT / f21 <1.2 (7c) 1.75 <N22 (8c) .

(A-2) When the refractive indices of the materials of the 21st and 22nd lenses are N21 and N22, respectively, and the focal length of the 21st lens is f21, 1.61 <N21... (6d) 1 <fT / f21 <1.6 (7d) 1.75 <N22 (8d)

Here, conditional expressions (6c) and (6d) satisfy
This defines the refractive index of the glass component (material) of the lens component, and conditional expressions (7c) and (7d) define the ratio between the focal length f21 of the 21st lens component and the focal length fT at the telephoto end. is there. When conditional expression (6c) is satisfied, it is preferable to satisfy conditional expression (7c). The conditional expression (6
When d) is satisfied, it is preferable to satisfy the conditional expression (7d).

When conditional expression (6c) is satisfied, if the value exceeds the upper limit of conditional expression (7c), the Petzval sum tends to increase in the plus direction, which is not good because it becomes difficult to correct aberrations. If the value exceeds the lower limit, the Petzval sum tends to increase in the minus direction, which is not good because it becomes difficult to correct aberrations.

In order to obtain higher optical performance, it is preferable to set the upper limit of conditional expression (7c) to 1.1. The lower limit is preferably set to 0.8.

When conditional expression (6d) is satisfied, if the value exceeds the upper limit of conditional expression (7d), the Petzval sum tends to increase in the plus direction, which is not good because it becomes difficult to correct aberrations. If the value exceeds the lower limit, the Petzval sum tends to increase in the minus direction, which is not good because it becomes difficult to correct aberrations.

In order to obtain even higher optical performance, it is preferable to set the upper limit of conditional expression (7d) to 1.5. The lower limit is preferably set to 1.2.

The conditional expressions (8c) and (8d) define the refractive index of the glass material of the 22nd lens component, and are mainly used to satisfactorily correct the image plane characteristics. Above the lower limit, the Petzval sum tends to increase in the negative direction, which is not good because the image surface characteristics deteriorate.

(A-3) When the Abbe numbers of the materials of the twelfth lens and the thirteenth lens are respectively ν12 and ν13, the following condition is satisfied: 0 <ν12−ν13 (9) It is.

Conditional expression (9) is mainly for favorably correcting chromatic aberration in the entire zoom range. The twelfth lens component is different from the thirteenth lens component in that the off-axis luminous flux passes through a position relatively far from the optical axis, particularly at the wide-angle end.
The chromatic aberration of magnification is greatly affected by the Abbe number of the lens component. If the Abbe number of the twelfth lens component is smaller than that of the thirteenth lens below the lower limit of conditional expression (9), it becomes difficult to correct lateral chromatic aberration, especially at the wide-angle end, and the axial chromatic aberration and lateral chromatic aberration are reduced over the entire zoom range. In this case, it is difficult to make a good correction in a balanced manner.

(A-4) When the axial air gap between the thirteenth lens and the fourteenth lens is DL34, the condition of 0.002 <DL34 / fT <0.05 (10) is satisfied. To be satisfied.

Conditional expression (10) is particularly useful for the first lens having an aspherical surface.
The arrangement of the three lens components is for efficiently using an aspheric surface, and is mainly for satisfactorily correcting on-axis aberrations and off-axis aberrations. Exceeding the upper limit is advantageous for correction of off-axis aberrations, but it is difficult to correct on-axis aberrations and is not good because the lens system becomes large. If the lower limit is exceeded, it is advantageous for correcting axial aberration, but it is not good because it becomes difficult to correct off-axis aberration.

In order to further improve the balance between the on-axis aberration and the off-axis aberration, the upper limit of conditional expression (10) is set to 0.035.
It is preferable that The lower limit is preferably set to 0.005.

Next, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness or air gap, N
i and νi are the refractive index and Abbe number of the material of the i-th lens. In the aspherical shape, the radius of curvature at the center of the lens surface is R, the optical axis direction (the traveling direction of light) is the X axis, the direction perpendicular to the optical axis is the Y axis, and A, B, C, D, E Are the aspheric coefficients, respectively.

