Tracking system for optical record medium
US4406000A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 31, 1981 |
| Grant date | Sep 20, 1983 |
| Priority date | — |
| Expiry date | Mar 31, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0948
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Tracking apparatus and related method for use in a playback system for recovering information from a selected recording track on an optical record medium such as a video disc. The tracking apparatus produces a tracking error signal representative of the deviation of a scanning reading beam from the centerline of the selected track, and couples this error signal to a movable tracking mirror to form a servo for controllably positioning the beam in alignment with the track. The tracking apparatus further includes a defect detection circuit for monitoring the tracking error signal and producing a pair of control signals that indicate when video disc defects of prescribed types are being scanned, and a threshold detector circuit for comparing the error signal to prescribed positive and negative thresholds that are selectively-variable in accordance with the pair of control signals. A tracking loop disable signal is produced whenever the magnitude of the error signal exceeds either threshold, and this disable signal is used to uncouple the tracking error signal from the tracking mirror, so that the reading beam is maintained at its current position until the dimple has been passed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.