Imaging optical system, and photographing device using the same

Abstract

To provide a zoom lens that enables small-sized and light-weight focusing, has less aberration fluctuation in zooming, and can obtain high optical performance over the entire object distance.SOLUTION: A zoom lens of the present invention is a zoom lens comprising, from an object side, a lens group Bp having a positive refractive power, a lens group Bn having a negative refractive power, and a rear group having a positive refractive power, and the groups change intervals to vary magnification. The rear group has a group Fp having a positive refractive power, a group Fn having a negative refractive power, and a final lens group Br, which are arranged adjacent to each other from the object side. The groups Fp and Fn move while changing the interval therebetween in zooming and focusing. The groups Fp and Fn each comprise one lens element. When the amount of movement of the group Fp is defined as mFp and the amount of movement of the group Fn is defined as mFn in zooming, the following conditional expression is satisfied. (1) mFn / mFp>1.28.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a photographic lens suitable for use in photographic devices such as digital cameras and video cameras. [Background technology]

[0002] As a photographic optical system, a telephoto zoom lens with a fast FNO and a half angle of view of around 20 to 5 degrees is ideal for indoor sports photography, taking advantage of fast shutter speeds, and portrait photography, taking advantage of bokeh. Telephoto zoom lenses need to focus on the subject quickly, so the focus group needs to be extremely lightweight in order to be able to move as quickly as possible.

[0003] On the other hand, there is a demand for good performance from infinity to close range, and as a result, the use of floating focus, in which two focus drive groups move independently, has become more common. Examples of the use of floating focus are seen in Patent Document 1 and Patent Document 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-16808 [Patent Document 2] Patent No. 6071465 specification Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, focusing is performed using a positive group and a negative group adjacent from the object side, and high image plane characteristics are obtained, but this configuration tends to increase the lens diameter of the positive group on the image side, making it insufficient for weight reduction. On the other hand, in Patent Document 2, floating force is performed using a positive and a negative group adjacent from the object side, and a lightweight focus group is obtained because it is configured with a small number of lenses. However, in Patent Document 2, the refractive power of the focus group is strong because the F-number is relatively slow, and therefore a sufficiently lightweight focus group cannot be obtained even if the aperture is increased.

[0006] Therefore, an object of the present invention is to provide a zoom lens that is small and lightweight, capable of focusing, has little aberration fluctuation during zooming, and provides high optical performance over the entire object distance range. [Means for solving the problem]

[0007] In order to achieve the above object, the zoom lens of the present invention comprises, from the object side, a lens group Bp of positive refractive power, a lens group Bn of negative refractive power, and a rear group also of positive refractive power, wherein the zoom ratio is varied by varying the spacing between each group, and the rear group has a lens group Fp of positive refractive power and a lens group Fn of negative refractive power arranged adjacent to each other from the object side, and a final lens group Br, wherein Fp and Fn move while varying the spacing between them during zooming and focusing, and each of Fp and Fn consists of a single lens element, and wherein when the amount of movement of Fp during zooming is mFp and the amount of movement of Fn is mFn, the following conditional expression is satisfied: mFn / mFp > 1.28 …(1) In the present invention, mFn / mFp > 1.30 is preferred. Also, mFn / mFp > 1.35 is preferred. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce the weight of the focus group in a large-aperture telephoto zoom lens. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of a lens in an optical system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a longitudinal aberration diagram of the optical system according to the first embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view of a lens in an optical system according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a longitudinal aberration diagram of the optical system according to the second embodiment of the present invention. [Figure 5] FIG. 10 is a cross-sectional view of a lens in an optical system according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a longitudinal aberration diagram of the optical system according to the third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0011] Figure 1 is a cross-sectional view of Example 1 of the present invention at the wide-angle end. This is a telephoto zoom lens with a half angle of view of 16.7 to 9.1 degrees, and achieves a bright F-number of 2.8 to 4.0. A group is defined as one whose spacing changes during magnification change from the wide-angle end to the telephoto end or during focusing, and Example 1 has a seven-group configuration with, from the object side, positive, negative, positive, positive, positive, negative, and negative refractive powers.