[0063]

(Equation 1) It is assumed that The notation of “ex” is “× 1”.
0- ^X ". Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples. (Numerical Example 1) F = 39.0 to 102.00 FNO = 3.50 to 9.15 2ω = 58.0 to 23.9 R 1 = 23.74 D 1 = 2.00 N 1 = 1.51822 ν 1 = 59.0 R 2 = 89.01 D 2 = 0.98 R 3 = -28.02 D 3 = 1.70 N 2 = 1.83400 ν 2 = 37.2 R 4 = -200.31 D 4 = 5.58 R 5 = -55.05 D 5 = 1.60 N 3 = 1.67270 ν 3 = 32.1 R 6 = -81.53 D 6 = 1.43 R 7 = 37.32 D 7 = 3.70 N 4 = 1.48749 ν 4 = 70.2 R 8 = -13.58 D 8 = 0.50 R 9 = Aperture D 9 = Variable R10 = -76.21 D10 = 2.70 N 5 = 1.58306 ν 5 = 30.2 R11 = -35.26 D11 = 5.48 R12 = -11.93 D12 = 1.50 N 6 = 1.80400 ν 6 = 46.6 R13 = -87.54

[0064]

[Table 1] Aspheric coefficient 5 plane A = 0 B = -9.317e-05 C = -4.151e-07 D = -2.719e-09 E = -8.405e-11 10 plane A = 0 B = 5.269e-05 C =- 2.569e-07 D = 7.769e-09 E = -4.160e-11 (Numerical Example 2) F = 39.0 to 102.00 FNO = 3.50 to 9.15 2ω = 58.0 to 23.9 R 1 = 24.48 D 1 = 1.80 N 1 = 1.51633 ν 1 = 64.2 R 2 = 67.58 D 2 = 1.17 R 3 = -30.71 D 3 = 1.20 N 2 = 1.80609 ν 2 = 41.0 R 4 = -87.81 D 4 = 4.83 R 5 = -38.68 D 5 = 1.30 N 3 = 1.69894 ν 3 = 30.1 R 6 = -82.60 D 6 = 2.24 R 7 = 43.10 D 7 = 3.20 N 4 = 1.48749 ν 4 = 70.2 R 8 = -13.83 D 8 = 0.50 R 9 = Aperture D 9 = Variable R10 =- 72.14 D10 = 2.40 N 5 = 1.58306 ν 5 = 30.2 R11 = -34.44 D11 = 5.89 R12 = -11.80 D12 = 1.40 N 6 = 1.77249 ν 6 = 49.6 R13 = -60.04

[0065]

[Table 2] Aspheric coefficient 5 plane A = 0 B = -8.048e-05 C = -4.069e-07 D = -4.754e-09 E = -3.271e-11 10 plane A = 0 B = 4.137e-05 C = 7.262 e-08 D = 2.051e-09 E = -5.218e-12 (Numerical Example 3) F = 39.00-112.00 FNO = 3.50 -10.05 2ω = 58.0-21.9 R 1 = 23.23 D 1 = 1.80 N 1 = 1.48749ν 1 = 70.2 R 2 = 44.14 D 2 = 1.36 R 3 = -29.45 D 3 = 1.30 N 2 = 1.83400 ν 2 = 37.2 R 4 = -81.81 D 4 = 4.36 R 5 = -49.70 D 5 = 1.70 N 3 = 1.69894 ν 3 = 30.1 R 6 = -85.79 D 6 = 2.29 R 7 = 45.45 D 7 = 3.70 N 4 = 1.48749 ν 4 = 70.2 R 8 = -13.79 D 8 = 0.50 R 9 = Aperture D 9 = Variable R10 = -81.53 D10 = 2.80 N 5 = 1.67270 ν 5 = 32.1 R11 = -34.32 D11 = 5.45 R12 = -12.57 D12 = 1.40 N 6 = 1.78800 ν 6 = 47.4 R13 = -111.47

[0066]

