Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1989-03-27
1992-03-31
Envall, Jr., Roy N.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
360 7702, G11B 7095, G11B 2000
Patent
active
051013908
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a track-jump device for a disc drive apparatus, such as an optical disc reproducing apparatus, for effecting a jump from one track to a neighboring track on the disc.
BACKGROUND OF ART
In a disc drive apparatus for recording and/or reproducing on or from a disc-shaped recording medium such as an optical disc or a magneto-optical disc, using the optical or magneto-optical recording and/or reproducing method, for example, it becomes necessary to perform a so-called track-jump in which the recording and/or reproducing head is to be moved rapidly along the radial direction, as when seaching a desired data, number or image, or when performing a specialized playback or reproducing operation, such as slow reproduction. This track-jump is classified into a medium to long distance jump over several or more tracks and a track-by-track-jump. Even in the medium to long distance jump, a track-by-track-jump ultimately becomes necessary to perform for positioning the head on the target track.
For effecting the track-jump, the conventional practice is to cancel the so-called tracking servo and to supply track-jump drive pulses, composed of acceleration and deceleration pulses, to for example, a head shifting device. Inasmuch as the servo is deenergized temporarily during such track-jump, safety problems are presented, while a deficiency may arise that it takes long time until the tracking servo starts its operation effectively directly after the head arrives at the target track.
In view of the above described problems of the prior art device, it is an object of the present invention to provide a track-jump device for a disc drive apparatus wherein a stable operation may be provided without deenergizing the tracking servo at least at the time of track-by-track-jump.
DISCLOSURE OF THE INVENTION
For achieving the above object, the present invention provides a track-jump device for a disc drive apparatus for effecting track-jump from a track to an adjacent track on a disc-shaped recording medium, comprising a circuit for generating a tracking error signal, an on-track signal dephased by 90.degree. from said tracking error signal and reaching a peak value when it is disposed on a track, a reverse-phase signal of said tracking error signal and a reverse-phase signal of said on-track signal, and switching means for switching the aforementioned four signals before outputting of said four signals, characterized in that said four signals are sequentially switched by said switching means and the thus switched signals are transmitted to a tracking control circuit to effect track-jump from one track to an adjacent track.
According to the present invention, having the above feature, the four signals dephased sequentially by 90.degree. along the widthwise direction of the track, or the radial direction of the disc, are switched sequentially at the time of track jump to effect a track-by-track-jump without deenergizing the tracking servo.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block circuit diagram showing an embodiment of the present invention;
FIG. 2 is a diagrammatic view for illustrating the track-jump operation;
FIG. 3 is a circuit diagram showing an example of the output circuit of on-track signals S.sub.OT ;
FIG. 4 is a chart showing tracking control characteristics; and
FIG. 5 is a diagrammatic view showing tracking control signals at the time of track-jump.
BEST EMBODIMENT OF PRACTICING THE INVENTION
An embodiment of a track-jump device for the disc drive apparatus according to the present invention will be explained hereinbelow by referring to the drawings. The disc drive apparatus in the present embodiment is assumed to be that disclosed in the specifications of the present Applicant's Japanese Patent Application Nos. 180925/1986, 190274/1986 and 232512/1986. FIG. 1 shows diagrammatically the tracking servo system of the present disc drive apparatus. The recording medium employed in the present disc drive apparatus is a magneto-optical disc or an optical disc having
REFERENCES:
patent: 4506149 (1985-03-01), Utsumi
patent: 4660191 (1987-04-01), Maeda et al.
patent: 4724494 (1988-04-01), Koide
patent: 4896309 (1990-01-01), Yamakawa et al.
Envall Jr. Roy N.
Nabil Hindi
Sony Corporation
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