Range finder for passive-type autofocusing device
US5257061A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 8, 1992 |
| Grant date | Oct 26, 1993 |
| Priority date | — |
| Expiry date | Oct 8, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B7/36
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A range finder circuit for a passive-type autofocusing device includes three line photosensors. Secondary differences of their output signals and zero-cross points of these secondary differences are computed and detected so long as these zero-cross points are those appearing when primary differences derived from computation of the secondary differences have absolute values larger than a predetermined value. The range to the scene is computed based on the amount of shifting of these signals into coincidence so that substantially no erroneous range finding occurs even when two objects composing the scene overlap each other. In a preferred embodiment also, signals from pixels of each photosensor are smoothed so that no erroneous range finding occurs even when the scene has on the surface thereof a fine repetitive pattern. The range finder circuit also responds to the output signals of the sensors to initiate write-in of zero-cross point data into associated zero-cross memory circuits which can be electrically position-adjusted so that the range to the scene can be computed substantially without error even when there is a certain error involved in mounting of the photosensors.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.