JP2016014800A - Zoom lens and optical instrument having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wide-angle zoom lens having a bright and uniform open F value throughout the whole zoom range and an optical instrument having the same, in which a drop in peripheral light intensity at the wide angle end is made less noticeable and whose performance is made high.SOLUTION: A zoom lens has a positive lens group arranged closest to the image side. At the position closest to the image side of a lens group adjacent to the object side of the positive lens group, a variable diaphragm is provided which determines an F value during open use times at least at the wide angle end, and a surface apex position on the object side of the positive lens group is arranged closer to the image side than the variable diaphragm position at the wide angle end and arranged closer to the object side than the variable diaphragm position at the telephoto end.

Description

  The present invention relates to a zoom lens and an optical apparatus having the same, and is suitable for a photographing lens such as a single-lens reflex camera, a digital still camera, and a digital video camera.

  2. Description of the Related Art Conventionally, optical systems having various specifications are required for photographing optical systems such as single-lens reflex cameras depending on applications. One of them is a wide-angle zoom lens capable of zooming from a wide-angle region with a full field angle of 80 degrees or more.

  On the other hand, there is also a demand for a zoom lens that has a bright F value of about 2.8 and can use the same open F value throughout the entire zoom range so that exposure changes do not occur due to zooming.

  In Patent Document 1, the zoom lens has a zoom ratio of about 1.7 times and a zoom ratio of about 1.7 times with a total angle of view of 113 degrees at the wide angle end, which includes a negative first lens group and a positive second lens group. Introducing a wide-angle zoom lens that is 2.8 throughout.

  In Patent Document 2, the total angle of view at a wide angle end of 106 degrees, which is composed of a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group, is 2.1 times. A wide-angle zoom lens having a zoom ratio of about 2.8 and an open F value of 2.8 over the entire zoom range is introduced.

JP 2008-233284 A JP 2008-046208 A

  Normally, a wide-angle lens uses a retrofocus type optical system in which a lens group having a negative combined power is disposed on the object side from the exit pupil position and a lens group having a positive combined power is disposed on the image side. In the retrofocus type optical system, the effective diameter is the largest in the most object-side lens of the object-side lens group, and this is a factor that determines the outer diameter of the lens body. For this reason, normally, when downsizing with a wide-angle lens, the peripheral light amount ratio is reduced within a range that does not cause adverse effects during photographing so as to minimize the outer diameter of the object-side lens group. Also in the wide-angle zoom lens disclosed in Patent Document 1 or 2, the amount of light at the outermost periphery at the wide-angle end is set to 30% or less with respect to the center.

  As described above, when the light amount ratio at the outermost periphery is reduced in the wide-angle lens, for example, when a uniform luminance surface such as the sky is photographed, the light amount drop at the outermost periphery of the photographed image can be visually discriminated. The quality of the photo may be impaired. In particular, peripheral dimming tends to be conspicuous at the wide-angle end of a wide-angle zoom lens in which the open F value is uniform in the entire zoom range as in Patent Documents 1 and 2.

  In general, as the light amount of the off-axis light beam is cut, the burden of aberration correction at each lens is reduced and the performance can be improved. However, as shown in Patent Document 1 or 2, at the wide angle end of a wide-angle zoom lens in which the open F value is uniform in the entire zoom range, the light flux at the intermediate image height is not sufficiently cut, and high performance is difficult. It had the following characteristics.

  In view of the above, the present invention has an object to make a wide-angle zoom lens having a wide open F value and uniform in the entire zoom range and an optical apparatus having the same so as to make the peripheral light amount drop at the wide-angle end inconspicuous and to improve performance.

  The zoom lens structure according to the present invention has a positive lens group closest to the image side, and is at least at the wide-angle end when the lens is adjacent to the object side of the positive lens group. It has a variable aperture for determining the value, and the surface apex position on the object side of the positive lens group is located closer to the image side than the variable aperture position at the wide angle end, and closer to the object side than the variable aperture position at the telephoto end. Features.

