JPS63221312A - Small-sized high variable power lens - Google Patents

Abstract

PURPOSE:To satisfactorily correct aberrations over the entire zooming range by providing lens groups of 5 groups having positive, negative, positive, positive, and negative refracting powers successively from an object side to the titled zoom lens so that the lens of a telephototype as a whole is constituted and satisfying the prescribed conditions. CONSTITUTION:The 1st group I, the 3rd group III, the 4th group IV, and the 5th group V are moved to an object side and the 2nd group II is moved to an image plane side at the time of zooming the lens from a wide angle to telephoto. Furthermore, the conditions expressed by equation I, equation II, and equation III are satisfied. In equations, f4: the focal length of the 4th group IV, f5: the focal length of the 5th group V, fW: the focal length of the 3rd group III and the 4th group IV at the wide angle end, D3W: the spacing between the 3rd group III and the 4th group IV at the wide angle end, D3M: the spacing between the 3rd group III and the 4th group IV when the focal length of the entire system is fM, ft: the focal length of the entire system at the telephoto end.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a zoom lens with a high zoom ratio, and particularly to a zoom lens that includes a wide angle, is compact, and is suitable for use in a 35m+ size single-lens reflex camera.

(Prior art) As a zoom lens for a 35m single-lens reflex camera, 3.
62 with a high zoom ratio of 6 or more and an angle of view including wide angle
Several zoom lenses with an angle of about 8 to 19 degrees are known. An example of this is as follows.

JP-A-56-133713: F4 fm36
~132 L=149 (configuration) Positive, negative, positive, L/ft
J, 129 JP 57-164709: F4-4.
5 fm36~133 L=173.3 (Configuration) Positive, negative, positive, negative, positive L/f*=1.303 JP-A-59-1601
21: F4 fm36~13L L=15
6.9 (Configuration) Positive, negative, positive L/f*=1.198 JP-A-60-14212: F3.5 to 4.5 f=36
〜133 L=142.6 (Configuration) Positive, negative, positive (or negative) L/f*=1.069 JP-A-61-62012:
F3,5-4.5 f=35.7~131 L=1
41.9 (Configuration) Positive/Negative/Positive L/ft"1.083 JP-A-61-69016: F3.5~4.5 f=3
6 to 132 L=138.8 (configuration) positive, negative, positive (or negative) L/ft"1.05, but F is F number,
L is the total length of the lens from the front surface of the lens to the image plane at the wide-angle end, and ft is the focal length of the entire system at the telephoto end.

As mentioned above, a zoom lens with an angle of view of about 62'' to 19@ and L/f* smaller than 1 is not yet known.

(Problems to be Solved by this Invention) This invention includes 5 wide angles of view of about 62° and has a high zoom ratio of about 3.6 or more, but the total length of the lens at the wide-angle end is the same as that at the telephoto end. Although it is ultra-compact with a total focal length of less than 1,
The objective is to obtain a zoom lens that has good performance and can secure a space for the finder mirror of the lens.

(Means to solve the problem) The zoom lens of this invention is as shown in the drawings.

In order from the object side, the first group I has a positive refractive power, the second group ■ has a negative refractive power, the third group ■ has a positive refractive power,
4th group ■ with positive refractive power, 5th group with negative refractive power
It consists of group V and has a telephoto type lens structure as a whole, and when zooming from wide-angle to telephoto, the first group is used.

This zoom lens is characterized in that the third, fourth, and fifth groups are moved toward the object side, and the second group is moved toward the image plane side, and the following conditions are satisfied.

(4) 1.5<If, /fwl<6 (2) L > If, 1 (3) DEW > D-M However, f4: 4th fresh fish point distance f,: 5th fresh fish point distance f轡: Wide angle Distance between the 3rd and 4th groups at the end D■: Distance between the 3rd and 4th groups at the wide-angle end 03M: Focal length of the entire system is fw
Distance ft between the third group and the fourth group when: Focal length of the entire system at the telephoto end (effect) The meaning of each of the above conditions will be explained below.

The zoom lens of the present invention has the shortest overall length at the wide-angle end shown in the figure. At this time, since the first to fourth groups have a combined positive refractive power and the fifth group has a negative refractive power, the lens as a whole becomes a telephoto type, and the overall length can be shortened.

Now, the refractive power of the 1st group to the 4th group is φ1-〇 The refractive power of the 5th group is ψ, and the rear principal point of the composite system from the 1st group to the 4th group and the front principal point of the 5th group. d, the refractive power of the entire system is ψ,
The distance from the front principal point to the rear principal point of the composite system from the first group to the fourth group is HH'1 to 4, and the distance from the front principal point to the rear principal point of the fifth group is HH'. Letting TL be the distance from the front principal point of the composite system from the 1st group to the 4th group to the image plane of the entire system, TL = ``Yomi Doki ψ(1-ψ5・d, +HH'・～・+l( Δψ is the minute change in the refractive power of the S-th group that becomes H'.

