Optical pickup head with holographic servo signal detection using a spot size detection system
US4929823A · kind A · utility
54Cited by
5References
16Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Oct 4, 1988 |
| Grant date | May 29, 1990 |
| Priority date | — |
| Expiry date | Oct 4, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0903
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical pickup head apparatus comprises a hologram element disposed in the flux of light reflected back from an optical disc, and first and second photodetectors respectively having linear element boundaries extending in a predetermined direction and disposed so as to receive two-focal-point images on their coplanar detection surfaces, whereby the tolerable width of variation in the light source wavelength and the tolerable range of error in the assembling adjustment of the optics can be extended considerably to permit stable differential signal detection.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.