JPH05128572A - Driving apparatus of laser - Google Patents

Abstract

PURPOSE:To provide a laser driving apparatus which can automatically adjust the offset and control the emitting power of lasers to be optimum. CONSTITUTION:This laser driving apparatus for an optical recording/reproducing apparatus modulates the intensity of a laser light in accordance with a recording signal, and records the signal on an optical recording medium or reproduces the signal recorded on the optical recording medium while monitoring and controlling the average value of the intensity of the laser light emitted from a laser device to be a predetermined value. This apparatus includes an offset timing detecting means 9 for detecting that an optical head is not performing erasure, recording or reproduction of data and turning OFF the laser device for a moment with the detected timing, and an offset adjusting circuit 6 which adjusts the offset of the apparatus with the timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention monitors the intensity of laser light emitted from a laser device and controls it so that its average value becomes a predetermined value, while modulating the intensity of laser light according to a recording signal. The present invention relates to a laser driving device of an optical recording / reproducing apparatus for recording a signal on an optical recording medium or reproducing a signal recorded on an optical recording medium, and particularly to an offset process thereof.

[0002]

2. Description of the Related Art A conventional magneto-optical disk device uses a magneto-optical disk having a two-layer film structure in which a first film and a second film having perpendicular magnetic anisotropy are used as a recording / reproducing layer and a recording auxiliary layer, respectively. Light that uses a so-called light intensity modulation method that modulates the output of the laser light that irradiates this magneto-optical disk between the maximum output and the minimum output according to the value of the recording signal, and thereby overwrites the recording signal on the recording track. Magnetic disk devices have been proposed (for example, JP-A-62-175948 and JP-A-63-174695).

The optical pickup used in such a magneto-optical disk device is designed to modulate the output of the laser light between the maximum output and the minimum output according to the value of the recording signal. APC (auto output) which receives light from the light receiving section and controls so that the average value of the received light output becomes constant.
2. Description of the Related Art A laser driving device having an automatic power control circuit configuration is used.

FIG. 3 is a block diagram showing the structure of such a laser driving device. In this laser drive circuit, a part of the laser light L1 emitted from the semiconductor laser LD is received by the photodetector PD1, and the received light output S
_{After the PD} is amplified by the amplifier circuit 2, the low-pass filter circuit 3
Have averaged. By this averaging process, the average value signal S _AV which is the average value of the received light output _SPD is obtained, and the average value signal S _AV is compared with the predetermined average value reference voltage V _RAV in the error amplifier circuit 4 to obtain the average value. The error voltage V _ZRR , which is the difference between the signal S _AV and the average value reference voltage V _RAV , is input to the laser drive amplifier circuit 5. The laser drive amplifier circuit 5, the recording signal S _REC is driven and controlled based on the semiconductor laser LD in accordance with the level of the input recording signal S _REC
Drive current is controlled.

[0005]

When controlling the laser light output in the laser driving device having the above-described structure, it is difficult to control the laser light output to a desired power because of the offset. Further, since the offset changes due to external factors such as temperature, it also changes during the operation of the device. Therefore, the influence of the offset cannot be removed by adjustment or the like during manufacturing. As a result, the emission power of the laser deviates from what it should be because the error due to the offset is superimposed on the control device.
The following problems have been pointed out. (1) Optimal recording cannot be performed on a magneto-optical disk. (2) If the laser power shifts to a weaker side, erasing becomes impossible. (3) The recorded signal cannot be correctly read (a reading error occurs).

The present invention has been made to solve the above problems, and provides a laser driving device capable of automatically adjusting the offset and optimally controlling the emission power of the laser. The purpose is to do.

[0007]

A laser driving device according to the present invention comprises a monitor means for monitoring a laser beam and an error detecting means for comparing an output level from the monitor means with a predetermined value to output an error signal. And a laser drive circuit that controls the intensity of the laser light based on the error signal, and detects that neither the erasing operation nor the recording and reproducing operations are performed on the recording medium irradiated with the laser light. However, it includes an extinguishing means for extinguishing the laser light at the detected timing, and an offset adjusting circuit for adjusting an offset in controlling the laser light intensity when the laser light is extinguished.

[0008]

In the present invention, when the optical head is not performing erasing, recording or reproducing operation, the laser device is turned off and the offset adjustment of the laser driving device is performed.

[0009]

【Example】

(Embodiment 1) FIG. 1 is a block diagram showing the configuration of a laser drive device according to an embodiment of the present invention. In this example,
The offset adjustment circuit 6 is an amplifier 7 for reading and amplifying the output (OV is an appropriate value) of the error amplification circuit 4 when the laser is off.
And a sample hold circuit 8 for holding the output of the amplifier 7. When the seek end signal is output from the CPU 9 functioning as a controller, the drive of the laser drive amplification circuit 5 is stopped by the signal, and the laser LD is turned off. Then, the output of the error amplifier 4 at that time is output to the error amplifier 4 as an offset setting voltage via the amplifier 7 and the sample hold circuit 8.

