Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2003-03-05
2004-04-13
Edun, Muhammad (Department: 2655)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044280, C369S047100, C369S053230
Reexamination Certificate
active
06721243
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application Nos. 98-35421, filed Aug. 29, 1998, 98-35422, filed Aug. 29, 1998, and 99-8482, filed Mar. 13, 1999, in the Korean Patent Office, the disclosures of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical recording/reproducing apparatus for recording digital data on a disk and reproducing digital data from a disk, and more particularly, to a method for detecting servo error by comparing the levels of synchronous signals recorded on the header area of a disk, an apparatus suitable for the method, a disk which guarantees the quality of a push-pull signal which is the basis of optimally controlling the servo, a method for controlling the servo of the recording/reproducing apparatus, a method for detecting a tracking error, and a method for detecting a tilt error.
2. Description of the Related Art
The quality of a signal remarkably deteriorates due to a servo error such as the tilt and detrack of a disk as recording density becomes higher not only in a disk only for reproduction such as a DVD-ROM but also in a recordable disk such as a DVD-RAM. In particular, in the recordable disk, the recording quality deteriorates due to the influence of the servo error when the servo error exists during recording and the deterioration of the quality of the signal becomes severe due to the servo error during the reproduction of a concerned part.
In a DVD-RAM disk, information is recorded on a track. The track is comprised of a land track and a groove track. The land track and the groove track alternate when the disk rotates once. The land track and the groove track are alternated in the DVD-RAM disk in order to provide a tracking guide in an initial stage and to reduce crosstalk between adjacent tracks in high density narrow tracks.
Each track is comprised of sectors having a uniform length. A pre-embossed header area is provided during the manufacturing of the disk as a means of physically dividing the sectors. The physical addresses of the sectors are recorded in the pre-embossed header area.
Each sector is comprised of a header area in which physical identification data (PID) is recorded and a data area.
FIG. 1A
shows the physical shape of the land track in a DVD-RAM disk.
FIG. 1B
shows the waveform of a push-pull signal in the land track.
The header area is repeatedly arranged in every sector of the track. Four PIDs (PID
1
through PID
4
) having the same value are recorded in one header area. The PID
1
and the PID
2
are arranged to deviate from the center of the track by a certain amount and the PID
3
and the PID
4
are arranged to deviate from the center of the track in a direction opposite to that of the PID
1
and PID
2
so that the PIDs can be correctly read even if a laser spot
25
deviates from the center of the track. Also, the arrangements of the PID
1
and PID
2
and the PID
3
and PID
4
in the land track are opposite to those in the groove track. The push-pull signal shown in
FIG. 1B
can be obtained in the land track.
FIG. 2A
shows the physical shape of the groove track in a DVD-RAM disk.
FIG. 2B
shows the waveform of the push-pull signal in the groove track.
FIG. 3
shows the enlarged header area shown in
FIGS. 1A and 2A
. In the structure of the header area, the PID
1
and PID
2
and the PID
3
and PID
4
are arranged to deviate from the center of the track in opposite directions by a uniform amount. A vfo signal having a specified frequency for synchronizing and detecting ID and an ID signal showing the physical addresses of the sectors are recorded in the respective PIDs. The vfo signal has a recording pattern of 4T (T is a period of the clock signal).
As shown in
FIG. 3
, the header area is comprised of vfo
1
33
and ID
1
(PID
1
)
34
, vfo
2
35
and ID
2
(PID
2
)
36
, vfo
3
37
and ID
3
(PID
3
)
38
, and vfo
4
39
and ID
4
(PID
4
)
40
.
In
FIG. 3
, when the laser spot passes through the header area of the groove track, a push-pull signal RF_pp shown in
FIG. 4A and a
sum signal RF_sum shown in
FIG. 4B
are obtained. In
FIG. 4A
, a vfo
1
signal
42
corresponds to the vfo
1
signal area
33
of
FIG. 3. A
vfo
3
signal
43
corresponds to the vfo
3
signal area
37
.
FIG. 5
shows the structure of an apparatus for obtaining the push-pull signal shown in FIG.
4
A and the sum signal shown in FIG.
4
B. In
FIG. 5
, reference numeral
50
denotes a photodetector divided into four sections. Reference numerals
52
and
54
denote adders. Reference numeral
56
denotes a calculator.
The apparatus shown in
FIG. 5
outputs the sum signal RF_sum of signals detected by light receiving elements A through D of the photodetector divided into four, sum signals V
1
and V
2
of radial pairs B and C, and A and D of respective light receiving elements, and the push-pull signal RF_pp which is a subtraction signal V
2
−V
1
of V
1
and V
2
.
FIG. 10
shows a conventional technology for compensating for tilt and a method for detecting the amount of tilt by a specific pattern recorded on the track of a disk. The specific pattern coincides with the proceeding direction of the track and the center of the track and is realized in the form of a reference pit A and/or a reference pit B.
It is possible to obtain tilt information by comparing signals reproduced from the reference patterns shown in
FIG. 10
with each other and to thus operate tilt compensating equipment according to the obtained tilt information or to compensate for the signals by changing the equalizer coefficient of the reproducing signal.
The reference patterns shown in
FIG. 10
are located in an arbitrary position in the disk and are useful for detecting tangential tilt (tilt in a track direction).
However, in the conventional technology shown in
FIG. 10
, the length of the reference pattern for detecting the tilt is too short. Another pattern is necessary in order to detect the correct position of the tilt pattern. Also, radial tilt (tilt in a radial direction) cannot be detected. Since the radial tilt is larger than the tangential tilt in practice, the reference patterns are not so useful.
Since it is necessary to precisely manage the servo for the recording/reproducing apparatus to maintain an optimal recording/reproducing state, it is necessary to manage the servo error signal in high resolution.
However, the precision of the servo error signal varies depending on the disk or the reproducing apparatus. Accordingly, it is difficult to precisely manage the servo.
SUMMARY OF THE INVENTION
To solve the above problem, it is a first object of the present invention to provide an improved method of detecting a servo error.
It is a second object of the present invention to provide an apparatus for detecting a servo error suitable for the above method.
It is a third object of the present invention to provide a disk having an improved specification for maintaining the quality of a reproducing signal which is the basis of optimally controlling a servo.
It is a fourth object of the present invention to provide a method of controlling the servo of a recording/reproducing apparatus.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the first and other objects of the present invention, there is provided a method of detecting servo error of an apparatus for recording data on and reproducing data from a disk in a data area of which reference patterns having a uniform size are recorded, wherein the servo error of the recording/reproducing apparatus is detected by the ratio of the magnitude of the reference patterns recorded on at least two positions separated from each other to the magnitude of the reproducing signal corresponding to the reference patterns.
To achieve the second and other objects of the present invention, there is provided an appa
Chung Chong-sam
Joo Seong-sin
Ko Jung-wan
Lee Kyung-geun
Ma Byung-in
Edun Muhammad
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
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