# US 4,395,092 A · Compact telephoto zoom lens

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- Number: US 4,395,092 A
- Document ID: US4395092A
- Status: Granted
- Kind: A
- Application number: 06/240,421
- Filed: 1981-03-04
- Granted: 1983-07-26
- Earliest claimed: 1980-03-10
- Assignees: Asahi Kogaku Kogyo Kabushiki Kaisha
- Inventors: Takayuki Itoh
- Web page: https://patentgrep.com/patent/US4395092A

## CPC

- G02B 15/1441: {the first group being positive}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A compact telephoto zoom lens is composed of twelve lenses grouped into nine lens groups. These include, from the object side, a variator system including a first lens group functioning as a focusing group having a positive focal length, a second lens group functioning as a main variator having a negative focal length, a third lens group functioning as a compensator for maintaining an image plane constant which has a positive focal length, and a relay lens system. The first lens group includes a positive meniscus lens convex on the object side and a positive cemented lens composed of a negative meniscus lens convex on the object side and a positive lens. The second lens group includes a negative lens whose lens concave surfaces confront one another and a negative cemented lens composed of a biconcave and a positive lens. The third lens group includes a positive cemented lens composed of a biconvex lens and a negative meniscus lens while the relay lens system includes first and second fourth lens groups.

## Claims

### Claim 1

A compact telephoto zoom lens comprising, in order from the object side, a variator system including a first lens group functioning as a focusing group having a positive focal length, a second lens group functioning as a main variator having a negative focal length, a third lens group functioning as a compensator for maintaining an image plane constant having a positive focal length, and a relay lens system, said first lens group including a positive meniscus lens convex on the object side and a positive cemented lens comprising a negative meniscus lens convex on the object side and a positive lens, said second lens group including a negative lens whose lens concave surfaces confront each other and a negative cemented lens comprising a biconcave lens and a positive lens, said third lens group including a positive cemented lens composed of a biconvex lens and a negative meniscus lens, said relay lens system including a fourth lens group a comprising a positive lens having a stronger convex surface on the object side and a biconcave negative lens and a fourth lens group b comprising a biconvex positive lens and a negative meniscus lens having a stronger concave surface on the object side, said fourth lens group b being disposed a predetermined distance from said fourth lens group a, said zoom lens satisfying the following conditions:
______________________________________ F No. 1:4.5 f = 82.0 .about. 195.0 .omega. = 15.2.degree. .about. 6.2.degree. LENS NO. r d N .nu. ______________________________________ 1 87.373 3.95 1.51633 64.1 FIRST 2 284.393 0.10 LENS 3 69.120 2.30 1.80518 25.4 GROUP 4 46.684 8.05 1.48749 70.1 5 -1885.831 4.409 6 -161.880 1.70 1.69680 55.5 SECOND 7 46.010 4.45 LENS 8 -60.000 1.50 1.69680 55.5 GROUP 9 40.111 3.80 1.80518 25.4 10 -1590.000 30.980 THIRD 11 114.300 5.00 1.58913 61.0 LENS 12 -42.520 1.60 1.80518 25.4 GROUP 13 -83.000 11.897 14 39.214 4.10 1.58913 61.0 FOURTH 15 -2275.000 1.79 LENS 16 -269.221 2.10 1.80518 25.4 GROUP a 17 269.221 32.87 18 71.700 3.50 1.62588 35.7 FOURTH 19 -265.000 8.45 LENS 20 -30.398 1.70 1.80610 40.9 GROUP b 21 -79.717 ______________________________________ Vari- able f Distance 82.0 135.0 195.0 ______________________________________ d.sub.5 4.409 26.751 37.624 d.sub.10 30.980 17.429 1.718 d.sub.13 11.897 3.105 7.943 ______________________________________ f.sub.min /f.sub.I = 0.759, f.sub.min /f.sub.I.about.II = -1.246, f.sub.min /f.sub.I.about.III = -0.085, f.sub.min /f.sub.I.about.IVa = 1.088, f.sub.min /f.sub.I.about.IVb.sbsb.1 = 1.920, (n.sub.II.sbsb.1 + n.sub.II.sbsb.2)/.sub.2 = 1.6968, r.sub.IVa.sbsb.1 /f.sub.min = r.sub.14 /f.sub.min = 0.478, l.sub.IVaIVb /f.sub.min = d.sub.17 /f.sub.min = 0.401, l.sub.IVb.sub.2 /f.sub.min = d.sub.19 /f.sub.min = 0.103, .vertline.r.sub.IVb.sbsb.3 .vertline./f.sub.min = .vertline.r.sub.20 .vertline./f.sub.min = 0.371, and n.sub.IVb.sbsb.2 = 1.80610, ______________________________________
where:
f.sub.min is the overall focal length of said zoom lens at a wide angle position thereof;
f.sub.I is the focal length of said first lens group;
f.sub.I.about.II is the resultant focal length of said first and second lens groups at said wide angle position;
f.sub.I.about.III is the resultant focal length of said first, second and third lens groups at said wide angle position;
f.sub.I.about.IVa is the resultant focal length from said first lens group to said fourth lens group a at said wide angle position;
f.sub.I.about.IVb.sbsb.1 is the resultant focal length from said first lens group to said positive lens of said fourth lens group b at said wide angle position;
n.sub.II.sbsb.1 is the refractive index of said first negative lens of said second lens group at the d-line thereof;
n.sub.II.sbsb.2 is the refractive index of said second negative lens of said second lens group at the d-line thereof;
r.sub.IVa.sbsb.1 is the radius of curvature of the first lens surface of said fourth lens group a;
l.sub.IVaIVb is the distance between said fourth lens groups a and b;
l.sub.IVb.sbsb.2 is the distance between said positive lens and said negative meniscus lens of said fourth lens group b;
r.sub.IVb.sbsb.3 is the radius of curvature of the first lens surface of said negative meniscus lens of said fourth lens group b;
n.sub.IVb.sbsb.2 is the refractive index of said negative meniscus lens of said fourth lens group b at the d-line thereof;
f is the overall focal length;
.omega. is the half viewing angle of the designated lens;
r is the radius of curvature of the designated lens;
d is the lens thickness or distance between adjacent lenses;
N is the refractive index at the d-line; and
.nu. is the Abbe number.