[Table 3] Aspheric coefficient 5 plane A = 0 B = -8.512e-05 C = -4.382e-07 D = -2.208e-09 E = -7.429e-11 10 plane A = 0 B = 3.371e-05 C = 1.862 e-08 D = 1.605e-09 E = -5.619e-12 (Numerical example 4) F = 39.00 to 120.00 FNO = 3.50 to 10.77 2ω = 58.0 to 20.4 R 1 = 24.03 D 1 = 1.90 N 1 = 1.51453 ν 1 = 54.7 R 2 = 54.52 D 2 = 1.17 R 3 = -29.10 D 3 = 1.30 N 2 = 1.83400 ν 2 = 37.2 R 4 = -100.80 D 4 = 4.51 R 5 = -48.32 D 5 = 1.80 N 3 = 1.72824 ν 3 = 28.5 R 6 = -76.86 D 6 = 1.80 R 7 = 44.61 D 7 = 3.90 N 4 = 1.48749 ν 4 = 70.2 R 8 = -13.97 D 8 = 0.50 R 9 = Aperture D 9 = Variable R10 = -81.19 D10 = 2.80 N 5 = 1.69894 ν 5 = 30.1 R11 = -36.30 D11 = 5.56 R12 = -12.61 D12 = 1.40 N 6 = 1.80400 ν 6 = 46.6 R13 = -85.10

[0067]

[Table 4] Aspheric coefficient 5 plane A = 0 B = -7.607e-05 C = -3.868e-07 D = -2.727e-09 E = -4.235e-11 10 plane A = 0 B = 3.298e-05 C = 4.619 e-08 D = 9.442e-10 E = -5.921e-13 (Numerical example 5) F = 36.0-102.00 FNO = 3.50-9.92 2ω = 62.0-23.9 R 1 = 24.03 D 1 = 2.10 N 1 = 1.51741 ν 1 = 52.4 R 2 = 61.92 D 2 = 1.15 R 3 = -28.65 D 3 = 1.60 N 2 = 1.83400 ν 2 = 37.2 R 4 = -139.29 D 4 = 5.01 R 5 = -45.29 D 5 = 2.00 N 3 = 1.58306 ν 3 = 30.2 R 6 = -86.81 D 6 = 0.96 R 7 = 34.05 D 7 = 4.00 N 4 = 1.48749 ν 4 = 70.2 R 8 = -13.64 D 8 = 0.50 R 9 = Aperture D 9 = Variable R10 = -82.71 D10 = 2.90 N 5 = 1.58306 ν 5 = 30.2 R11 = -35.94 D11 = 5.73 R12 = -12.01 D12 = 1.40 N 6 = 1.80400 ν 6 = 46.6 R13 = -71.07

[0068]

[Table 5] Aspheric surface coefficient 5 plane A = 0 B = -1.017e-04 C = -6.330e-07 D = 1.232e-09 E = -2.618e-10 6 plane A = 0 B = 1.297e-06 C = 2.267e -07 D = -5.069e-09 E = 0 10 side A = 0 B = 4.197e-05 C = 2.435e-07 D = -3.820e-10 E = 1.157e-11 11 side A = 0 B = 6.658 e-07 C = 1.665e-07 D = -1.816e-09 E = 1.566e-11

[0069]

[Table 6]

[0070]

As described above, according to the present invention, in a so-called two-unit zoom lens, by appropriately setting the lens configuration of each lens unit and effectively using an aspherical lens, a zoom ratio of 2 is obtained. With a high zoom ratio of about 0.5, a compact zoom lens having high optical performance over the entire zoom range in which the overall length of the lens is reduced can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 2 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 3 is a sectional view of a lens according to a numerical example 3 of the present invention.

FIG. 4 is a sectional view of a lens according to a numerical example 4 of the present invention.

FIG. 5 is a sectional view of a lens according to a numerical example 5 of the present invention.

FIG. 6 is an aberration diagram at a wide angle end according to Numerical Embodiment 1 of the present invention.

