Optical information processor and method for accessing rotating record carrier utilizing acousto-optic light deflector including holding a focus error signal during track jumping
AssigneeHitachi, Ltd.
InventorsKeiji Kataoka, Takeshi Maeda, Yoshito Tsunoda
Life of this patent
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Abstract
Accessing method and an apparatus therefor in an optical disc apparatus having an acousto-optic light deflector for deflecting a light spot to a different address or different track on an optical disc are disclosed. An auto-focus signal is held at a constant level for a predetermined period when the acousto-optic light deflector deflects the light spot. Thus, an affect caused by coexistence of a plurality of acoustic frequencies in the acoustic-optic device is eliminated and fast light accessing is attained.
Claims20
An accessing method in an auto-focus control system for irradiating a light spot onto a recording surface of a rotating record carrier having tracks formed thereon, photo-electrically converting a light beam reflected from the record carrier, producing a focus error signal indicating a deviation of a focus point of the light spot from the recording surface of the record carrier based on the photo-electrically converted output and controlling the focus point of the light spot by the focus error signal so that the focus point of the light spot coincides with the recording surface, comprising the steps of:
- deflecting the light spot by an acousto-optic light deflector;
- and
- holding, during movement of the light spot by said acousto-optic light deflector from said one track to another, the focus error signal in the state prior to said movement.
An optical information processor comprising;
- optical means for directing a light spot to a recording surface of a rotating record carrier having tracks formed thereon;
- focus control means for producing a focus error signal indicating a deviation of a focus point of the light spot from the recording surface based on a light beam reflected by said recording surface and controlling the focus point of the light spot in accordance with the focus error signal so that the focus point of the light spot coincides with the recording surface;
- an acousto-optic light deflector arranged in an optical path of said optical means for deflecting the light spot;
- first means for supplying signals of different frequencies to said acousto-optic light deflector to deflect the light spot from one track to another track;
- and
- second means arranged in said focus control means for holding said focus error signal for said one track for a period of movement of the light spot from said one track to said other track by said light deflector.
An optical information processor comprising;
- light irradiation means having an acousto-optic light deflector for irradiating a light spot to a recording surface of an optical disc and deflecting the optical spot;
- focus control means for producing a focus error signal indicating a deviation of a focus point of the light spot from the recording surface in accordance with a light flux reflected from the recording surface and controlling the focus point of the light spot by said focus error signal so that the focus point of the light spot coincides with the recording surface;
- first means for supplying to said acousto-optic light deflector a signal having a frequency representing a magnitude of an input signal;
- second means for producing a pulse of a predetermined width in synchronism with a change of the magnitude of the input signal to said first means;
- and
- third means arranged in said focus control means for receiving said focus error signal and said pulse and holding said focus error signal at a constant level for a period of said pulse.
Dependencies are inferred from the claim text.