Devices for detecting defects of disc-shaped record media
US4817077A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 29, 1987 |
| Grant date | Mar 28, 1989 |
| Priority date | — |
| Expiry date | Sep 29, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B27/36
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A defect in an information signal recorded in a spiral track on an optical disc is detected based on a low level portion of an envelope of a reproduced information signal. When periods between detection output pulses each measured from the leading edge of the detection output pulse are equal to each other, a pulse having its leading edge at a time point after the leading edge of said detection output pulse and its trailing edge at a time point of the trailing edge of said detection output pulse or a time point after the trailing edge of said detection output pulse is produced to be used as a defect detection signal. The defect detection signal is used for preventing tracking servo-control and focus servo-control for an optical head from being performed abnormally.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.