FIG. 7 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 8 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention;

FIG. 9 is an aberration diagram at a wide angle end according to Numerical Example 2 of the present invention.

FIG. 10 is an intermediate aberration diagram of the numerical example 2 of the present invention.

FIG. 11 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention.

FIG. 12 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 13 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 14 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

FIG. 15 is an aberration diagram at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 16 is an intermediate aberration diagram of the numerical example 4 of the present invention.

FIG. 17 is an aberration diagram at a telephoto end in Numerical Example 4 of the present invention.

FIG. 18 is an aberration diagram at a wide angle end according to Numerical Example 5 of the present invention.

FIG. 19 is an intermediate aberration diagram of the numerical example 5 of the present invention.

FIG. 20 is an aberration diagram at a telephoto end in Numerical Example 5 of the present invention.

[Explanation of symbols]

 L1 First lens unit L2 Second lens unit L3 Third lens unit L4 Fourth lens unit SP Aperture IP Image plane d d line g g line ΔS Sagittal image plane ΔM Meridional image plane Y Image height

Claims (8)

[Claims] 1. A zoom lens having a first lens unit having a positive refractive power and a second lens unit having a negative refractive power in order from the object side, and performing zooming by changing the distance between both lens units. The first group includes four lenses, a positive eleventh lens having a convex surface facing the object side, a negative twelfth lens, a negative thirteenth lens having an aspheric surface, and a positive fourteenth lens. The second group includes two lenses, a positive twenty-first lens having an aspheric surface and a negative twenty-second meniscus lens having a convex surface facing the image surface side,
When the focal length of the i-th lens unit is fi, the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and fT, and the radius of curvature of the i-th lens surface is Ri from the object side, 3 <fT / A zoom lens characterized by satisfying the following condition: f1 <63 <| fT / f2 | <9 2.5 <fT / fw <3.6 | R3 / R4 | <0.35 2. The zoom lens according to claim 1, wherein, when the focal length of said twelfth lens is f12, the following condition is satisfied: 1 <(fT / f12) ² <10. 3. A zoom lens which has two lens groups, a first group having a positive refractive power and a second group having a negative refractive power, in order from the object side, and performs zooming by changing the distance between both lens groups. The first group includes four lenses, a positive eleventh lens having a convex surface facing the object side, a negative twelfth lens, a negative thirteenth lens having an aspheric surface, and a positive fourteenth lens. The second group includes two lenses, a positive twenty-first lens having an aspheric surface and a negative twenty-second meniscus lens having a convex surface facing the image surface side,
When the focal length of the i-th unit is fi, the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and fT, respectively, and the refractive index and Abbe number of the material of the thirteenth lens are N13 and ν13, 3 < A zoom lens characterized by satisfying the following condition: fT / f1 <63 <| fT / f2 | <9 2.5 <fT / fw <3.6 1.60 <N13 v13 <40 4. The zoom lens according to claim 3, wherein when a focal length of the thirteenth lens is f13, a condition of 0.01 <(fT / f13) ² <2 is satisfied. 5. When the refractive indices of the materials of the twenty-first lens and the twenty-second lens are N21 and N22, respectively, and the focal length of the twenty-first lens is f21, N21 <1.6 0.7 <fT / f21 < 4. The condition of 1.1.7 <N22 is satisfied.
Or 4 zoom lenses. 6. When the refractive indices of the materials of the twenty-first lens and the twenty-second lens are N21 and N22, respectively, and the focal length of the twenty-first lens is f21, 1.61 <N211 <fT / f21 <1. 6. The condition of 1.75 <N22 is satisfied.
Or 4 zoom lenses. 7. The optical system according to claim 1, wherein when the Abbe numbers of the materials of the twelfth lens and the thirteenth lens are ν12 and ν13, respectively, a condition of 0 <ν12−ν13 is satisfied. 2. The zoom lens according to claim 1. 8. The condition of 0.002 <DL34 / fT <0.05, wherein DL34 is the on-axis air gap between the thirteenth lens and the fourteenth lens. A zoom lens according to any one of the preceding claims.