| 摘要 |
A method for inscribing a modulated spiral groove on a memory disk in which a turntable is rotated at a nominally constant rotational velocity and a digital angular encoder is fixed to the shaft of the turntable providing a stream of output pulses which varies proportionally to variations in the angular velocity. This stream of output pulses is compared in a phase comparator with a stream of pulses derived from a voltage controlled oscillator and the output from the phase comparator is applied as the control input to the voltage controlled oscillator, thereby forming a phase locked loop. The output from the voltage controlled oscillator is divided down by appropriate amounts to provide timing digital signals to control the period of the modulation waveforms applied to a cutting head, which is inscribing a spiral groove on the memory disk. The output from the voltage controlled oscillator may also be used to control the radial position of the cutting head, thereby controlling the pitch of the spiral.
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