Focusing screen unit for single lens reflex camera
US4104651A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 14, 1977 |
| Grant date | Aug 1, 1978 |
| Priority date | — |
| Expiry date | Feb 14, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B17/20
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
In an automatic focusing screen unit transparent photoelectric transducing means at a central portion of the image receiving surface area of a glass plate are capable of generating an output signal commensurate with the sharpness of an image formed thereon by an objective lens of a camera. An electrical circuit for processing the output signal of the transducing means produces an output during sharp focus. In a preferred embodiment, this circuit is constructed in the form of an integrated circuit chip for incorporation in the unit together with indicating means responsive to the output signal of the circuit for indicating a sharp focus condition.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.