JPH06267076A - Method for recording/reproducing optical data - Google Patents

Abstract

PURPOSE:To obtain a laser driving apparatus which is effective not only when data is reproduced, but when data is recorded and deleted. CONSTITUTION:The apparatus uses a semiconductor laser 1 and a high frequency oscillator 22. The semiconductor laser 1 is driven by the high frequency oscillator 22, whereby laser noises generated from the semiconductor laser 1 are reduced. Driving of the high frequency oscillator 22 is stopped when the semiconductor laser is driven with high output pulses, for example, when data is recorded or deleted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser driving device using a high frequency oscillator for reducing laser noise of the semiconductor laser, and more particularly to a semiconductor laser driving device at the time of pulse oscillation of the semiconductor laser for recording and erasing.

[0002]

2. Description of the Related Art Semiconductor lasers are widely used as light sources for optical information processing devices such as optical discs and optical printers. In recent years, the lateral mode control technology for semiconductor lasers has been developed, and the number of those that perform fundamental transverse mode oscillation and uniform longitudinal mode oscillation has increased. However, this improves coherence, and conversely, when incorporated in a device, feedback noise occurs when the light emitted from the semiconductor laser is reflected from the end surface of the optical component or the disk surface and returns to the laser again. The problem has arisen.

This noise is due to the fact that the light with good coherence interferes with the emitted light and the reflected light, and the oscillation longitudinal mode of the laser becomes unstable due to jumping or multiple longitudinal mode oscillation. is doing. Instability of the oscillation longitudinal mode is also induced by temperature changes. That is, the wavelength of the single longitudinal mode oscillation shifts due to the temperature change and not only shifts continuously but also jumps discretely and shifts. Noise is generated during this mode jump. These noises cause deterioration of signal S / N in optical communication and optical disks.

As a method for reducing these noises, Japanese Patent Publication Sho
As described in No. 59-9086, it is considered that a laser driving circuit is provided with a high frequency oscillator and the laser is modulated by high frequency. However, this method is a continuous D
The purpose was only to reduce laser noise in the case of C drive.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laser driving device which is effective not only when reproducing information but also when recording and erasing information.

[0006]

The basic idea of the present invention is to drive at high frequency only during reproduction, and stop at high frequency during recording and erasing modes.

[0007]

[Operation] The semiconductor laser records and erases at the maximum rated output, and if the high frequency weight is applied in this state, the rated output will be exceeded and the life of the laser itself will be adversely affected.
According to the present invention, the high frequency drive is stopped in the recording mode and the erasing mode.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. This is the case when applied to a magneto-optical disk device,
The light emitted from the semiconductor laser 1 is condensed by the coupling lens 7, becomes parallel light, passes through the beam split 8, the galvano mirror 9, and the focusing lens 10, and is placed on the disk 11 on which the magneto-optical recording film is formed. The spot size is about 1 μm.

The magneto-optical recording film is an amorphous compound of a transition metal and a rare earth metal, such as Tb-Fe or Tb-.
Fe-Co and the like are used, and the film is a perpendicular magnetic film in which the magnetization is oriented in the direction perpendicular to the plane. When this film is irradiated with a high-power laser beam, heat is generated and the temperature rises, and when it reaches the Curie temperature, the magnetization disappears. At this time, when a magnetic field is applied by the electromagnetic coil 12 as an external magnetic field, only the portion where the temperature rises is magnetized in that direction, and information recording is executed when it is opposite to the surrounding magnetization direction. Information is erased. In addition, signal reproduction utilizes the Kerr effect in which the angle of optical rotation changes when linearly polarized light incident on the film is reflected depending on the direction of magnetization. When the rotation angle is θ _K , for example, if it is + θ _{K with} respect to the upward magnetization,
For downward, it becomes −θ _K. This optical rotation angle is called the Kerr rotation angle, and although it depends on the composition of the recording film and the disk structure, it is as small as about 0.35 degree. The Kerr rotation angle, which is the signal component, is included in the light reflected from the disk 11, passes through the focusing lens 10 and the galvanometer mirror 9, and the optical path is separated by the beam splitter 8, and then passes through the lens 13 and the beam splitter. At 14, the servo system and the signal detection system are separated. Servo system is lens 15 and photo detector 1
The AF system, which is well known in the art, positions the optical spot on the disk by the astigmatism method and the TR system by the diffraction differential method (the drive circuit is not shown).

In the signal detection system, a λ / 2 plate 17 (λ is a semiconductor laser wavelength) and a polarization beam splitter 18 divide the light quantity into two equal parts, and the outputs of the photodetectors 19 and 20 are differentiated by a differential amplifier 23. A differential method is used to obtain a magneto-optical signal. This method has an effect of reducing noises caused by non-quantity fluctuations such as laser noises and disk noises. The sum of the outputs of the two photodetectors 19 and 20 is obtained by the adder 24,
Since this detects the amount of reflected light from the disk, it is used to detect the address information or the like that has been recorded beforehand in the form of unevenness on the disk. The detected magneto-optical signal and address information signal are input to the controller 5.

