Three-unit compact zoom lens system
US5353159A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 23, 1991 |
| Grant date | Oct 4, 1994 |
| Priority date | — |
| Expiry date | Dec 23, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/143103
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
This invention relates to a three-unit compact zoom lens system having a zoom ratio of about 2, whose telephoto ratio at the wide angle end is as short as 1.3 or lower and in which the lens diameter of the first lens unit is reduced. This zoom lens system comprises a first positive lens unit G1, a second positive lens unit G2 and a third negative lens unit G3, and in zooming from the wide angle to telephoto end, the first and third lens units are movable toward the object side and the second lens unit is movable toward the object side at a speed relatively lower than that at which the first and third lens units are moved. Furthermore, the present zoom lens system satisfies the following condition: EQU 0.5<.vertline.f.sub.3 /f.sub.W .vertline.<0.9, (1) EQU 1.3<.beta..sub.3W <2.0, (2) EQU 1.7<f.sub.1 /f.sub.W <5.0, (3) and EQU 0.5<f.sub.2 /f.sub.W <1.3. (4) Here f.sub.W is the focal length of the total system at the wide angle end f.sub.1, f.sub.2 and f.sub.3 are the focal lengths of the first, second and third lens units, respectively, and .beta..sub.3W is the image-formation magnification of the third lens unit.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.