  According to the present invention, in a wide-angle zoom lens having a wide open F value and uniform in the entire zoom range and an optical apparatus having the same, it is possible to make the peripheral light amount drop at the wide-angle end inconspicuous and to improve performance.

Sectional drawing of the optical system of Embodiment 1 in this invention The graph showing the relationship between the image height and the peripheral light amount of the optical system according to the first embodiment of the present invention. Aberration diagram at the infinite object distance at the wide-angle end when the optical system of Numerical Example 1 according to the present invention is expressed in mm. Aberration diagram when the object distance at the telephoto end is infinite when the optical system of Numerical Example 1 according to the present invention is expressed in mm. Sectional drawing of the optical system of Embodiment 2 in this invention The graph showing the relationship between the image height and the peripheral light amount of the optical system according to the second embodiment of the present invention. Aberration diagram at infinite object distance at the wide-angle end when the optical system of Numerical Example 2 according to the present invention is expressed in mm. Aberration diagram when the object distance at the telephoto end is infinite when the optical system of Numerical Example 2 according to the present invention is expressed in mm. Ray diagram of a general wide-angle zoom lens that has a bright F value and is invariable throughout the entire zoom range Comparison of the graph showing the relationship between the image height and the amount of peripheral light, and the brightness distribution image on the imaging surface when photographing a uniform luminance surface (upper right part when the photographed image is divided into four parts vertically and horizontally)

  FIG. 9 shows an example of a wide-angle zoom lens having an F value of 2.8 over the entire zoom range. Normally, wide-angle zoom lenses used for interchangeable lenses for single-lens reflex cameras, etc. need to ensure a long back focus, so the rear principal point at the wide-angle end is located closer to the image side than the image-side lens. The Therefore, the final lens group is set to have a strong positive power and is arranged on the image side as much as possible. During zooming from the wide-angle end to the telephoto end, in order to move the rear principal point position to the object side, the positive lens group is largely moved to the object side. In addition, the distance from the lens group adjacent to the object side is narrowed in order to suppress the fluctuation of the image plane toward the over side at that time.

  In a wide-angle zoom lens with a bright F-number as shown in FIG. 9, the axial light beam at the telephoto end determines the effective diameter of each lens except for the image side lens and the first lens group in the final lens group. I understand that For the lens near the image side and the first lens group in the final lens group, the outermost peripheral light beam at the wide angle end determines the effective diameter. Therefore, normally, in order to reduce the outer diameter of the main body, a method of cutting the underline of the most peripheral light beam as much as possible in the first lens group is employed.

  Further, in order to improve performance, it is necessary to shorten the block length of each lens group as much as possible to secure a moving space for each group.

  The positive element in the final lens group is an extraordinary partial dispersion glass with low refractive index and low dispersion in order to reduce the Petzval sum and correct lateral chromatic aberration at the wide-angle end and axial chromatic aberration at the telephoto end. Use a biconvex shape with a large curvature in order to use the effect sufficiently. In the biconvex shape having a large curvature, as the effective diameter increases, the center thickness becomes extremely thick, the block length becomes long, and the moving space of each lens group is compressed. For this reason, the uppermost peripheral light flux at the wide-angle end is also cut as much as possible to reduce the effective diameter of the biconvex lens to reduce the wall thickness and to improve performance.

  Next, the F value is represented by FNO = | f / D |, where f is the focal length and D is the aperture diameter at the rear principal point position. In the lens, as can be seen from FIG. 9, the aperture diameter at the telephoto end is larger than the aperture diameter at the wide-angle end.

  In other words, when the wide-angle end is used in an open state, it is necessary to narrow the axial light beam by some method even though it is in the open state.

  In the zoom lens of FIG. 9 and Patent Document 1, the diameter of an aperture (hereinafter referred to as a main aperture) itself that changes the aperture diameter by an external command is changed according to zooming, thereby narrowing the axial light beam at the wide-angle end. Yes. In this method, the diameter of the glass placed near the aperture is larger than the aperture at the wide-angle end, so that the light beam at the intermediate image height is hard to be cut by the glass around the aperture on both the upper and lower lines. There were many.

