Zoom lens system
US5548445A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 6, 1995 |
| Grant date | Aug 20, 1996 |
| Priority date | — |
| Expiry date | Mar 6, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/145129
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A zoom lens system consists of a positive first lens group G1, a negative second lens group G2, a stop, a positive third lens group G3, a positive fourth lens group G4 and a positive fifth lens group G5 arranged in this order from the object side. The second and fourth lens groups G2 and G4 are moved with the other lens groups G1, G3 and G5 fixed when zooming. The focal length of the total lens system is changed by moving the second lens group G2 along the optical axis and the change in the image-forming position generated by the movement of the second lens group G2 is compensated for and the zoom lens system is focused by moving the fourth lens group G4 along the optical axis. The following formulae (1) and (2) are satisfied, EQU 1.1<f.sub.w(G4+G5) /(f.sub.w .multidot.f.sub.t).sup. 1/2 <1.3(1) EQU 1.2<f.sub.G3 /(f.sub.w .multidot.f.sub.t).sup. 1/2 <1.8 (2) wherein f.sub.w(G4+G5) represents the combined focal length of the fourth and fifth lens groups G4 and G5 at the wide-side end, f.sub.w represents the focal length of the total lens system at the wide-side end, f.sub.t represents the focal length of the total lens system at the tele-side end and f.sub.G3 represents the focal len…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.