JP2003241095A - Zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens possessing a vibration-proof function and having a high-performance and simple mechanism. <P>SOLUTION: The zoom lens is equipped with a 1st lens group G1 having positive refractive power, a 2nd lens group G2 having negative refractive power, a 3rd lens group G3 having negative refractive power, a 4th lens group G4 having positive refractive power, and a 5th lens group G5 having positive or negative refractive power in order from an object side. In the case of varying power from a wide angle end to a telephoto end, the 1st and the 5th lens groups G1 and G5 are fixed with respect to an image surface, space between the 1st and the 2nd lens groups G1 and G2 is changed, space between the 2nd and the 3rd lens groups G2 and G3 is changed, space between the 3rd and the 4th lens groups G3 and G4 is decreased, and space between the 4th and the 5th lens groups G4 and G5 is changed. The 4th lens group G4 can be moved in a direction nearly orthogonal to an optical axis. <P>COPYRIGHT: (C)2003,JPO

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 an image stabilizing function, and more particularly to an image stabilizing function of a zoom lens used in a film photographic camera, a digital camera, a video camera or the like.

[0002]

2. Description of the Related Art Conventionally, in a zoom lens having an image stabilizing function, as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-316342, at the time of zooming, a large number of lens groups are used for zooming. In order to correct the fluctuation of the image position due to camera shake and the like by moving the entire lens length, a part of the lens group is moved in the direction orthogonal to the optical axis for correction.

[0003]

However, in the zoom lens having the image stabilizing function as described above, there is a problem that the mechanism becomes complicated because the zoom lens group is composed of multiple groups. Furthermore, it has been necessary to impose restrictions on the arrangement of each mechanical component for compensating for changes in the image position such as the image stabilization mechanism and the camera shake detection mechanism.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a vibration-proof zoom lens having a simple mechanism.

[0005]

In order to solve the above-mentioned problems, the present invention has a first lens group G1 having a positive refractive power and a second lens group G having a negative refractive power in order from the object side.
2, a third lens group G3 having a negative refracting power, a fourth lens group G4 having a positive refracting power, and a fifth lens group G5 having a positive or negative refracting power, and a telephoto end from the wide angle end. At the time of zooming to the edge, the first lens group G1 and the fifth lens group G5 are fixed with respect to the image plane, the distance between the first lens group G1 and the second lens group G2 changes, and Second lens group G
The distance between the second lens group G3 and the third lens group G3 changes, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the distance between the fourth lens group G4 and the fifth lens group G5 changes. It was configured to do.

Further, as displacement means for vibration isolation,
The fourth lens group G4 is configured to move in a direction substantially orthogonal to the optical axis, and the first lens group G1 includes, in order from the object side, a first lens group front portion GL1 having a positive refractive power and a positive lens group G1. The rear part GL2 of the first lens group having a refractive power is provided, and the rear part GL2 of the first lens group is used for focusing.

Further, when the focal length of the fourth lens group G4 is f4 and the focal length at the telephoto end is ft, the condition of 0.15 <f4 / ft <0.3 (1) is satisfied. Be satisfied.

The fourth lens group G4 comprises a negative lens and a positive lens, and when the average refractive index is nG4, the condition of 1.6> nG4 (2) is satisfied.

The rear portion GL2 of the first lens group is composed of a negative lens and a positive lens, and when the average refractive index is nG2, the condition of 1.6> nG2 (3) is satisfied.

When the focal length of the rear portion GL2 of the first lens group is fL2 and the focal length of the first lens group G1 is f1, the ratio is 2.2 <fL2 / f1 <4 (4) ) Is satisfied.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, a first lens group G1 having a positive refractive power and a negative lens group are sequentially arranged from the object side so as to be suitable for a zoom lens for a film photographic camera, a digital camera or a video camera. Second lens group G having refractive power
2, a third lens group G3 having a negative refracting power, a fourth lens group G4 having a positive refracting power, and a fifth lens group G5 having a positive or negative refracting power, and a telephoto end from the wide angle end. At the time of zooming to the edge, the first lens group G1 and the fifth lens group G5 are fixed with respect to the image plane, the distance between the first lens group G1 and the second lens group G2 changes, and Second lens group G
The distance between the second lens group G3 and the third lens group G3 changes, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the distance between the fourth lens group G4 and the fifth lens group G5 changes. The basic configuration of doing is adopted.

