Method and apparatus for detecting minute defects on magnetic di

Details Method and apparatus for detecting minute defects on magnetic di Method and apparatus for detecting minute defects on magnetic di

1986-11-07

1989-11-14

Faber, Alan

Dynamic magnetic information storage or retrieval

Checking record characteristics or modifying recording...

360 31, 360 45, 324212, G11B 5455, G11B 2736, G01R 3312

Patent

active

048811360

ABSTRACT:
Because of increase in data recording density on a magnetic disk in recent years, a minute defect which posed no problem in the past exerts adverse influence upon the recording and reproducing characteristics. An object of the present invention is to provide a method and an apparatus for detecting minute defects on a magnetic disk. In order to achieve this object, the present invention was made on the basis of the recognition that a large defect on the magnetic disk largely decreases the amplitude of the reproduced signal and shifts its phase, whereas a small defect does not decrease the amplitude of the reproduced signal so largely but causes a phase shift. Therefore, defects on the magnetic disk are detected by monitoring the amplitude decrease and phase shift of the reproduced signal.

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Katz et al., IEEE Transactions on Magnetics, vol. Mag-15, No. 3, May 1979, pp. 1050-1053.

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