Optical information recording/reproducing apparatus, and optical head apparatus
US6563099B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 10, 2001 |
| Grant date | May 13, 2003 |
| Priority date | — |
| Expiry date | Aug 10, 2021 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0013
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
To reduce an effect of reflected light from a layer (or layers) other than a layer to be read upon focus position control when reading a multilayer optical disk in an optical disk drive. In an optical system where a focus error signal is generated by the knife edge method, a photodetector 53 that is divided into four parts is used. Each of two pairs of light detecting elements on the right or left side are formed by division of a detection plane of the photodetector such that the reflected light from a neighboring layer falls half-and-half on that pair of the light detecting elements. Signals from the photodetector are given with alternating polarities in such a way that any adjacent light detecting elements have mutually different polarities and are added up together to form the focus error signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.