First, the features and advantages of the zoom lens having the above-mentioned basic structure will be described.

An optical system having a large number of zoom lens groups and moving the entire lens length at the time of zooming has an advantage that the total lens length can be greatly shortened on the short focus side. Compared with a fixed-length fixed-type zoom lens such as a group zoom, it has drawbacks such as being mechanically complicated. Further, when the optical system for correcting the fluctuation of the image position due to the camera shake is incorporated like the present invention, there are additional elements such as a mechanism for driving the correction optical system and a camera shake detection mechanism, so that the mechanical layout is further improved. Limits are needed. It is desirable that the zoom optical system be simple in order to reduce costs and ensure reliability. The present invention mechanically simplifies by adopting a configuration in which the first lens group G1 and the final lens group are fixed to the image plane regardless of zooming. Moreover, since the diaphragm is located in the fifth lens group G5 which is a fixed group, driving of the diaphragm becomes easy. Further, by focusing on the rear portion GL2 of the first lens group G1 having a positive refractive power in the first lens group G1, inner focusing becomes possible without using a complicated cam, and the weight of the focusing group is further reduced. You can measure.

The conditional expression of the present invention will be described in detail below.
In general, it is desirable for the image stabilization optical system to be small and lightweight, and it is necessary to suppress deterioration of optical performance during image stabilization in the entire zoom range as much as possible, and especially off-axis rays pass near the optical axis. Is desirable. Therefore, the optical system in the vicinity of the diaphragm should be the image stabilization optical system. In the present invention, since the fourth lens group G4 near the diaphragm is used as the anti-vibration lens group, the above conditions can be satisfied.

Conditional expression (1) is a condition for defining the ratio between the image stabilizing lens unit and the focal length at the telephoto end. If the lower limit of conditional expression (1) is exceeded and the power of the anti-vibration lens group becomes strong, the eccentricity sensitivity becomes large and the movement amount of the anti-vibration lens group becomes small, but the deterioration of the optical performance at the time of anti-vibration becomes large. Not preferable. Further, in order to prevent the deterioration of the optical performance, the number of constituent lenses of the anti-vibration lens group increases, so that the weight becomes heavy and the anti-vibration drive cannot be performed. When the upper limit of conditional expression (1) is exceeded and the power of the anti-vibration lens group becomes weak, the anti-vibration effect cannot be obtained unless the anti-vibration drive amount is increased. The optical system of becomes larger.

Conditional expression (2) is a condition for reducing the weight of the image stabilizing optical system. In order to improve the followability of the anti-vibration lens group to the vibration of the photographing system, it is essential to reduce the weight of the anti-vibration lens group. The existing optical glass tends to have a higher specific gravity as the refractive index increases, and the classical glass has a lower specific gravity. Since this boundary is near the refractive index of 1.6, in order to reduce the weight, it is necessary to use classical glass having a small specific gravity. Further, the anti-vibration lens group must have a structure of doublet or more. With a single lens, color coma and the like due to decentering occur, and it is not possible to prevent deterioration of optical performance. For these reasons, the anti-vibration lens group consists of doublets and the average refractive index must be 1.6 or less.

Further, according to the present invention, by focusing on the rear portion GL2 of the first lens group having a positive refracting power in the first lens group G1, it becomes possible to perform inner focusing without using a complicated cam. The weight of the group can be reduced.

Conditional expression (3) is a condition for defining the average refractive index of the inner focus portion. As described in the conditional expression (2), the refractive index of the glass material and the specific gravity are in a substantially proportional relationship, and therefore, in order to use a lightweight glass material, it is necessary to restrict the refractive index. Further, for super-telephoto zoom, since it is necessary to suppress the variation of chromatic aberration due to focusing, a doublet is required in the inner focus portion, and further weight reduction cannot be achieved unless the average refractive index is 1.6 or less.