[0012] The movement of the groups when changing magnification from the wide-angle end to the telephoto end is indicated by arrows, and the zoom lens of Example 1 is configured so that the first group (Bp) moves toward the object side, the second group (Bn) remains fixed during magnification, the third group moves toward the object side, the fourth group moves toward the object side, the fifth group (Fp) moves toward the object side, the sixth group (Fn) moves toward the object side, and the seventh group (Br) moves toward the object side.

[0013] When considering weight reduction for the focus group, in a telephoto zoom lens with a relatively large aperture, the lens diameters of the first to third groups are determined by the FNO, and as the aperture increases, the lens diameter also increases, making them unsuitable for use as a focus group.

[0014] On the other hand, in interchangeable lenses for mirrorless cameras with short back focal lengths, the lens diameter of the lens group closest to the image side is determined by the size of the sensor, so the lens diameter tends to be large, making it unsuitable for use as a focus group.

[0015] Therefore, in this lens, focusing from infinity to close range is performed by moving the fifth lens group (Fp) and the sixth lens group (Fn). During focusing, at the wide-angle end, both Fp and Fn move toward the object side, and at the telephoto end, Fp moves toward the object side and Fn moves toward the image side. The trajectory of the focus group at close range after movement is shown by the dotted line in Figure 1.

[0016] In rear-focus types, when the focus lens element moves toward the image side, vignetting tends to increase, and to prevent this, it was necessary to increase the lens diameter, but in this lens, the focus group moves toward the object side from the wide-angle end to the intermediate position, preventing the lens diameter from becoming larger. Also, at the telephoto end, where the amount of movement of the focus group tends to be large, the Fp group moves toward the object side and the Fn group moves toward the image side, which increases focus sensitivity and reduces the amount of lens movement, preventing the lens diameter from becoming larger.

[0017] When the amount of movement of Fp during zooming is mFp and the amount of movement of Fn is mFn, it is preferable to satisfy the following conditional expression. mFn / mFp > 1.28 …(1) Equation (1) represents the ratio of the amount of movement of the Fp group and the Fn group, and indicates that they move so that the distance between Fp and Fn becomes narrower when zooming. By setting the range of equation (1), Fp and Fn have a magnification relationship with respect to zooming, which reduces the burden of zooming on the other zooming groups, making it easier to achieve high performance.

[0018] In addition, by increasing the distance between Fp and Fn at the wide-angle end, the lens diameter of the Fn group is reduced by utilizing the converging effect of the Fp group.

[0019] The lens group Br preferably has negative refractive power and includes, from the object side, at least a positive lens group Lp and a negative lens group Ln, with the widest lens spacing dpn between them. In particular, when a large sensor size is required, increasing the angle of incidence onto the sensor allows the lens diameter to be reduced. Therefore, it is preferable that the final lens group have negative refractive power and the lens exit pupil be shortened.

[0020] When the wide-angle end focal length is fw, the distance from the exit pupil at the wide-angle end to the image is Expw, the telephoto end focal length is ft, and the distance from the exit pupil at the telephoto end to the image is Expt, it is preferable to satisfy the following conditional expression:

[0021] -1.4 < |Expw / fw| < -0.2 …(2) -0.8 < |Expt / ft| < -0.2 …(3) Equations (2) and (3) represent the appropriate ranges for the exit pupil position for the focal length at the wide-angle and telephoto ends, respectively. If the lower limit is exceeded, the exit pupil becomes long, which tends to increase the lens diameter. On the other hand, if the upper limit is exceeded, the exit pupil becomes too short, making it difficult to ensure the required back focus.

