JPS61188512A - Photographing lens of long back focus - Google Patents

Abstract

PURPOSE:To obtain the photographing lens of the long back focus where the satisfactory aberration is corrected by satisfying a prescribed condition among a focus distance in seven groups ten lenses, a radius of curvature and an Abbe number. CONSTITUTION:A whole system focus distance composed of seven groups ten lenses is (f), a synthetic focus distance of the first - third lenses from the substance is fA, and the synthetic focus distance of the fourth - tenth lenses is fB. When the synthetic focus distance of the second third lenses is f23, the radius of curvature the i-th lens surface from the substance is Ri, the average value of the Abbe number of the glass of the positive refractive force lens of cemented lenses L4,5, L7,8 and L9,10 of the fourth - tenth lenses is nu+, the average value of the Abbe number of the glass the negative refractive power lens is nu-, and then, the conditions of the formula I are set to be satified. Thus, the phtotgraphing lens of the long back focus, to which a satisfactory aberration is corrected, can be obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a photographic lens with a long pack focus, and in particular has a wide angle of view of about 63 degrees, which is suitable for electrophotographic cameras, and also has good aberration correction. This relates to a photographic lens with a long focus.

(Prior Art) In recent years, with the development of video cameras, various types of electrophotographic cameras, so-called still video cameras (SV left cameras), have been researched and developed. It is small compared to the screen, and has a diagonal length of about 111 m1.Also, Sv
For example, a reflector is used to guide a portion of the photographic light flux to the finder system, similar to a single-lens reflex camera for photography on the left.
It must be placed in front of the original material. Furthermore, in the Sv left camera, various glass materials such as a low-pass filter and a color filter are often placed in front of the photosensitive material. For this reason, even though the effective screen of the Sv left camera is relatively small, it is necessary to make the back focus considerably longer than that of a single-lens reflex camera for photography. For example, in a 35-inch film single-lens reflex camera for photography, if the diagonal length of the effective thi plane is L, the puck focus is about α8L, whereas the S
In the V-camera 2, if the diagonal length of the effective screen is tt, then the puck focus is required to be llzs degrees.

In this way, the SV left camera can have a relatively long back focus and has good optical performance compared to conventional single-lens reflex cameras and shutter cameras for photography.
There is a need for a photographic lens with a new configuration, which is different from the conventional photographic lenses used in such applications.

□ A photographic lens with a shooting angle of view of about 60 degrees and a comparatively large pack focus compared to the focal length, for example,
This has been proposed in Japanese Patent Laid-Open No. 179808 and Japanese Patent Laid-Open No. 147607/1983, but in both cases, the back 7 orcus is insufficient for a seismic intensity Sv left camera, which is about 26 times larger than the focal length from IWr to L.

(Object of the present invention) An object of the present invention is to provide a photographic lens with a long pack focus, which is suitable for an SV left camera with a wide field of view of 63 degrees, and an F number of about 28, and which is well-corrected for aberrations.

(Main features of the present invention) Starting from the object side, a meniscus-shaped first lens with a positive refractive power with a convex surface facing the object side, and a meniscus-shaped second lens with a negative refractive power with a convex surface facing the object side. , a meniscus-shaped third lens with a negative refractive power that also has its convex surface facing the object side, a fourth lens with a negative refractive power, a fifth lens with a positive refractive power, and a t-stick 9
9 laminated lenses L4, 5, a meniscus-shaped 6th lens with a convex surface facing the object side, an aperture n, a 7th lens with positive refractive power and an 8th lens with negative refractive power are laminated together. Combined lens L7, 8 Two lenses, the 9th lens and the 10th lens, are bonded together so that both the object side and image side lens surfaces are convex. □0's 7 groups 1
The focal length of the entire system composed of 0 lenses 'tf, the composite focal length from the first lens to the third lens tt/A1, the composite focal length from the fourth lens to the tenth lens 1/the second lens
, the combined focal length of the third lens kf, the radius of curvature of the first lens surface from the object side 'lRi, the three laminated lenses L4,5'L7,8'' 9.1
Let ν be the average value of the Atbe's number of a glass with a positive refractive power of 0, and similarly let C be the average value of the Abbe's number of a lens with a negative refractive power, then 0.7<ge A/f+ (, t, s ・−・・−
...(1)L2 (GeB/fA1<λ1...
...(21α6 kugeza // I guri, O...-
----+3118 (lR2/R1l (14...-
...(4:0.5 (l R67R151, (R8
5..."-"" (5) 0.8 (RIO/R11(L
4 ・・・・・・・・・(6)20 (y+-y
-(35...-(7)) is to 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 this example, the composite refractive power of the three lenses of the 1S second and third lenses in the front group is negative, and all three lenses have a meniscus shape with a convex surface facing the object side, so that the focal point of the entire system is In addition to ensuring a pack focus of 26 degrees of seismic intensity at a distance, off-axis aberrations, particularly distortion and astigmatism, are reduced. In particular, the first lens has positive refractive power to reduce negative distortion that accompanies widening the angle of view.

