Zoom lens
US4934796A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 5, 1989 |
| Grant date | Jun 19, 1990 |
| Priority date | — |
| Expiry date | Oct 5, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/1451
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A zoom lens comprising, from front to rear, a positive first group for focusing, a negative second group as the variator, a negative third group as the compensator, a positive fourth group and a fifth group as the relay lens, the fourth group in the form of a bi-convex singlet and the fifth group in two parts with a widest spacing therebetween, of which the front part comprises a bi-convex first lens, a negative second lens whose front surface is concave toward front, and a positive third lens whose front surface is of strong curvature, and the rear part comprises a negative lens whose rear surface is concave toward rear, a bi-convex lens and a positive lens whose front surface is of strong curvature, satisfying the following conditions: EQU 3.9<f4/fw<4.5 EQU 3.7<f5F/fw<5.2 EQU 1.0<R5,2/R5,3<1.6 EQU 1.4<(D5F-D5R)/fw<1.75 where f4 and f5F are the focal length of the fourth group and the front part of the fifth group, (D5F-D5R) is the spacing between the front and rear parts, R5,2 and R5,3 are the radii of curvature of the rear surface of the first lens and the front surface of the second lens, and fw is the shortest focal length of the entire system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.