Waveform shaping method and apparatus for optical recording

A waveform shaping circuit for use in 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 surface discontinuities in the moving recording medium when the writing beam is above the threshold and incapable of forming surface discontinuities in the moving recording medium when the writing beam is below the threshold, said waveform shaping circuit comprising:

• waveform processing means for receiving a substantially rectangular waveform, having leading and trailing edges, provided as said modulator drive signal to modulate the writing beam, and for producing a shaped modulator drive signal having steep leading edges reaching a first level sufficient to cause said writing beam to have an intensity above the threshold of the moving medium, and having ramped trailing edges changing amplitude at a prescribed rate to reach a second level sufficient to cause said writing beam to have an intensity below the threshold of the moving medium prior in time to the occurrence of the respective next leading edges of the received rectangular waveform.

A waveform shaping circuit for use in 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 in the moving recording medium when the writing beam is above threshold and incapable of forming said track of surface effects in the moving recording medium when the writing beam is below threshold, said waveform shaping circuit comprising:

• means for receiving a substantially rectangular waveform having leading and trailing edges, provided as said modulator drive signal to modulate the writing beam to a peak power above threshold and to a minimum power level below threshold, respectively;
• and
• waveform shaping means coupled to said receiving means for producing a shaped modulator drive signal which increases the peak power of the writing beam responsive to the occurrence of said leading edges, decreases the time said shaped modulator drive signal is above the threshold to maintain a prescribed duty cycle in the track of surface effects in the moving recording medium, and produces a symmetrical geometry at the leading and trailing edges of said track of said surface effects.

A method for improving the characteristics in the indicia 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 in the moving recording medium when the writing beam is above the threshold and incapable of forming said track of surface effects in the moving recording medium when the writing beam is below the threshold, said method comprising the steps of:

• receiving a substantially rectangular waveform having leading and trailing edges, provided as said modulator drive signal to modulate the writing beam;
• and
• producing a shaped modulator drive signal having steep leading edges reaching a first level sufficient to cause said writing beam to have an intensity above the threshold of the moving medium, and having ramped trailing edges changing amplitude at a prescribed rate to reach a second level sufficient to cause said writing beam to have an intensity below the threshold of the moving medium prior in time to the occurrence of the respective next leading edges of the received rectangular waveform.

A method for improving the characteristics in the indicia 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 in the moving recording medium when the writing beam is above threshold and incapable of forming said track of surface effects in the moving recording medium when the writing beam is below threshold, said method comprising the steps of:

• receiving a substantially rectangular waveform having leading and trailing edges, provided as said modulator drive signal to modulate the writing beam to a peak power above threshold and to a minimum power level below threshold, respectively;
• and
• producing a shaped modulator drive signal by increasing the peak power of the writing beam responsive to the occurrence of said leading edges, decreasing the time said shaped modulator drive signal is above threshold to maintain a prescribed duty cycle in the track of surface effects in the moving recording medium, and producing a symmetrical geometry at the leading and trailing edges of said track of said surface effects.