  In addition to the main aperture, the zoom lens of Patent Document 2 has a variable aperture whose effective diameter changes in conjunction with zooming on the image side of the third lens group, and the open F value is uniform according to zooming. The axial luminous flux is cut so that In this method, the axial light beam at the wide-angle end is determined by the variable stop, and at the same time, the upper line of the intermediate image height is cut to some extent. Compared with the method of FIG. It was.

  However, in order to secure the amount of movement of the final lens group in the object side direction, the variable aperture must be disposed as close as possible to the lens surface closest to the image side of the third lens group, and the upper line of the intermediate image height is exceeded. The effect of cutting was not sufficient.

  In addition, the amount of movement of the final lens group is limited by the space where the variable aperture is arranged, which does not necessarily lead to high performance.

  From the above, the conventional wide-angle zoom lens has extra light flux at the intermediate image height, so the amount of peripheral light falls off sharply from the intermediate image height to the peripheral image height, and the attenuation is conspicuous. It increases, and it turns out that it became a burden in performance enhancement.

  Therefore, in the present invention, the most object side surface of the final lens group is shaped to have a strong convex surface facing the object side. In addition, the variable stop is arranged on the most image side in the lens group adjacent to the object side, and the position of the variable stop is arranged at a position somewhat away from the lens surface on the most image side, so that it is intermediate at the wide-angle end. Effectively cut the luminous flux. Further, when the variable aperture is opened at the telephoto end, the strongest convex surface on the most object side of the final lens group is adjacent to the central portion by avoiding contact with the variable aperture while allowing the variable aperture to be hidden in the center. The distance from the image side surface of the lens group was reduced to the limit.

  By doing so, we succeeded in securing a sufficient space for moving the lens group while arranging the variable stop at the most effective position.

  As a result, the intermediate image height at the wide-angle end is effectively cut, the peripheral light amount drop at the wide-angle end is made inconspicuous near the periphery, and at the same time, high performance is achieved.

  The present inventor hypothesized that, in carrying out the present invention, even if the peripheral light amount at the maximum image height is the same, the peripheral light reduction is more conspicuous when the light attenuation rate toward the maximum image height is large. And verifying it.

  It is based on the fact that the human eye is less accurate in measuring absolute brightness and, on the contrary, is sensitive to relative changes in brightness.

  Based on this hypothesis, the amount of decrease in the amount of peripheral light will not be noticeable if the characteristic is always attenuated at the same rate with respect to the change in image height. Specifically, it is as follows.

R _y = R _Y ^{(y / Y)}
Y: Maximum image height y: Evaluation image height R _Y : Peripheral light intensity at maximum image height Three models with the same peripheral light intensity ratio at the maximum image height and different dimming characteristics are prepared to verify this hypothesis. A photographed image simulation was actually performed. The simulation image represents the upper right portion when the shooting screen is divided into four equal parts in the vertical and horizontal directions. Therefore, the lower left corner of the simulation image is the center of the captured image, and the upper right corner is the outermost periphery of the captured image.

  The first model shown in FIG. 10A has a characteristic that, as in Patent Documents 1 and 2, the amount of light at the intermediate image height is large and the light is rapidly reduced toward the periphery. The second model shown in FIG. 10B is a characteristic that linearly attenuates toward the maximum image height. The third model shown in FIG. 10C has characteristics according to the above-described mathematical formula.

It can be seen from these captured image simulations that in the third model that follows the hypothesis of the present case, it is difficult for the peripheral portion to be dimmed. The peripheral light quantity ratio T at an arbitrary image height is represented by T = E × cos ⁴ θ, where θ is the angle of view at the image height and E is the aperture efficiency.

  Briefly describing the aperture efficiency, ray tracing is performed on the object side from the corresponding image height and optical axis position on the image plane, and those blurs on any non-imaging plane perpendicular to the optical axis on the object side are detected. It represents the area ratio of the image.

