JPH0498628A - Laser power control circuit for reloadable optical disk - Google Patents

Abstract

PURPOSE:To stablize laser power by executing feedback control for the power of laser beam irradiating from an optical head based on the sampled/held value of laser power. CONSTITUTION:The output laser beam is detected by a photosensor 12 and the output is inputted to a laser output monitor circuit 2. The circuit 2 receives the output of the sensor 12 and outputs an electric signal, which is proportional to the laser power of a laser diode 11, to a sample/hold amplifier 3. The amplifier 3 samples/holds the electric signal outputted from the circuit 2 sinchronously with a timing signal outputted from a timing generation circuit 6. Corresponding to the value of the electric signal sampled/held by the amplifier 3, a laser output control circuit 4 controls a laser driving circuit 5. Thus, the laser driving circuit 5 controls the value of a current supplied to the laser diode 11.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laser power control circuit for a rewritable optical disk, and is particularly applicable to a laser power control circuit for a rewritable optical disk, and is particularly applicable to a phase change type rewritable optical disk. The present invention relates to a laser power control circuit for a rewritable optical disk suitable for accurately controlling power and erase power of a magneto-optical rewritable optical disk.

(Prior Art) A laser diode installed in an optical head generally generates heat due to continuous light emission, which causes the laser output to fluctuate.Therefore, in conventional write-once optical disk devices, the laser diode generates heat only when reading. Then, feed puncture control was performed, which stabilized the read power.When writing, the laser diode emits pulsed light, so fluctuations in laser output can be ignored.
Therefore, the feed bank control described above was not performed.

[Problem to be solved by the invention]

In phase-change engraving rewritable optical discs, when writing, write power is superimposed on a constant read power,
Since the laser beam is emitted continuously, it is necessary to stabilize the laser beam. Furthermore, in a magneto-optical rewritable optical disk, since a constant laser beam is continuously emitted during erasing, it is necessary to stabilize the laser beam.

However, until now, no technology has been developed to stabilize the laser power when writing to a phase-change rewritable optical disk or to stabilize the laser power when erasing a magneto-optical rewritable optical disk. This is the current situation. In particular, when writing a phase change type rewritable optical disk, the write power is superimposed, so there is a problem that a method of monitoring the laser power and performing continuous feedback control cannot be adopted.

The present invention was devised in view of the problems of the prior art described above, and it stabilizes the laser light power when writing a phase change type rewritable optical disk, and also stabilizes the laser power when erasing a magneto-optical type rewritable optical disk. It is an object of the present invention to provide a laser power control circuit for a rewritable optical disc that can be stabilized.

[Means to solve the problem]

The laser power control circuit for a rewritable optical disc of the present invention performs feedback control of the power of the laser light irradiated from the optical head to the rewritable optical disc, and in particular controls the power of the laser light irradiated to the optical disc at a constant level. Consisting of a first means for sample-holding at the timing, and a second means for feedback-controlling the power of the laser beam irradiated from the optical head based on the value of the laser power sampled and held by the first means. It is characterized by

[Effect]

In a rewritable optical disk, write/erase operations are performed sector by sector, and actual write/erase operations are performed intermittently. Therefore, by sampling the power of the laser beam at a certain timing and performing feedback control, it is possible to stabilize the laser beam power when writing a phase change type rewritable optical disk, and to stabilize the laser beam power when erasing a magneto-optical type rewritable optical disk. It becomes possible to stabilize the laser power.

Here, the above-mentioned certain timing is, for example, the timing when the light spot is positioned in the gap part provided between the ID part and the data part of the sector, or the timing when the light spot is located in the area of the data part and the data is recorded. This may be due to the timing being positioned in a part where this is not done. This makes it possible to perform feedback control without the influence of light pulses.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the accompanying drawings. The accompanying drawings are block diagrams illustrating one embodiment of the invention. In the accompanying drawings, 1 is an optical head, 2 is a laser output monitoring circuit, 3 is a sample hold amplifier, 4 is a laser output control circuit, 5 is a laser drive circuit, 6 is a timing generation circuit, and 7 is an optical disk.

Further, 11 indicates a laser diode provided within the optical head, and 12 indicates an optical sensor also provided within the optical head 1.

Next, the operation of the embodiment shown in the attached drawings will be described. A laser diode 11 in the optical head 1 is driven by a laser drive circuit 5 and outputs laser light. The output laser light is detected by the optical sensor 12, and its output is input to the laser output monitoring circuit 2. The laser output monitoring circuit 2 receives the output of the optical sensor 12 and outputs an electric signal proportional to the laser power of the laser diode 11 to the sample and hold amplifier 3. Sample hold amplifier 3
samples and holds the electrical signal output from the laser output monitoring circuit 2 in synchronization with the timing signal output from the timing generation circuit 6. The laser output control circuit 4 controls the laser drive circuit 5 according to the value of the electrical signal sampled and held by the sample and hold amplifier 3. Thereby, the laser drive circuit 5 controls the current value supplied to the laser diode 11.

