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Browse Prior Art Database

SINGLE EDGE DELAY PRECOMPENSATION FOR OPTICAL DISK WRITING

IP.com Disclosure Number: IPCOM000025383D
Original Publication Date: 1985-Feb-28
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 79K

Publishing Venue

Xerox Disclosure Journal

Abstract

In laser optical systems which employ a moving spot of light to write information in an optical disk system, the physical boundaries of marks caused by falling edges of electrical signals due to the writing laser do not occur in the same location as the boundaries caused by rising edges. This is due to the finite size of the writing beam. As system requirements become more demanding, this effect can become quite important.

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XEROX DISCLOSURE JOURNAL

SINGLE EDGE DELAY PRECOMPENSATION FOR OPTICAL DISK WRITING
Donald J. Curry
Robert A. Sprague

Proposed Classification
U.S. CI. 346/76

Int. CI. Gold 15/10

d+ DELAY

21 Volume 10 Number 1 January/February 1985

FIG. 1

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SINGLE EDGE DELAY PRECOMPENSATION FOR OPTICAL DISK WRITING (Cont'd)

In laser optical systems which employ a moving spot of light to write information in an optical disk system, the physical boundaries of marks caused by falling edges of electrical signals due to the writing laser do not occur in the same location as the boundaries caused by rising edges. This is due to the finite size of the writing beam. As system requirements become more demanding, this effect can become quite important.

The leading edges of marks will appear to be advanced from their proper position by a time which is directly proportional to the size of the spot and inversely proportional to the velocity of the disk surface. Since the most efficient data modulation schemes require accurate positioning of both edges, a means of correcting this edge bias is needed. The write precompensation technique shown in Figures 1 and 2 delays the occurrence of the rising edge of the laser drive signal bv an amount programmed into a programmable delay line. Two cases are suggested. In low density systems and systems which hold the bit density constant by holding; the media velocity constant, this delay tim...