When there is no vignetting of the off-axis light beam, and both the upper line and the underline are determined by the same stop as that for determining the on-axis light beam, the aperture efficiency is expressed by 1 / cos ³ θ. At this time, the peripheral light amount ratio is represented by T = cos θ, and this characteristic is different from the ideal peripheral dimming characteristic described above, and the dimming rate increases from the intermediate image height toward the most peripheral area. Therefore, in order to obtain an ideal peripheral dimming characteristic, it is important to reduce the aperture efficiency at the intermediate image height.

  In recent years, a method of correcting peripheral light reduction by image processing on the optical device side using data on peripheral light reduction of a lens is becoming common. In that case, by using the reciprocal of the peripheral light amount ratio as the correction gain, it is possible to eliminate the peripheral light amount drop over the entire area. At this time, if there is a sudden drop in the peripheral light amount as in Patent Documents 1 and 2, the correction is performed. Gain will also increase sharply.

  When an optical axis shift occurs due to an optical system manufacturing error, an image stabilization function, or the like, a location where the peripheral light amount falls sharply and a location where the correction gain rises suddenly deviate, resulting in a significant correction error.

  From this point of view, it is preferable that the characteristic is close to the ideal peripheral dimming of the present case because the correction gain also changes smoothly and good correction can be made.

  Next, specific configuration requirements of the present invention will be described. The wide-angle zoom lens according to the present invention has a positive lens unit closest to the image side, and determines an F value at the wide-angle end when the lens is adjacent to the object side of the positive lens unit, at least at the wide-angle end. The surface apex position of the positive lens unit closest to the object side is located closer to the image side than the variable aperture position at the wide-angle end, and closer to the object side than the variable aperture position at the telephoto end. The fact that the surface vertex position of the positive lens group is disposed closer to the object side than the variable aperture at the telephoto end indicates that the surface vertex has penetrated the variable aperture and moved further to the object side.

  Next, more preferable conditions for implementing the present invention will be described. The wide-angle zoom lens of the present invention preferably satisfies the following conditional expression (1).

0.50 <Rp / Svt <1.50 ... (1)
Rp: radius of curvature of the most object side surface of the last lens
Svt: Effective diameter of the variable stop at the telephoto end Conditional expression (1) is a conditional expression for increasing the curvature of the surface closest to the object side in the final lens group and making the surface apex easy to dive the variable stop. If the upper limit value of conditional expression (1) is deviated, the convex surface becomes loose, and when the interference with the variable aperture is avoided at the periphery of the surface, the amount of the center of the surface that enters the variable aperture decreases, and the object side It becomes impossible to close the space between the adjacent lens groups. If the lower limit of conditional expression (1) is deviated, the convex surface becomes too strong and the spherical aberration at the telephoto end becomes large. Conditional expression (1) preferably satisfies conditional expression (1) ′.

0.60 <Rp / Svt <1.20 ... (1) '
Next, the zoom lens of the present invention preferably satisfies the following conditional expressions (2) and (3).

1.40 <Ndp <1.58 (2)
0.020 <θgFp−0.6438 + 0.001682 × νdp <0.100 (3)
Ndp: refractive index of the positive lens closest to the object side in the final lens group
Νdp: Abbe number of the positive lens closest to the object side in the final lens group
・ ΘgFp: Abnormal partial dispersion ratio of the g-line of the positive lens closest to the object side in the final lens group Conditional expression (2) is for reducing the Petzval sum and improving the field curvature in the final lens group with positive power. This is a conditional expression. When deviating from the upper limit value of the conditional expression (2), the Petzval sum increases and the field curvature increases. If the lower limit value of conditional expression (2) is deviated, the curvature of the positive lens closest to the object side becomes too large and the block length becomes large.

  Conditional expression (2) more preferably satisfies the following conditional expression (2) ′.

1.42 <Ndp <1.52 ... (2) '
The positive lens satisfying the conditional expression (2) is arranged on the most object side of the final lens group, thereby making it easy to obtain the strong curvature of the conditional expression (1).

