Method and apparatus for checking the quality of CD-ROMS or the

Details Method and apparatus for checking the quality of CD-ROMS or the Method and apparatus for checking the quality of CD-ROMS or the

1997-07-10

1998-12-01

Hindi, Nabil

Dynamic information storage or retrieval

Condition indicating, monitoring, or testing

Including radiation storage or retrieval

369 52, G11B 700

Patent

active

058448667

ABSTRACT:
CD-ROMS of more or less poor quality, such as those having eccentric center holes or uneven weight distributions circumferentially, tend to overload tracking and focusing servos and hence to invite read errors and retries. Each disk on being loaded into the disk drive is therefore checked as to its eccentricity and wobbling preparatory to reading. The disk is set into rotation at a predetermined speed of, typically, eight times the standard audio CD speed. Disk eccentricity is checked by counting the pulses produced by the transducer as the spot of the read beam crosses the track turns, the tracking servo being cut off for this check. The greater the number of pulse generated during a complete disk revolution, the more eccentric is the disk. Wobble check is done by measuring the maximum amplitude of a focusing servo signal being applied to a focusing actuator coil. The disk is read at eight times the standard audio CD speed if it clears both checks, and at four times the standard audio CD speed if it fails to clear either check.

REFERENCES:
patent: 5384761 (1995-01-01), Hashimoto
patent: 5479389 (1995-12-01), Ann
patent: 5701284 (1995-06-01), Lee

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