[0022] When the widest lens spacing in the lens group Br is dpn and the back focus at the wide-angle end is BFw, the following conditional expression is satisfied. 0.1 < dpn / BFw < 1.5 …(4)

[0023] Equation (4) shows the appropriate range for the distance between Lp and Ln; maintaining a certain distance has the effect of shortening the exit pupil position and correcting the field curvature that is exacerbated by strong negative refractive power. If the upper limit is exceeded, the distance becomes too large, which leads to an increase in the overall lens length. If the lower limit is exceeded, it is not desirable because the field curvature cannot be sufficiently corrected or it becomes difficult to maintain a short exit pupil position.

[0024] When the refractive power of Fp is Np and the refractive power of FN is Nn, it is preferable that the following conditional expression be satisfied. Np < 1.75 …(5) Nn < 1.75 …(6)

[0025] To reduce the weight of the focus group, it is also necessary to reduce the specific gravity of the material. In this case, by limiting the refractive power within the range of equations (5) and (6), it becomes easier to select glass with a low specific gravity. If the upper limits of equations (5) and (6) are exceeded, it becomes necessary to select lanthanum-based glass, which has a high specific gravity, with current materials, which is not desirable.

[0026] When the focal length of the Fp group is fFp, the focal length of the Fn group is fFn, and the focal length at the telephoto end is ft, it is preferable that the following conditional expression be satisfied. 0.30 < fFp / ft < 1.0 …(7) -1.0 < fFn / ft < -0.25 …(8) Equations (7) and (8) indicate the appropriate range for the refractive power of the focus group. Setting the refractive power of the focus group to a relatively weak range can prevent an increase in lens volume. If the upper limit of equation (7) or the lower limit of equation (8) is exceeded, the focus group becomes too weak, which is undesirable because the required amount of focus correction cannot be obtained. If the lower limit of equation (7) or the upper limit of equation (8) is exceeded, the refractive power of the focus group becomes too strong, which reduces the lens curvature and increases the lens volume, which is undesirable.

[0027] When the focal length of the Lp group is fLp, the focal length of the Ln group is fLn, and the focal length of the Br group is fBr, the following conditional expression is satisfied. -1.0 < fLp / fBr < 0.0 …(9) 0.0 < fLn / fBr < 1.0 …(10)

[0028] Equations (9) and (10) indicate the preferred ranges for the refractive power of the Lp and Ln groups. Exceeding the upper limit of equation (9) or the lower limit of equation (10) undesirably results in the refractive power of Lp and Ln becoming too strong, resulting in excessively large changes in field curvature relative to errors in the relative spacing between Lp and Ln. Exceeding the lower limit of equation (9) or the upper limit of equation (10) undesirably results in the refractive power of Lp and Ln becoming too weak, making it difficult to shorten the exit pupil position.

[0029] FIG. 2 shows aberration diagrams at the wide-angle end and the telephoto end of Example 1, and it can be seen that good performance can be obtained with the configuration of this example.

[0030] Figure 3 is a cross-sectional view of the wide-angle end of Example 2 of the present invention. This is a telephoto zoom lens with a half angle of view of 16.7 to 9.1 degrees, and achieves a brightness of F-number of 2.8 to 4.0. Example 2 has a seven-group configuration with refractive powers of positive, negative, positive, positive, positive, negative, negative from the object side, and the group configuration and movement are the same as in Example 1.

[0031] Here, the focus groups Fp and Fn are considered to be a single lens element, but a so-called composite aspherical lens, in which a thin resin layer is molded onto the surface of a spherical lens as in Example 2, does not hinder the weight reduction of the lens and is therefore included in the gist of this invention.

[0032] FIG. 4 shows aberration diagrams at the wide-angle end and the telephoto end of Example 2, and it can be seen that good performance can be obtained with the configuration of this example.

[0033] FIG. 5 is a cross-sectional view of the wide-angle end of Example 3 of the present invention. This is a telephoto zoom lens with a half angle of view of 16.7 to 9.1 degrees, and achieves a bright F-number of 3.6. Example 2 has a seven-group configuration with refractive powers of positive, negative, positive, negative, positive, negative, negative from the object side. Even if the F-number at the telephoto end becomes even brighter, the weight of the focus group can be reduced by adopting this configuration.

