Focus detection device for reading information from an optical recording medium
US5345072A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 23, 1992 |
| Grant date | Sep 6, 1994 |
| Priority date | — |
| Expiry date | Dec 23, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0912
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A focus detection device for use in a focus detection device includes a main light source and two auxiliary light sources. These auxiliary light sources are offset to the main light source along the optical axis of the main optical system while being symmetrically positioned perpendicular to the optical axis. A exposure units having apertures are provided above the two auxiliary light sources for constricting the amount of auxiliary lights so that the convergence of the auxiliary beams on the optical disk is less than that of the main light beam. As a result, an optical system with a broad focus error detection range can be constructed while increasing the convergence of the main light beam.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.