Zoom lens system
US5914820A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 30, 1997 |
| Grant date | Jun 22, 1999 |
| Priority date | — |
| Expiry date | Oct 30, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/143507
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A Zoom lens system, from the enlargement side, has the first to fourth lens units having the negative, positive, negative, positive optical power, respectively. The third lens unit has a meniscus lens having a convex surface on the enlargement side. The fourth lens unit has two positive lenses. During zooming from the shortest focal length condition to the longest focal length condition, the second and third lens units move along the optical axis so that a distance between the second and third lens units increases and a distance between the third and fourth lens units decreases. The zoom lens system fulfills the following conditions: EQU 0.30<.vertline..PHI.3.vertline..multidot.fs<0.90 EQU 3.ltoreq..vertline.(r.sub.MB +r.sub.MA)/(r.sub.MB -r.sub.MA).vertline. Here, .PHI.3 represents an optical power of the third lens unit; fs reprents a focal length of the entire zoom lens system in the shortest focal length condition; r.sub.MB and r.sub.MA represent radiuses of curvature of the enlargement side and reduction side surfaces of the menicus lens.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.