The offset of the laser driving device fluctuates due to external factors such as temperature even during operation. In order to adjust the offset, it is necessary to turn off the laser, but if the laser is turned off during the erasing, recording or reproducing operation of the optical head, these operations are interrupted. Therefore, when these operations are not performed, the laser is turned off and the offset adjustment is performed. By the way, even when the erasing, recording, and reproducing operations are not performed, it is common to turn on the laser in order to perform tracking control and focusing control of the optical head in the operation standby state. Therefore, when turning off the laser, it is preferable to turn off the laser only for a time period during which the control of the optical head cannot be lost. Further, it is preferable to perform the offset adjustment immediately before the erasing, recording or reproducing operation is started. Usually, before these operations are started, a seek operation for moving the optical head to a desired position is performed. Therefore, it is preferable to perform the offset adjustment immediately after the seek. That is, when the CPU 9 commands the seek operation and receives the end signal thereof, the seek end signal is supplied to the laser drive amplification circuit 5 as an offset operation command signal to stop the drive and turn off the laser LD. When the laser LD is turned off, the output signal of the photodiode PD1 in the absence of laser light is supplied to the error amplification circuit 4 via the low pass filter 3. The output of the error amplification circuit 4 at this time corresponds to an offset voltage. The offset operation command signal from the CPU 9 is also supplied to the offset adjustment circuit 6, and the offset adjustment circuit 6 enters the operating state by the input of this signal, and the output of the error amplification circuit 4 (the output when the laser is turned off) is output. After being amplified by the amplifier 7, it is sampled and held by the sample and hold circuit 8 and supplied as an offset voltage to the error amplification circuit 4.

In this way, as the timing when the optical head is not performing the erasing, recording or reproducing operation, the timing immediately after the seek is detected, the offset is adjusted, and then the erasing, recording or reproducing operation is performed. Therefore, the error due to the offset during these operations is eliminated.

(Embodiment 2) FIG. 2 is a block diagram showing the configuration of a laser driving device according to another embodiment of the present invention. The magneto-optical disk has an area for each sector in the format in which no erasing, recording or reproducing operation is performed. In this area, if the laser is momentarily turned off and the offset is adjusted, the magneto-optical disk device is performing erasing, recording or reproducing operations (the optical head does not perform erasing, recording or reproducing operations). Not.),
Offset adjustment can be performed. Taking advantage of this point, in this embodiment, the inversion signal of the erase gate signal, the write gate signal and the read gate signal used as the timing signal of the magneto-optical disk device is used as the timing signal for the offset adjustment.

In FIG. 2, a photodiode PD2 receives a laser beam and outputs the received light signal to a reproducing circuit 10, which reproduces the received signal by a predetermined signal and outputs a control signal to a timing generating circuit 11. To do. The timing generation circuit 11 outputs an erase gate signal, a write gate signal and a read gate signal based on the input control signal. Then, these signals are sent as signals for controlling the timing of the erasing, recording or reproducing operation.
In the present embodiment, the erase gate signal, the write gate signal, and the read gate signal (hereinafter referred to as the write gate signal) are fed to the inverter 13 via the OR circuit 12.
Output to. The write gate signal and the like are inverted by the inverter 13. Therefore, when all the write gate signals and the like are in the off state, the inverted signal is output to the laser drive amplifier 5 and the offset adjustment circuit 6 as an offset operation command signal. The operation after the offset operation command signal is supplied to the laser drive amplifier 5 and the offset adjustment circuit 6 is the same as that of the embodiment of FIG. As described above, in this embodiment, the offset adjustment can be performed even while the magneto-optical disk device continues the erasing, recording and reproducing operations. That is, the laser drive device can be adjusted to the optimum offset state in real time.

The timing for adjusting the offset is not limited to the embodiment shown in FIGS. 1 and 2, and for example, it is detected when the optical head is in the follow-up control state and the erasing, recording or reproducing operation is not performed. You may go. In this case, the AND operation of the seek operation signal or operation end signal from the CPU 9 of FIG. 1 and the output of the inverter 13 of FIG. 2 is ANDed, and the result is output as an offset operation command signal. Alternatively, for example, a sector mark provided for each sector may be detected and an offset operation command signal may be output at that timing. Although the magneto-optical disk device capable of erasing, recording and reproducing operations has been described in the above embodiments, the present invention can perform at least one operation of erasing, recording and reproducing by irradiating laser light. It can be applied to a device.

[0015]

As described above, according to the present invention, when the optical head is not performing erasing, recording or reproducing operation, the laser device is momentarily turned off and the offset adjustment of the entire laser drive system is performed. The erasing, recording, or reproducing operation can be performed with the offset adjusted, and each operation can be optimally performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a laser driving device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a laser driving device according to another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional laser driving device.

[Explanation of symbols]

 2 amplification circuit 3 low pass filter circuit 4 error amplification circuit 5 laser drive amplification circuit 6 offset adjustment circuit 8 sample hold circuit

Claims (1)

[Claims] 1. A monitor means for monitoring laser light, comparing an output level from the monitor means with a predetermined value,
An error detection unit that outputs an error signal, a laser drive circuit that controls the intensity of the laser light based on the error signal, and any operation of erasing, recording, and reproducing on a recording medium irradiated with the laser light. And a turn-off means for turning off the laser light at the detected timing, and an offset adjusting circuit for adjusting an offset in controlling the laser light intensity when the laser light is turned off. A laser drive device comprising: