System for detecting height fluctuations of a surface on a recording medium in an optical recording or reproducing apparatus
US4110607A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 21, 1976 |
| Grant date | Aug 29, 1978 |
| Priority date | — |
| Expiry date | Dec 21, 1996 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0924
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The invention relates to a system for detecting the height fluctuations of a surface on a recording medium in an optical recording or reproducing apparatus. A light source emits a main light beam for recording or reproducing. An optical system, including an objective lens, focuses the main light beam into a spot on the surface. A first reflecting mirror introduces a sublight beam into the peripheral part of the main light beam. The sub-light beam advances in a forward path through the objective lens to be projected onto the recording surface and reflected thereby. The sub-beam returns again through the objective lens along the peripheral part of the main light beam, but on the opposite side from said forward path. A second reflecting mirror extracts the sub-light beam in the return path out of the light to operate a detector which detects fluctuations in the distance between the objective lens and the recording surface and to produce control signals maintaining a constant distance between the objective lens and recording surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.