  Conditional expression (3) is a conditional expression for effectively correcting axial chromatic aberration at the telephoto end and lateral chromatic aberration at the wide-angle end. If the upper limit of conditional expression (3) is deviated, the anomalous partial dispersion is too strong, and the axial chromatic aberration at the telephoto end and the lateral chromatic aberration at the wide-angle end are overcorrected. When deviating from the lower limit value of conditional expression (3), the anomalous partial dispersion is too weak, and the axial chromatic aberration at the telephoto end and the lateral chromatic aberration at the wide-angle end are insufficiently corrected.

  Conditional expression (3) more preferably satisfies conditional expression (3) ′.

0.025 <θgFp−0.6438 + 0.001682 × νdp <0.070 ... (3) '
Next, the zoom lens according to the present invention preferably satisfies the following conditional expression (4).

0.15 <Svt / En <0.80 ... (4)
• En: Maximum effective diameter in the optical system Conditional expression (4) is a conditional expression for preventing the outer diameter of the main body from increasing even when a variable aperture is disposed. If the upper limit value of the conditional expression (4) is deviated, the diameter of the variable diaphragm exceeds the maximum effective diameter of the lens when combined with the variable diaphragm drive mechanism arranged on the outside thereof, and the main body becomes large. Further, when deviating from the lower limit value of the conditional expression (4), it is preferable for downsizing, but it is not preferable because positive power before and after the variable aperture needs to be increased and spherical aberration occurs.

  In addition, it is preferable that the conditional expression (4) satisfies the following conditional expression (4) ′.

0.20 <Svt / En <0.60 ... (4) '
Next, the zoom lens according to the present invention is most effective in a zoom lens that needs to ensure a certain degree of back focus so as to satisfy the following conditional expression (5).

1.00 <bkw / fw <4.00 ... (5)
Conditional expression (5) is a condition that the rear principal point position at the wide-angle end is closer to the image side than the image-side lens and is strong enough to have a retrofocus power arrangement.

  For example, it is particularly suitable for a zoom lens used in a single-lens reflex camera, a projection apparatus or the like in which a color synthesizing prism needs to be disposed, in which a reflecting mirror needs to be disposed between the last lens surface and the image sensor. . Of course, the present invention can be variously applied to other optical devices.

  The lens group referred to in the present invention refers to the distance between the front surface of the optical system or the surface where the distance between the lens adjacent to the front and the lens adjacent to the front changes by zooming, and the lens adjacent to the rear surface or the rear of the optical system. Suppose that the surface changes by zooming.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 5 are optical path diagrams at the wide-angle end and the telephoto end of the optical systems according to Embodiments 1 and 2 of the present invention. 2 and 6 show the image height characteristics of the peripheral light amount ratio at the wide-angle end in the first and second embodiments of the present invention. FIGS. 3 and 7 are aberration diagrams of the first and second embodiments of the present invention when the object distance at the wide angle end is infinite. 4 and 8 are aberration diagrams of the first and second embodiments of the present invention when the object distance at the telephoto end is infinite.

  Each aberration diagram represents spherical aberration (axial chromatic aberration), astigmatism, distortion, and lateral chromatic aberration in order from the left. In the diagrams showing spherical aberration and lateral chromatic aberration, the solid line represents the d line (587.6 nm), and the broken line represents the g line (435.8 nm). In the diagram showing astigmatism, the solid line represents the sagittal direction of the d line, and the broken line represents the meridional direction of the d line. Moreover, the figure which shows distortion represents the distortion in d line | wire. Numerical examples 1 and 2 show lens data of the optical systems of the first and second embodiments.

  In these numerical examples, the order of each surface from the object side, the radius of curvature r of each optical surface, the distance d between each optical surface, the refractive index nd of each optical member at the d-line, the Abbe number νd, and the effective beam diameter. Show.

  In addition to specifications such as focal length and F number, the angle of view is the half angle of view of the entire system, the image height is the maximum image height that determines the half angle of view, and the total lens length is the distance from the first lens surface to the final lens surface , BF represents the length from the final lens surface to the image plane.

  The zoom group data represents the focal length of each lens group, the length on the optical axis, the front principal point position, and the rear principal point position.

