Optical head including multiple photo detectors for reading signals and error signals for servoing from both a read-only recording medium and a magneto-optical recording medium
US5479387A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 13, 1994 |
| Grant date | Dec 26, 1995 |
| Priority date | — |
| Expiry date | Dec 13, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0943
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical recording/reproducing head device which includes a diffraction grating for splitting a light beam radiated from a light source into at least three light beams, an objective lens for converging the three light beams on a signal recording surface of a disc-shaped optical recording medium, driving means for driving the objective lens along a direction parallel to its optical axis and within a plane perpendicular to the optical axis, a beam splitter for splitting the light beam incident via the objective lens, a first photodetector having a light-receiving surface divided by two boundary lines into four sections, second and third photodetectors arrayed in a direction parallel to one of the boundary lines on both sides of the first photodetector and fourth and fifth photodetectors arrayed in a direction perpendicular to the one of the boundary lines on both sides of the first photodetector, a splitting optical element arranged between the photodetectors and the beam splitter for splitting each of the three light beams from the diffraction grating into three more light beams, and a focusing error detection optical element arranged between the photodetectors and the beam splitt…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.