JPH04217219A - Zoom lens - Google Patents

Abstract

PURPOSE:To provide a change by zooming to the overall length of a zoom lens very little even in high variable power ratio zooming and make the length shorter under the whole conditions from a wide side to telescopic side. CONSTITUTION:A zoom lens consists of the first negative group, the second positive group and the third positive group, where respective groups are moved relatively so that the distance between the first group and the second group may be decreased and the distance between the second group and the third group may be increased at the time of zooming from short focal distance side to long focal distance side to satisfy respective conditions (1), (2), (3), 0.3<If2/f1I<0.9...(1) 2.0<f3/f2<8.0...(2) 0.6<D2/fW<1.5...(3), where f1, f2, f3 are focal distances of the first group, the second group and the third group, fW is the focal distance of the whole system at a wide end, and D2 is a distance from the first surface of the second group to the final surface.

Description

Detailed Description of the Invention [0001] The present invention relates to a photographic lens system for a lens-shutter type camera, etc., in which a finder optical system is provided separately from a photographic lens. This invention relates to a compact zoom lens that has a short overall length over the entire zoom range in terms of variable power ratio. 2. Description of the Related Art Today, zoom cameras have become mainstream among lens-shutter type cameras, and the zoom ratio of lenses is increasing. Commonly used types of zoom lenses include: ■ Two-group zoom lens in which the first group is positive and the second group is negative; ■ Three-group zoom lens in which the first group is positive, the second group is positive, and the third group is negative.
There are group zooms, etc. Furthermore, among zoom cameras with high zoom ratios, cameras that hold the camera in the direction of the optical axis (a camera that is held like holding binoculars with one hand) have begun to be widely used because of the stability of the camera holding. There is. For this type of camera, it is desirable to have a lens that has little variation in overall length due to zooming and is compact in all conditions from the wide-angle side to the telephoto side. Examples of such lens types include JP-A-56-158316 and JP-A-61-2.
Like the one in No. 21719, ■ The first group is negative, the second group is negative.
There is a three-group zoom in which the first group is positive and the third group is positive. Problems to be Solved by the Invention: ■ and ■ of the above-mentioned prior art
Although the total length of the lens can be shortened on the wide side, the total length becomes longer on the long focal length side (telephoto side), and in a zoom lens with a high zoom ratio of over 3x, the length of the lens can be shortened from the short focal length side to the long focal length side. The variation in the total length on the distance side becomes extremely large. As a result, the lens play caused by the lens extension mechanism becomes large, and the effect on performance cannot be ignored. Furthermore, since these lenses are of a telephoto type, the more you try to obtain a wide angle of view on the short focal length side, the more difficult it becomes to secure the back focus. [0006] JP-A-56-158316 and JP-A-61
-221719 is suitable for application to cameras with improved holding stability, as mentioned above.
Also, the above problem does not occur. However, since these conventional techniques are aimed at single-lens reflex cameras, the back focus is extremely long. Therefore, when this is applied to a lens-shutter type camera, the overall length cannot be said to be short. The present invention was developed in view of the above circumstances, and its purpose is to solve the problems of the prior art described above by improving the zoom lens of type (2) above, and to achieve a high zoom ratio. To provide a zoom lens that exhibits little variation in the overall length due to zooming and has a reduced overall length in all states from the wide side to the telephoto side. Means for Solving the Problems The zoom lens of the present invention includes, in order from the object side, a first group with negative refractive power, a second group with positive refractive power, and a third group with positive refractive power. When zooming from the short focal length side to the long focal length side, the distance between the first and second groups narrows, and the distance between the second and third groups increases. , the above groups are moved relatively, and the following conditions (1), (2), and (3) are satisfied. 0.3<|f2/f1|<0.9