The aspherical surface is Sag (R) when the surface position in the optical axis direction at a position R apart in the direction perpendicular to the optical axis is

The aspherical coefficient of each aspherical surface is shown in each table.

  Also, the portion where the distance d between the optical surfaces is (variable) changes during zooming, and the surface distance corresponding to the focal length is shown in the separate table. In addition, the portion where the effective diameter of each optical surface is (variable) changes during zooming, and the effective diameter corresponding to the focal length is shown in the separate table. Table 1 shows the calculation results of the conditional expressions based on the lens data of Numerical Examples 1 and 2 described below.

(Numerical example 1)

Unit mm

Surface data surface number rd nd vd Effective diameter
1 ∞ 1.50 73.23
2 * ∞ 2.70 1.88300 40.8 55.40
3 * 20.815 6.44 37.98
4 * 28.682 2.50 1.49710 81.6 37.90
5 * 24.899 9.80 35.42
6 -59.892 1.80 1.88300 40.8 35.34
7 151.068 1.83 35.84
8 68.843 6.99 1.71736 29.5 37.14
9 -78.402 (variable) 37.23
10 212.989 3.17 1.90366 31.3 29.01
11 -218.328 0.15 29.17
12 74.874 1.50 1.80809 22.8 29.66
13 21.208 8.39 1.72825 28.5 29.40
14 359.085 (variable) 29.52
15 60.043 1.60 1.78472 25.7 30.40
16 38.161 6.42 1.59522 67.7 29.98
17 -83.207 (variable) 29.84
18 (Aperture) ∞ 2.48 24.88
19 -76.055 1.30 1.83400 37.2 24.37
20 23.026 4.85 1.80809 22.8 24.18
21 94.090 3.50 24.15
22 ∞ (variable) (variable)
23 21.485 8.41 1.43875 94.9 25.13
24 -45.039 0.15 24.57
25 * 151.495 1.40 1.85400 40.4 24.10
26 17.150 9.45 1.49700 81.5 23.76
27 -63.520 25.26


Aspheric data 2nd surface
K = 0.00000e + 000 A 4 = 1.67816e-005 A 6 = -1.95957e-008 A 8 = 1.12167e-011 A10 = 8.37907e-016 A12 = -2.75787e-018

Third side
K = 0.00000e + 000 A 4 = -1.30662e-005 A 6 = 5.37976e-008 A 8 = -9.33801e-011 A10 = 8.35718e-015 A12 = 1.70966e-016

4th page
K = 0.00000e + 000 A 4 = -3.07990e-005 A 6 = 6.18939e-008 A 8 = 5.32496e-011 A10 = -2.03073e-013 A12 = -1.65934e-020

5th page
K = -5.07911e-001 A 4 = 3.47138e-006 A 6 = -3.20927e-010 A 8 = 1.66488e-010 A10 = -5.79829e-013 A12 = 1.25393e-019

25th page
K = 0.00000e + 000 A 4 = -1.05418e-005 A 6 = -1.55453e-008 A 8 = -1.43527e-011 A10 = -1.53317e-014 A12 = -1.54462e-016

Various data Zoom ratio 2.06

Wide angle Medium telephoto focal length 16.48 23.60 33.95
F number 2.90 2.91 2.91
Angle of view 52.70 42.51 32.51
Image height 21.64 21.64 21.64
Total lens length 175.98 164.19 160.08
BF 37.99 44.61 56.87

d 9 30.11 12.12 1.00
d14 15.75 12.84 5.16
d17 1.00 7.96 13.22
d22 4.81 0.33 -2.50

ea22 17.14 19.60 24.55



(Numerical example 2)

