Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2001-03-02
2004-02-03
Patel, Gautam R. (Department: 2655)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044350, C369S044290
Reexamination Certificate
active
06687202
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pickup control device for an optical disk drive, and, more particularly, the invention relates to a control system and the saving of electricity in writing or reading information on or from a rotating optical disk with the pickup of the optical disk drive comprising a focus servo system for controlling the operation of focusing a laser beam on the optical disk (hereinafter abbreviated as “focusing operation”) and a tracking servo system for controlling the operation of tracing an information storing track (hereinafter abbreviated as “track”) of the optical disk (hereinafter the tracing operation is abbreviated as “tracking operation”).
BACKGROUND ART
In recent years, under the circumstance that the rotational velocity of an optical disk increases in operating an optical disk drive, the increase of the data processing speed in the operation of the pickup of the optical disk drive is also required. However, when the data processing speed is increased, the consumption of electricity increases in the focus servo system and the tracking servo system for the control of the operation of the pickup, and, when these servo systems comprises digital processing circuits, the frequency of a clock pulse for operating the digital processing circuits increases, which also causes the increase of the consumption of electricity.
Hereinafter a conventional pickup control device for an optical disk drive is described on reference to
FIG. 3
which is a block diagram showing the structure of the conventional pickup control device. In
FIG. 3
, a spindle motor
102
rotates an optical disk
100
. A pickup
101
writes information on the optical disk
100
or reads information from the optical disk
100
. An error signal detector
103
detects a focus error signal from the output signal of the pickup
101
. A signal amplifier
104
amplifies the focus error signal. A driving circuit
106
receives the amplified signal through a compensating arithmetic unit
105
, and operates the pickup
101
based on the received signal. The above structure forms a focus servo system.
On the other hand, a position detector
107
detects a track position (of a disk
100
) where the pickup
101
is located. A gain selector
108
adjusts the loop gain for the focus servo system by controlling the signal amplifier
104
based on the signal on the track position where the pickup
101
is located, which (i.e., the signal) is generated by the position detector
107
.
In general, the superficial fluctuation of the optical disk
100
is smaller at the inner tracks of the optical disk
100
comparing with the superficial fluctuation at the outer tracks of the optical disk
100
. Therefore, when the pickup
101
is located at one of the inner tracks of the optical disk
100
, the loop gain for the focus servo system is adjusted to a smaller value comparing with the loop gain in the occasion that the pickup
101
is located at one of the outer tracks of the optical disk
100
.
The position detector
107
, for detecting the track position where the pickup
101
is located, is formed, for instance, in such a manner that a reflecting portion is formed on the pickup
101
, and a light emitted from a light emitter (not illustrated) is reflected by the reflecting portion of the pickup
101
, and the reflected light is received by a light sensor (not illustrated), or, the position detector
107
is formed, for instance, in such a manner that track numbers are stored in advance on the optical disk
100
(i.e., formatted), and the stored track numbers are read by the pickup
101
in the occasion of the operation of writing or reading.
Based on the track position where the pickup
101
is located, which is detected by either of the above methods, the gain selector
108
controls the signal amplifier
104
in such a manner as to optimize the loop gain for the focus servo system.
The operation of a tracking servo system is performed in a manner similar to the above description on the focus servo system.
However, in the conventional pickup control device described in the above, a light emitter, light sensor and the like, which are exclusively used for detecting the track position where the pickup is located, are needed, which causes the increase of the consumption of electricity and the cost of the optical disk drive having the above conventional pickup control device. Also, in the conventional pickup control device having the structure of detecting the track position where the pickup is located by reading stored track numbers, the effective saving of electricity is not realized because it takes time before the tracking servo system becomes stable for reading the stored track numbers rightly after switching on the optical disk drive, such that the saving of electricity in this method is also insufficient.
DISCLOSURE OF INVENTION
The object of the present invention is to address the conventional problems and to provide a pickup control device for an optical disk drive, which enables the saving of electricity and cost in the optical disk drive.
For realizing the above object, the pickup control device of the present invention has the following structure. That is, in an optical disk drive which performs the operation of writing or reading information on or from an optical disk with the pickup of the optical disk drive comprising a focus servo system for controlling the focusing operation of the pickup and a tracking servo system for controlling the tracking operation of the pickup, a pickup control device for the optical disk drive in the present invention comprises,
(a) a first control system which comprises an angular velocity detector for detecting the angular velocity of the optical disk, and controls the optical disk based on the angular velocity detected by the angular velocity detector in such a manner that the optical disk enters into the state of rotation at a predetermined constant angular velocity, and
(b) a second control system which comprises a linear velocity detector for detecting the linear velocity of the optical disk at the track position of the optical disk where the pickup is located, and controls the linear velocity in such a manner that the linear velocity enters into the state of a predetermined constant linear velocity,
wherein the first control system and the second control system are alternatively operated in such a manner that the loop gains for at least one of the focus servo system and the tracking servo system are adjusted based on the linear velocity detected by the linear velocity detector of the second control system when the optical disk is rotated under the control of the first control system, and, the loop gains for at least one of the focus servo system and the tracking servo system are adjusted based on the angular velocity detected by the angular velocity detector of the first control system when the optical disk is rotated under the control of the second control system.
In the above structure of the pickup control device in the present invention, the operation of the pickup of the optical disk drive is optimally performed by utilizing the signal on the track position where the pickup is located, which (i.e., the signal) is generated by the angular velocity detector and the linear velocity detector which (i.e., both detectors) are also used for controlling the rotational velocity of the optical disk, without installing an additional unit comprising various component parts for detecting the track position where the pickup is located.
Also, for realizing the above object, the pickup control device of the present invention has the following structure. That is, in an optical disk drive which performs the operation of writing or reading information on or from an optical disk with the pickup of the optical disk drive comprising a focus servo system for controlling the focusing operation of the pickup and a tracking servo system for controlling the tracking operation of the pickup, a pickup control device for the optical disk drive in the present invention com
Imamura Yasushi
Kobayashi Yuichi
Okita Masaaki
Watanabe Takahiro
Matsushita Electric - Industrial Co., Ltd.
Patel Gautam R.
RatnerPrestia
LandOfFree
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