Optical head device, optical information apparatus, and method for detecting focus error signal
US6292441A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 16, 1998 |
| Grant date | Sep 18, 2001 |
| Priority date | — |
| Expiry date | Apr 16, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/1381
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical head device includes a light source for emitting a light beam having a predetermined wavelength, an optical system for converging the light beam emitted from the light source on an information medium, and a light detector for receiving the light beam reflected from the information medium and detecting a focus error signal based on the received light beam. The light detector includes a plurality of pairs of photodetectors. The light detector generates the focus error signal based on a differential signal generated by each pair of the plurality of pairs of photodetectors. The plurality of pairs of photodetectors are arranged so that a fluctuation in the differential signal generated by at least one of the pairs of the plurality of pairs of photodetectors is cancelled by a fluctuation in the differential signal generated by at least another of the pairs of the plurality of pairs of photodetectors.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.