Storing digital data on a recording disk with the data time base proportional to disk angular velocity

Claim 2

Apparatus for inscribing a modulated path including generally circular and concentric segments on a disk comprising, a turntable for supporting said disk; means for rotating said turntable at a selected rotational velocity; a digital angular encoder mounted to sense the rotation of said turntable and producing a series of output pulses, the spacing of said pulses being precisely related to the rotational velocity of said turntable; an inscribing head for inscribing a path on said record; first control means responsive to control signals for controlling the radial position of said inscribing head; second control means for modulating the position of said inscribing head in response to applied analog signals at a generally periodic rate; a generator for analog signals providing, in response to applied clocking pulses a superposed series of analog waveforms to said second control means; a controlled frequency oscillator providing on an output terminal a series of pulses at a frequency which varies in accordance with a signal supplied at a control input; a phase comparator having first and second inputs and providing an output signal which varies in value in proportion to differences in phase of signals applied to said first and second inputs; means coupling the output of said oscillator to one input of said phase comparator and means coupling the output of said digital angular encoder to the other of said inputs of said phase comparator; the output signal from said phase comparator being coupled to the control input of said oscillator; and means coupling the output pulses from said oscillator to said generator for analog signals as a supply of clocking pulses.

Claim 3

Apparatus for inscribing a modulated spiral groove on a disk comprising, a turntable for supporting said disk; means for rotating said turntable at a selected rotational velocity; a digital angular encoder mounted to sense the rotation of said turntable and producing a series of output pulses, the spacing between said pulses being precisely related to the rotational velocity of said turntable; an inscribing head for inscribing a groove on said disk; first control means responsive to electrical control signals for controlling the radial position of said inscribing head as said turntable rotates to inscribe a spiral groove at a selected pitch; second control means for modulating the position of said inscribing head in response to variations in applied analog signals varying at a generally periodic rate; a generator for analog signals providing, in response to applied clocking pulses, a superposed series of analog waveforms to said second control means; the period of said waveforms being controlled by said clocking pulses, a controlled frequency oscillator providing on an output terminal a series of pulses at a frequency which varies in accordance with the signal supplied at a control input; a phase comparator having first and second inputs and providing an output signal which varies in value in proportion to differences in phase signals applied to said first and second inputs; means coupling the output of said oscillator to one input of said phase comparator and means coupling the output of said digital angular encoder to the other of said inputs of said phase comparator; the output of said phase comparator being coupled to the control input of said oscillator; and means coupling the output pulses from said oscillator to said generator of analog signals as a supply of clocking pulses.

Claim 4

Apparatus for inscribing a modulated spiral groove on a disk comprising, a turntable for supporting said disk; means for rotating said turntable at a selected rotational velocity; a digital angular encoder mounted to sense the rotation of said turntable and producing a series of output pulses, the spacing between said pulses being precisely related to the rotational velocity of said turntable; an inscribing head for inscribing a groove on said disk; first control means responsive to electrical control signals for controlling the radial position of said inscribing head as said turntable rotates to inscribe a spiral groove at a selected pitch; second control means for modulating the position of said inscribing head in response to variations in applied analog signals varying at a generally periodic rate; a generator for analog signals providing, in response to applied clocking pulses, a superposed series of analog waveforms to said second control means; the period of said waveforms being controlled by said clocking pulses, a controlled frequency oscillator providing on an output terminal a series of pulses at a frequency which varies in accordance with the signal supplied at a control input; a phase comparator having first and second inputs and providing an output signal which varies in value in proportion to differences in phase signals applied to said first and second inputs; means coupling the output of said oscillator to one input of said phase comparator and means coupling the output of said digital angular encoder to the other of said inputs of said phase comparator; the output of said phase comparator being coupled to the control input of said oscillator; and means coupling the output pulses from said oscillator to said generator of analog signals as a supply of clocking pulses.

Claim 5

Apparatus in accordance with claim 2 wherein said digital angular encoder is an optical encoder having a first disk fixed to the shaft of said turntable and a second disk fixed to a point of mechanical reference.

Claim 6

Apparatus in accordance with claim 2 wherein said controlled frequency oscillator is a voltage controlled oscillator.

Claim 7

Apparatus in accordance with claim 2 wherein said oscillator has a nominal center frequency at a frequency substantially higher than output frequency of pulses from said digital angular encoder at the selected rotational velocity of said turntable and wherein said means coupling the output from said oscillator to the input of said phase comparator includes a first divider means for dividing the frequency of the output signals from said oscillator by a factor such that the signals from said divider to the input of said phase comparator are substantially equal to the frequency of the pulses from said digital angular encoder at said selected turntable velocity.

Claim 8

Apparatus in accordance with claim 5 and further including a second divider means coupling the output from said oscillator and to said first control means to control the pitch of said spiral by the frequency of pulses received from said divider.

Claim 9

Apparatus in accordance with claim 6 wherein said first control means includes a stepper motor providing rotation of an output shaft at a velocity which varies with variations in the frequency of pulses supplied to said stepper motor.