# US 4,395,094 A · Large aperture ratio photographic lens with means for correcting aberrations

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- Number: US 4,395,094 A
- Document ID: US4395094A
- Status: Granted
- Kind: A
- Application number: 06/222,539
- Filed: 1981-01-05
- Granted: 1983-07-26
- Earliest claimed: 1980-01-31
- Assignees: Nippon Kogaku K.K.
- Inventors: Yoshinari Hamanishi
- Web page: https://patentgrep.com/patent/US4395094A

## CPC

- G02B 13/00: Optical objectives specially designed for the purposes specified below (with variable magnification {in general} G02B15/00)
- G02B 9/62: having six components only
- G02B 27/0025: {for optical correction, e.g. distorsion, aberration}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

This specification discloses a large aperture ratio photographic lens with means for correcting aberrations comprising a forward group including at least one negative lens and having a composite positive refractive power, a rearward group also including at least one negative lens and having a composite positive refractive power, and a diaphragm provided between the two groups, characterized in that during the shift from an infinity object photography condition to a short distance object photography condition, focusing is effected by moving both of the two groups toward the object side while enlarging the diaphragm space between the two groups and that the photographic lens satisfies predetermined conditions.

## Claims

### Claim 1

In a large aperture ratio photographic lens with means for correcting aberrations comprising a forward group including at least one negative lens and having a composite positive refractive power, a rearward group also including at least one negative lens and having a composite positive refractive power, and a diaphragm provided between said two groups, the improvement residing in that during the shift from an infinity object photography condition to a short distance object photography condition, focusing is effected by moving both of said two groups toward the object side while enlarging the diaphragm space between said two groups and that said photographic lens satisfies the following conditions:
2.4<f.sub.1 /f<4.5 (1)
2.5<f.sub.1 /f.sub.2 <5.5 (2)
where f is the total focal length of the entire system during the infinity photography condition, f.sub.1 is the focal length of said forward group, and f.sub.2 is the focal length of said rearward group.

### Claim 2 (depends on 1)

A photographic lens according to claim 1, further satisfying the following conditions:
1.75<N<1.81
29.6<.nu.<59
where N is the average refractive index of the glass of the positive lens in said forward group, and .nu. is the Abbe number of the glass of the negative lens in said forward group.

### Claim 3 (depends on 2)

A photographic lens according to claim 2, wherein the amount of variation, y, in the diaphragm space between said two groups and the amount of variation, x, in the back focal length have a functional relationship y=f(x) with the infinity photography condition being at y=0 and x=0 such that when the shift from the infinity photography condition to the near distance photography condition takes place, the first -order differentiated value dy/dx of said functional relationship is in the range of
0.2<dy/dx<0.6.

### Claim 4 (depends on 3)

A photographic lens according to claim 3, wherein said forward group includes, in succession from the object side, a positive lens, a positive meniscus lens having its convex surface facing the object side, and a negative meniscus lens having its convex surface facing the object side, and said rearward group includes, in succession from the object side, a meniscus lens comprising a negative lens and a positive lens cemented together and having its concave surface facing the object side, and at least one positive lens.

### Claim 5 (depends on 4)

A photographic lens according to claim 4, wherein when the curvature radii of the front and rear surfaces of the positive lens in said forward group which is most adjacent to the object side are r.sub.1 and r.sub.2, respectively, the shape factor defined as .delta.=(r.sub.2 +r.sub.1)/(r.sub.2 -r.sub.1) satisfies the condition that 0.9<.delta.<1.3.

### Claim 6 (depends on 5)

A photographic lens according to claim 5, wherein numerical data are as follows:
______________________________________ Focal length f = 51.6 F-number 1.8 Angle of view 2.omega. = 45.43.degree. Forward Group G.sub.1 r.sub.1 = 45.900 d.sub.1 = 4.6 n.sub.1 = 1.80411 .nu..sub.1 = 46.4 r.sub.2 = 353.259 d.sub.2 = 0.1 r.sub.3 = 21.215 d.sub.3 = 4.7 n.sub.2 = 1.71300 .nu..sub.2 = 54.0 r.sub.4 = 35.262 d.sub.4 = 1.4 r.sub.5 = 63.100 d.sub.5 = 1.1 n.sub.3 = 1.67270 .nu..sub.3 = 32.2 r.sub.6 = 16.120 d.sub.6 = Variable Rearward Group G.sub.2 r.sub.7 = -16.588 d.sub.7 = 1.3 n.sub.4 = 1.74000 .nu..sub.4 = 28.3 r.sub.8 = -100.000 d.sub.8 = 5.4 n.sub.5 = 1.76684 .nu..sub. 5 = 46.8 r.sub.9 = -20.429 d.sub.9 = 0.1 r.sub.10 = 204.300 d.sub.10 = 3.45 n.sub.6 = 1.80411 .nu..sub.6 = 46.4 r.sub.11 = -54.861 ______________________________________
wherein when the object distance d.sub.0 =.infin., d.sub.6 =12.867 and when the object distance d.sub.0 =286.916, d.sub.6 =17.622, Photographing magnification .beta.=-0.2, and wherein the diaphragm lies 5.8 ahead of the foremost lens surface of the rearward group G.sub.2, and
______________________________________ f.sub.1 = 132.289 .delta. = 1.299 f.sub.1 = 48.279 f.sub.1 /f = 2.564 f.sub.1 /f.sub.2 = 2.740 ______________________________________
wherein r represents the radius of curvature of each lens surface, d represents the center thickness of each lens and the air space between adjacent lenses, n and .nu. represent refractive index and Abbe number, respectively, and the subscripts represent the order from the object side.

