Zoom lens
US5050972A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 6, 1990 |
| Grant date | Sep 24, 1991 |
| Priority date | — |
| Expiry date | Feb 6, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/145
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A zoom lens comprising, from front to rear, a first group of positive power for focusing, a second group of negative power for varying the image magnification, a third group of negative power for compensating for the image shift, a fourth lens group of positive power in the form of a bi-convex lens whose rear surface is stronger in curvature than the front surface, a stop, and an image forming fifth group, the fifth groug being divided into two parts of which the front part comprises a bi-convex first lens, a negative second lens having a concave front surface and a positive third lens of stronger front curvature and the rear part comprises a negative fourth lens having a concave rear surface, a bi-convex fifth lens and a positive sixth lens of stronger front curvature, and the zoom lens satisfying the following conditions: EQU 3.9<f4/fw<4.5 EQU 3.8<f51/fw<4.2 EQU 1.05<R5,2/R5,3<1.2 EQU 1.25<D51-52/fw<1.39 where f4 and f51 are the focal lengths of the fourth group and the front part respectively, fw is the shortest focal length of the entire lens system, R5,i is the radius of curvature of the 1-th surface counting from front in the fifth group and D51-52 is the axial air separation…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.