Direct read after write verify using differential detection

Details Direct read after write verify using differential detection Direct read after write verify using differential detection

1984-02-08

1986-07-08

Richardson, Robert L.

Dynamic information storage or retrieval

Condition indicating, monitoring, or testing

Including radiation storage or retrieval

369 59, 360 53, G11B 700

Patent

active

045997179

ABSTRACT:
Disclosed is an apparatus for verifying data written on an optical disk by simultaneously reading the data during writing and using differential detection to verify that the data has been written correctly. The data is written in a fixed-block format defining a symbol having a predetermined number of symbol positions and a predetermined number of holes which may be written in the symbol positions, an equal number of holes in the odd positions and in the even positions. In this regard, the holes written in the odd positions are independently verified from the holes written in the even positions. Immediately after the laser has been operated at write power, it is returned to read power and a signal associated with the hole associated power of the reflected beam is sampled. This signal is compared to the signal power generated at the previous even or odd position. The highest signal is retained and compared to the next even or odd position's signal. At the end of the symbol, the location of the even and odd symbol positions having the highest signal power is determined and compared to the location of the write pulse to determine whether the location of the hole corresponds with the location of the write pulse.

REFERENCES:
patent: 4145758 (1979-03-01), Drexler et al.
patent: 4198701 (1980-04-01), Reddersen et al.

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