### Claim 7 (depends on 5)

A photographic lens according to claim 5, wherein numerical data are as follows:
______________________________________ Focal length f = 51.6 F-number 1.4 Angle of view 2.omega. = 45.43.degree. Forward Group G.sub.1 r.sub.1 = 59.500 d.sub.1 = 4.5 n.sub.1 = 1.77279 .nu..sub.1 = 49.4 r.sub.2 = 4804.893 d.sub.2 = 0.15 r.sub.3 = 25.448 d.sub.3 = 5.0 n.sub.2 = 1.80411 .nu..sub.2 = 46.4 r.sub.4 = 43.781 d.sub.4 = 1.8 r.sub.5 = 78.162 d.sub.5 = 1.8 n.sub.3 = 1.64831 .nu..sub.3 = 33.8 r.sub.6 = 17.822 d.sub.6 = Variable Rearward Group G.sub.2 r.sub.7 = -17.711 d.sub.7 = 1.65 n.sub.4 = 1.75520 .nu..sub.4 = 27.6 r.sub.8 = -200.000 d.sub.8 = 6.15 n.sub.5 = 1.78797 .nu..sub. 5 = 47.5 r.sub.9 = -26.332 d.sub.9 = 0.15 r.sub.10 = -135.239 d.sub.10 = 4.6 n.sub.6 = 1.77279 .nu..sub.6 = 49.4 r.sub.11 = -33.578 d.sub.11 = 0.2 r.sub.12 = 124.264 d.sub.12 = 2.15 n.sub.7 = 1.80411 .nu..sub.7 = 46.4 r.sub.13 = -82604.571 ______________________________________
wherein when the object distance d.sub.0 =.infin., d.sub.6 =13.623 and when the object distance d.sub.0 =364.224, d.sub.6 =16.577, Photographing magnification .beta.=-0.15, and wherein the diaphragm lies 6.4 ahead of the foremost lens surface of the rearward group G.sub.2, and
______________________________________ f.sub.1 32 146.0 .delta. = 1.025 f.sub.2 = 45.369 f.sub.1 /f = 2.829 f.sub.1 /f.sub.2 = 3.218 ______________________________________
wherein r represents the radius of curvature of each lens surface, d represents the center thickness of each lens and the air space between adjacent lenses, n and .nu. represent refractive index and Abbe number, respectively, and the subscripts represent the order from the object side.

### Claim 8 (depends on 5)

A photographic lens according to claim 5, wherein numerical data are as follows:
______________________________________ Focal length f = 51.6 F-number 1.4 Angle of view 2.omega. = 45.43.degree. Forward Group G.sub.1 r.sub.1 = 45.529 d.sub.1 = 4.8 n.sub.1 = 1.74400 .nu..sub.1 = 45.1 r.sub.2 = 490.732 d.sub.2 = 0.1 r.sub.3 = 27.052 d.sub.3 = 5.9 n.sub.2 = 1.79631 .nu..sub.2 = 41.0 r.sub.4 = 46.072 d.sub.4 = 1.3 r.sub.5 = 87.913 d.sub.5 = 1.6 n.sub.3 = 1.69895 .nu..sub.3 = 30.1 r.sub.6 = 17.602 d.sub.6 = Variable Rearward Group G.sub.2 r.sub.7 = -17.356 d.sub.7 = 1.0 n.sub.4 = 1.72825 .nu..sub.4 = 28.3 r.sub.8 = -500.0 d.sub.8 = 7.0 n.sub.5 = 1.80411 .nu..sub. 5 = 46.4 r.sub.9 = -26.968 d.sub.9 = 0.2 r.sub.10 = -94.634 d.sub.10 = 4.4 n.sub.6 = 1.71300 .nu..sub.6 = 54.0 r.sub.11 = -31.468 d.sub.11 = 0.1 r.sub.12 = 114.654 d.sub.12 = 2.5 n.sub.7 = 1.76684 .nu..sub.7 = 46.8 r.sub.13 = -260.047 ______________________________________
wherein when the object distance d.sub.0 =.infin. d.sub.6 =16.121 and when the object distance d.sub.0 =354.649 d.sub.6 =17.894, Photographing magnification .beta.=-0.15, and wherein the diaphragm lies 7.7 ahead of the foremost lens surface of the rearward group G.sub.2, and
______________________________________ f.sub.1 = 177.786 .delta. = 1.205 f.sub.2 = 41.768 f.sub.1 /f = 3.445 f.sub.1 /f.sub.2 = 4.257 ______________________________________
wherein r represents the radius of curvature of each lens surface, d represents the center thickness of each lens and the air space between adjacent lenses, n and .nu. represent refractive index and Abbe number, respectively, and the subscripts represent the order from the object side.