Unit mm

Surface data surface number rd nd vd Effective diameter
1 209.053 2.10 1.84666 23.8 65.93
2 75.294 7.06 1.77250 49.6 62.34
3 339.444 0.15 61.46
4 56.915 6.73 1.77250 49.6 56.42
5 154.669 (variable) 54.97
6 * 113.791 1.60 1.88300 40.8 33.10
7 17.096 8.15 24.68
8 -42.698 1.15 1.59522 67.7 23.02
9 23.718 4.05 1.88300 40.8 21.07
10 111.835 0.79 20.58
11 -433.154 3.11 1.59270 35.3 20.61
12 -36.335 1.32 20.91
13 -21.892 1.15 1.72916 54.7 20.89
14 438.081 3.08 1.84666 23.8 23.19
15 -60.156 (variable) 24.15
16 (Aperture) ∞ 1.90 (Variable)
17 38.427 8.95 1.49700 81.5 28.47
18 -50.859 0.93 29.09
19 53.285 3.50 1.58313 59.4 28.75
20 * 144.845 3.62 28.17
21 -39.498 1.40 1.72047 34.7 28.13
22 -242.790 2.50 28.82
23 ∞ (variable) (variable)
24 27.659 9.30 1.43875 94.9 30.29
25 -56.801 0.20 29.75
26 73.911 6.46 1.49700 81.5 28.19
27 -59.314 0.15 26.93
28 * -51.050 2.10 1.85400 40.4 26.65
29 * 1270.569 1.96 25.86
30 -115.600 1.40 1.83400 37.2 25.90
31 74.664 9.09 1.51742 52.4 26.80
32 -40.258 29.29


Aspheric data 6th surface
K = 0.00000e + 000 A 4 = 7.32729e-006 A 6 = -7.39275e-009 A 8 = 1.73961e-011 A10 = -3.16147e-014 A12 = 7.73415e-017

20th page
K = 0.00000e + 000 A 4 = 2.47012e-006 A 6 = 7.87983e-009 A 8 = -3.87316e-011 A10 = 1.67858e-013 A12 = -9.43064e-017

28th page
K = 0.00000e + 000 A 4 = 3.25623e-005 A 6 = -1.71295e-007 A 8 = 4.91327e-010 A10 = -9.18257e-013 A12 = 6.95925e-016

29th page
K = 0.00000e + 000 A 4 = 4.89882e-005 A 6 = -1.42530e-007 A 8 = 4.38496e-010 A10 = -6.15162e-013 A12 = 2.53228e-016

Various data Zoom ratio 2.77

Wide angle Medium Telephoto focal length 24.76 34.99 68.45
F number 2.90 3.34 4.28
Angle of View 41.15 31.73 17.54
Image height 21.64 21.64 21.64
Total lens length 155.43 163.05 187.00
BF 38.45 47.15 64.31

d 5 2.72 11.70 30.33
d15 13.74 7.75 0.26
d23 6.61 2.54 -1.80

ea16 18.46 20.48 25.20
ea23 19.22 22.37 29.55

  Hereinafter, a detailed configuration in each embodiment will be described. In the first embodiment, in order from the object side, a negative first lens unit L1, a positive second lens unit L2, a positive third lens unit L3, a negative fourth lens unit L4, and a positive fifth lens unit L5. A 5-group zoom lens having a wide angle of view of 105 degrees, a zoom ratio of 2.1 times, and an open F value of 2.9 over the entire zoom range is introduced. The distance from the image side surface of the fifth lens unit L5 to the image surface satisfies the conditional expression (5), thereby providing a strong retrofocus power arrangement.

  Each group is driven by zooming from the wide-angle end to the telephoto end, narrowing the distance between L1 and L2, narrowing the distance between L2 and L3, widening the distance between L3 and L4, and narrowing the distance between L4 and L5. ing. Further, focusing is performed by moving the positive second lens unit L2 to the image side.

  A variable stop is provided on the image side of L4, and the F value from the wide-angle end to the telephoto end is determined. The position of the variable aperture is a position slightly away from the surface closest to the image side of L4, and effectively cuts the upper line of the intermediate image height at the wide-angle end. At the telephoto end, the variable aperture is opened, and the most object-side convex surface of L5 that satisfies the conditional expression (1) is narrowed away from the lens surface on the image side of L4 through the variable aperture. In Numerical Example 1, this indicates that the distance between the 23rd surfaces is negative at the telephoto end. By doing so, the intermediate luminous flux is effectively cut without pressing the driving space of each lens group.

