Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Reexamination Certificate
2001-03-22
2003-09-02
Psitos, Aristotelis M. (Department: 2653)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
C369S116000
Reexamination Certificate
active
06614735
ABSTRACT:
This application is based on applications Nos. 2000-81204 and 2001-44942 filed in Japan, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disc device and, more specifically, to the device for setting the optimal recording power in the optical disc device that records information by emitting a laser beam to an optical disc recording medium.
2. Description of the Related Art
Optical disc devices of various types have been developed in recent years as a means for recording and reproducing large volumes of data, and various approaches have been taken to achieve ever higher recording densities. Phase change type optical disc devices that use the ability to effect a reversible change between crystalline and non-crystalline (amorphous) phases in the recording medium to record data are exemplary of one such approach.
A phase change type optical disc device records data by forming marks (amorphous parts) and spaces (crystalline parts) between the marks on the optical disc medium. The amorphous marks are formed by setting a semiconductor laser to a peak power level at which crystalline parts are changed to amorphous marks, and the crystalline spaces are formed by setting the semiconductor laser to a bias power level at which amorphous parts are converted to a crystalline state.
Reflectivity is different in marks and spaces. It is therefore possible to use this difference in reflectivity to read the recorded signal during data reproduction (reproduction).
The configuration of a conventional phase change type optical disc device is shown in FIG.
10
. As shown in
FIG. 10
, the optical disk device comprises an optical head
1002
, a reproduction section
1003
, a reproduction signal quality detection section
1004
, an optimal recording power determining section
1005
, a recording section
1006
, a laser drive circuit
1007
, and a recording power setting section
1008
.
FIG. 11
shows a track configuration of the optical disc
1001
in the prior art. This optical disc
1001
has recording areas in both a groove-shaped track (groove track
1101
) and a track between the grooves (land track
1102
). The groove track
1101
and land track
1102
form a continuous spiral by alternating with each other at each revolution of the disc.
When the optical disc
1001
is loaded into an optical disc device, the optical disc device performs trial recording to a predetermined area on the disc
1001
, thereby determining an optimal laser power to be emitted for recording data to the disc
1001
.
For that, when the optical disc
1001
is loaded into an optical disc device, specific operations are first performed to detect the disc type and information for controlling disc rotation. The optical head
1002
then moves to an area reserved for setting the optimal recording power.
Both the peak power level and bias power level must be determined in a phase change type optical disc device. Determining the peak power level is explained below.
The recording power setting section
1008
first sets initial peak power and bias power levels for the laser drive circuit
1007
. The power level set for recording to land tracks and the power level set for recording to groove tracks are equal at this time.
The recording section
1006
then sends a signal for continuously recording a land track for one revolution and a groove track for one revolution from a specified starting point to the laser drive circuit
1007
for recording by the optical head
1002
. The output beam from the semiconductor laser that is a component of the optical head
1002
is focused on the optical disc
1001
as a spot to form a mark. The shape of the mark is determined by the waveform of the emitted laser beam.
When recording the land and groove tracks is completed, the semiconductor laser of the optical head
1002
is driven at the reproduction power level to reproduce the signal previously recorded to the land and groove tracks. The reproduction signal
1009
, which varies according to the presence or absence of a recording mark on the optical disc
1001
, is input to the reproduction section
1003
. The reproduction section
1003
then amplifies, waveform-equalizes, and digitizes the reproduction signal
1009
, and passes the resulting signal
1010
to the reproduction signal quality detection section
1004
.
The reproduction signal quality detection section
1004
detects the signal quality of signal
1010
, and inputs the result to optimal recording power determining section
1005
.
It should be noted that the reproduction signal quality detection section
1004
detects BER (Byte Error Rate) of the recorded signal when it is reproduced. The BER detected here is the average over the reproduced track.
FIG. 12
shows the relationship between peak power and BER.
Peak power is shown on the axis of abscissas and BER on the axis of ordinates in FIG.
12
. In general, a lower BER indicates that recording is more accurate, under the same reproduction conditions. An “OK” (good) detection result is therefore output if the BER is less than a specific threshold value, and a “NG” (no good) detection result is output if the BER is greater than or equal to the threshold value.
The optimal recording power determining section
1005
determines the recording power (peek power), for example, according to a procedure indicated by a flowchart shown in FIG.
13
.
The optical head moves to a predetermined area provided for setting a laser power emitted onto the optical disc
1001
(S
101
) and an initial value of the recording power is set (S
102
). Subsequently, data are recorded onto the power setting area on the disc
1001
with the set recording power and then the recorded data are reproduced (S
103
). The quality of the reproduced signal is detected by detecting BER from the reproduced signal (S
104
). Based on the current detection result and the previous detection result, two peak powers are determined with which the quality of the reproduced signal changes “OK” to “NG” or “NG” to “OK” (S
104
to S
108
). After determining those two powers, the optimal power is determined by averaging values of those powers (S
109
) and adding a predetermined margin to the averaged value (S
110
).
For example, when the first detection result from the reproduction signal quality detection section
1004
is “NG” the peak power level is set higher than the initial peak power (S
108
). When the result is “OK”, the peak power level is set below the initial peak power (S
106
). The reset peak power level is then used to record and reproduce the land track and groove track again, and repeat the above evaluation.
Then, when the first detection result from the reproduction signal quality detection section
1004
is “NG” (S
104
) and the second result is “OK” (S
107
), the optimal recording power determining section
1005
takes the average of the previous peak power setting and the subsequent or current peak power setting, adds a predetermined margin, and uses the result as the optimal recording power (S
109
, S
110
).
When the first detection result from the reproduction signal quality detection section
1004
is “OK” (S
104
) and the second result is “NG” (S
105
), the optimal recording power determining section
1005
takes the average of the previous and current peak power settings, adds a predetermined margin, and uses the result as the optimal recording power (S
109
, S
110
).
With the conventional method as described above, the detected BER is the average for the reproduced track. Therefore, reproduction errors increase if there are fingerprints, for example, on the track used for BER detection, causing the BER to be higher than expected. As a result, this causes a power level greater than the actual optimal peak power level to be set as the optimal recording power level.
SUMMARY OF THE INVENTION
The present invention is directed to a solution for the aforementioned problem by providing an optical disc device and a recording power determining method used in the disc
Akagi Toshiya
Ishida Takashi
Ito Ariaki
Shoji Mamoru
Yamasaki Yukihiro
Psitos Aristotelis M.
Wenderoth , Lind & Ponack, L.L.P.
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