[0034] In order to ensure the effects of the present invention, it is preferable to set each conditional expression within the following range. mFn / mFp > 1.30 …(1a) mFn / mFp > 1.35 …(1b) -1.2 < |Expw / fw| < -0.25 …(2a) -1.0 < |Expw / fw| < -0.30 …(2b) -0.7 < |Expt / ft| < -0.25 …(3a) -0.6 < |Expt / ft| < -0.30 …(3b) 0.2 < dpn / BFw < 1.2 …(4a) 0.3 < dpn / BFw < 1.0 …(4b) Np < 1.72 …(5a) Np < 1.68 …(5b) Nn < 1.70 …(6a) Nn < 1.65 …(6b) 0.35 < fFp / ft < 0.85 …(7a) 0.30 < fFp / ft < 0.8 …(7b) -0.8 < fFn / ft < -0.30 …(8a) -0.7 < fFn / ft < -0.35 …(8b) -0.8 < fLp / fBr < 0.0 …(9a) -0.6 < fLp / fBr < 0.01 …(9b) 0.0 < fLn / fBr < 0.6 …(10a) 0.0 < fLn / fBr < 0.4 …(10b)

[0035] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention.

[0036] For example, arranging a lens group with a weak refractive power on the object side or image side of this lens does not deviate from the scope of the present invention.

[0037] <Explanation of Numerical Examples> Numerical examples for each embodiment are described below. In each numerical example, surface numbers are assigned to each lens surface in order from the magnification side, and surfaces with an s to the left of the surface number indicate aperture surfaces. B indicates the lens group number, indicating that the spacing changes with magnification or focusing. R is the radius of curvature of each lens surface, d is the surface spacing, and surface spacings in parentheses indicate the group spacing. nd and vd are the refractive index and Abbe number of the glass material at the d line (587.56 nm).

[0038] Lens surfaces with an asterisk (*) to the right of the surface number indicate that they have an aspheric shape according to the following function, and the coefficients are shown in the numerical examples: y is the radial coordinate when the vertex of the lens surface is used as the reference, and x is the coordinate in the optical axis direction when the vertex of the lens surface is used as the reference. x = (y 2 / R) / [1+{1-(1+K)(y 2 / R 2 )} 1 / 2 ] + Ay 4 +By 6 +Cy 8 +Dy 10 +Ey 12 +Fy 14 +Gy 16

[0039] In various data tables, the focal length and F-number are listed as values ​​assuming an object distance of infinity. The total lens length indicates the distance from the first lens surface to the image position. BF indicates the back focus, which is the distance from the lens with refractive power closest to the image side to the image plane; if there is an element with no refractive power, such as a flat plate, between these, this is excluded from the calculation and is the air-equivalent length.

[0040] Figures 2, 4, and 6 show aberration diagrams illustrating the imaging performance of the imaging optical system of this embodiment. Each diagram shows aberration diagrams for the wide-angle end (W) and the telephoto end (T), respectively. From the left side of the page, the diagrams show spherical aberration, astigmatism, and distortion, respectively. For spherical aberration, the solid line shows aberration for the d-line (587.56 nm), the dashed line shows aberration for the f-line (486.13 nm), the rough dashed line shows aberration for the C-line (656.27 nm), and the two-dot chain line shows aberration for the g-line (435.83 nm). The horizontal axis scales the defocus amount, ranging from -0.4 to +0.4 mm. For astigmatism diagrams, the solid line shows the curvature of field for the sagittal image plane, and the dotted line shows the curvature of field for the meridional image plane. The horizontal axis is the same as for spherical aberration. For distortion, the horizontal axis scales from -5 to +5%.