...(1)
2.0<f3/f2<8.0
...(2) 0.6<
D2/fW <1.5
...(3) However, f1, f2, f3
are the focal lengths of the first, second, and third groups, respectively, and fW
is the focal length of the entire system at the wide end, and D2 is the distance from the first surface to the final surface of the second group. In particular, the zoom lens of the present invention having such a configuration is used as a photographing lens system for a lens-shutter type camera or the like in which the finder optical system is provided separately from the photographing lens. It is preferable that the movement of the first lens group during zooming from the wide end to the telephoto end be such that it moves farthest from the object point at a focal length intermediate between the wide end and the telephoto end. [Operation] Each condition of the present invention will be explained below. Conditions (1) and (2) are both conditional expressions related to overall length and performance. When the lower limit of condition (1) is exceeded, it becomes difficult to suppress the occurrence of distortion on the wide side. Moreover, the overall length becomes long, making it difficult to achieve compactness. If the upper limit is exceeded, the effective diameter of the first lens becomes too large, making it difficult to make it compact, and the power of the second group becomes strong, resulting in significant spherical aberration mainly on the telephoto side, which is undesirable. If the lower limit of condition (2) is exceeded, the magnification change effect between the second and third groups becomes large, which is advantageous for downsizing, but the power burden on the third group becomes large and distortion occurs. occurs, which is not desirable. If the upper limit is exceeded, the effect of changing the magnification between the second and third groups becomes small, and as a result, it is impossible to achieve a reduction in the overall length. [0016] Furthermore, the second group is constructed of a telephoto type. As a result, at the wide end, the back focus is kept short while maintaining a sufficient distance between the first and second groups, thereby shortening the overall length. Furthermore, at the tele end, in addition to the second group being a telephoto type, the distance between the first and second groups secured at the wide end allows for a high zoom ratio while keeping the overall length short. . Condition (3) is a conditional expression for effectively obtaining the effect of the above telephoto type configuration. If the lower limit is exceeded, in order to make the second group a telephoto type, both the negative and positive powers in the second group must be greatly strengthened, making it impossible to obtain good aberration correction. If the upper limit is exceeded,
Due to the increase in the overall length due to the lengthening of the second group, it becomes impossible to achieve the reduction in overall length, which is the objective of the present invention. [0018] Furthermore, it is desirable that the following condition (4) be satisfied. 0.6<fW×1/fA<2
...(4) However,
1/fA =1/f1 +1/f2 -dW/f1
- f2 (dW: distance between the principal points of the first group and the second group at the wide end). [0020] This roughly indicates the zooming ability from the wide end to the telephoto end and the stability of aberrations. Exceeding the lower limit and obtaining a high zoom ratio of more than 3 times is undesirable because it greatly increases the power of the first or third group, which mainly increases the occurrence of distortion. If the upper limit is exceeded, although the variable power capability increases, the effect of making the second group a telephoto type becomes too strong, and various aberrations in the second group become significant. With the above configuration and conditional expressions, it is possible to obtain a zoom lens that has a high zoom ratio, has little variation in overall length due to zooming, and has a reduced overall length in all conditions from the wide end to the telephoto end. can. [Examples] Next, Examples 1 to 5 of the zoom lens of the present invention
