JP4142305B2 - Zoom lens - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens having an anti-vibration function, and more particularly to an anti-vibration function of a zoom lens used in a film photographic camera, a digital camera, a video camera, and the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a zoom lens having an image stabilization function, as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-316342, when zooming, a lens group used for zooming is configured in multiple groups. When correcting the fluctuation of the image position caused by camera shake or the like by moving the entire length, correction is performed by moving a part of the lens unit in a direction perpendicular to the optical axis.
[0003]
[Problems to be solved by the invention]
However, the zoom lens having the above-described image stabilization function has a problem in that the mechanism is complicated because the zoom lens group is composed of multiple groups. Furthermore, it has been necessary to place restrictions on the arrangement of each mechanical component for correcting fluctuations in the image position, such as an image stabilization mechanism and a camera shake detection mechanism.
[0004]
The present invention has been made in view of the above-described problems, and an object thereof is to provide a vibration-proof zoom lens having a simple mechanism.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention sequentially includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a negative refractive power in order from the object side. A third lens group G3, a fourth lens group G4 having a positive refractive power, and 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 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 third lens The interval between the group G3 changes, the interval between the third lens group G3 and the fourth lens group G4 decreases, and the interval between the fourth lens group G4 and the fifth lens group G5 changes.
[0006]
Further, as a displacement means for anti-vibration, the fourth lens group G4 is moved in a direction substantially orthogonal to the optical axis, and the first lens group G1 has a positive refractive power in order from the object side. The first lens group front portion GL1 and the first lens group rear portion GL2 having a positive refractive power, and the first lens group rear portion GL2 is focused.
[0007]
Further, when the focal length of the fourth lens group G4 is f4 and the focal length of the telephoto end is ft,
0.15 <f4 / ft <0.3 (1)
Satisfy the conditions.
[0008]
The fourth lens group G4 includes a negative lens and a positive lens, and when the average refractive index is nG4,
1.6> nG4 (2)
Satisfy the conditions.
[0009]
The first lens group rear part GL2 includes a negative lens and a positive lens, and when the average refractive index is nG2,
1.6> nG2 (3)
Satisfy the conditions.
[0010]
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,
2.2 <fL2 / f1 <4 (4)
Satisfy the conditions.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a first lens group G1 having a positive refractive power and a second lens having a negative refractive power in order 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. A group G2, a third lens group G3 having a negative refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive or negative refractive power, from the wide-angle end. At the time of zooming to the telephoto end, the first lens group G1 and the fifth lens group G5 are fixed with respect to the image plane, and 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, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the fourth lens group G4 and the fifth lens group. A basic configuration is adopted in which the interval of G5 changes.
[0012]
First, features and advantages of the zoom lens having the above basic configuration will be described.
[0013]
An optical system in which the zoom lens group is composed of multiple groups and moves the entire lens length at the time of zooming has the advantage that the entire lens length can be greatly shortened on the short focus side. Compared with such a full length fixed zoom lens, it has a drawback that it is mechanically complicated. Furthermore, as in the present invention, when an optical system that corrects fluctuations in the image position due to camera shake or the like is incorporated, there are additional elements such as a mechanism for driving the correction optical system and a camera shake detection mechanism. Restrictions are required. In order to ensure cost reduction and reliability, it is desirable that the zoom optical system is simple. In the present invention, the first lens group G1 and the final lens group are mechanically simplified by adopting a configuration in which the first lens group G1 and the final lens group are fixed with respect to the image plane regardless of the zoom. Further, since the aperture is located in the fifth lens group G5, which is a fixed group, the aperture driving is also facilitated. Further, by focusing with the first lens group rear portion GL2 having positive refractive power in the first lens group G1, the inner focus can be achieved without using a complicated cam, and the weight of the focus group is further reduced. Can measure.
[0014]
Hereinafter, the conditional expressions of the present invention will be described in detail. In general, it is desirable that the image stabilization optical system is small and light, and it is necessary to suppress a decrease in optical performance during image stabilization as much as possible in the entire zoom range. In particular, off-axis rays pass near the optical axis. It is desirable. Accordingly, the optical system in the vicinity of the stop may be replaced with an image stabilization optical system. In the present invention, since the fourth lens group G4 in the vicinity of the stop is set as an anti-vibration lens group, the above-described conditions can be satisfied.
[0015]
Conditional expression (1) is a condition for defining the ratio of the focal length between the image stabilizing lens group and the telephoto end. If the lower limit of Conditional Expression (1) is exceeded and the power of the image stabilizing lens group is increased, the decentering sensitivity increases and the amount of movement of the image stabilizing lens group decreases, but the optical performance during image stabilization decreases greatly. It is not preferable. Further, in order to prevent the optical performance from deteriorating, the number of components of the anti-vibration lens group increases, so that the weight increases and the anti-vibration driving cannot be performed. If the upper limit of conditional expression (1) is exceeded and the power of the image stabilizing lens group becomes weak, the image stabilizing effect cannot be obtained unless the image stabilizing drive amount is increased. The optical system becomes larger.
