Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1998-11-10
2001-08-28
Huber, Paul W. (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044320, C369S053280, C369S124150
Reexamination Certificate
active
06282157
ABSTRACT:
BACKGROUND OF THE INVENTION
In a compact disk player (CDP) or a digital video disk player (DVDP), an optical pick-up applies laser energy to a predetermined position on a spiral-shaped disk track, and retrieves the reflected light. A tracking servo directs the light beam to trace the spiral track in all cases, even where the central shaft of the spindle motor driving the disk is eccentric. A focusing servo spaces a pick-up lens from the disk surface at a constant distance, to allow for stability in reading the optical signal.
In a conventional tracking servo, if a mirror warning signal is detected, this is an indication that the disk is out of track. However, when the disk is severely eccentric or deviated, or has many fine scratches, the mirror warning signal is generated too frequently and renders the tracking system unstable, which may cause track jumping.
When a track is selected, for example by a user, a predetermined voltage is applied to a sled motor, which drives a sled, having an optical pickup mounted thereto. The optical pickup is moved to a track position selected by the sled motor, and is focused at the selected track position by the optical pickup lens attached to the sled motor. When a data reproduction command is applied to the sled motor, the lens of the optical pickup may be swayed by a high initial voltage level, or focus drop may occur due to disk defects. Focus loop muting may be applied to prevent the focus drop due to the defect. However, when disk reflectivity is low or if the pickup RF level is reduced, the focus drop cannot be prevented.
SUMMARY OF THE INVENTION
The present invention relates to an optical disk system such as a compact disk player or a digital video disk player, and more particularly, to a tracking and focusing servo control apparatus for muting a tracking servo loop according to a defined mirror signal or for muting a focusing servo loop according to a detected RF level.
To solve the above problem, it is an objective of the present invention to provide an apparatus for controlling a tracking servo, which mutes a tracking servo loop by defining a mirror signal generated when the system is out of track for a predetermined time interval.
It is another objective of the present invention to provide an apparatus for controlling a focusing servo, which prevents focus drop by muting a focusing servo loop according to the level of a detected RF signal.
It is still another objective of the present invention to provide an optical disc drive in an optical disk system for detecting a stable RF signal, including a control apparatus for muting the tracking servo loop and the focusing servo loop.
Accordingly, to achieve the first objective, there is provided a tracking servo control apparatus in an optical disk system for compensating for tracking gain and phase according to a tracking error signal, and for muting the tracking error signal when a mirror signal is generated. The apparatus comprises: a mirror setting unit for receiving the generated mirror signal and generating a modified mirror signal having minimum and maximum time intervals; a selector for outputting a muted tracking error signal while the defined mirror signal is activated, otherwise, outputting the tracking error signal; and a tracking gain/phase compensator for receiving the output signal from the switch and compensating for the tracking gain and phase.
To achieve the second objective, there is provided a focusing servo control apparatus in an optical disk system for compensating for focusing gain and phase according to a focusing error signal. The apparatus comprises: an optical detector for converting an optical signal into an electrical signal; a convertor and amplifier for converting the electrical signal into a voltage signal and amplifying the voltage signal; a radio frequency (RF) level detector for detecting the level difference between the amplified voltage signal and a voltage signal formed by removing an alternating component from the amplified voltage signal; a switch for outputting a signal formed by muting the focusing error signal, when the detected level difference is smaller than a predetermined level or a defect signal is input, otherwise, outputting the focusing error signal; and a focusing gain/phase compensator for receiving the output signal of the switch and compensating for focusing gain and phase.
To achieve the third objective, there is provided an optical disk drive comprising: a pickup for projecting light onto the recording surface of an optical disk, converting a reflected light into a voltage signal, and generating an optical signal; a spindle motor for rotating a turn-table on which the optical disk is loaded; a sled servo unit for moving the pickup in the inner or outer circumference direction of the optical disk; and a servo signal processor for processing an optical signal from the pickup and generating a tracking control signal, a focusing control signal, and an RF signal while generating a sled control signal for controlling the position of the pickup, wherein the servo signal processor comprises: a tracking servo unit for receiving a generated mirror signal, generating a new mirror signal by defining the original mirror signal to predetermined minimum and maximum time intervals, and compensating for tracking gain and phase according to a muted tracking error signal, while the defined mirror signal is turned on or when a defect signal is generated, otherwise, according to the tracking error signal; and a focusing servo unit for detecting the level difference between a voltage signal converted according to a detected optical signal and a new voltage signal obtained by removing an alternating component from the voltage signal, and compensating for focusing gain and phase according to a muted focus error signal when the detected level difference is smaller than a predetermined level or a defect signal is input, otherwise, according to a focus error signal.
REFERENCES:
patent: 4796247 (1989-01-01), Vogelsang
patent: 5696757 (1997-12-01), Ozaki et al.
patent: 6014354 (2000-01-01), Nomura et al.
Jang Young-wook
Kim Je-kook
Lee Suk-jung
Shin Jeong-Cheol
Huber Paul W.
Mills & Onello LLP
Samsung Electronics Co,. Ltd
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