Focus servo circuit apparatus with automatic bias adjustments
AssigneeSony Corporation
InventorsKazutoshi Shimizume, Mamoru Akita, Shigeru Inohana, Hidenobu Noda
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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.
Claims8
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, wherein
- focus servo is carried out in accordance with the added output signal.
A disk player apparatus comprising:
- 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.
Dependencies are inferred from the claim text.