If the minute change in TL is ΔTL, then ΔTL=−'μ辷凰L ψ(1−ψ,・d)′6ψ゛, and when 1−ψ・d>O, if φ3 becomes negative and large, the total lens length TL is shortened. If BF is the distance from the rear principal point of the fifth group to the image plane of the entire system, then BF= -L-
If ΔBF is the minute change in BF that becomes
−Δφ5 ψ(1−ψ3d)2, and therefore ΔBF=ΔTL.

Therefore, if ψ becomes negative and large, the total length and back focus are shortened by the same amount. If this amount is increased too much to shorten the overall length, the back focus will be too short, making it unusable for an eye reflex camera. Condition (1) is for this purpose; if the lower limit is exceeded, the refractive power of the 5th group becomes stronger. Too much, and you won't be able to get enough back focus. Furthermore, since the last group has a strong negative refractive power, the Petzval sum of the entire system tends to be negative, making it difficult to correct the image plane. Furthermore, aberration fluctuations due to zooming also increase. On the other hand, if the upper limit is exceeded, it becomes difficult to shorten the overall length, which is the objective of the present invention. Also, since the variable power ratio of the 5th group during zooming becomes smaller, the variable power ratios of the 2nd and 3rd groups must be increased, and the distance between the 2nd and 3rd groups at the telephoto end must be ensured. becomes difficult.

Condition (2) is mainly a condition for ensuring the distance between the second group and the third group at the telephoto end and shortening the overall length.

The magnification of the fourth group decreases when zooming from wide-angle to telephoto. That is, when the focal length of the entire system becomes large during zooming, the fourth group works to decrease the focal length of the entire system.

On the other hand, the magnification of the fifth group increases when zooming from wide-angle to telephoto, and serves to increase the focal length of the entire system. Therefore, if the focal length of the 4th group is made smaller than the absolute value of the focal length of the 5th group, the magnification ratio of the 2nd and 3rd groups must be increased, and the distance between the 2nd and 3rd groups must be increased. It becomes difficult to secure. Furthermore, if this condition is satisfied, the effect as a telephoto type is further increased, and the overall length can be shortened.

The fourth group is a lens group that supplements the imaging function of the third group, and the combined system of the third and fourth groups has the imaging function. The zoom lens of the present invention changes the image plane correction amount of the fourth group depending on the zooming time, and maintains the image plane of the entire system appropriately. Near the midpoint between the wide-angle end and the telephoto end (near the focal length fm''=f轡・ft), the over-corrected image plane can be maintained appropriately by reducing the distance between the third and fourth groups. Condition (3) is satisfied.

(Example) By satisfying the above conditions, the angle of view is 62°.
It is possible to provide a compact zoom lens with good performance and a variable power ratio of 3.6 or more. However, when implementing this invention, in order to simplify the mechanical mechanism, the third
It is desirable to move the lens group and the fifth group as one unit, and it is also preferable for the zoom lens of the present invention to have the following configuration in order to correct aberrations.

a) The second group consists of three negative lenses and one or more positive lenses, the first lens is a meniscus negative lens with a concave surface facing the image side, and the second lens is a negative lens with a concave surface facing the object side6. b) When the radius of curvature of the object side surface in contact with the air of the positive lens of the second group is R or F, and the focal length of the second group is f2, (4) 1<lR+p/fl<1.6. Satisfied R
and F exist.

C) The fourth lens is a biconvex lens in which the second lens has a surface with a small radius of curvature facing the image plane, and the second lens is a negative meniscus lens with a concave surface facing the object side.

d) The radius of curvature of the image plane side surface of the positive lun of the fourth group is R4
,□, the radius of curvature of the object side of the negative second lens is R,3,
When (5) 1.1<R,,2/R,,1<1.8 is satisfied.

In the zoom lens of the present invention, when zooming from wide angle to telephoto, the magnification of the second group is increased by widening the distance between the first group and the second group. Further, when zooming from wide-angle to telephoto, the third group moves toward the object and approaches the second group.

Therefore, the height of the light ray passing through the second lens group changes greatly due to zooming, and as a result, the situation in which aberrations occur also changes greatly, making it extremely difficult to correct aberrations. In order to solve this problem, the configuration a) is required, and the positive lens in the second group also needs to satisfy condition (4) of b). If the upper limit of this condition is exceeded, the Petzval sum becomes small and it becomes difficult to maintain it at an appropriate value. If the lower limit is exceeded, the power of this surface becomes too strong and high-order coma aberration occurs, making correction difficult.