In order to widen the angle of view and increase focus, the negative spherical aberration generated by the second and third lenses with negative refractive power placed in front of the aperture diaphragm is mainly compensated for by bonding and laminating lens L.
This is corrected by making the combined refractive power of 7 and 8 positive.

Also, since positive comatic aberration occurs from the lens surface on the image side of the third lens, it can be corrected by making the lens surface on the image side of the laminated lens L7.8 convex to the tgR surface side in the following shape. are doing.

Furthermore, the negative Peratsuno (-R) sum due to the second and third lenses is mainly calculated by the bonded lens L7.8 and the bonded lens L.
91,. By making both of them positive refractive powers, the curvature of field is prevented from increasing.

If at least one aperture/aperture is arranged between the diaphragm V, lateral chromatic aberration is particularly well corrected. In the lens configuration of this example, the axial rays become relatively high behind the aperture, so by placing two laminated lenses behind the aperture, the axial chromatic aberration can be corrected, and the axial chromatic aberration can be corrected even further. Spherical aberration is overcorrected.

By arranging a sixth lens in the form of a single meniscus with a convex surface facing the object side just before the aperture stop, comatic aberration toward the middle of the screen is effectively corrected.
・Next, I will explain the technical meaning of each conditional expression mentioned above.

I will clarify.

Conditional expression (1) relates to the combined focal length of the front group consisting of nine lenses including the first, second and third lenses, and conditional expression (2) relates to the refraction of the rear group consisting of the fourth to tenth lenses relative to the front group. Regarding the power ratio, the refractive power arrangement, which is the basis of the entire lens system, is appropriately set, the back focus is ensured for a sufficiently long time, and the occurrence of various aberrations is reduced to obtain good optical performance.

If the refractive power of the front group becomes weaker by exceeding the upper limit tti of conditional expression +11 or the lower limit value of conditional expression (2), the occurrence of off-axis aberrations will decrease, but the back focus will become shorter and the lower limit value of conditional expression (11) will decrease. Alternatively, if the upper limit of conditional expression (2) is exceeded and the refractive power of the front group is too strong, the pack focus will become longer, but the negative Petzval sum will increase, the curvature of field will increase, and various aberrations will be reduced over the entire screen. Good correction becomes difficult.

Conditional expression (3) relates to the combined refractive power of the second lens and the third lens, and is intended to appropriately set the Petzval sum and to satisfactorily correct spherical aberration.

If the lower limit value is exceeded and the composite refractive power becomes too strong (9), the Petzval sum increases in the negative direction, the curvature of field increases in the positive direction, and spherical aberration becomes overcorrected. Moreover, if the upper limit is exceeded, the curvature of field increases in the negative direction, which is not preferable.

Conditional expression (4) is used to properly correct distortion regarding the refractive power ratio between the object-side and image-side lens surfaces of the first lens. If the value is exceeded, distortion increases in the positive direction. - Conditional expression (5) relates to the refractive power ratio of the image side lens surface of the third lens to the object side lens surface of the ninth lens, and conditional expression (6) concerns the refractive power ratio of the object side lens surface of the sixth lens. Regarding the refractive power ratio of the lens surface on the image side and the image side, both conditional expressions are intended to correct spherical aberration in a well-balanced manner.

If the negative refractive power becomes too strong, exceeding the lower limit of conditional expression (5) or the upper limit of conditional expression (6), spherical aberration will be over-corrected; Conditional expression (
If the positive refractive power is too strong, exceeding the lower limit of 6), spherical aberration will be insufficiently corrected.

Conditional expression (7) relates to the difference in the aperture number of the glasses of the lenses with positive and negative refractive powers that make up the three laminated lenses, and if the lower limit value is exceeded, the chromatic aberration becomes excessive and the upper limit value is exceeded. This results in under-correction of chromatic aberration.