[0016]
Conditional expression (2) is a condition for reducing the weight of the image stabilizing optical system. In order to improve the followability of the image stabilizing lens group to the vibration of the photographing system, it is essential to reduce the weight of the image stabilizing lens group. Existing optical glass tends to have a higher specific gravity as the refractive index is higher, and classical glass has a lower specific gravity. Since this boundary is in the vicinity of a refractive index of 1.6, classic glass having a small specific gravity must be used in order to reduce the weight. In addition, the anti-vibration lens group must have a doublet structure or more. If it is a single lens, color frames and the like due to eccentricity occur, and the optical performance cannot be prevented from deteriorating. For these reasons, the anti-vibration lens group is composed of doublets, and the average refractive index must be 1.6 or less.
[0017]
Further, according to the present invention, by focusing with the first lens group rear portion GL2 having a positive refractive power in the first lens group G1, inner focusing can be performed without using a complicated cam, and the weight of the focus group is increased. Mitigation can be done.
[0018]
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. Therefore, in order to use a light glass material, it is necessary to restrict the refractive index. For super telephoto zoom, it is necessary to suppress fluctuations in chromatic aberration due to focusing. Therefore, the inner focus portion needs a doublet, and if the average refractive index is not less than 1.6, the weight cannot be reduced.
[0019]
Conditional expression (4) is a condition for defining the ratio between the focal length of the inner focus portion and the focal length of the first lens group G1. When 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 decreases, but the variation in spherical aberration and chromatic aberration increases, making correction difficult. If the upper limit of conditional expression (4) is exceeded and the power of the inner focus group becomes relatively weak, the amount of focusing increases, so the diameter of the focusing group increases and the lens weight increases.
[0020]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. The zoom lens of the present invention includes, 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 and 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 The fifth lens group G5 is fixed with respect to the image plane, the distance between the first lens group G1 and the second lens group G2 changes, and the distance between the second lens group G2 and the third lens group G3 is As a result, 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.
[0021]
The first lens group G1 includes, in order from the object side, a first lens group front part GL1 having a positive refractive power and a first lens group rear part GL2 having a positive refractive power. Focus on the rear group GL2. The fourth lens group G4 is a displacing unit that corrects fluctuations in the image position by moving in a direction substantially orthogonal to the optical axis. A diaphragm is disposed in the fifth lens group G5.
[0022]
The specification value of each Example of this invention is 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 represents the refractive index of the d line, and Vd represents the Abbe number.
[0023]
Example 1
f = 138.5-387.2
FNO = 5.87
2ω = 17.6 ° ～ 6.2 °
Number R (I) D (I) ND Vd
[1] 136.7027 3.2468 1.723342 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] 823.759 18.0164 Variable interval
[7] 107.4880 2.4997 1.62004 36.3
[8] 67.0585 8.2840 1.48749 70.4
[9] 686.6027 6.0588 Variable interval
[10] −418.6005 1.8975 1.77250 49.6
[11] 36.0489 5.2908 1.83400 37.3
[12] 100.5149 4.0425 Variable interval
[13] 130.7419 1.4217 1.80610 40.7
[14] 55.1088 3.8822
[15] -59.0834 1.3725 1.77250 49.6
[16] 65.6068 3.6265 1.84666 23.8
[17] -326.323 63.2043 Variable interval
[18] 62.7711 1.5405 1.62004 36.3
[19] 30.8271 8.5058 1.48749 70.4
[20] −90.5788 12.4290 Variable interval
[21] −63.2920 1.3089 1.78590 43.9
[22] 206.9558 3.36693 1.54814 45.8
[23] −67.5334 1.5000
[24] 0.0 1.6000 aperture
[25] 39.2783 4.3451 1.49700 81.6
[26] 416.0399 56.1724
[27] -22.3433 1.3751 1.77250 49.6
[28] -91.8863 63980
[29] 249.33307 3.4814 1.62004 36.3
[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 18.016
D (9) 6.087 16.6.372 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
Movement amount of anti-vibration lens group (mm) 0.7
[0024]
Example 2
f = 137.9-386.1
FNO = 5.87
2ω = 17.8 ° ～ 6.2 °
Number R (I) D (I) ND Vd
[1] 142.0371 3.2468 1.732342 38.0
[2] 78.9709 0.1000
[3] 76.8159 11.7976 1.49700 81.6
[4] -564.8824 0.1000
[5] 150.2047 5.5265 1.49700 81.6
[6] 1418.0726 17.9922 Variable interval
[7] 113.466 2.4997 1.62004 36.3
[8] 72.5338 7.5577 1.48749 70.4
[9] 794.7210 2.0943 variable interval
[10] -1324.88834 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] 59.82525 4.1259
[15] −67.8972 1.5676 1.77250 49.6
[16] 59.9532 4.0517 1.84666 23.8
[17] -1414.3864 67.1430 Variable interval
[18] 65.7865 1.5499 1.62004 36.3
[19] 31.7920 8.7817 1.48749 70.4
[20] -86.2339 5.5127 Variable interval
[21] -61.2733 1.4557 5785590 43.9
[22] 157.2314 4.0803 1.54814 45.8
