Compact high ratio zoom lens system
US5185678A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 10, 1991 |
| Grant date | Feb 9, 1993 |
| Priority date | — |
| Expiry date | Jul 10, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/145113
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A zoom lens system comprises from the object side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power, a fourth lens unit of positive refractive power, and a fifth lens unit of negative refractive power. The first, third and fourth lens units move towards the object side in a zooming operation from the shortest focal length condition to the longest focal length condition. Further, the zoom lens system fulfills the following conditions: EQU 0.4<.vertline.f.sub.2 .vertline./f.sub.w <0.5 EQU 1.0<.vertline.f.sub.5 .vertline./f.sub.4 <5.0 EQU 2.5<e.sub.3T /e.sub.3W <4.5 wherein f.sub.2 represents a focal length of the second lens unit, f.sub.w represents a focal length of the whole zoom lens system in the shortest focal length condition, f.sub.5 represents a focal length of the fifth lens unit, f.sub.4 represents a focal length of the fourth lens unit, e.sub.3T represents an axial distance between the third and fourth lens units in the longest focal length condition, and e.sub.3W represents an axial distance between the third and fourth lens units in the shortest focal length condition.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.