Focusing servo controlling apparatus
AssigneeSony Corporation
InventorsSumihiro Okawa, Takayasu Muto, Shuji Uehara
Life of this patent
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Abstract
A magneto-optical disc recording or reproducing device focusing control servo system which uses a digital signal processor (DSP) to control a pulse width modulation (PWM) circuit so that if the focusing servo is to be in operation alone, such as during a focusing search or seek, fixed clocks of a fixed frequency are used for processing focusing servo signals and after engagement of the focusing servo, focusing servo is effected responsive to focusing servo signals which are formed based upon a reproduced servo pattern of the magneto-optical disc.
Claims16
An apparatus for reproducing signals recorded on an optical disc having a plurality of equal angular servo areas each having servo patterns for providing control of tracking, focusing and clocks, the apparatus comprising:
- drive means for rotating the optical disc and including an optical pickup for tracing a track formed on the optical disc, the drive means reproducing signals from the rotating optical disc;
- servo clock generating means for deriving servo clocks from the reproduced signals output by the drive means;
- servo control means for controlling the focusing and tracking of the optical pickup based upon the servo clocks supplied therewith so as to establish a focusing servo and a tracking servo;
- fixed clock generating means for producing fixed clocks so that the servo control means performs a focusing search based upon the fixed clocks;
- switching means for selectively supplying either the servo clocks or the fixed clocks to the servo control means;
- and
- switching control means for controlling the switching means so that the fixed clocks, as a substitute for the servo clocks, are supplied to the servo control means in the focusing search, and for controlling the switching means so that the servo clocks are supplied to the servo control means after engagement of the focusing servo.
In a recording/reproducing apparatus for recording/reproducing an optical disc, a focusing servo operation controlling device of a phase-locked loop configuration in which a focusing servo operation is effected based upon focusing servo clocks formed by a playback output of pre-set servo patterns from the optical disc on which the servo patterns are arrayed at pre-set intervals, comprising:
- fixed clock outputting means for outputting fixed clocks for a focusing servo operation of a fixed frequency;
- switching means for switching between outputting the focusing servo clocks or the fixed clocks;
- and
- control means for effecting switching control of the switching means for selecting and outputting the fixed clocks when effecting the focusing servo operation alone and selecting and outputting the focusing servo clocks directly after engagement of the focusing servo operation.
Dependencies are inferred from the claim text.