Method and apparatus for detecting tracking error
US4544838A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 29, 1982 |
| Grant date | Oct 1, 1985 |
| Priority date | — |
| Expiry date | Sep 29, 2002 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0901
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A tracking error of a light spot focused on an optical record disc by means of an objective lens with respect to an information track recorded on the disc is detected by processing outputs from a light detector arranged in a far field of the track and having four light receiving regions on which a light reflected by the disc is incident. A tracking error signal of a differential detection system, i.e. a difference between two sums of outputs from two pairs of two regions aligned in a direction tangential to the track is derived, and a push-pull signal, i.e. a difference between two sums of outputs of two pairs of two light receiving regions aligned in a radial direction is also obtained. Zero crossings of the push-pull signal are detected to produce sampling pulses and the tracking error signal of differential system is sampled by the sampling pulses to derive a tracking error signal which is substantially free from disturbance due to a possible shift of the light impinging upon the light detector with respect to the optical axis of objective lens.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.