Apparatus and method for focus control of read light irradiated on a recording surface
US6101157A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 26, 1998 |
| Grant date | Aug 8, 2000 |
| Priority date | — |
| Expiry date | Jun 26, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0013
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Apparatus and method for focus control are devised to cope with a fluctuation of an optimum gain of a focus servo loop due to a difference between light reflectance of recording surfaces or the like and to allow an optimum focal position of read light to preferably trace a target recording surface. The focus control apparatus of the invention includes: reading device for generating a read signal of a recording medium 1; a focus servo loop for allowing an optimum converging position of the read light to trace the target recording surface in accordance with a focus error signal FE by using a focusing actuator to displace the optimum converging position of the read light in the optical axial direction; a level detecting unit of the read signal; a level detecting unit of an error signal FE; amplifiers and of a read signal RF and the error signal FE; and a control unit for driving the actuator so as to allow the optimum converging position of the read light to approach the recording surface in the set-up mode and for controlling gains of the amplifiers so that a detection level by the detecting unit in the set-up mode reaches a predetermined level and a detection level by a detecting un…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.