Auto-focus arithmetic device
US4831405A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 6, 1987 |
| Grant date | May 16, 1989 |
| Priority date | — |
| Expiry date | Oct 6, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B7/36
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An auto-focus arithmetic device suitable for use in a photographic camera is provided. The device includes a photographic lens which is movable along a predetermined optical axis and a CCD for detecting light coming from a subject of interest through the lens. An arithmetic unit for determining the direction and amount of movement of the lens with respect to the subject of interest based on a detection signal from the CCD is provided. The arithmetic unit includes an integer portion calculating sub-unit for calculating an integer portion of the detection signal and a fractional portion calculating sub-unit for calculating a fractional portion of the detection signal. The fractional portion calculating sub-unit remains deactivated as long as the detected amount of discrepancy from the in-focus condition is larger than a predetermined level; however, it is activated when the detected amount of discrepancy becomes equal to or less than the predetermined level. In this manner, in accordance with the present invention, the integer and fractional portion calculating sub-units are used alternately.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.