Focus servo circuit apparatus with automatic bias adjustments
First Claim
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1. A focus servo circuit comprising:
- a focus error signal generator for generating a focus error signal;
a time difference measuring circuit for measuring a time difference between an edge of a clock synchronized with a digital signal reproduced from a disk and a transition point of the digital signal;
a bias voltage generator for generating a focus bias voltage determined by the time difference; and
a processing means for adding the focus bias voltage to the focus error signal to produce an added output signal, whereinfocus servo is carried out in accordance with the added output signal.
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Abstract
In a recording and reproducing apparatus of CD or the like, it is adapted such that the time difference between an edge of a PLL clock synchronized with an EFM signal and a transition point of the EFM signal is measured in a time difference measuring circuit, a focus bias voltage to bring the time difference to a minimum is established in a bias voltage generator, the established focus bias voltage is added in an adder to a focus error signal generated in a focus error signal generator, and, thereby, the focus bias is automatically adjusted and focus servo is executed in accordance with the bias-adjusted focus error signal.
59 Citations
8 Claims
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1. A focus servo circuit comprising:
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a focus error signal generator for generating a focus error signal; a time difference measuring circuit for measuring a time difference between an edge of a clock synchronized with a digital signal reproduced from a disk and a transition point of the digital signal; a bias voltage generator for generating a focus bias voltage determined by the time difference; and a processing means for adding the focus bias voltage to the focus error signal to produce an added output signal, wherein focus servo is carried out in accordance with the added output signal. - View Dependent Claims (2, 3, 4)
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5. A disk player apparatus comprising:
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a pick up means for receiving a signal from a disk; a signal generating means for generating a focus error signal, a time measuring means for measuring a time difference between an edge of a clock synchronized with a digital signal reproduced from the disk and a transition point of the digital signal, control signal means for generating a focus bias signal corresponding to the time difference, a processing means for processing the focus error signal and the focus bias signal to produce an output signal; and a phase control means for compensating the output signal from said processing means and controlling the pickup means in response to the output signal. - View Dependent Claims (6, 7, 8)
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Specification