In this embodiment, one of the #I9 lens and the #10 lens may have a positive refractive power and the other a negative refractive power, and either one may be placed in the front. Further, the sixth lens may have either positive refractive power or negative refractive power. Focusing may be performed by extending the entire lens system, or may be performed by moving only the front lens group or only the rear lens group.

Next, numerical examples of the present invention will be shown.In the numerical examples,
81 is the radius of curvature of the first lens surface in order of 9 from the object side,
Dl is the thickness and air gap of the first lens from the object side, and Ni and νl are the refractive index and Abbe number of the glass of the 11i-th V lens, respectively (from the object side). R19 to R26
is a glass material for faceplates, filters, etc.

Numerical Example 1 F-9FNO-1:t8 2m=61FR1-3
1130141N1-L6u74y 1-47.1
R2-40a09 D242 R3ml&07 D3-LON2-L58913
y24LOR4-6, 3804-46 m5-gly D5s0.8 Ni-1696
80y3-55.5R8-7,7306-aO B 7- (453D 7-0.9 N 4-
172600 y 4-515n8P'jA29
Dshi 4 N S-L 80518 Shishi murmur &4R9--5&04 D Kahe 1 RIG-19,19DIG-ya N 6-L
64769 ν 6 33.8R11-19L
41 Dll-L2R12-Aperture D12 7 1IC13P-157-88Dl3-15 N 7
-L 54G72 y 747.2R141m-7
,11TX4p4.6 N 8-L 76180
y 8=27.1R15--1α81 Dimin I E; 16- u 65 D16Md3.8
N? L 80518 y 9 Bow 5 4R17-LL
50 017-5.2 N1G=L 5
8913 y10 Shizuku 6L 0R18--21L
22 Dl8-40R1G= =e 01
945 Ni1-L 51633 ulln4
1R2G-40 pieces-LO R21-m Dzx-40Nl>L 54427
Crystal R22--022-10 R23-ae D2B@1.95
N15-L 53000 y13-6a O'
R24-' = e D2←LOR25-
os DZ510.5 N14-
L 48700 y144 & 0R26-am Pack focus 2173 Numerical implementation 912 F-9FNO-1:18 2cm-6LfR1-
2&S6 D 1ril N1 ridge 62374 v
147. lR2-9413D>0.2 R3-17,06na-t, o N2458913
y>6LOR4-a 34 D 4-4.6 R5-1&89 Ds-o,s N5=L6968
0 v 3p4B,, SR← 7.88D6-a.

, R7--8a 95 D7<, 9
N 4-172600 y 4j515R
8-・3(L54D IIP4.4
N S-L 80518 y 5-25.
489--25141D9→, 1 RIO-2L 96 D10m114.4
N S-L 64769 y 6=3&
8R11-2α75 Dll own 1.2R12-
Aperture C01M7 R13--131L71 013-&5 N
7-L 54072 w 7 (7,2B1← -
& OX 014-0.6 N 8-L
7g180 ν B-27,1RIS--1
α68 DIH! R16= 27.13 01342 N 9=
L 60729 y 9-5 & 4m? --IL
36 Dl7-α8 Nl0-L 80
518 Shi10-12 & 4R18--2436
01840 R1← W Di Tuna 5 Nil Meng L 516
33 Shi11-ChaoslRen-(To) n Momme-1
0 am--021-40N12=L54427
Crystal R22-W D22-LOR23--
D22-α95 N15-L 53000 y
13-60.0 Introduction ← 輔 D 訳 LO R2 し -025-as Nl ← L 48700
ν14咄0R26-@@Pack 2 Orcus 2 Near 3 Numerical Example 3 F-9FNO-11820-6 Koshiki! R1-2&19 Dx-11Nu-t6 device 74 Si1→7. IR2-10a 53 D 2-a 2R3
= 17.37 D>LON>L58913y
2nLOR4-& 56 D4-46 R5-2α08 D shi →, 8 N3-
1.69680 Shi3-55.5R6-7,88
06-N O R7--9L82 D 7→, 9 N4-L
72600 Shi4-4λ5R8, -27,2408
-4,4NshiL 805 audience νζ device 4R9--740
7Dpe1 R1G-2'1L7ODlk No. N6-1.6476
9 ν←3 8R11-1&79 Dll-
L2R13-Aperture 01247 R13--20 & 98 DI3-15 N
7-L 54072 v 7+7.2B14--
7.94 D1d6 N 11-L 7618O
yBdl'1. IRIS--11,2F D
is-11LIR1fk= 2! 77 D1G
=a 8 N K80318 y 94 wire 4
R17-' IL 50 D171142 N
10=L 58913 ylOmL 0R1B--
2195016-λG axs--019-0,5Ni1-L 51633
ul141R20-=-020-LO R21-ω -N21-1ON1>L 54427
Crystal R22-” D22=LO R23-Korea α!3-4 fi N15-
L 5B (N) yl Sea α0R24-Zeng
024-L, 0R5--D2shi →, 5 Aki←
L 48700 y14-6 & 0 &! ← ■ Back focus 2λ73 Numerical example 4 F-11FNO=1:18 2m-6 "R1-2t@
D 1a41 N l-L 6237
4 y 1→7. lR2-13&68D'
b42' R3-2a 38 D 3-L ON! -L
58913 ν 2-6LOR4-N47 D
4-46 RSp= 2486 D 54.8 N)L
69680y 9s4S, SR← 7.50
Dh4.0 117--1449 D 746 N
4-L 80518 w 4-2 & 4BB-
-m, 49 08→, 9 Nshi L 72600
v N415RITh -6a7! DI-0,1
R1o-19,87Dlo-4,4N fsL 647
69 v 64 & 8R11-17,si on-
&5 R12-Aperture D DIMI R13-151K 00 DI3-&5 N?
-L 54072 Schiff→L2R1← -110D1
4→L 6 N S-L 76180 ν, 1k
L15--11.3OL) 15L R16-Muro4 01648 N9-L Lead 51
8 ν佽) & 4R17-10, 5501742Nl
0-L 5813 Shi1G-8L 0R18--
2a30 01g-10 11<- (to) D19→, s N
i1-L 51 profit 3 ν11→11R20-(to)
020-LO R21-o= 02140 Nl>L 54
427 Crystal R=ζ Korean D22 0 1'LZB--DZshi0.95 N15-L 53
000 w1 sea go.

