System for focusing an optical head onto a flat surface
US4495407A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 29, 1982 |
| Grant date | Jan 22, 1985 |
| Priority date | — |
| Expiry date | Mar 29, 2002 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0908
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A system for focusing an optical head onto a flat surface has a mechanism for moving the optical head in the direction of the optical axis of the head and a mechanism for moving an objective lens in the optical head in the direction of the optical axis of the lens. A laser beam projected from the objective lens of the optical head is reflected on the flat surface, is reflected on the beam splitter, and is introduced into a detector unit. The detector unit thus generates a focusing signal having a level responsive to the distance between the objective lens and the surface. The optical head is lowered by the mechanism for moving the optical head in accordance with the focusing signal when it passes a predetermined point, and is operated to locate the focal point of the objective lens on the surface. Thereafter, the mechanism for moving the optical head becomes inoperative, and the mechanism for moving the objective lens is operated. This mechanism operates in accordance with the focusing signal and locates the focal point of the objective lens always on the surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.