JPS62244012A - Small-sized zoom lens - Google Patents

Abstract

PURPOSE:To satisfactorily correct an aberration without using an aspherical surface, by providing three lens groups consisting of the first group having a positive refractive power, for moving on an optical axis, the second group having a negative refractive power for variable power, and the third group which has been fixed, and also, making focal distances of the first and the second groups satisfy a specific condition. CONSTITUTION:In order from an object side, the first group consists of a cemented lens which has joined a negative lens and a positive lens, and a positive lens, the second group consists of a negative lens, and a cemented lens which has joined a negative lens and a positive lens, and the third group consists of a positive lens, diaphragm, a positive lens, a negative lens, a positive lens and a positive lens in order. In this case, by setting a refractive power ratio of the first group and the second group, as shown in the inequality in three group zoom lenses, a small-sized zoom lens which has an F-number of about 1.4, scarcely causes an aberration variation which follows variable power, and in which the overall length of the lens is short is obtained. When the refractive power of the first group exceeds the lower limit value of the inequality and becomes too strong, it becomes difficult to correct an abberation in the vicinity of 1.4 F-number, and also, when the refractive power of the second group exceeds the upper limit value and becomes too strong, the interval becomes larger than required.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a compact zoom lens, and in particular, a high-resolution lens system that is lightweight and has a high zoom ratio suitable for photographic cameras, video cameras, etc. The invention relates to a compact zoom lens.

(Prior art) Recent video cameras have improved the performance of image pickup tubes, CCDs, etc., and the overall size of the camera has been miniaturized. The zoom lens is sub-φ.

For example, regarding resolution, if the video signal is 4MH2, it is required to have high resolution at a spatial frequency of up to 24ILp/11m if the imaging surface is % inches, and 33i1. High resolution is required at spatial frequencies up to p/mm.

Various types of zoom lenses are used in video cameras, but a particularly simple zoom type that can relatively easily achieve high variable power and a large aperture ratio is, for example, the Japanese Patent Application Laid-Open No. 57-1995 by the present applicant. There is a three-group zoom lens proposed in Japanese Patent No. 27219.

This three-group zoom lens consists of, in order from the object side, a first group with positive refractive power for focusing function and correcting image plane fluctuations due to zooming, a second group with negative refractive power for zooming, and a fixed lens. It consists of the third group of

This 3-group zoom lens utilizes an aspherical surface to achieve an F-number of 1.
．． 6 has been achieved. Although aspherical surfaces are generally difficult to process, they require a highly accurate shape, so they have the disadvantage that they cannot be easily used.

(Means for Solving the Problems of the Invention) The present invention improves the three-group zoom lens previously proposed by the applicant, and achieves good aberration correction without using an aspheric surface, has a zoom ratio of 3, and an F number of 1.4. The objective is to provide a compact zoom lens with a relatively large diameter ratio of 1.

(Means for solving the problem) Starting from the object side, the first group has a positive refractive power that moves along the optical axis to correct the focusing function and the image plane fluctuation during zooming, and the negative refractor for zooming. It has three lens groups: a fixed second group and a fixed third group; The focal length of the second group is F, respectively.
When F2, 2.9 < F r / F 2 <
3.6...The condition (1) must be satisfied.

Other features of the invention are described in the Examples.

(Example) FIG. 1 is a sectional view of a lens according to Numerical Example 1 of the present invention.

In the same figure, SEM is the first group with refractive power for focusing function and correcting image plane fluctuations due to zooming, ■ is the second group with negative refractive power for zooming, and ■ is the fixed third group. It is. ST is the aperture.

In this example, by setting the refractive power ratio of the first group and the second group as shown in conditional expression (1) in the three-group zoom lens described above, the zoom lens has a variable power ratio of 3 and an F number of about 1.4. The result is a compact zoom lens with a short overall lens length and minimal fluctuations in aberrations associated with zooming.

If the lower limit of conditional expression (1) is exceeded and the refractive power of the first group becomes too strong, it becomes difficult to correct aberrations near the F number of 1.4, and it is especially difficult to correct spherical aberrations well at the telephoto end. It's getting difficult. Furthermore, if the refractive power of the second group becomes too strong beyond the upper limit, the distance between the first and second groups becomes larger than necessary, the total length of the lens becomes longer, and aberration fluctuations during zooming become larger. not good.