  Further, the lens closest to the object side of L5 satisfies the conditional expressions (2) and (3), thereby correcting the curvature of field in the entire zoom range, correcting the chromatic aberration of magnification at the wide angle end, and on the axis at the telephoto end. At the same time that the chromatic aberration correction is effectively performed, a convex shape that satisfies the conditional expression (1) is effectively obtained.

  Next, the diameter of the variable diaphragm satisfies the conditional expression (4), and the variable diaphragm is disposed without increasing the outer diameter of the main body.

  In Embodiment 2, the first lens unit L1, the second lens unit L2, the third lens unit L3, and the fourth lens unit L4, which are configured in order from the object side, include all the wide-angle ends. A four-group zoom lens with an angle of view of 82 degrees, a zoom ratio of 2.8 times, and an open F value of 2.9 over the entire zoom range is introduced. The distance from the image side surface of the fourth lens unit L4 to the image surface satisfies the conditional expression (5), thereby providing a strong retrofocus power arrangement.

  Here, although Embodiment 2 is a positive lead type, the positive power of L1 is very weak, and the combined power on the object side from the exit pupil position is a strong negative, so it is expressed as a retrofocus type. . Each group is driven by zooming from the wide-angle end to the telephoto end to widen the interval between L1 and L2, narrow the interval between L2 and L3, and narrow the interval between L3 and L4. Further, focusing is performed by moving the negative second lens unit L2 toward the object side.

  A variable stop is provided on the image side of L3, and the F value from the wide angle end to the telephoto end is determined. The position of the variable stop is a position slightly away from the most image side surface of L3 and effectively cuts the upper line of the intermediate image height at the wide angle end.

  At the telephoto end, the variable aperture is opened, and the most object-side convex surface of L4 that satisfies the conditional expression (1) goes under the variable aperture and narrows the distance from the L3 image-side lens surface.

  In Numerical Example 2, this indicates that the interval between the 23rd surfaces is negative at the telephoto end. By doing so, the intermediate luminous flux is effectively cut without pressing the driving space of each lens group.

  Further, the lens on the most object side of L4 satisfies the conditional expressions (2) and (3), thereby correcting the curvature of field in the entire zoom range, correcting the chromatic aberration of magnification at the wide angle end, and on the axis at the telephoto end. At the same time that the chromatic aberration correction is effectively performed, a convex shape that satisfies the conditional expression (1) is effectively obtained.

  Next, the diameter of the variable diaphragm satisfies the conditional expression (4), and the variable diaphragm is disposed without increasing the outer diameter of the main body.

  As mentioned above, although the Example of the preferable optical system of this invention was described, it cannot be overemphasized that this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary.

STO Aperture driven by external drive command (main aperture), STV variable aperture,
IP imaging surface, L1 to L6 first lens group to sixth lens group,
The group that moves by Focus Focusing and its moving direction

Claims (6)

  A positive lens group on the most image side, a variable stop for determining an F value at the wide-angle end when the lens is adjacent to the most image side of the lens group adjacent to the object side of the positive lens group, and A zoom lens, wherein the object side surface vertex position of the positive lens group is disposed closer to the image side than the variable aperture position at the wide-angle end, and closer to the object side than the variable aperture position at the telephoto end. 2. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.50 <Rp / Svt <1.50
Rp: radius of curvature of the surface closest to the object side in the positive lens group
Svt: Effective diameter of the variable aperture at the telephoto end The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.40 <Ndp <1.58
0.020 <θgFp−0.6438 + 0.001682 × νdp <0.100
Ndp: refractive index of the positive lens closest to the object side in the final lens group
Νdp: Abbe number of the positive lens closest to the object side in the final lens group
・ ΘgFp: Abnormal partial dispersion ratio of the g-line of the positive lens closest to the object side in the final lens group The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
0.15 <Svt / En <0.80
En: Maximum effective diameter in the optical system, The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.00 <bkw / fw <4.00   An optical apparatus comprising the zoom lens according to any one of claims 1 to 5.