Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2000-02-03
2004-06-22
Patel, Gautam R. (Department: 2655)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S044320, C369S053340, C369S053370, C318S696000
Reexamination Certificate
active
06754154
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk driving apparatus, an optical disk driving method and an optical disk apparatus. The present invention can be applied to the adjustment of a disk tilt in case of recording or reproducing information recorded on, for example, an optical disk (MO), a compact disk (CD), a compact disk recordable (CD-R) or a digital video disk (DVD) serving as a disk-shaped recording medium.
2. Description of the Related Art
In the present optical disk field, there exist optical disks of not only the conventional CD format but also various formats such as a compact disk recordable (CD-R) coated with a color film of organic color, a magnetic disk (MO), a phase change optical disk (DVD-RAM).
A recording and reproducing apparatus for such optical disks controls a radial tilt angle indicating the radial gradient of an optical disk with respect to a light spot applied from an optical pickup. As recording density increases, demand for accurately detecting the radial tilt (radial warp) of an optical disk, controlling the radial tilt of the optical disk and thereby ensuring reliability, rises.
To satisfy the demand, the development of an optical disk recording and reproducing apparatus having a tilt mechanism for automatically adjusting the tilt of an optical pickup to accurately read a reproduction signal installed therein is underway. If the radial tilt of an optical disk is to be detected in the optical disk recording and reproducing apparatus of this type, a tilt sensor utilizing, for example, a reflection type sensor is mounted on an optical pickup and the sensor detects a radial tilt based on the difference in the quantity of reflected light when the optical pickup is moved in the radial direction of the optical disk. Then, the tilt mechanism using a DC motor is employed to control the tilt of the optical disk so as to minimize an error signal caused by the tilt of the optical disk from the tilt sensor.
There is also developed an optical disk apparatus which does not include a tilt sensor, processes a readout signal of an optical pickup and controls the tilt of the optical disk.
Japanese Patent Unexamined Application Publication No. 8-255360 discloses an optical disk apparatus for detecting a reflected light from an optical disk by means of two photo-detector elements to generate a difference signal, sensing an envelope of the detection signal to thereby detect differential components and conducting tracking control based on the differences to thereby remove DC offset.
Japanese Patent Unexamined Application Publication No. 9-212891 discloses an optical head apparatus which divides a laser light into a main light flux and a sub-light flux, individually generates push-pull signals from these light fluxes and generates a tilt signal corresponding to a disk tilt from these push-pull signals. Further, Japanese Patent Unexamined Application Publication No. 9-245357 discloses a servo control apparatus for an optical disk recording and reproducing apparatus, which apparatus converts a push-pull signal and a phase difference detection signal into a de-tracking signal and a radial tilt signal and controls a tracking servo and a thread servo.
FIG. 12
shows a conventional disk drive mechanism having a tilt mechanism using a tilt sensor.
In
FIG. 12
, the disk drive mechanism comprises a spindle chassis
202
made of a plate frame having an opening portion of generally rectangular shape provided therein, a pickup chassis
203
made of a plate frame which is slightly smaller than the spindle chassis
202
and which has an opening portion provided therein, and a tilt operation mechanism
204
rocking the pickup chassis
203
relative to the spindle chassis
202
based on the rotating force of a motor. The pickup chassis
203
is provided with a pair of shaft portions
203
a
protruding to both sides of the chassis
203
in width direction. The spindle chassis
202
is provided with a pair of bearing portions
202
a
rotatably supporting the shaft portions
203
a
. The combination of the paired bearings
202
a
and the paired shafts
203
a
supports the pickup chassis
203
to be rockable to the spindle chassis
202
in longitudinal direction.
The tilt operation mechanism
204
is provided on one longitudinal side of the spindle chassis
202
. When the tilt operation mechanism
204
operates, the pickup chassis
203
rocks in the longitudinal direction of the spindle chassis
202
. A spindle motor
205
is fixed to the other longitudinal side of the spindle chassis
202
in a state in which the rotary shaft of the motor
205
is directed upward. A turn table
206
onto which an optical disk is installed is attached integrally with the rotary shaft of the spindle motor
205
.
Further, a guide shaft
203
b
and a guide portion which is not shown in
FIG. 12
are attached parallel to the pickup chassis
203
at a predetermined distance between the guide shaft
203
b
and the guide portion to extend longitudinally. The slide member
208
of an optical pickup unit
207
is slidably supported by the guide shaft
203
b
and the guide portion. A rack which is not shown in
FIG. 12
is fixed to the slide member
208
. A gear positioned at the distal end portion of a head feed mechanism
209
is engaged with the rack. By driving the head feed mechanism
209
and transmitting the rotating force of the mechanism
209
to the slide member
208
, the optical pickup unit
207
is moved to approach and separate from the turn table
206
.
A tilt sensor
210
which detects a distance to the information recording surface of the optical disk installed onto the turn table
206
, is mounted on the slide member
208
. The tilt sensor
210
emits a light toward the information recording surface and detects the warp of the optical disk reflected by the information recording surface. Based on the detection result of the tilt sensor
210
, the tilt operation mechanism
204
controls the optical disk so as to minimize an error signal caused by the warp of the optical disk. By doing so, the tilt of the pickup chassis
203
is modified and the tilt of the optical axis of the optical head
207
a
of the optical pickup unit
207
with respect to the tilt of the information recording surface of the optical disk can be adjusted. If the tilt sensor
210
is used, the mechanism
204
controls the optical disk so as to minimize an error signal from the tilt sensor
210
which signal is caused by the tilt of the optical disk. Thus, there is no need to know a tilt operation neutral point (mechanical center which will be referred to as “mecha-center” hereinafter).
In the above-stated conventional optical disk recording and reproducing apparatus utilizing the tilt sensor, the tilt sensor and a DC motor for tilt operation are mounted on the optical pickup. Due to this, the conventional optical disk recording and reproducing apparatus has disadvantages in that production cost is pushed up and the optical pickup becomes larger in size.
Moreover, in an optical disk apparatus which does not include a tilt sensor and conducts tilt control by processing the readout signal of an optical pickup, when an optical disk for initiating the rotation of a spindle motor, is started, a reproduction signal cannot be read yet. Due to this, the quantity of the warp of the optical disk is not known and the optical disk is, therefore, required to be positioned at the tilt operation neutral point as the mecha-center in advance. If so, a sensor capable of obtaining the tilt operation neutral point is required. Besides, since a tilt operation angle is about ± one degree, the apparatus is disadvantageously required to have higher sensor attachment accuracy.
In addition, in the conventional disk drive mechanism having the tilt mechanism utilizing the tilt sensor shown in
FIG. 12
, the DC motor is used as a driving source of the tilt operation mechanism. The DC motor may be replaced by a stepping motor capable of conducting positioning control easily. The stepping motor is
Oishi Seiichiro
Shiomi Tetsuhiro
Takeda Ryuji
Frommer William S.
Frommer & Lawrence & Haug LLP
Patel Gautam R.
Smid Dennis M.
Sony Corporation
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