Zoom lens of the internal focus type
US5136431A · kind A · utility
22Cited by
2References
14Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Dec 21, 1990 |
| Grant date | Aug 4, 1992 |
| Priority date | — |
| Expiry date | Dec 21, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/144109
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A zoom lens is disclosed comprising a front lens unit, an intermediate lens unit having two lens sub-units with their axial separation varying for zooming purposes, and a rear lens unit, wherein at the wide-angle end, focusing is performed by moving at least the rear lens unit, and, at the telephoto end, focusing is performed by moving the intermediate lens unit and the rear lens unit, whereby the amount of focusing movement of the intermediate lens unit from an infinitely distant object to an object at a certain short distance is greater at the telephoto end than at the wide-angled end.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.