Image focussing mechanism
US3938893A · kind A · utility
3Cited by
1References
8Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Nov 4, 1974 |
| Grant date | Feb 17, 1976 |
| Priority date | — |
| Expiry date | Nov 4, 1994 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B17/12
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A mechanism for determining the focus by an objective lens of an image on a focal plane includes a needle shaped or other narrow scanning mask transversely oscillated in the focal plane between the lens and a transversely extending photoelectric element exposed to the mask intercepted image. The output of the photosensitive element is coupled by way of a high pass filter or differentiating circuit and a rectifier to a meter, the maximum meter reading indicating maximum AC output and hence maximum focus. The output of the photosensitive element is also connected through a low-pass filter to a meter or exposed control mechanism.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.