I will explain about it. Lens data for each example will be shown later, but lens cross sections at the wide end (W), standard (S), and telephoto end (T) of Examples 1, 4, and 5 are shown in Figures 1, 2, and 3, respectively. show. Further, aberration diagrams at the wide end (W), standard (S), and telephoto end (T) of each example are shown in FIGS. 4 to 8. [0023] In the following, symbols other than the above,
f is the focal length of the entire system, FNO is the F number, 2ω is the angle of view, fB is the back focus when the object distance is infinite, r
1, r2... are the radius of curvature of each lens surface, d1, d2
... is the distance between each lens surface, nd1, nd2... is the d-line refractive index of each lens, νd1, νd2... is the Abbe number of each lens, and the aspherical shape is defined by the optical axis direction being x, the light When the direction perpendicular to the axis is y, it is expressed by the following formula. x=(y2/r)/[1+{1-P(y2/r2
)}1/2 ]+A4y4 +A6y6 +A8y8 Where, r is the paraxial radius of curvature, P is the conic coefficient, A4, A6
, A8 is an aspheric coefficient. Example 1 f=28.7-48.5-82.0FNO=3.5
~4.7 ~6.5 2ω=73.9~48.0~2
9.5°fB = 11.2~13.0~23.7r1
= ∞ d1 =
1.8040 nd1 = 1.80610 ν
d1 = 40.95r2 = 25.5777
d2 = 4.4414 r3
= 184.0974 d3
= 1.4158 nd2 = 1.80440
νd2 = 39.58 r4 = 46.617
2 d4 = 0.9004 r
5 = 31.9792 d
5 = 5.2236 nd3 = 1.7215
1 νd3 = 29.24 r6 = -3630.6
200 d6 = (variable) r
7 = 15.7299 d
7 = 5.0000 nd4 = 1.6072
9 νd4 = 59.38 r8 = -58.0
640 d8 = 1.5000
nd5 = 1.80518 νd5 = 25.4
3 r9 = -168.6544
d9 = 1.0000 r10 = ∞ (
Aperture) d10= 1.0000
r11= 19.2104 (aspherical surface) d11
= 4.8169 nd6 = 1.51633
νd6 =64.15 r12= -15.826
2 d12= 2.0000
nd7 =1.80610 νd7 =40.95
r13= 19.1937
d13= 2.5630 r14= -232.2
091 d14= 3.7000
nd8 = 1.59551 νd8 = 39.2
1 r15=-17.5731
d15= 9.0117 r16= -11
．． 1640 d16= 1.000
0 nd9 =1.74100 νd9 =52
．． 68 r17=-48.9742
d17= (variable) r18= -154.1
875 d18= 4.5761
nd10=1.57250 νd10=57.7
6 r19=-34.1504 In this embodiment, the wide end (
As shown in the lens cross sections at W), standard (S), and telephoto end (T), the first group is composed of two negative lenses and one positive lens, and has negative power. The second group consists of two cemented lenses, a positive lens and a negative lens, and a positive lens.
It consists of six negative lenses and has positive power. The third group has one positive lens. It has a total of 10 elements in 8 groups. The movement of the first group during zooming from the wide end to the telephoto end is farthest from the object point at a focal length between the wide end and the telephoto end. When changing the magnification from the wide side to the telephoto side, the second group moves in a direction closer to the object point. Furthermore, the third group moves from the wide side to the telephoto side so that the distance between it and the second group increases. Note that the second group is of a telephoto type. In this embodiment, the negative meniscus lens, which is the final lens of the second group, effectively corrects the positive distortion occurring in the first and third groups, and also corrects the telephoto type of the second group. We are trying to make this happen. Also, the second
By using at least one aspherical surface in the group, various axial and off-axial aberrations are effectively corrected. With the above configuration, there is little variation in the overall length due to zooming, and a high zoom ratio of approximately 3 times is achieved while reducing the overall length in all conditions from the wide end to the telephoto end. Note that the wide end (W) of this example
, standard (S), and telephoto end (T) are shown in FIG. Example 2 f=29.0-54.0-102.5FNO=3.
5 ~4.8 ~6.5 2ω=73.4~43.6~
23.8°fB =10.0~12.1~18.1r1
= 148.6230 d1
=1.8040 nd1 =1.83400
νd1 = 37.16r2 = 31.286
2 d2 = 6.0002 r
3 = 92.9381 d
3 = 1.6164 nd2 = 1.8340
0 νd2 = 37.16 r4 = 43.1
627 d4 =3.0005
r5 = 37.7577
d5 =5.3597 nd3 =1.84
666 νd3 = 23.78 r6 = 102
．． 2288 d6 = (variable)
r7 = 19.9071
d7 =5.5011 nd4 =1.56
883 νd4 = 56.34 r8 = -65
．． 0904 d8 =1.8000
nd5 =1.84666 νd5 =23
．． 78 r9 = -110.2040
d9 = 1.0000 r10 = ∞
(Aperture) d10=1.0000
r11= 20.9198 (aspherical surface) d
11=5.5979 nd6=1.4978
2 νd6 =66.83 r12= -23.0
099 d12=1.5000
nd7 = 1.83400 νd7 = 37.1
6 r13= 31.7353
d13=7.0874 r14=-611
．． 9823 d14=3.0862
nd8 =1.59270 νd8 =35
．． 29 r15=-26.8949
d15=9.3831 r16=-
11.7850 d16=1.00
00 nd9 = 1.78590 νd9 =
44.18 r17=-37.0224
d17=(variable) r18= -12
21.4696 d18=6.00
00 nd10=1.63636 νd10=
35.37 r19=-56.4546
Example 3 f=29.1-54.0-102.5FNO=3.
5 ~4.8 ~6.5 2ω=73.2~43.6~
23.8°fB =9.0 ~10.1~15.2r1
= 148.1478 d1
=1.8040 nd1 =1.83400
νd1 = 37.16r2 = 32.525
7 d2 = 6.0005 r
3 = 100.2553d
