Variable-focal-length objective
US4368955A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 2, 1980 |
| Grant date | Jan 18, 1983 |
| Priority date | — |
| Expiry date | Jun 2, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/1441
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The variable-focal-length objective for motion-picture cameras and especially color television cameras comprises two movable groups of lens elements placed between two stationary groups of lens elements and capable of displacement so as to produce a variation of the focal distance. In this objective, the two movable groups each take part in the total variation of magnification; each elementary magnification has a minimum and maximum absolute value during the variation, such that the ratio of maximum value to minimum value is higher than 1:1. However, only one of the two movable groups which does not pass through a magnification of unity performs both a magnification function and an additional focusing function. On the other hand, the other movable group which may pass through a position corresponding to a magnification of unity performs only a magnification function.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.