Method and apparatus for scanning a recording medium for defects
US4571716A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 29, 1984 |
| Grant date | Feb 18, 1986 |
| Priority date | — |
| Expiry date | Jun 29, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B20/1833
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for recording a data signal on a light-reflective record disc, wherein an intensity-modulated write beam of light is focused onto the disc as the disc is rotated in a prescribed fashion, to produce a sequence of spaced non-reflective regions representative of the data signal. Additionally, a relatively low intensity pre-write beam of light scans the disc in advance of, but synchronous with, the write beam to detect the presence of non-reflective defects in the disc that could inhibit the recording of the data signal thereon. Whenever such a defect is detected, a special defect flag code is recorded in advance of and over the defective region, whereby when the data signal is recovered from the disc at a subsequent time, it can be recognized that the data signal is being temporarily interrupted.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.