Conditional expression (4) is a condition for defining the ratio of the focal length of the inner focus portion to the focal length of the first lens group G1. If the lower limit of conditional expression (4) is exceeded and the power of the inner focus group becomes relatively strong, the amount of extension of the focus group will decrease, but spherical aberration and chromatic aberration will vary greatly, and correction will be difficult. If the upper limit of the conditional expression (4) is exceeded and the power of the inner focus group becomes relatively weak, the focusing amount becomes large and the diameter of the focusing group becomes large, so that the lens weight increases, which is not preferable.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. The zoom lens of the present invention comprises, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a negative refractive power. , A fourth lens group G4 having a positive refractive power,
A fifth lens group G5 having a positive or negative refractive power, and at the time of zooming from the wide-angle end to the telephoto end, the first lens group G1 and the fifth lens group G5 are fixed with respect to the image plane, The distance between the first lens group G1 and the second lens group G2 changes, the distance between the second lens group G2 and the third lens group G3 changes, and the third lens group G3 and the fourth lens group change. The distance between the group G4 decreases, and the fourth lens group G4 and the fifth lens group G5
The interval of changes.

The first lens group G1 includes, in order from the object side, the first lens group front portion GL1 having a positive refractive power.
And a rear portion GL2 of the first lens group having a positive refractive power, and focusing is performed at the rear portion GL2 of the first lens group. The fourth lens group G4 is a displacement unit that moves in a direction substantially orthogonal to the optical axis to correct the fluctuation of the image position.
A diaphragm is arranged in the fifth lens group G5.

The specifications of each embodiment of the present invention are as follows. f is the focal length, FNO is the F number, 2ω is the angle of view, the number is the surface number, the order of the lens surface from the object side, R
(I) is the radius of curvature of the lens surface, D (I) is the distance between the lens surfaces, ND is the d-line refractive index, and Vd is the Abbe number.

[0023]   Example 1 f = 138.5-387.2 FNO = 5.87 2ω = 17.6 ° to 6.2 ° Number R (I) D (I) ND Vd [1] 136.7027 3.2468 1.72342 38.0 [2] 77.7391 0.1000 [3] 75.6236 11.6305 1.49700 81.6 [4] -783.2980 0.1000 [5] 144.3549 5.4965 1.49700 81.6 [6] 823.7759 18.0164 Variable spacing [7] 107.4880 2.4997 1.62004 36.3 [8] 67.0585 8.2840 1.48749 700.4 [9] 686.6027 6.0587 Variable spacing [10] -4182.6005 1.8975 1.77250 49.6 [11] 36.0489 5.2908 1.83400 37.3 [12] 100.5149 4.0425 Variable spacing [13] 130.7419 1.4217 1.80610 40.7 [14] 55.1088 3.8822 [15] -59.0834 1.3725 1.77250 49.6 [16] 65.606068 3.6265 1.8846 23.8 [17] -326.4323 63.2043 Variable spacing [18] 62.7711 1.5405 1.62004 36.3 [19] 30.2871 8.5058 1.48749 70.4 [20] -90.5788 12.4290 Variable spacing [21] -63.2920 1.3089 1.78590 43.9 [22] 206.9558 3.3693 1.554814 45.8 [23] -67.5334 1.5000 [24] 0.0 1.6000 aperture [25] 39.2783 4.3345 1.49700 81.6 [26] 416.0399 56.1724 [27] -22.3433 1.3751 1.77250 49.6 [28] -91.8863 0.6980 [29] 249.33073073.48141.6200436.3 [30] -59.5431 4.9982 [31] 0.0 Focal length 138.5848 289.2258 387.2197 Back focus 48.5059 48.5850 48.8957 FNO 5.8730 5.87 5.87 D (6) 18.0164 18.0164 18.0164 D (9) 6.0587 16.3972 11.8961 D (12) 4.0425 19.3441 47.3668 D (17) 63.2043 22.1381 4.2500 D (20) 12.4290 27.9110 21.4830 f1: 115.78 fL2: 320.43 f2: -148.35 f3: -56.08 f4: 92.79 f5: −1000.00 f4 / ft = 0.24 fL2 / f1 = 2.77 Moving amount of anti-vibration lens group (mm) 0.7