The compact zoom lens that is the object of the present invention is achieved by satisfying the above conditions.
-Koi i exist *ri817h? -n1117Z7115A
h1w-A>? , - In order to downsize the comb and the entire lens system, it is preferable to satisfy the following conditions.

In order from the object side, the first lens group consists of a bonded lens made by bonding a negative lens and a positive lens together, and a positive lens, and the second group consists of a negative lens and a bonded lens made by bonding a negative lens and a positive lens. , the third group consists of a positive lens, an aperture, a positive lens, a negative lens, a positive lens, and a positive lens, and the radius of the first lens surface and the focal length are Ri, fi, respectively, and the third group focal length F3,
When fw is the focal length of the entire system at the wide-angle end, -30
,9<(fr+f,+f
9 +f++)/fa ku 17.0...
...(2) -27,5< (ft + f 4 )
/ fy < 9.3 ・ ・ ・
・ ・ ・ (3)! , 76 ku 1
f 7 / f w 1 〈 2.63
・ ・ ・ ・ ・ ・ (4) 0.82 <
l F1/ fW l < 1.12 --------
(5) 0.069<l R7/Ra
l < 0.341 ・ ・ ・
・ ・ ・ The following condition (6) must be satisfied.

Conditional expression (2) is the refractive power of the second Luns surface in the second group relative to the refractive power of the first Luns surface and fourth lens surface, the bonded lens surface of the second group, and the 7JJ Luns surface of the third group. This ratio is mainly used to satisfactorily correct spherical aberration over the entire zoom range. If the lower limit of conditional expression (2) is exceeded, the spherical aberration will be under-corrected overall, and if the upper limit is exceeded, the spherical aberration will be over-corrected.

Conditional expression (3) relates to the ratio of the refractive power of the second lens surface of the second group to the refractive power of the first lens surface and fourth lens surface of the first group, and is mainly intended to satisfactorily correct coma aberration. If the lower limit value is exceeded, a large amount of inward coma aberration will occur, whereas if the upper limit value is exceeded, a large amount of outward coma aberration will occur, which is not good.

Conditional expression (4) concerns the negative refractive power of the second lens surface of the second group, and conditional expression (5) concerns the refractive power of the entire third group, both of which are intended to maintain a good field curvature. be. Conditional expression (
4) If the lower limit of conditional expression (5) is exceeded, the image plane will curve significantly toward the image side, and conversely, if the upper limit of conditional expression (4) or conditional expression (5) is exceeded, the image plane will curve toward the object side. This is not desirable because it curves greatly.

Conditional expression (6) relates to the ratio of the negative refractive powers of the second lens and the third lens surface of the second group, and is L) that mainly maintains distortion well. If the lower limit of conditional expression (6) is exceeded, the distortion will increase in the negative direction at the wide-angle end, and if the upper limit is exceeded, the distortion will increase in the positive direction at the telephoto end, which is not good.

In this embodiment, it is preferable to arrange the diaphragm between the third lens and the second lens because flare light flux around the screen can be effectively removed.

Next, numerical examples of the present invention will be shown. In numerical examples R
i is the radius of curvature of the first lens surface from the object side, D
i is the first lens thickness and air gap from the object side, Ni
and νi are the refractive index and Abbe number of the glass of the first lens, respectively, in order from the object side. Note that R22 and R23 are optical members such as a face plate and a filter.