3 = 1.6164 nd2 = 1.8340
0 νd2 = 37.16 r4 = 39.7
545 d4 =3.0004
r5 = 37.5499
d5 =6.0005 nd3 =1.84
666 νd3 = 23.78 r6 = 123
．． 3795 d6 = (variable)
r7 = 21.6039
d7 =5.5009 nd4 =1.56
883 νd4 = 56.34 r8 = -49
．． 6040 d8 =1.8000
nd5 =1.84666 νd5 =23
．． 78 r9 = -95.0738
d9 = 1.0000 r10 = ∞
(Aperture) d10=1.0000
r11 = 25.8921 (aspherical surface) d11 = 5
．． 7859 nd6 = 1.49782 νd
6 = 66.83 r12 = -30.7152
d12=1.5000n
d7 =1.83400 νd7 =37.16 r1
3 = 42.6611 d1
3=8.1819 r14=458.150
2 d14=5.4035
nd8 = 1.59270 νd8 = 35.29
r15 = -34.0660
d15=9.8173 r16=-12.8
529 d16=1.0000
nd9 =1.78590 νd9 =44.1
8 r17 = -45.3334
d17=(variable) r18=4337.1
321 d18=6.0000
nd10=1.63636 νd10=35.3
7 r19 = -61.5087
The movement of each group and lens structure in the second and third embodiments described above are almost the same as in the first embodiment, and a high zoom ratio of approximately 4 times is achieved. Wide end (W) of Examples 2 and 3,
Aberration diagrams at the standard (S) and telephoto end (T) are shown in FIGS. 5 and 6, respectively. Example 4 f=28.7-48.5-82.0FNO=4.5
~5.7 ~7.2 2ω=73.9~48.0~2
9.5°fB =10.3~8.9~19.5r1
= -118.4316 d1
=1.8040 nd1 =1.83481
νd1 = 42.72r2 = 19.1453
d2 =3.0130 r3
= 29.9051 (aspherical surface) d3 = 5
．． 0000 nd2 = 1.72825 νd
2 = 28.46 r4 = -1886.6195
d4 = (variable) r5 =
19.1711 d5 =3
．． 5000 nd3 = 1.58313 νd
3 = 59.36 r6 = -29.3131
d6 =1.5000n
d4 =1.80518 νd4 =25.43 r7
= -69.6547 d7
=1.0000 r8 = ∞ (aperture)
d8 =1.0000 r9 =
17.4853 d9 =
4.0360 nd5 = 1.49831 ν
d5 = 65.03 r10 = -24.6204
d10=2.0191
nd6 = 1.83481 νd6 = 42.72 r
11=44.0568d
11=5.8025 r12=-268.23
78 d12=3.0000
nd7 = 1.59270 νd7 = 35.29
r13= -32.4737 (aspherical surface) d1
3=9.5589 r14=-9.733
5 d14=1.0000
nd8 = 1.72916 νd8 = 54.68
r15=-29.4775
d15=(variable) r16= -65.301
5 d16=4.5000
nd9 =1.62280 νd9 =57.06
r17=-30.1780 0
[033] Figure 2 shows wide end (W), standard (S),
As shown in the lens cross section at the telephoto end (T), the movements of each group and the configurations of the second and third groups in this example are almost the same as in Example 1, but the first group has a negative It consists of two elements, a lens and a positive lens, making a total of 9 elements in 7 groups. By making one surface in the first group aspherical, it is possible to achieve good aberration correction while reducing the overall length. FIG. 7 shows aberration diagrams of this example at the wide end (W), standard (S), and telephoto end (T). Example 5 f=28.7-48.5-82.0FNO=3.5
~4.7 ~6.5 2ω=73.9~48.0~2
9.5°fB =10.7~10.7~10.7r1
= 6650.4217 d1
=1.8040 nd1 =1.80610
νd1 = 40.95r2 = 26.8309
d2 =5.3654 r3
= 441.3474 d3
=1.0000 nd2 =1.80440
νd2 = 39.58 r4 = 51.65
45 d4 =0.8909
r5 = 34.8202
d5 =5.9939 nd3 =1.721
51 νd3 =29.24 r6 = -294.
1355 d6 = (variable)
r7 = 17.2303
d7 =5.0000 nd4 =1.607
29 νd4 =59.38 r8 = -46.
7341 d8 =1.5000
nd5 =1.80518 νd5 =25.
43 r9 = -121.5260
d9 = 1.0000 r10 = ∞
(Aperture) d10=1.0000
r11= 19.3413 (aspherical surface) d1
1=4.9489 nd6=1.51112
νd6 =60.48 r12= -19.07
95 d12=2.0000
nd7 =1.80610 νd7 =40.95
r13=20.5905
d13=4.1317 r14=-743.
1396 d14=3.7000
nd8 =1.59551 νd8 =39.
21 r15=-22.2865
d15=9.3684 r16=-1
1.4041 d16=1.000
0 nd9 =1.74100 νd9 =5
2.68 r17=-35.7289
d17=(variable) r18=-36
9.0335 d18=4.752
3 nd10=1.57250 νd10=5
7.76 r19=-48.4368
FIG. 3 shows cross sections of the lens of this embodiment at the wide end (W), standard (S), and telephoto end (T). The lens configuration and the movements of the first and second groups are the same as in Example 1, but in this example, the third group is
Fixed when zooming. As a result, in addition to obtaining the same effects as in Example 1, the structure of the lens barrel can be simplified because the third group does not need to be moved. FIG. 8 shows aberration diagrams of this example at the wide end (W), standard (S), and telephoto end (T). As explained above, according to the zoom lens of the present invention, although it has a high variable power ratio, there is little variation in the overall length of the lens due to zooming. Therefore, it is possible to suppress the occurrence of lens play due to lens extension, which often occurs during zooming with a high zoom ratio. Furthermore, despite having a high zoom ratio, it is possible to achieve a compact overall length and good optical performance in all conditions from the wide-angle side to the telephoto side. The zoom lens of the present invention is suitable for a photographic lens system for a lens-shutter type camera in which a finder optical system is provided separately from a photographic lens.