### Claim 2

A compact telephoto zoom lens comprising, in order from the object side, a variator system including a first lens group functioning as a focusing group having a positive focal length, a second lens group functioning as a main variator having a negative focal length, a third lens group functioning as a compensator for maintaining an image plane constant having a positive focal length, and a relay lens system, said first lens group including a positive meniscus lens convex on the object side and a positive cemented lens comprising a negative meniscus lens convex on the object side and positive lens, said second lens group including a negative lens whose lens concave surfaces confront each other and a negative cemented lens comprising a biconcave lens and a positive lens, said third lens group including a positive cemented lens composed of a biconvex lens and a negative meniscus lens, said relay lens system including a fourth lens group a comprising a positive lens having a stronger convex surface on the object side and a biconcave negative lens and a fourth lens group b comprising a biconvex positive lens and a negative meniscus lens having a stronger concave surface on the object side, said fourth lens group b being disposed a predetermined distance from said fourth lens group a, said zoom lens satisfying the following conditions: ##EQU2## where: f.sub.min is the overall focal length at the wide angle end;
f.sub.I is the focal length of the first lens group;
f.sub.I.about.II is the resultant focal length of the first and second lens group at the wide angle end;
f.sub.I.about.III is the resultant focal length of the first, second and third lens groups at the wide angle end;
f.sub.I.about.IVa is the resultant focal length from the first lens group to the fourth lens group a at the wide angle end;
f.sub.I.about.IVb.sbsb.1 is the resultant focal length from the first lens group to the positive lens of the fourth lens group b at the wide angle end;
n.sub.II.sbsb.1 is the refractive index of the first negative lens of the second lens group at the d-line;
n.sub.II.sbsb.2 is the refractive index of the second negative lens of the second lens group at the d-line;
r.sub.IVa.sbsb.1 is the radius of curvature of the first lens surface of the fourth lens group a;
l.sub.IVaIVb is the distance between the fourth lens groups a and b;
l.sub.IVb.sbsb.2 is the distance between the positive lens and the negative meniscus lens of the fourth lens group b;
r.sub.IVb.sbsb.3 is the radius of curvature of the first surface of the negative meniscus lens of the fourth lens group b; and
n.sub.IVb.sbsb.2 is the refractive index of the negative meniscus lens of the fourth lens group b at the d-line.