[0024]   Example 2 f = 137.9 to 386.1 FNO = 5.87 2ω = 17.8 ° ~ 6.2 ° Number R (I) D (I) ND Vd [1] 142.0371 3.24.868 1.7342 38.0 [2] 78.9970 0.1000 [3] 76.8159 11.7976 1.49700 81.6 [4] -5644.8824 0.1000 [5] 150.2047 5.6265 1.49700 81.6 [6] 1418.0726 179922 Variable spacing [7] 113.3466 2.4997 1.62004 36.3 [8] 72.5338 7.55577 1.48749 70.4 [9] 794.7210 2.0943 Variable spacing [10] -1324.8834 2.2809 1.77250 49.6 [11] 38.5570 6.4963 1.83400 37.3 [12] 106.7858 2.6980 Variable spacing [13] 123.6498 1.4217 1.80610 40.7 [14] 59.7825 4.1259 [15] -67.8972 1.5676 1.77250 49.6 [16] 59.9532 4.0517 186.4666 23.8 [17] -141.43864 67.1430 Variable spacing [18] 65.78665 1.5499 1.62004 36.3 [19] 31.7920 8.7817 1.48749 70.4 [20] -86.2339 5.5127 Variable spacing [21] -61.2733 1.4557 1.78590 43.9 [22] 157.2314 4.0803 1.554814 45.8 [23] -64.4.398 1.5000 [24] 0.0 1.6000 aperture [25] 39.2783 4.8217 1.49700 81.6 [26] 388.7399 57.5996 [27] -22.0959 1.3328 1.77250 49.6 [28] -129.2669 1.0442 [29] 305.7365 3.8234 1.62004 36.3 [30] -49.8686 7.7942 [31] 0.0 Focal length 137.9283 299.0804 386.1451 Back focus 48.3100 48.0162 48.5913 FNO 5.8696 5.8593 5.8863 D (6) 179922 17.9922 17.9922 D (9) 2.0943 7.9715 6.5387 D (12) 2.6980 41.5447 55.0914 D (17) 67.1430 23.2207 4.2500 D (20) 5.5127 4.9802 11.3456 f1: 114.03 fL2: 326.64 f2: -147.61 f3: -60.22 f4: 93.29 f5: -500.13 f4 / ft = 0.24 fL2 / f1 = 2.86 Moving amount of anti-vibration lens group (mm) 0.7

[0025]   Example 3 f = 139.8 to 388.1 FNO = 5.83 2ω = 17.6 ° to 6.2 ° Number R (I) D (I) ND Vd [1] 109.2620 3.2468 1.72342 38.0 [2] 70.2508 0.1000 [3] 69.1700 11.6270 1.49700 81.6 [4] 9410.4495 0.1000 [5] 134.7214 5.8208 1.49700 81.6 [6] 895.1680 17.64448 Variable spacing [7] 96.8656 2.4997 1.62004 36.3 [8] 57.9851 8.7405 1.48749 70.4 [9] 417.5120 9.1734 Variable spacing [10] -958.3380 1.8526 1.77250 49.6 [11] 31.3337 8.1424 1.83400 37.3 [12] 79.2256 3.3315 Variable spacing [13] 107.3454 1.4217 1.80610 40.7 [14] 45.2915 3.7821 [15] -50.1418 1.3789 1.77250 49.6 [16] 50.1453 3.7529 1.84666 23.8 [17] -334.1180 46.8922 Variable spacing [18] 62.1409 2.4084 1.62004 36.3 [19] 29.3501 9.0551 1.48749 70.4 [20] -72.4664 12.5285 Variable spacing [21] -54.1107 1.3315 1.78590 43.9 [22] 271.9739 3.1690 1.554814 45.8 [23] -67.8245 1.5000 [24] 0.0 1.6000 aperture [25] 39.2783 4.7867 1.49700 81.6 [26] -651.9249 49.4312 [27] -23.0048 1.3631 1.77250 49.6 [28] -44.4602 0.1000 [29] 1942.7156 2.8006 1.62004 36.3 [30] -75.7080 21.9910 [31] 0.0 Focal length 139.7805 284.2072 388.1634 Back focus 48.4234 47.9760 48.6400 FNO 5.8289 5.8103 5.8383 D (6) 17.6448 17.6448 17.6448 D (9) 9.1734 20.7182 20.2920 D (12) 3.3315 17.1069 30.9196 D (17) 46.8922 19.6142 4.2500 D (20) 12.5285 14.9770 16.4484 f1: 110.34 fL2: 332.23 f2: −107.26 f3: -46.00 f4: 83.82 f5: 420.74 f4 / ft = 0.22 fL2 / f1 = 3.01 Moving amount of anti-vibration lens group (mm) 0.7

[0026]

As described above, according to the present invention, it is possible to realize a zoom lens having a simple lens structure and having a vibration proof mechanism that allows a sufficient arrangement of components such as a vibration proof mechanism and a camera shake detection mechanism. .

