Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2000-02-24
2004-04-27
Hudspeth, David (Department: 2697)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S047510, C369S047520, C369S053260, C369S116000
Reexamination Certificate
active
06728183
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk device used in particular to an apparatus and method of controlling the output power of a laser on recording and reproduction of signals to and from an optical disk.
Prior art method of recording information on a disk in a recording area by using laser light includes magneto-optical recording method and phase change recording method. Both methods record information on a recording layer by focussing a laser light upon the recording layer to heat it. In these recording methods, the distribution of the temperature over the recording layer will give a large influence upon the shape of a recording mark, that is, the quality of reproduced signals. The factors, which determine the temperature distribution, include the pulse width and power of recording light, etc. The current-emitted power characteristics of the semiconductor laser depends upon the temperature. Since the laser light having a power, which is ten times larger than that on reproduction, is necessary on recording, heating of the semiconductor laser becomes larger so that the temperature of the semiconductor laser is elevated. As a result, the current-emitted power characteristics may change. Accordingly, in order to record information in a good manner, it is also necessary to control the power of emitted light of the semiconductor laser on recording.
Under such a circumstance, a method of power control on recording has been proposed as is represented by Japanese Laid-Open Patent Publication No. 09-288840.
Now, a prior art power control system, which is disclosed in the above-mentioned publication, will be described.
FIGS. 1 and 2
are a block diagram and timing chart showing the prior art power control system, respectively.
In
FIG. 1
, a laser light emitted from a semiconductor laser
4
is passed through a collimator lens (not shown) and a rise mirror and focussed on a recording layer of an optical disk by portion of an objective lens. A part of the laser light is split in the course of its optical path and is incident upon a photodiode
5
. On reproduction, the semiconductor laser
4
is supplied with a current which is obtained by voltage/current converting by portion of a V/I converting circuit
3
an output of the adding circuit
2
which is a sum of an output of a reproduced power presetting circuit
1
and an output of an amplifying circuit
13
-
1
which will be described hereafter, so that the laser generates a laser light having a power depending upon the supplied current value. A current output from the photodiode
5
is converted into a voltage signal by portion of an I/V converting circuit
6
, and is then input to S/H (sample and hold) circuits
21
-
1
-
3
. The S/H circuit
21
-
1
samples/holds the output from the I/V converting circuit
6
in response to timing pulses from a timing pulse generating circuit
11
for outputting it to a subtracting circuit
12
-
1
.
Since timing pulses each having a given period are input to the S/H circuit
21
-
1
from the timing pulse generating circuit
11
, the output of the S/H circuit
21
-
1
becomes an output signal of the I/V converting circuit
6
, that is, the signal which is obtained by sampling/holding the magnitude of the light emitted from the semiconductor laser
4
at intervals of a given period of time.
In a subtracting circuit
12
-
1
, the output signal from the S/H circuit
21
-
1
is compared with a signal from a reference signal generating circuit
10
. The difference is input to an amplifying circuit
13
-
1
and is amplified at a given gain and then input to an adding circuit
2
.
In such a manner in a reproducing mode of operation, a closed loop (is formed by a reproduction power presetting circuit
1
, adding circuit
2
, V/I converting circuit
3
, semiconductor laser
4
, photodiode
5
, I/V converting circuit
6
, S/H circuit
21
-
1
, subtracting circuit
12
-
1
, reproducing power reference signal generating circuit
10
and the amplifying circuit
13
-
1
. The power emitted from the semiconductor laser
4
is controlled to a predetermined power.
In recording mode of operation, a peak power ON signal and an erasing power ON signal corresponding to a recording signal and recording gate signal (/WG) are input to current switch circuits
16
,
18
from a recording pulse generating circuit
15
.
The current switching circuits
16
,
18
conducts or blocks the current signals output from the V/I converting circuits
27
-
1
,
27
-
2
in response to the peak power ON signal and the erase power ON signal to impress the semiconductor laser
4
with it. An output signal from the adding circuit
26
-
1
which is a sum of the output signal from the peak power presetting circuit
24
and the signal from the amplifying circuit
13
-
3
is input to the V/I converting circuit
27
-
1
. An output signal from the adding circuit
26
-
2
which is a sum of the output signal from the erasing power presetting circuit
25
and the signal from the amplifying circuit
13
-
2
is input to the V/I converting circuit
27
-
2
.
On the other hand, the semiconductor laser
4
is constantly impressed with a current which is obtained by voltage/current converting by the V/I converting circuit
3
the output from the adding circuit
2
which is a sum of outputs of the reproducing power presetting circuit
1
and the amplifying circuit
13
-
1
. When the current switching circuit
16
is turned on, the semiconductor laser
4
is impressed with a sum current of the output currents from the V/I converting circuits
3
and
27
-
1
. When the current switching circuit
18
is turned on, the semiconductor laser
4
is impressed with a sum current of the output currents from the V/I converting circuits
3
and
27
-
2
. Pulse light that is shown in
FIG. 2
is emitted from the semiconductor laser
4
.
A part of the emitted light is input to the photodiode
5
similarly to the reproducing mode. The photodiode
5
outputs a current corresponding to the incident light quantity to the I/V converting circuit
6
. The I/V converting circuit
6
converts the output current from the photodiode
5
into a voltage signal for outputting the signal to the S/H circuits
21
-
1
through
21
-
3
.
Three kinds of timing pulses are output from the timing signal generating circuit
11
. When the pulse emitted light from the semiconductor laser
4
is the reproducing power, a timing pulse for holding the output signal of the I/V converting circuit
6
is output to the S/H circuit
21
-
1
. When the pulse emitted light from the semiconductor laser
4
is the erasing power, a timing pulse for holding the output signal of the I/V converting circuit
6
is output to the S/H circuit
21
-
2
. When the pulse emitted light is the peak power, a timing pulse for holding the output signal of the I/V converting circuit
6
is output to the S/H circuit
21
-
3
. Accordingly, the S/H circuits
21
-
1
through
21
-
3
output the output signals of the I/V converting circuit
6
corresponding to the reproducing, erasing and peak powers, respectively.
The output signals of the S/H circuits
21
-
1
through
21
-
3
is input to the subtracting circuits
12
-
1
through
12
-
3
, in which they are compared with the output signals from reproducing power reference signal generating circuit
10
, erasing power reference signal generating circuit
22
and peak power reference signal generating circuit
23
, respectively. The differences are input to the amplifying circuits
13
-
1
through
13
-
3
as the outputs from the subtracting circuits
12
-
1
through
12
-
3
, respectively.
The amplifying circuits
13
-
1
through
13
-
3
amplify the input signals at predetermined gains and output the signals to the adding circuits
2
,
26
-
2
and
26
-
1
.
In the prior art method, the peak, erase and reproducing (bias) powers of the pulse light for recording can be controlled to respective predetermined powers as well as the emitted light power for reproducing by the above-mentioned arrangement.
In the above-mentioned prior art method prior art me
Nakajima Junsaku
Takeuchi Hitoshi
Colon Rocio
Hudspeth David
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