By making the fourth group a telephoto type as shown in C), it is possible to secure the distance between the third and fourth groups, and furthermore, d
) By satisfying condition (5), it becomes possible to appropriately correct spherical aberration and coma aberration. If the upper limit is exceeded, spherical aberration and coma aberration will be overcorrected, and if the lower limit is exceeded, spherical aberration will be undercorrected.

Examples of the present invention that satisfy all of the above conditions will be shown below. However, rB radius of curvature of the i-th lens from the object side dI: i-th wall thickness or air gap from the object side nI: refractive index for the d-line of the i-th lens from the object side 1: of the i-th lens from the object side Atsube's number f: Focal length of the i-th group from the object side bf: Back focus of the entire system (Σdl+bf), : Total lens length at the wide-angle end ft: Focal length of the entire system at the telephoto end R+r: Positive lens of the second group Radius of curvature R, 11, of the object side surface in contact with the air: Radius of curvature R4, 3s of the image plane side surface of the positive lens of the 4th group F: Radius of curvature of the object side surface of the negative lens of the 4th group: F number Example 1 f =36~131 F4.33~5.76 Angle of view 65.
0'～18.2゜rdn
Vl 237.379 1.6 1
．． 80518 25.52 60.13
6.7 1.58913 61.33
-145.218 0.24 3
8.181 4.1 1.64000 60.
25 109.906 Variable 6 99.716 1.2 1.7
7250 49.67 16.875
5.68 -50.155 1.3
1.77250 49.69 656.
049 0.210 25.518
4.2 1.59270 35.511
-59.831 0.812 -35
．． 009 1.1 1.77250 49.6
13 20.273 2.7 1.
74077 27.814 158.762
Variable 15 52.227 1.9 1.
69680 55.516 -1999.4
96 0.217 19.087 3
．． 30 1.72000 50.318
106.225 1.2019 -4
4.144 4.00 1.75520 27.
520 34.707 0.8021
112.149 4.30 1.516
80 64.222 -29.261 Variable 23 38.873 5.10 1.
56732 42.824 -23.42
9 2.0025 -18.390 1
．． 20 1.83400 37.326 -
6L335 Variable 27 -14.278 1.60 1.
83400 37.328 -19.21
1 f 36.0 68.673 1
31.0d, 0.844 12.58
5 23.156d, 4 23.404 1
2.791 2.548d,, 5.8
08 3.531 3.024d,,
7.064 9,342 9.84
8bf 33.539 43.166
51.263f,: 66.385f
,: -18,518f3= 33.569
f4 = 116.279fs = -78
,2f0 1fs/fwl =2.173(Σd
livestock + bf) crocodile = 125.959 (Σd++bf
)*/f dragon=0.962IR+F/fzl=1-37
8 R4-a/R4-5=1-274 Example 2 f=36-131 F4.6-5.6 Angle of view 65.0"
~18.0”r d n ν1
180.973 1.32 1.80518
25.52 62.658 6.16 1.58
913 61.33 -201.201 0.20 4 39.959 4.00 1.58913
61.35 100.434 Variable 6 49.003 1.20 1.77250
49.67 14.628 5.50 8 -75.848 1.10 1.75500
52.39 106.880 0.20 10 21.192 3.50 1.59270
35.511 -79.297 1.0012
-31.606 1.10 1.77250
49.613 24.900 2.50 1.7
61g2 26.614 118.848 Variable 15 51.373 1,96 1.69680
55.516 -195.181 0.2117
19.697 3.04 1.69
680 55.518 96.517
1.4019 -40.1133 3.9
0 1.67270 32.220
24.709 1.2021 109.05
8 4.40 1.51680 64.222
-23.670 Variable 23 40.892 4.99 1.5
4072 47.224 -22.137
2.0025 -18.975 1.
53 1.83400 37.326 -7
9.874 Variable 27 -24.495 2.49 1.
69680 55.528 -37.45
1 f 36.0 68.673 1
31.0d, 0.851 15.64
8 30.339d14 22.160 1
1.91j 2.688dt2 5.596
2.973 3.612d,,
8.661 16.076 18.855bf
33.403 36.749 37
．． 040f1= 76.923 f, =
-18,518f, = 33.569
f4 = 142.857f, = -110,3
201fs/f*I=3-064(Σd++bf)=
125.571 (Σd, +bf) Cucumber/ft=o,
9591R+F/fzl=1-144 R4-
z/R4*3 =1.167 Example 3 f=36~131 F4.58~5.63 Angle of view 6
5.2' ~ 1g, 2'r d
n ν1 148.311
1.32 1.84666 23.82 61
．． 973 6.16 1.62299 58.13
-222.055 0.2 4 37.155 4.00 1.62041
60.35 69.283 Variable 6 66.906 1.32 1.75500
52.37 14.857 6.00 8 -43.768 1.22 1.64000
60.29 203.394 0.10 10 21.662 6.00 1.59270
35.511 -17.542 1.00 1
72916 54.712 59.207 Variable 13 52.349 2.45 1.69680
55.514 -213.731 0.2
115 18.574 3.33 1.
64000 60.216 87.930
1.4017 -42.002 3.6
8 1.67270 32.218 2
7.167 1.2019 98.708
4.57 1.516130 64.220
-25.829 Variable 21 37.758 5.00 1.5
4072 47.222 -23.442
2.0023 -18.510 1.5
0 1.83400 37.324 -71
．． 031 Variable 25 -19.923 2.49 1.8
0420 46.526 -27.124 f 36.0 68.673 131
．． 0d, 1.097 14.969
29.714d1□ 22.412 11,
579 2.538d2゜ 5.43g
2.240 1.083dz4 8.
905 17.549 19.774bf
32.793 35.621 37.87
8f, = 76.923 f□= -1
8,518f,=33.569f,=
142.857f, = -110,3201f,
/f cape 1=3.064(Zd++bf)*=125.7
96 (Ed++bf)n/ft=o, 9601R+
r/f,l'':1.17OR4,/R4,,=1.2
66 Example 4 f=36-131 F4.4-5.59 Angle of view 65
．． 1°～17.9”r d n
ν1 175.652 1.60 1.805
18 25.52 5g, 706 6.20 1
．． 58913 61.33 ~230.877 0.
20 4 43.587 4.10 1.64000
60.25 205.503 Variable 6 146.648 1.20 1.77250
49.67 16.627 5.60 8 -50.249 1.30 1.7?250
49.69 51523.284 0.2010
25.518 4.20 1.59270 3
5.511 -59.831 0.8012
-35.289 1.10 1.7410 (152
,613 23.123 2.70
1.74077 27.814 128.6
48 Variable 15 51.101 1.90 1.
69680 55.516 -256.0
38 0.2017 23.855
3.30 1.71300 53.918
272.492 1.2019 -5
7.766 4.00 1.75520 27.
520 35.961 0.8021
56.773 4,30 1.487
49 70.422 -47.187 Variable 23 68.663 5.10 1.
56732 42.824 -26.63
9 3.5025 -18.36 1
,20 1.83400 37.326 −
45.207 Variable 27 -16.38 1.60 1J
5030 32.228 -19.942 f 36.0 68.673 1
31.0d, 0.991 13.473
24.919d,, 23.422
13.007 2.693d,, 9.94
2 7.537 8.771d□ 4.
003 7.002 5.177bf
34.060 43.012 50.4
12f, = 66.385 f, = -
18,518f3= 33.569f4
= 178.571L = -135,8911L
/fwl=3,775(Σd++bf)w=128,
718 (Σd++bf)w/ft=0.9831R
+r/fzl =1.378 R4,-/R4
, 3=1.451 (Effects of the Invention) As is clear from the above embodiments and drawings, one angle of view includes a wide angle of 65° or more.

