Optical Disc Corporation

Shigang Li

Richard L Wilkinson

John H Rilum

John F Browne

William W Boyle

Stephen P Brown

Method and apparatus for improving the characteristics of the surface effects on a replicated optical disc the master for which is recorded on an optical recording apparatus which includes a writing light beam source and an optical modulator for modulating the intensity of the writing beam of light above and below a threshold level of a relatively moving recording medium in response to a modulator drive signal for recording information on the medium, the light beam being capable of forming a track of surface effects or indicia in the relatively moving master recording medium when the writing beam is above threshold and incapable of forming surface effects in the relatively moving recording medium when the writing beam is below threshold. The method includes receiving a substantially rectangular waveform intended to control the optical modulator. In one aspect of the invention, a radius dependent duty cycle ramp function is introduced into the optical modulator drive signal for altering the depth or height of recorded pits or bumps on the recording medium to compensate for the depth or height versus radius phenomenon experienced in the molding process. In another aspect, a pit or bump type dependent correction function is introduced into the optical modulator drive signal, whereby individual pit or bump physical characteristics are altered in accordance with pit or bump type to compensate for the depth or height versus pit or bump type phenomenon experienced in the molding process.

Method and means for varying pit duty cycle and changing pit depth on an

Method and apparatus for improving the characteristics of the surface effects recorded on an optical disc, for use with an optical recording apparatus which includes a writing light beam source and an optical modulator for modulating the intensity of the writing beam of light above and below a threshold level of a moving recording medium in response to a modulator drive signal for recording information on the medium, the light beam being capable of forming a track of surface effects or indicia in the moving recording medium when the writing beam is above threshold and incapable of forming surface effects in the moving recording medium when the writing beam is below threshold. The method includes receiving a substantially rectangular waveform having leading and trailing edges, provided as a modulator drive signal to modulate the writing beam to a peak power above threshold and to a minimum power level below thresholds, respectively, and producing a shaped modulator drive signal by increasing the peak power of the writing beam responsive to the occurrence of the leading edges, by decreasing the time the shaped modulator drive signal is above threshold in order to maintain a prescribed duty cycle in the track of surface effects in the moving recording medium, and by producing symmetrical leading and trailing edges of the surface effects.

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Norwalk, CA, United States of America

Shigang Li