[23] -64.3498 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 137.92833 299.0804 386.451
Back focus 48.3100 48.0162 48.5913
FNO 5.8696 5.8593 5.8863
D (6) 17.9922 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
Movement amount of anti-vibration lens group (mm) 0.7
[0025]
Example 3
f = 139.8-388.1
FNO = 5.83
2ω = 17.6 ° ～ 6.2 °
Number R (I) D (I) ND Vd
[1] 109.62020 3.2468 1.732342 38.0
[2] 70.2508 0.1000
[3] 69.1700 11.6270 1.49700 81.6
[4] 94104495 0.1000
[5] 134.7214 5.8208 1.49700 81.6
[6] 895.1680 17.64448 Variable interval
[7] 96.8656 2.4997 1.62004 36.3
[8] 57.9851 8.7405 1.48749 70.4
[9] 417.5120 9.1734 Variable interval
[10] -958.3380 1.8526 1.77250 49.6
[11] 31.3337 8.1424 1.83400 37.3
[12] 79.2256 3.3315 Variable interval
[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 interval
[18] 62.1409 2.4084 1.62004 36.3
[19] 29.3501 9.0551 1.48749 70.4
[20] −72.4664 12.5285 Variable interval
[21] -54.1107 1.3315 1.78590 43.9
[22] 271.99739 3.1690 1.54814 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 29.2920
D (12) 3.3315 17.1069 39.9196
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
Movement amount of anti-vibration lens group (mm) 0.7
[0026]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a zoom lens having an anti-vibration mechanism with a sufficient arrangement of components such as an anti-vibration mechanism and a camera shake detection mechanism with a simple lens configuration.
[Brief description of the drawings]
FIG. 1 is a lens configuration diagram of Example 1. FIG. 2 is an aberration diagram at the wide-angle end during non-vibration prevention according to Example 1. FIG. 3 is an aberration diagram of intermediate focal length during non-vibration prevention according to Example 1. 4 is a diagram showing aberrations at the telephoto end during non-vibration according to Example 1. FIG. 5 is a diagram showing coma aberration at the wide-angle end during anti-vibration according to Example 1. FIG. FIG. 7 is a coma aberration diagram at the telephoto end during image stabilization of Example 1. FIG. 8 is a lens configuration diagram of Example 2. FIG. 9 is an aberration diagram at the wide angle end during non-image stabilization of Example 2. FIG. 10 is an aberration diagram of the intermediate focal length when the image stabilization is not performed according to the second embodiment. FIG. 11 is an aberration diagram at the telephoto end when the image stabilization is not performed according to the second embodiment. FIG. 13 is a graph showing coma aberration at an intermediate focal length during vibration isolation in Example 2. FIG. FIG. 15 is a lens configuration diagram of Example 3. FIG. 16 is an aberration diagram at the wide-angle end during non-vibration prevention according to Example 3. FIG. 17 is an intermediate focal length during non-vibration prevention according to Example 3. FIG. 18 is an aberration diagram at the telephoto end during non-vibration prevention in Example 3. FIG. 19 is a coma aberration diagram at the wide-angle end during vibration isolation in Example 3. FIG. 20 is during vibration isolation in Example 3. Fig. 21 shows the coma aberration at the intermediate focal length in Fig. 21. Fig. 21 shows the coma aberration at the telephoto end during image stabilization in Example 3.
G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group GL1 1st lens group front part GL2 1st lens group rear part

Claims (3)

In a zoom lens having an image stabilization 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 third lens having a negative refractive power a group G3, the fourth lens group G4 having positive refractive power, and a fifth lens group G5 having positive or negative refractive power, upon 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 third lens group G3 In the zoom lens, the interval changes, the interval between the third lens group G3 and the fourth lens group G4 decreases, and the interval between the fourth lens group G4 and the fifth lens group G5 changes . ,
Displacement means for moving the fourth lens group G4 in a direction substantially perpendicular to the optical axis to provide vibration isolation, when the focal length of the fourth lens group G4 is f4 and the focal length of the telephoto end is ft. ,
0. 15 <f4 / ft < 0. 3 ····· (1)
Zoom lens that satisfies the conditional expression The fourth lens group G4 includes a negative lens and a positive lens, and when the average refractive index is nG4,
1.6> nG4 (2)
The zoom lens according to claim 1 , wherein the following conditional expression is satisfied. The first lens group G1 includes, in order from the object side, a first lens group front part GL1 having a positive refractive power and a first lens group rear part GL2 having a positive refractive power, and the first lens group rear part. The first lens group rear portion GL2 is composed of a negative lens and a positive lens, and the average refractive index is nG2.
1. 6> nG2 (3)
Is satisfied,
And the ratio when the focal length of the rear part GL2 of the first lens group is fL2 and the focal length of the first lens group G1 is f1,
2. 2 <fL2 / f1 < 4 ····· (4)
The zoom lens according to claim 1 or claim 2 satisfies the conditional expression.

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