Method and apparatus for scanning a recording medium for defects

Details Method and apparatus for scanning a recording medium for defects Method and apparatus for scanning a recording medium for defects

1985-10-02

1990-12-25

Levy, Stuart S.

Dynamic information storage or retrieval

Condition indicating, monitoring, or testing

Including radiation storage or retrieval

369 58, G11B 2736, G11B 708

Patent

active

049808788

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 nonreflective 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.

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Broadbent, A Review of the MCA Disco-Vision System, J. of the SMPTE, vol. 83, 7/74 pp. 554-559.

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