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Method and apparatus for recording a pattern of areas of modified optical properties on an optical record carrier

  • US 5,255,007 A
  • Filed: 11/13/1990
  • Issued: 10/19/1993
  • Est. Priority Date: 01/22/1990
  • Status: Expired due to Term
First Claim
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1. A method of recording an information signal on a record carrier having a recording layer possessing an optical property which changes in any local area thereof upon heating of said local area above a predetermined write temperature, the change in said optical property constituting a detectable write mark in said local area;

  • said method comprising the steps of;

    (a) producing a radiation beam having an adjustable power level and which is focussed into a scanning spot of radiation incident on a local area of the recording layer;

    (b) scanning the recording layer with said scanning spot so that said scanning spot is successively incident on successive local areas thereof, the scanning spot radiation being reflected or transmitted by a scanned local area as modified in accordance with said optical property of the recording layer in said local area;

    (c) controlling the radiation beam in accordance with said information signal so as to produce a write pulse of the scanning spot radiation during scanning of each of a plurality of local areas of the recording layer, each said write pulse being of a power level sufficient to heat at least a portion of a scanned local area above said write temperature so as to form a write mark therein, formation of said write mark occurring at a speed dependent on the power level of said write pulse, said write mark being of a size dependent on said speed of formation thereof;

    (d) detecting the modified radiation from each said scanned local area during formation of a write mark therein, and producing a detection signal indicative of changes in said radiation during formation of said write mark;

    (e) deriving from said detection signal a speed-forming signal indicative of the speed of formation of each of said write marks; and

    (f) adjusting the power level of the radiation beam during each said write pulse in accordance with said speed-forming signal, thereby maintaining the speed of formation and consequently the size of each said write mark substantially independent of variations in recording conditions which affect heating of a scanned local area by a write pulse.

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