Focus servo control device for an optical system having an initial focus locking operation
US4544837A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 23, 1982 |
| Grant date | Oct 1, 1985 |
| Priority date | — |
| Expiry date | Dec 23, 2002 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0919
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A focus servo control device for an optical system having a focus servo loop including an objective lens movable between a nearest position and a farthest position relative to an object, and a focus error signal generator for producing a focus error signal including at least first and second in-focus signals, the first in-focus signal corresponding to a shorter one of two distance values between the objective lens and the object at which the first and second in-focus signals are generated and indicating a real in-focus state. The device is constructed to open the focus servo loop and move the objective lens from the farthest position to the nearest position, and then to move the objective lens from the nearest position to the farthest position, while monitoring the focus error signal, and closes the focus servo loop upon receipt of the first in-focus signal, thereby preventing a malfunction of the focus servo loop which might occur by locking the objective lens at a false in-focus position.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.