Numerical Example I F = 9.55-28.08F
No=l:1.4 2ω=45.5~16.2°R1
-121,26D 1 serving 1.65 N l-1,
80518ν l snow 25.4n 2- 39.8
2 D 2-5.60 N 2-1.6031
1 ν 2-60.7R3--75,60D:
l-0,10R4-23,41D 4■:1.40
N 3 fable 1.60311 υ 3 snow 60.7R
5-59,3705-1,45 ~15.20 R6-59,0206-0,75N 4-1.772
50 ν 4-49.6R7-12, 3307-2
,70 R8--15,0808-0,60N 5-1.69
680 ν 5-55.5R9= 19.68
0 9-2.20 N B-1,84666v
6-23.9RIO--118,610IG-15,
00~l, 59 R11= 40.08 011-2.10 N
7-1.60311 v 7-60.7R12
Wing -: 18.59 D12-1.20R13-Aperture Di3-1.00 R14-12, 12014-2, 40N 8-1.7
1:100 ν 8-53.8R15-35,32
015-5,20 R16--11,65016-0,80N 9-1.
80518 ν 9-25.4R17-18,38
Di7-0.90 R18 meal 217.09 D18-2.40 NI
O Tan 1.65160 ν lO■58.6R19■
-9,85019 0.101120 Seal 16.
65 020-2.00 N11-1.77250
Shi11■49.6R21--64,53D21-3
．． 00R22-ao 022-5.50 N
12=1.51633 v 12-64. lR23
Setting ω Numerical Example 2 F = 9.55~28.08F
No=l:1.4 2ω=45.5~16.2
”11 1-89.98 D 1-1.90
N 1-1.805+8 ν l-25,4R
2= 37.48 0 2-7.00 N 2
-1i, 60311 v 2-60.7R3■
-80,14D 3-0.10R4 Seal 21.95
D 4-4.20 N:l-1,6031
1υ 3-60.7R5-: 19.67 D 5-
1.88-15.62 R6-9: 1.73 0 6-1.00 N 4-
1.77250 υ 4-49.6R7~ 12
．． 15 0 7-2.70R8--14,82D 8
-0.90 N 5-1.69680 ν 5
-55.5It 9- 19.45 0 9-2.
40 N 6-1.84666 υ 6-23
．． 9RIO--69, 62010-16, 11-2.7
1 R11-1-299,3rJ Dll-2,40N
7-1.60:]11 ν 7-60.7R12-
-22,91012-1,50R13-Aperture 013-
1.10 R14-12,06014-3,20N B-1,7
1:100 ν 8fable 53.8RI5- 192.
73 015-1.90r (16--18,42016
-5,50N 9~1.80518 ν 9-2
5.41117- 15.42 017 1.30R
I8- 202.11 D18 fight 2.40 NIO
Dew 1.65160 ν 10-58.6119-
-11.81 019-0.10120= 16.
06 020-'2.40 NIL-1,77250
v 11=49.611218140.64 021
-3.00R22-oo D22-5.50
N! 2 fable 1.5163: l v 12-64.
In2: l-ω Numerical Example 3 F = 9.55-28.08F
No=1:1.4 2(J)=45.5~16
．． 2'RI=95.51 DI-1,65N
I-1,80518v 1-25.48 2-
38.43 D 2-5.50 N 2-1.
603+1 v 2-60.7R3--81,7
003-0,10 R4-24,3404-3,50N 3-1.603
+1 υ 3-60.7R5-56,0005-1
,94 ~15.69 R6-58,7206-0,75N 4-1.772
50 ν 4-49.6R7-12,50D 7
2.70 II 8- -15.30 0 8-0.60 N
5-1.69680 v 5-55.589
Maro 17.55 0 9-2.20 N 6 rin 1
．． 84666 ν 6-23.9RIG-171,
42010-15,00~1.59 R11-42,50Dll-2,10N 7-1.6
0311 v 7-60. lR12--32,9
8DI2-1.20R13-Aperture 013-1.00 R14-112,51014-2,40N 8-1.7
1300 v 8-53.8H15-76, 7401
5-1,90 R16=-17,36016-5,30N 9-1.
805+8 v 9-25.4n17- 15.2
4 017-0.90R18= 42.65018-
2.40 N10s11.65160 v 10-5
8.6RI9- -11.53 019-0.10R2
0-16,46020-2,00N11=1.7725
0 vll-49,6R21 89.84 02
1-3.00R22-■ D22-5.50 N
12-1.51633 C12-64. lR23 electric
(1) Numerical Example 4 F = 9.55-28.08F
No=l:1.4 2ω=45.5~+6.2゜II
l・ 104.87 DI-1,65N
11.80518 v 1-25.482- 38
．． 9f D 2-5.60 N 2-1.60:111
v 2-60.7R3--79,91D 3~
0.10R4-24,4! ] D 4・3.40
N:l-1,603+1 2/31160.
7R5-62, 1405-1,80 ~ 15.55 R6-66, 4006-0,75N 4-1.772
50 Z/ 4-49.6R7-12,61
07 Mai 2.70 n 8= -15,2008-0,60N 5-1
．． 69680v! +1I55.5R9-17,
69D 9=2.20N 6-1.84666
v 6=23.9RIO-137,47010
-15,00~1.59 Old 1- 33.19 Dll-2,10N 71.60
311 v 71160.7R12--32,53D
I2-1.20R13-Aperture 013-1.00 R14= 13.02 DI4-2.40 N 8-
1.71300 v 8-53.8H15-72,1
2DI5-1.90 R16=-16,14DI6115. :10N
9-1.80518 v 9-25.4R17
-16,60017-0,90 R18= 89.10 DI8-2.40 Nl0-
1.65160 v 10=58.6RI9--1
0.83 019-0.10R20-16,09D20
112.00 Ni1-1.77250 Ni11-
49.6R21-89, 87D21-3.00 R22-oo D22=5.50 N+2-
1.51633 v 12-64. lR23-c
.

