Method and apparatus for recording a pattern of areas of modified optical properties on an optical record carrier
First Claim
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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Accused Products
Abstract
A method and apparatus for recording an information signal on the recording layer of an optical record carrier by writing areas of modified optical properties in such layer. The layer is heated locally to a temperature above the write temperature by scanning with a laser beam whose power (P) is pulsed between a low level (Pl) and a write level (Ps) in accordance with the information signal. A signal (α(t)) which is indicative of the speed with which the write areas are formed, and therefore of the dimensions of such areas, is derived by a measurement circuit (50) from the radiation reflected from the recording layer. The measurement circuit is part of an adjustment circuit (12) which also includes a control circuit (60) which derives an adjustment signal (Ih) for a laser drive circuit (13) to control the write power (Ps) of the laser beam in accordance with the area forming-speed signal (α). This substantially reduces the effect of changing recording conditions on the dimensions of the write areas having modified optical properties, permitting substantially optimum dimensions of such areas to be maintained during recording.
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Citations
11 Claims
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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. - View Dependent Claims (2, 3, 4, 5, 6)
- said method comprising the steps of;
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7. Apparatus for 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 apparatus comprising;
means for producing an 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; means for scanning the recording layer with said scanning spot so that said scanning spot is successively incident on successive local areas thereof, the incident 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; control means for 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; means for 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; measurement circuit means coupled to said detecting means to receive said detection signal and derive therefrom a speed-forming signal indicative of the speed of formation of each of said write marks; and adjusting circuit means for adjusting the power level of the radiation beam during each said write pulse in accordance with said speed-forming signal so as to maintain the speed of formation and consequently the size of each write mark substantially independent of variations in recording conditions which affect heating of a scanned local area by a write pulse. - View Dependent Claims (8, 9, 10, 11)
- said apparatus comprising;
Specification