R2← ψ N24-L 0R25-a
o DZS-0,5N14-L 48700
y144 & 0R26-BACK FOCUS 2173 (Effects of the present invention) As described above, according to the present invention, with a shooting angle of view of 63 degrees and a wide angle of view suitable for the Sv camera 5), F/par zO or so, the pack focus is the focal point. It is possible to achieve a photographic lens with a long puck focus and excellent optical performance of 27 times the distance.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 each show a numerical example l of the present invention. 2, 3, 4, 5, and 6 are aberration diagrams of numerical examples 1, 2, and 3.4 of the present invention, respectively. The four companies dillSg in the diagram are gl! , S is the sagittal image plane, and M is the meridional image plane. Ganto Toyoda Canon Building Shiki Company No. 1 Shinao 3 Figure 4

Claims (1)

[Claims] In order from the object side, a first lens in the form of a meniscus with a positive refractive power with a convex surface facing the object side, a second lens in the form of a meniscus with a negative refractive power with a convex surface facing the object side, and also with the object. Meniscus-shaped third lens with negative refractive power with the convex surface facing the side, laminated lenses L_4_,_5, which are made by bonding together the fourth lens with negative refractive power and the fifth lens with positive refractive power, toward the object side A meniscus-shaped sixth lens with a convex surface, an aperture, a laminated lens L_7_,_8 in which a seventh lens with a positive refractive power and an eighth lens with a negative refractive power are laminated together, and a ninth lens and a tenth lens. A laminated lens L_9_ in which both the object side and image side lens surfaces are convex, which is made by laminating two lenses together.
The focal length of the entire system is f, the combined focal length from the first lens to the third lens is f_A, and the fourth lens to the first lens is composed of 10 elements in 7 groups of _1_0.
The combined focal length up to the 0 lens is f_B, the combined focal length of the second and third lenses is f_2_3, the radius of curvature of the i-th lens surface from the object side is Ri, and the three bonded lenses L_4_,_5 ,L_7_,_8,L_9_
,_1_0, where the average value of the Abbe number of the glass of the lens with positive refractive power is ν_+, and similarly the average value of the Abbe number of the glass of the lens with negative refractive power is ν_-, then 0.7<|f_A/f |<1.5 1.2<|f_B/f_A|<2.1 0.6<|f_2_3/f|<1.0 2.8<|R2/R1|<14 0.5<|R6/R15 A photographing lens with a long back focus, characterized in that it satisfies the following conditions: |<0.85 0.8<R10/R11<1.4 20<ν_+−ν_−<35.