Capacitance distance sensor apparatus for video disc player/recorder
US4183060A · kind A · utility
35Cited by
7References
6Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Sep 14, 1978 |
| Grant date | Jan 8, 1980 |
| Priority date | — |
| Expiry date | Sep 14, 1998 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B7/14
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A non-contact type, capacitance distance sensing probe having one or two electrodes disposed about one end of an objective lens system in an optical video disc system is used with a focus control servo loop to maintain focus of a light beam on the surface of a reflective disc record despite undesirable axial displacements of the surface when the record is rotated. The two electrode probe is balanced to provide immunity to variations in the impedance of the external circuit which grounds the disc.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.