Numerical Example 5 F = 9.55-28.08F
No=l:1.4 2ω=45.5~16.2°RI-95,96D bow, 80 N 1-1.
80518 v l-25,4R2=38
．． +6 D 2-6.50 N 2-1.60
311 v 2-60.7R3 proverb -79,68
0:l-0,10R4-23,42D 4=3.90
N 3 eyes 1.60311 v 3=60.785
~ 48.71 0 5-1.88 ~ 15.63 R61I 64.63 D 6-0.90 N
4111.77250 v 4-49.68
7-12.28 0 7-2.70R8--15
,01D 8-IO,65N 5-1.69680
v 5-55.5R9= 17.95 09-12
．． 30 N 6-1.84666 v 6-123
．． 9RIO-109,740IG-15,00~1.5
9 Old 1- 85.83 Dll-2,10N 7-1.6
0311 v 7-60.7812--28.06
D12-1.30R13-Aperture 013-1.10 R14= 12.22014-2.90 N 8-1
．． 71300 v 8-53.8 Old 5th grade 83.7
4 015 proverb 1.90R16= -17,64016-
5,40N 9-11.805+8 v 9-25.
41117-15.17017-1.20R18=
48.03 018-2.40 Nl0-1.651
60 Si1O-58.619- -11.77 D
19 Maro 0.10R20= 15.62 020=2.
10 Ni1-1.77250 v 11-49. f
iR21 Electric 86.47 D21-3.00R22
-oo 022-5.50 N12-1.516
33 v 12-64. In2: l-o.

(Effects of the Invention) According to the present invention, by setting each lens group and each lens in the three-group zoom lens as described above, the zoom ratio is 3,
It is possible to achieve a compact zoom lens with a high resolution and an F number of approximately 1.4, with excellent aberration correction.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a lens according to Numerical Example 1 of the present invention, and FIGS. 2 to 6 are aberration diagrams of Numerical Examples 1 to 5 of the present invention, respectively. In the aberration diagrams, (^) is an aberration diagram at the wide-angle end, and (B) is an aberration diagram at the telephoto end. In the figure, engineering, n, and m are respectively 1st. Second
．． In the third group, ST is the aperture, S is the sagittal image plane, M is the meridional image plane, d is the d-line, and g is the g-line. Patent applicant Canon Co., Ltd. Akira 2 Figure (A) Border 2 times (B) 3rd mouth (A) Akira 3 Concave (B) Figure 4 (A) End 4 Mouth (B) Ka S Mouth (Δ) Sato 5 Figure (B) Hem 6 Figure (A) p~(l L4 /, 1- PI I@et al.
Diagram (B)

Claims (1)

[Scope of Claims] (1) A first group with positive refractive power that moves along the optical axis in order to correct focusing function and image plane fluctuation during zooming from the object side;
It has three lens groups: a second group with negative refractive power for zooming and a fixed third group, and when the focal lengths of the first and second groups are F_1 and F_2, respectively, 2.9<F_1. /F_2<3
．． 6. A compact zoom lens characterized by satisfying the following conditions. (2) In order from the object side, the first group consists of a composite lens made by pasting together a negative lens and a positive lens, and a positive lens, and the second group consists of a negative lens and a composite lens made by pasting together a negative lens and a positive lens. The third group consists of a positive lens, an aperture, a positive lens, a negative lens, a positive lens, and a positive lens in order, and the radius of curvature and focal length of the i-th lens surface are Ri, fi, and the third group, respectively. -30.9<(f_1+f_4+f_9+f_1_1)
/f_6<17.0-27.5<(f_1+f_4)/
f_7<9.31.76<|f_7/f_w|<2.6
3. A small zoom lens according to claim 1, which satisfies the following conditions: 0.82<|F_3/f_w|<1.12 0.069<|R_7/R_8|<0.341 .