[0041] <Numerical Example 1> Unit: mm Surface Data |f|=72.00-195.00 F / 2.90-4.10 img=43.27 ang=16.7-9.1 B Surface number Effective diameter Curvature R Spacing d glass nd vd OBJ (INF) 1 1 50.04 90.7976 5.0000 SFSL5 1.48749 70.24 2 49.37 530.5169 0.5000 3 48.06 97.9376 2.0000 SLAM7 1.74950 35.28 4 46.19 52.8172 7.2000 SFPL51 1.49700 81.54 5 45.60 621.7358 (2.5000) 2 6 30.48 -415.4596 2.7000 STIH53 1.84666 23.78 7 29.64 -118.7367 4.1000 8 26.01 -95.4855 1.4000 SLAH89 1.85150 40.78 9 25.28 23.3679 4.9000 SNBH56 1.85478 24.80 10 25.05 114.2254 2.4500 11 25.04 -51.7297 1.2000 SLAH55V 1.83481 42.72 12 25.67 247.7360 (10.8614) 3 s13 27.13 1e+018 2.0000 14 28.10 -746.5962 3.5000 SLAH55V 1.83481 42.72 15 28.67 -63.4734 0.3000 16 29.17 68.8189 7.0000 SFPL51 1.49700 81.54 17 29.02 -47.8242 1.8000 TAFD25 1.90366 31.31 18 29.24 -113.8725 (21.7143) 4 19 28.56 108.7005 1.5000 TAFD55W 2.00100 29.13 20 28.16 40.3445 7.0000 SBSM14 1.60311 60.64 21 28.35 -76.6144 (13.0373) 5 22 27.26 51.0709 2.8000 SLAL54Q 1.65100 56.24 23 26.82 174.2063 (15.2477) 6 24 27.69 68.1712 1.2000 SFSL5 1.48749 70.24 25 27.41 27.7089 (12.4780) 7 26* 34.95 187.1969 3.0000 E48R 1.53113 55.75 27* 34.77 132.0473 0.2000 28 34.76 62.8365 5.0000 SLAM7 1.74950 35.28 29 34.31 -209.6877 8.5000 30 32.51 -24.7539 1.6000 SLAL14 1.69680 55.53 31 35.04 -112.5527 IMG Aspherical-data(A4,B6,C8,D10,E12,F16) surface 26 r = 1.87197e+002 K = 0.00000e+000 A = 6.44572e-006 B = 3.42704e-008 C = -1.19621e-010 D = 2.63661e-013 E = 0.00000e+000 F = 0.00000e+000 surface 27 r = 1.32047e+002 K = 0.00000e+000 A = -3.67116e-006 B = 2.48879e-008 C = -1.34212e-010 D = 2.43944e-013 E = 0.00000e+000 F = 0.00000e+000 Various データ Wide Mixle Tele Focal distance: 72.00 135.00 195.00 FNO 2.90 3.92 4.10 Half painting angle 16.72 9.10 6.33 Image height 21.64 21.64 21.64 Total length: 167.01m, 198.54m, 216.35m BF 14.32 37.79 51.21 Group Interval Data WIDE MIDDLE TELE WIDE to near MIDDLE to near TELE to near d0 INF INF INF 1031.50 999.96 982.17 d5 2.5000 34.0337 51.8405 d12 10.8614 5.6710 2.0000 d18 21.7143 16.4473 16.1925 d21 13.0373 11.1626 3.3603 1.0000 1.8176 1.0000 d23 15.2477 6.7775 1.8000 16.3010 13.6905 13.9805 d25 12.4780 9.8091 13.0967 23.4655 12.2251 3.3256 d31 14.3200 37.7900 51.2100 group データ Group initial face focal distance B1 1 151.4690 B2 6 -32.3434 B3 13 53.5592 B4 19 137.8858 B5 22 110.0011 B6 24 -96.7044 B7 26 -231.1906