Next, the operation of the phase change type rewritable optical disk during writing will be described in detail. In a phase change type rewritable optical disk, an ID is generally provided at the beginning of a sector.
After reading the data in the ID section by irradiating the data section with a laser beam with read power, change the read power to erase power, and perform a write operation by irradiating the data section with a laser beam with a write pulse superimposed on the erase power. conduct.

Generally, each sector has a configuration of an ID section, a gap section, and a data section, and the change of the laser power from the read power to the erase power is performed by the gear amplifier section provided between the ID section and the data section. It will be held in Therefore, the erase power is applied to the gap between the ID section and the data section, and the write pulse is superimposed on the erase power at a subsequent timing. Therefore, in order to monitor the erase power and perform continuous feedback control, it is necessary to sample and hold the intensity of the laser light at the gap portion and perform feedback control.

Therefore, the timing generation circuit 6 shown in the attached drawing outputs a timing signal at the following timing when writing a phase change type rewritable optical disk. That is, the optical head 1 outputs a signal indicating that the optical spot is positioned at the ID section provided at the beginning of each sector based on the reflected light of the optical spot positioned on the track on the optical disk. . The timing generation circuit 6 counts a predetermined time after receiving this signal, detects the timing when the light spot is positioned in the gap between the ID section and the data section, and at this time, the timing signal is sent to the sample and hold amplifier. Output to 3. therefore,
The sample and hold amplifier 3 samples and holds the output of the laser output monitoring circuit 3 at the timing when the light spot is positioned in the gap between the ID section and the data section, thereby controlling the laser power without being affected by the light pulse. Feedback control can be performed. Therefore, when writing to a phase change type rewritable optical disc, feedback control of laser power can be performed for each sector.

Although the above embodiment has been described as performing sample hold and feedback control in the gap section following the ID section, the present invention is not limited to this. Feedback control may be applied to areas where no data is written.

Next, the erase operation of the magneto-optical rewritable optical disk will be described in detail. In magneto-optical rewritable optical discs, the I
After reading the data in the ID section by irradiating the D section with a laser beam of read power, an erase operation is performed by irradiating the gap section and the data section with a laser beam of erase power.

Therefore, the timing generation circuit 6 shown in the attached drawing outputs a timing signal at the following timing when erasing a magneto-optical rewritable optical disk. That is, the optical head 1 outputs a signal indicating that the optical spot is positioned at the ID section provided at the beginning of each sector based on the reflected light of the optical spot positioned on the track on the optical disk. . Timing generation circuit 6
counts a predetermined time after receiving this signal, detects the timing when the light spot is positioned in the gap between the ID section and the data section, or the timing when the light spot is positioned in the data section, and at this time, the timing signal is detected. is output to sample hold amplifier 3. Therefore, the sample and hold amplifier 3 samples and holds the output of the laser output monitoring circuit 3 at the timing when the light spot is positioned in the gap between the ID section and the data section or at the timing when the light spot is positioned at the data section. Feedback control of laser power can be performed by Therefore, when erasing a magneto-optical rewritable optical disk, feedback control of laser power can be performed for each sector.

In the above embodiments, the case where the ID section and the data section are preformatted in advance on the phase change type rewritable optical disk and the magneto-optical type rewritable optical disk was explained as an example, but the present invention is limited to this. The present invention can also be applied to rewritable optical discs that are not preformatted. That is, even in a non-preformatted optical disc, a sector called a jump sector is defined for performing a one-track jump. Therefore, the timing generation circuit 6 can perform feedbank control of the laser power by detecting that the optical subbont is positioned in this jump sector and outputting a timing signal at this timing.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to stabilize the laser light power when writing a phase change type rewritable optical disk, and to stabilize the laser power when erasing a magneto-optical type rewritable optical disk. A laser power control circuit for a rewritable optical disk can be provided.

[Brief explanation of the drawing]

The accompanying drawings are block diagrams illustrating one embodiment of the invention. 1... Optical head, 2... Laser output monitoring circuit, 3
... Sample hold amplifier, 4... Laser output control circuit, 5... Laser drive circuit, 6... Timing generation circuit, 7... Optical disk, 11... Laser diode, 12... Light sensor.

Claims (1)

[Claims] 1. In a laser power control circuit for a rewritable optical disc that feedback controls the power of the laser light irradiated from the optical head to the rewritable optical disc, the power of the laser light irradiated to the optical disc is kept constant. and a second means for feedback controlling the power of the laser beam emitted from the optical head based on the value of the laser power sampled and held by the first means. A laser power control circuit for a rewritable optical disc, characterized in that: 2. The above-mentioned rewritable optical disk is a phase-change rewritable optical disk, and the power of the laser beam is the laser power at the time of writing, and furthermore, at the above-mentioned certain timing, the light spot is connected to the ID part of each sector and the data. 2. The laser power control circuit for a rewritable optical disk according to claim 1, wherein the timing is positioned at a gap portion provided between the two portions. 3. The above-mentioned rewritable optical disk is a magneto-optical rewritable optical disk, and the power of the laser beam is the laser power at the time of erasing, and furthermore, at the above-mentioned certain timing, the light spot is connected to the ID part of each sector and the data. 2. The laser power control circuit for a rewritable optical disk according to claim 1, wherein the timing is positioned at a gap provided between sections or at the beginning of a data section.