Focal length changeable lens system
US4983026A · kind A · utility
19Cited by
5References
6Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Dec 22, 1987 |
| Grant date | Jan 8, 1991 |
| Priority date | — |
| Expiry date | Dec 22, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/08
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The present invention provides a focal length changeable lens system which comprises a master lens group of a positive refractive power having at least one negative lens element made of a synthetic resin material; and a rear conversion lens group of a negative refractive power retractably arranged on the image side of the master lens group and having at least one positive lens element made of a synthetic resin material, in order to well compensate the change of back focal length of the lens system due to the change in temperature thereof without increasing the cost of the lens system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.