[0042] <Numerical Example 2> Unit: mm Surface Data |f|=72.00-195.00 F / 2.94-4.10 img=43.27 ang=16.7-9.1 B Surface number Effective diameter Curvature R Spacing d glass nd vd OBJ (INF) 1 1 50.06 85.0174 5.0000 SFSL5 1.48749 70.24 2 49.33 343.6245 0.5000 3 48.18 87.2794 2.0000 SLAM7 1.74950 35.28 4 46.39 49.2427 7.2000 SFPL51 1.49700 81.54 5 45.86 680.9384 (2.5000) 2 6 30.69 -386.6170 2.7000 STIH53 1.84666 23.78 7 29.81 -120.1601 4.1000 8 26.01 -98.7729 1.4000 SLAH89 1.85150 40.78 9 25.19 22.6025 5.0000 SNBH56 1.85478 24.80 10 24.92 99.4556 2.5300 11 24.91 -53.7298 1.2000 SLAH55V 1.83481 42.72 12 25.52 181.2248 (12.2646) 3 13 27.34 -934.2049 4.0000 SLAH55V 1.83481 42.72 14 28.06 -62.8345 0.3000 15 28.53 78.4604 6.5162 SFPL51 1.49700 81.54 16 28.47 -43.3247 2.0000 TAFD25 1.90366 31.31 17 28.89 -94.0356 1.5000 s18 28.79 1e+018 (25.4232) 4 19 27.95 98.8296 2.0000 TAFD55W 2.00100 29.13 20 27.51 40.3090 6.0000 SBSM14 1.60311 60.64 21 27.63 -69.7288 (12.3426) 5 22* 27.09 51.2497 0.1500 621000.26500 1.62100 26.50 23 27.05 49.7735 2.8000 SLAL54Q 1.65100 56.24 24 26.71 143.4933 (14.8886) 6 25 27.32 71.5602 1.2000 SFSL5 1.48749 70.24 26 27.02 26.9587 (11.7245) 7 27* 34.24 399.7254 3.0000 E48R 1.53113 55.75 28* 34.42 83.6371 0.2000 29 34.77 57.4811 5.8000 SLAM7 1.74950 35.28 30 34.56 -159.3730 7.8500 31 33.29 -30.0000 1.6000 SLAL14 1.69680 55.53 32 35.27 -165.1168 IMG Aspherical-data(A4,B6,C8,D10,E12,F16) surface 22 r = 5.12497e+001 K = 0.00000e+000 A = -1.38324e-007 B = 8.49545e-010 C = -2.04092e-013 D = -2.46522e-015 E = 0.00000e+000 F = 0.00000e+000 Surface 27 r = 3.99725e+002 K = 0.00000e+000 A = 7.39602e-006 B = 1.80281e-008 C = -7.40299e-011 D = 1.61648e-013 E = 0.00000e+000 F = 0.00000e+000 surface 28 r = 8.36371e+001 K = 0.00000e+000 A = -4.21013e-007 B = 1.24872e-008 C = -8.17293e-011 D = 1.49096e-013 E = 0.00000e+000 F = 0.00000e+000 Various データ Wide Mixle Tele Focal distance: 72.00 135.00 195.00 FNO 2.94 3.92 4.10 Half painting angle 16.72 9.10 6.33 Image height 21.64 21.64 21.64 Total length 170.02 mm, 197.95 mm, 214.80 mm. BF 14.33 40.12 53.80 Group interval データ WIDE MIDDLE TELE WIDE to near MIDDLE to near TELE to near d0 INF INF INF 1028.4851 1000.5489 983.7120 d5 2.5000 30.4342 47.2770 d12 12.2646 7.4359 4.1413 d18 25.4232 18.1903 16.0934 d21 12.3426 7.8674 0.5791 1.0000 2.2760 1.0000 d24 14.8886 6.5722 1.8000 17.1419 13.6476 12.5640 d26 11.7245 10.7862 14.5611 20.8198 9.2589 3.3748 d32 14.3300 40.1200 53.8000 Group Data Group starting plane focal length B1 1 140.3172 B2 6 -30.5330 B3 13 53.0681 B4 19 112.2618 B5 22 120.6950 B6 25 -89.5162 B7 27 -251.2677

