Dynamic magnetic information storage or retrieval – General processing of a digital signal
Reexamination Certificate
2000-04-13
2004-11-02
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
C360S027000, C360S071000, C360S072100, C369S047530, C369S053100, C369S047100
Reexamination Certificate
active
06813107
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for detecting an optimal writing power for recording data on a writable optical recording medium.
2. Description of the Related Art
FIG. 1
is a simplified block diagram of a conventional apparatus for recording data on a writable optical disk. The apparatus comprises an A/D converter
20
for digitizing an analog signal, an MPEG encoder
30
for encoding the digitized data into the MPEG format, a digital recording signal processing unit
70
a
for converting the MPEG-formatted data into recording-formatted EFM (Eight to Fifteen Modulation) data while adding additional data such as error correction codes, a channel bit encoder
80
for converting the recording-formatted data into writing signals, an optical driver
81
for yielding signals to drive a LD (laser diode), an optical pickup
11
for recording signals onto surface of a writable optical disk
10
and reproducing recorded signals from the optical disk
10
, a driving unit
90
for driving the optical pickup
11
and a motor M to move and rotate respectively, an R/F unit
100
for equalizing and shaping the signals reproduced by the pickup
11
to produce binary signals, a servo unit
110
for controlling the driving unit
90
based upon a tracking and a focusing error signal provided by the pickup
11
and the rotation speed of the optical disk
10
, a digital reproduced signal processing unit
70
b
for restoring compressed data from the binary signals using a self clock synchronized with the binary signals in phase, an MPEG decoder
120
for restoring original video and/or audio data by decoding the compressed data, and a microcomputer
60
for controlling overall operation of recording and reproduction.
Receiving a request of data recording, the microcomputer
60
controls the pickup
11
through the servo unit
110
and the driving unit
90
to read the indicative target writing power recorded on the writable disk medium
10
. In case where the disk
10
is a rewritable recording medium such as a CD-RW, the target writing power is recorded as 3-bit data W
1
,W
2
, and W
3
in the M
1
information byte in the field of ATIP (Absolute Time In Pre-Groove) located in the lead-in area of the optical disk
10
.
FIG. 2
shows the recording format of the bits ‘W
1
W
2
W
3
’ and the meaning of each value.
After reading the target writing power data W
1
,W
2
, and W
3
, that is, the indicative target writing power P
ind
, recorded as above, the microcomputer
60
transfers predetermined test data, for example, a byte of 10101010, to the channel bit encoder
80
through the digital recording signal processing unit
70
a
. For recording digital bit streams outputted from the digital recording signal processing unit
70
a
, the channel bit encoder
80
converts the bit streams into PWM (pulse-width-modulated) signals and applies the modulated signals to the optical driver
81
.
The microcomputer
60
applies a power adjusting data to the optical driver
81
and changes its value in sequence as shown in
FIG. 3
for changing the writing power within a given range with respect to the read target writing power whose intensity is assumed to 8 mW in FIG.
3
. In response to the power adjusting data, the optical driver
81
outputs writing signals whose power corresponds to the applied power adjusting data so that the pickup
11
records the digital bit streams for testing in the test area of the optical recording medium
10
. In case where the optical recording medium
10
is a rewritable CD such as a CD-RW, the test data are recorded in test area A of the PCA (Power Calibration Area) as shown in FIG.
4
.
Along with recording the digital bit streams for power testing, the microcomputer
60
controls the optical pickup
11
to write null data of one ATIP in the count area B located in the PCA to indicate how many times test writing is accomplished. For example, if this recording of the digital bit stream for power testing is executed thirdly for the disk
10
, the null data are written to the third ATIP of the count area B located in the PCA as shown in
FIG. 4
to indicate that test operations were executed three times.
On the condition that the test data have been recorded in the test area A of the PCA with the varying writing power, the microcomputer
60
controls the pickup
11
to reproduce the most recently recorded digital bit streams for power testing. While reproducing the test data, the microcomputer
60
keeps detecting the jitter magnitude of the binary signals converted from the reproduced RF (Radio Frequency) signals by the R/F unit
100
. Then, if the detected jitter magnitude is lowest, the microcomputer
60
determines the writing power used to record the test data whose jitter magnitude is lowest as an optimal writing power for the disk
10
. That is, the power Pop is chosen to optimal in FIG.
3
.
If external video and/or audio signals are received for recording after the optimal writing power Pop is determined, the received video and/or audio signals are digitized by the A/D converter
20
and encoded into the MPEG formatted data by the MPEG encoder
30
. The digital recording signal processing unit
70
a
generates digital bit streams modulated from the encoded data and error correction codes added to the encoded data by itself. The channel bit encoder
80
converts the digital bit streams into PWM signals and applies the modulated signals to the optical driver
81
to record the modulated bit streams to the disk
10
.
Meanwhile, the microcomputer
60
sets the optical driver
81
to generate a driving current corresponding to the optimal writing power Pop obtained through the previous procedure. Therefore, the PWM signals whose power is optimal for the disk
10
makes the received data be recorded in the program area of the optical disk
10
.
In the above-explained conventional method for recording data on an optical disk, when new data are requested to be recorded successively from the record-ending point of the program area after previous data recording operation is done, the microcomputer
60
accomplishes the afore-mentioned OPC (Optimal Power Calibration) again. In other words, the microcomputer
60
repeats the OPC whenever a data recording is requested.
However, the OPC needs to move a pickup inward and outward, that is, between PCA and program area, which takes a relatively long time to start data recording so that it delays the data recording operation.
Moreover, since the test area A of PCA for an optimal writing power calibration is located more inwardly than a lead-in area of an optical disk the characteristics of recording environment of the program area in which user data are to be recorded could be different from that of the test area. Accordingly, sometimes an optimal writing power detected from the test area is not optimal as a recording area where input data are to be written.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and an apparatus for detecting an optimal writing power, which reserves OPC areas in the user data area and detecting an optimal writing power through test writing and reading at the reserved OPC areas.
The optimal writing power detecting apparatus according to the present invention comprises a writing/reading means for recording and reproducing data to/from the recording medium; a servo controlling means for moving said writing/reading means to a reserved spare area adjacent to a data section recorded in the recording medium; and a controlling means for controlling said writing/reading means to record test data in the reserved spare area while changing a writing power and to reproduce the recorded test data from the spare area, and detecting an optimal writing power based upon the characteristics of the reproduced signals.
The optimal writing power detecting method according to this invention comprises the steps of searching for a marginal area adjacent to a data section recorded on an optical recording medium; recording t
Figueroa Natalia
LG Electronics Inc.
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