Focal point detecting device for SLR camera
US4180309A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 19, 1977 |
| Grant date | Dec 25, 1979 |
| Priority date | — |
| Expiry date | May 19, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B7/343
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A pair of wedge prisms 11, 11' are disposed at an optical position equivalent to that of the film 10 in an SLR camera, and light from the object is directed thereon by a mirror 4 or the like. The prisms split the object image into two halves which are projected onto a two row array of thin photocells or the like, whereby the relative lateral displacement between the image halves as well as their level of contrast is a function of the degree of correct image focus. The latter is sensed by subtractively of differentially comparing the outputs of paired, laterally offset photocells in the two rows, such pairing being implemented in both directions. The output summation signal exhibits an easily detectable sharp peak when the object is properly focused, thereby enabling automatic focal point detection.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.