[0043] <Numerical Example 3> Unit: mm Surface Data |f|=72.00-195.00 F / 3.60-3.60 img=43.27 ang=16.7-9.1 B Surface number Effective diameter Curvature R Spacing d glass nd vd OBJ (INF) 1 1 57.00 88.5779 6.0000 SFSL5 1.48749 70.24 2 56.08 305.7435 0.3000 3 55.11 116.4435 2.0000 SLAM7 1.74950 35.28 4 53.24 60.7645 8.5000 SFPL51 1.49700 81.54 5 52.73 -641.8255 (2.5000) 2 6 33.62 -229.2969 2.0000 SLAH60 1.83400 37.16 7 32.65 -1994.4432 1.8000 8 32.14 -139.3925 1.4000 SLAH89 1.85150 40.78 9 31.82 28.8506 6.4000 STIH53 1.84666 23.78 10 31.74 285.7527 2.5370 11 31.74 -68.9496 1.2000 SLAL10 1.72000 50.23 12 32.44 388.6205 (23.1408) 3 13 33.33 -2105.4532 3.5000 SNBH57 1.85025 30.05 14 33.76 -83.6238 0.3000 15 34.26 38.3068 8.0000 SFPL51 1.49700 81.54 16 33.61 -92.0911 1.5000 SNBH56 1.85478 24.80 17 33.23 -363.2887 1.5000 s18 25.01 1e+018 (10.6691) 4 19 27.19 98.2800 1.5000 TAFD55W 2.00100 29.13 20 25.88 23.9733 5.9500 SNBM51 1.61340 44.27 21 25.76 -599.6589 (8.8718) 5 22 25.02 37.3778 2.8000 SBSM81 1.64000 60.08 23 24.92 107.2872 (11.4354) 6 24 25.02 122.1947 1.2000 SNSL3 1.51823 58.90 25 24.92 35.0506 (21.2113) 7 26* 33.80 432.1672 3.0000 E48R 1.53113 55.75 27* 34.23 92.9060 0.5000 28 34.91 62.4622 6.0000 TAFD37 1.90043 37.37 29 34.85 -103.0678 9.7000 30 32.42 -32.0000 1.6000 SLAL14 1.69680 55.53 31 34.28 276.3379 IMG Aspherical-data(A4,B6,C8,D10,E12,F16) Surface 26 r = 4.32167e+002 K = 0.00000e+000 A = -1.63660e-006 B = 3.05246e-008 C = -4.86024e-011 D = 4.16232e-014 E = 0.00000e+000 F = 0.00000e+000 Surface 27 r = 9.29060e+001 K = 0.00000e+000 A = -5.59632e-006 B = 2.57322e-008 C = -4.61537e-011 D = 3.63379e-014 E = 0.00000e+000 F = 0.00000e+000 Various data WIDE MIDDLE TELE Focal length 72.00 135.00 195.00 FNO 3.60 3.60 3.60 Angle of view 16.72 9.10 6.33 Real image height 21.64 21.64 21.64 Total length 171.36 202.74 216.16 BF 14.35 27.94 28.39 Group Interval Data WIDE MIDDLE TELE WIDE to near MIDDLE to near TELE to near d0 INF INF INF 1027.1565 995.7641 982.3458 d5 2.5000 33.8760 47.3048 d12 23.1408 11.7158 2.5000 d18 10.6691 12.4888 15.2088 d21 8.8718 17.0286 13.9485 1.0000 5.4739 5.0384 d23 11.4354 5.9090 1.8000 13.0783 14.0519 19.8166 d25 21.2113 14.5894 27.8244 27.4390 18.0435 18.7734 d31 14.3500 27.9400 28.3900 group データ Group initial face focal distance B1 1 144.0758 B2 6 -38.4574 B3 13 46.8649 B4 19 -207.3682 B5 22 88.2495 B6 24 -95.2872 B7 26 -1264.2800