Despite the large zoom ratio of 3.6 or more, the ratio of the total length from the image plane to the tip of the lens to the focal length of the entire system at the telephoto end is less than 1, making it extremely compact. We were able to obtain an excellent zoom lens that has a large back focus to ensure space for the finder mirror, and also has good performance with well-balanced aberration correction over the entire zoom range.

[Brief explanation of drawings]

Figure 1, Figure 2, Figure 3, and Figure 4 are the first and second figures, respectively.
, a cross-sectional view showing the configuration of each of the third and fourth embodiments, a movement locus diagram of each lens group during zooming, and FIGS. 5, 6, 7, and 8. 3 and 4 show aberration curves for each example. In the figure, SA indicates spherical aberration, SC indicates sine condition, S indicates spherical focal line, and M indicates meridional focal line. Patent applicant: Ricoh Co., Ltd. Patent attorney: Fumio Sato (and 2 others) Figure 5: Figure 5

Claims (1)

[Claims] In order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power. , a fifth group with negative refractive power, and has a telephoto type lens configuration as a whole.When zooming from wide-angle to telephoto, the first, third, fourth, and fifth groups are used. is moved toward the object side, the second group is moved toward the image plane side, and the zoom lens is characterized in that it satisfies the following conditions. 1.5<|f_5/f_W|<6 f_4>|f_5| D_3_W>D_3_M However, f_4: 4th group focal length f_5: 5th group focal length f_W: Distance between 3rd and 4th groups at wide-angle end D_3_W: Distance between the third and fourth groups at the wide-angle end D_3_
M: Distance between the 3rd and 4th groups when the focal length of the entire system is f_M ft: Focal length of the entire system at the telephoto end