Optical head device for recording/reproduction for recording medium using plural light spots
US5295125A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 2, 1993 |
| Grant date | Mar 15, 1994 |
| Priority date | — |
| Expiry date | Feb 2, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/094
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
There is disclosed an optical head device in which at least two laser beams having different wavelengths are converged as light spots on a recording medium or optical disk by use of one objective lens and one of the two laser beams is subjected to a focusing control while the recording or reproduction of a signal on or from the optical disk is made using the other laser beam. When the one laser beam is subjected to the focusing control, the deviation of a converging position of the other laser beam for the optical disk may occur due to a difference in refractive index between transparent substrates of plural kinds of optical disks. In such a case, the converging position of the other laser beam is displaced to cancel the amount of deviation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.