[0044] Table 1

[0045] Table 2 [Explanation of symbols]

[0046] Bi iレンズ group Bp 1st positive lens group Bn 1st negative lens unit Fp 1st focus lens group Fn Second focus lens group Br lens group STO Aperture IMG imaging surface

Claims

1. A zoom lens comprising, from the object side, a lens group Bp of positive refractive power, a lens group Bn of negative refractive power, and a rear group of positive refractive power, wherein the magnification is varied by changing the spacing between the groups, the rear group having a lens group Fp of positive refractive power, a lens group Fn of negative refractive power, and a lens group Br arranged adjacent to each other from the object side, Fp and Fn move while changing the spacing between them during zooming and focusing, Fp and Fn each consisting of a single lens element, and wherein the zoom lens satisfies the following conditional expression, where mFp is the amount of movement of Fp during zooming and mFn is the amount of movement of Fn: mFn / mFp>1.28...(1)

2. 2. A zoom lens according to claim 1, wherein the Fp group, the Fn group, and the Br group each move toward the object side during zooming.

3. 2. The zoom lens according to claim 1, wherein the lens unit Br has negative refractive power and comprises, from the object side, at least a positive lens unit Lp and a negative lens unit Ln with the widest lens spacing dpn therebetween.

4. 2. The zoom lens according to claim 1, wherein the following condition is satisfied, where fw is the focal length at the wide-angle end, Expw is the distance from the exit pupil at the wide-angle end to the image, ft is the focal length at the telephoto end, and Expt is the distance from the exit pupil at the telephoto end to the image: -1.4 < |Expw / fw| < -0.2...(2) -1.2 < |Expw / fw| < -0.25...(2a) -1.0 < |Expw / fw| < -0.30...(2b) -0.8 < |Expt / ft| < -0.2...(3) -0.7 < |Expt / ft| < -0.25...(3a) -0.6 < |Expt / ft| < -0.30...(3b)

5. 2. The zoom lens according to claim 1, wherein the following condition is satisfied, where dpn is the widest lens spacing in the lens unit Br and BFw is the back focus at the wide-angle end: 0.1 < dpn / BFw < 1.5...(4) 0.2 < dpn / BFw < 1.2...(4a) 0.3 < dpn / BFw < 1.0...(4b)

6. 2. The zoom lens according to claim 1, wherein the following condition is satisfied, where Np is the refractive power of Fp and Nn is the refractive power of FN: Np < 1.75...(5) Np < 1.72...(5a) Np < 1.68...(5b) Nn<1.75...(6) Nn < 1.70...(6a) Nn < 1.65...(6b)

7. 2. The zoom lens according to claim 1, wherein the following condition is satisfied, where fFp is the focal length of the Fp group and ft is the focal length at the telephoto end: 0.30 < fFp / ft < 1.0...(7) 0.35 < fFp / ft < 0.85...(7a) 0.30 < fFp / ft < 0.8...(7b)

8. 2. The zoom lens according to claim 1, wherein the following condition is satisfied, where fFn is the focal length of the Fn group and ft is the focal length at the telephoto end: -1.0 < fFn / ft < -0.25...(8) -0.8 < fFn / ft < -0.30...(8a) -0.7 < fFn / ft < -0.35...(8b)

9. 2. The zoom lens according to claim 1, wherein the following condition is satisfied, where fLp is the focal length of the Lp group and fBr is the focal length of the Br group: -1.0 < fLp / fBr < 0.0...(9) -0.8 < fLp / fBr < 0.0...(9a) -0.6 < fLp / fBr < 0.01...(9b)

10. 2. The zoom lens according to claim 1, wherein the following condition is satisfied, where fLn is the focal length of the Ln group and fBr is the focal length of the Br group: 0.0 < fLn / fBr < 1.0 (10) 0.0 < fLn / fBr < 0.6...(10a) 0.0 < fLn / fBr < 0.4...(10b)

Images