Device and method for detecting a focusing state with reliability checking
US4960986A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 8, 1989 |
| Grant date | Oct 2, 1990 |
| Priority date | — |
| Expiry date | Sep 8, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B7/34
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A focus detecting device gathers first image data by a couple of linear arrays of photo diodes in a CCD, which are disposed oppositely with respect to an optical axis of an objective, and second image data by a couple of photo diodes arrayed disposed close to one of the photo diode arrays. A CPU calculates a integer part and fractional part of a displacement of first and second images represented by the first image data, and checks if the calculation results are reliable for focus detection, by using the first and second image data. A counter contained in the CPU counts the number of decisions of unreliable. When a count of counter reaches a preset value and when the latest decision of unreliability is made for the integer part calculation result, a subsequent lens drive is prohibited, and the integration by the CCD, and the integer part calculation are repeated, while presenting a display of "Unmeasurable". Further, an additional reliability check is made of the result of the latest integer part calculation. If the additional reliability check shows a satisfactory reliability, the CPU goes out of the repetitive operation of the integration and the integer part calculation, and rem…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.