[Brief description of drawings]

FIG. 1 is a lens configuration diagram of Example 1.

FIG. 2 is an aberration diagram of Example 1 at the wide-angle end without vibration isolation.

FIG. 3 is an aberration diagram of the intermediate focal length when the image stabilization is not performed in Example 1.

FIG. 4 is an aberration diagram of Example 1 at the telephoto end during non-vibration isolation.

5 is a coma aberration diagram at the wide-angle end during image stabilization in Example 1. FIG.

FIG. 6 is a coma aberration diagram of the intermediate focal length during image stabilization in Example 1.

7 is a coma aberration diagram at the telephoto end during image stabilization in Example 1. FIG.

FIG. 8 is a lens configuration diagram of Example 2.

FIG. 9 is an aberration diagram of Example 2 at the wide-angle end without vibration isolation.

FIG. 10 is an aberration diagram of the intermediate focal length when the image stabilization is not performed in Example 2;

FIG. 11 is an aberration diagram of Example 2 at the telephoto end without vibration isolation.

FIG. 12 is a coma aberration diagram at the wide-angle end during image stabilization in Example 2.

FIG. 13 is a coma aberration diagram of the intermediate focal length during image stabilization in the second embodiment.

FIG. 14 is a coma aberration diagram at the telephoto end during image stabilization in Example 2.

FIG. 15 is a lens configuration diagram of Example 3.

FIG. 16 is an aberration diagram of Example 3 at the wide-angle end without vibration isolation.

FIG. 17 is an aberration diagram of the intermediate focal length when the image stabilization is not performed in Example 3;

FIG. 18 is an aberration diagram of a telephoto end of the third embodiment without vibration isolation.

FIG. 19 is a coma aberration diagram at the wide-angle end during image stabilization in Example 3.

FIG. 20 is a coma aberration diagram of Example 3 at an intermediate focal length during image stabilization.

FIG. 21 is a coma aberration diagram at the telephoto end during image stabilization in Example 3;

[Explanation of symbols]

G1 first lens group G2 Second lens group G3 Third lens group G4 4th lens group G5 5th lens group GL1 Front of first lens group GL2 1st lens group rear part

Claims (7)

[Claims] 1. A zoom lens having an image stabilizing function, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a negative refractive power. And a fourth lens group G4 having a positive refracting power and a fifth lens group G5 having a positive or negative refracting power, and at the time of zooming from the wide-angle end to the telephoto end, The first lens group G1 and the fifth lens group G5 are fixed with respect to the image plane, the distance between the first lens group G1 and the second lens group G2 changes, and the second lens group G2 and the second lens group G2 change. Third
The distance between the lens groups G3 changes, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the fourth lens group G4 changes.
And the distance between the fifth lens group G5 changes. 2. The zoom lens according to claim 1, further comprising a displacement means for moving the fourth lens group G4 in a direction substantially orthogonal to the optical axis for vibration isolation. 3. The focal length of the fourth lens group G4 is f
4. When the focal length at the telephoto end is ft, the zoom lens according to claim 2, which satisfies the condition of 0.15 <f4 / ft <0.3 (1). 4. The fourth lens group G4 comprises a negative lens and a positive lens, and when the average refractive index is nG4, the condition of 1.6> nG4 (2) is satisfied. The zoom lens according to item 3. 5. The first lens group G1 includes, in order from the object side, a first lens group front portion GL1 having a positive refractive power and a first lens group rear portion GL2 having a positive refractive power, The zoom lens according to claim 1 or 2, wherein the rear part GL2 of the first lens group is focused. 6. The rear portion GL2 of the first lens group is composed of a negative lens and a positive lens, and when the average refractive index is nG2, the condition of 1.6> nG2 (3) is satisfied. The zoom lens according to item 5. 7. The ratio when the focal length of the rear portion GL2 of the first lens group is fL2 and the focal length of the first lens group G1 is f1 is 2.2 <fL2 / f1 <4. The zoom lens according to claim 6, wherein the condition (4) is satisfied.