Optical head using hologram lens for both beam splitting and focus error detection functions
US4731772A · kind A · utility
Inventor
Key dates
| Filing date | May 6, 1986 |
| Grant date | Mar 15, 1988 |
| Priority date | — |
| Expiry date | May 6, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B11/10532
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An improved optical head which eliminates the need for a biprism or cylindrical lens for focus detection and allows the placement of a photodetector immediately adjacent to the semiconductor laser to reduce alignment problems and vibrational errors. A semiconductor laser is provided which produces a laser beam which impinges upon a movable objective lens. The objective lens focuses the laser beam onto an information medium. A diffraction grating, which may be holographic, is placed between the laser and the objective lens. The diffracted beams on the forward path from the laser to the objective lens are not used, but on the return path, one of the diffracted beams is focused onto a photodetector which is in the same plane as the semiconductor laser.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.