Zoom lens system
US5644433A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 5, 1996 |
| Grant date | Jul 1, 1997 |
| Priority date | — |
| Expiry date | Apr 5, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/144113
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A zoom lens system is composed of a first lens group of a positive power, a second lens group of a negative power, a third lens group of a positive power, and a fourth lens groups of a positive power arranged in this order from the object side, the magnification of said zoom lens system being changed by moving the second and third lens groups relative to each other and to the first and fourth lens groups while the positions of the first and fourth lens groups are fixed, wherein focal lengths of the first to fourth lens groups are defined to satisfy the following conditions: EQU 100<f1/fw<500 EQU 2.3<.vertline.f2.vertline./fw<3.5 EQU 1<f4/f3<2 wherein f1, f2, f3 and f4 are the focal lengths of the first to fourth lens groups, respectively; and fw is the focal length of the zoom lens system in a wide-angle terminal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.