Zoom lens system
US5048939A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 17, 1990 |
| Grant date | Sep 17, 1991 |
| Priority date | — |
| Expiry date | Apr 17, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/145125
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A zoom lens system comprises, from an objective sequentially, a first lens group (1) having a positive power, a second lens group and a third lens group (2) and (3) having negative power and performing a zooming function by moving along an optical axis, a fourth lens group (4) having a positive power and being always stationary, and a fifth lens group (5) having a positive power and having a triplet structure including, from an object side sequentially, a first lens (9) having a positive power, a second meniscus lens (10) having a negative power and a third lens (11) having a positive power, the fourth lens group including a lens at least one surface of which is aspherical, the first or the fifth lens group being movable as a whole or partially along an optical axis to perform a focusing function. The first, second and third lens groups satisfy the following conditions: EQU 2.7<.vertline.f.sub.I /f.sub.II .vertline.<3.6 EQU 1.0<.vertline.f.sub.I /f.sub.III .vertline.<1.9 EQU 3.8<f.sub.I /f.sub.W <4.9 where f.sub.I is a focal length of the first lens group, f.sub.II is a focal length of the second lens group, f.sub.III is a focal length of the third lens group, and f.sub.W is a foca…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.