[Brief explanation of the drawing]

[Fig. 1] Wide end (W) and standard (S) of Example 1.
) is a sectional view of the lens at the telephoto end (T).

[Fig. 2] Wide end (W) and standard (S) of Example 4.
) is a sectional view of the lens at the telephoto end (T).

[Fig. 3] Wide end (W) and standard (S) of Example 5.
) is a sectional view of the lens at the telephoto end (T).

[Fig. 4] Wide end (W) and standard (S) of Example 1.
) is an aberration diagram at the telephoto end (T).

[Fig. 5] Wide end (W) and standard (S) of Example 2.
) is an aberration diagram at the telephoto end (T).

[Fig. 6] Wide end (W) and standard (S) of Example 3.
) is an aberration diagram at the telephoto end (T).

[Fig. 7] Wide end (W) and standard (S) of Example 4.
) is an aberration diagram at the telephoto end (T).

[Fig. 8] Wide end (W) and standard (S) of Example 5.
) is an aberration diagram at the telephoto end (T).

Claims (1)

[Claims] Claim 1: Consisting of three groups in order from the object side: a first group with negative refractive power, a second group with positive refractive power, and a third group with positive refractive power, from short focal length side to long focal length side. When zooming to the side, the second group,
A zoom lens characterized in that each of the above groups is moved relatively so that the interval between the third group is increased, and the following conditions (1), (2), and (3) are satisfied: 0.3 <|f2 /f1 |<0.9
...(1)
2.0<f3/f2<8.0
...(2) 0.6<
D2/fW <1.5
...(3) However, f1, f2, f3
are the focal lengths of the first, second, and third groups, respectively, and fW
is the focal length of the entire system at the wide end, and D2 is the distance from the first surface to the final surface of the second group.