# US 5,706,141 A · Photographing lens

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- Number: US 5,706,141 A
- Document ID: US5706141A
- Status: Granted
- Kind: A
- Application number: 08/745,463
- Filed: 1996-11-12
- Granted: 1998-01-06
- Earliest claimed: 1995-11-10
- Assignees: Asahi Kogaku Kogyo Kabushiki Kaisha
- Inventors: Tetsuya Abe
- Web page: https://patentgrep.com/patent/US5706141A

## CPC

- G02B 9/04: having two components only
- G02B 13/04: Reversed telephoto objectives
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A photographing lens includes a first lens group, a diaphragm, and a positive second lens group, in this order from the object side. The photographing lens satisfies the following relationships: .vertline.f/f.sub.1 .vertline.<0.2, and 0.7<h.sub.I-1 /h.sub.I-L <1.0. In the above relationships, "f" designates the focal length of the entire photographing lens, "f.sub.1 " the focal length of the first lens group, "h.sub.I-1 " the height of the incident point of paraxial rays on axis on the first surface of the first lens group, and "h.sub.I-L " the height of the incident point of paraxial on-axis rays on the last surface of the first lens group, respectively.

## Claims

### Claim 1

A photographing lens comprising a first lens group, a diaphragm, and a positive second lens group, in this order from the object side, wherein said photographing lens satisfies the relationships defined by the following:
.vertline.f/f.sub.1 .vertline.<0.2
0.7<h.sub.I-1 /h.sub.I-L <1.0
wherein
f represents the focal length of the entire optical system of the photographing lens,
f.sub.1 represents the focal length of the first lens group,
h.sub.I-1 represents the height of the incident point of paraxial on axis rays from the optical axis on the first surface of the first lens group, and
h.sub.I-L represents the height of the incident point of said paraxial on axis rays from the optical axis on the last surface of the first lens group.

### Claim 2 (depends on 1)

A photographing lens according to claim 1, wherein the first lens group comprises a negative lens element, an image-side surface of said negative lens element being a concave surface, and a positive lens element, an image-side surface of said positive lens element being a convex surface, arranged in this order from the object side, and wherein the first lens group satisfies:
0.3<d/f<1.0
0.5<r.sub.1-2 /f<1.0
wherein
d represents the distance from the first surface of the first lens group to the last surface of the first lens group, and
r.sub.1-2 represents the radius of curvature of the image side surface of the negative lens element of the first lens group.

### Claim 3 (depends on 1)

A photographing lens according to claim 1, wherein the first lens group has positive power and the second lens group is comprised of a cemented lens assembly of biconcave and biconvex lens elements and a biconvex lens in this order from the object side.