Zoom optical system
US6025960A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 23, 1998 |
| Grant date | Feb 15, 2000 |
| Priority date | — |
| Expiry date | Dec 23, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/143103
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The invention provides a compact zoom optical system which can be reduced in terms of the lens length upon collapsing, albeit having a zoom ratio as 3 or greater. The zoom optical system comprises a first lens group G1 having positive power, a second lens group G2 having positive power and a third lens group G3 having negative power. For zooming from the wide-angle end to telephoto end of the system, the lens groups move together toward the object side while the space between the first group G1 and the second group G2 becomes wide and the space between the second group G2 and the third group G3 becomes narrow. The second group G2 comprises a front lens subgroup G.sub.2A having negative power and a rear lens subgroup G.sub.2B, between which an aperture stop S is located. At least one aspheric surface is used in the rear subgroup G.sub.2B in the second group G2. The optical system satisfies 0.4<f.sub.W /f.sub.1G <1.0 where f.sub.W is the focal length of the optical system at the wide-angle end and f.sub.1G is the focal length of the first group G1.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.