The configuration and operation of the controller 5 will be described with reference to FIG. The magneto-optical signal obtained from the differential amplifier 23 and the address information signal obtained from the adder 24 are switched in the analog switch 51 by using the timing from the mark detection circuit 52 to which the address information signal is input, and the information signal with the address information is added. Becomes This information signal is digitized by the pulse conversion circuit 53, and a VFO (Variable Fres) which generates a read timing clock in the demodulation circuit 55.
Based on the clock from the quency oscillator circuit 54, information data and address data are read and input to the microprocessor 56 for recognition. Then, the information data and the address data sent from the microprocessor 56 are timed by the modulation circuit 57 and then modulated (for example, 2-7).
It is modulated and input to the automatic power control circuit 6. A sequence circuit 58, which controls the sequence of the apparatus, generates a mode signal for recording, reproduction, and erasing in response to a command from the microprocessor 56, and generates the drive signal of the laser and the automatic power control circuit 6 for performing automatic power control. It is input to the high frequency oscillation circuit 22 provided in the drive circuit 2. The automatic power control circuit 6 sends a laser drive signal (DC + pulse drive) to the drive circuit 2 and receives a control signal from the monitor photodetector of the semiconductor laser 1 to perform automatic power control.

Next, high frequency driving of the semiconductor laser will be described with reference to FIG. The semiconductor laser 1 is driven by the drive circuit 2. The semiconductor laser 1 comprises a laser chip 3 and a photodetector 4 for monitoring. The laser chip 3 is connected to a drive line 31 and the photodetector 4 for monitoring is connected to a detection line 41. The drive circuit 2 includes a driver amplifier 21 that normally drives the laser chip 3 and a high frequency oscillation circuit 22, and the output line of the driver amplifier 21 and the high frequency oscillation circuit 2
The second output line is directly connected to the drive line 31 through the capacitor C. The driver amplifier 21 sends a pulse from the host controller 5 during recording and erasing, and oscillates the pulse in response to the pulse.

A recording mode, a reproducing mode and an erasing mode in the magneto-optical disk will be described with reference to FIGS. FIG. 4 shows the waveform in each mode. (A) is a reproduction mode, the mode signal a remains "L", the information data signal b remains "L", and the driver amplifier output C is _IR.
(MA), the high frequency oscillation circuit output d remains ON, the laser drive current waveform e is the sum of the driver amplifier output C and the high frequency oscillation circuit output d, and high frequency weighting is performed continuously. (B) is the recording mode, and the mode signal a
Becomes "H" for each sector to perform recording in sector units, a data pulse is generated in the information data signal b during the sector period, and the driver output C has the information data I _W superimposed on the reproduction current I _R. The high frequency oscillator output d becomes a waveform which oscillates only when the mode signal a is "L" by the mode signal a (ON for each sector), and the laser drive waveform e shows the driver output C and the high frequency oscillator output d. It becomes the sum, and the high frequency weight is added only when the header signal between the sectors is read. (C) is an erase mode,
Compared with the recording mode of (B), the information data b has no data pulse and is "H" in the sector, and other operations are the same.

FIG. 5 shows a laser driving state in each mode and is a reference diagram of FIG. Further, FIG. 6 shows a basic example of the high frequency oscillation circuit 22. The detection line 41 from the monitor photodetector 4 is guided to the laser power automatic power control circuit 6 and controls the driver amplifier 21 using the detected control signal to perform power control.

According to the present invention, a semiconductor laser HL-8314E manufactured by Hitachi is used.
As a result of confirming using the shape (830 nm, 30 mW output), it is possible to reduce the relative noise level RIN value by about 2 digits at the time of reproduction, and no error occurs in the recorded data even when the high frequency weight is stopped at the time of recording and erasing. all right. At this time, the high frequency oscillation frequency is 600 MHz and the current modulation degree is 14
It was 0 to 160%.

[0016]

As described above, according to the present invention, by controlling the high frequency weight during recording, reproduction and erasing, recording,
This has the effect of reducing laser noise during playback and erasing.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram for explaining an embodiment of the present invention.

FIG. 3 is a diagram for explaining an example of the present invention.

FIG. 4 is a diagram for explaining an example of the present invention.

FIG. 5 is a diagram for explaining an example of the present invention.

FIG. 6 is a diagram for explaining an example of the present invention.

[Explanation of symbols]

1 ... Semiconductor laser, 2 ... Driving circuit, 3 ... Laser chip,
4 ... Photodetector for monitor, 5 ... Controller, 6 ... Automatic power control circuit, 22 ... High frequency oscillation circuit.

Claims (4)

[Claims] 1. An optical information recording / reproducing method in which driving of a semiconductor laser is controlled by superposition of high frequencies, and light emitted from the semiconductor laser is irradiated onto a recording medium to record or reproduce information. An optical information recording / reproducing method, characterized in that the superposition of the high frequencies is stopped. 2. An optical information recording / reproducing method for recording or erasing information by controlling driving of a semiconductor laser by superimposing a high frequency and irradiating a recording medium with light emitted from the semiconductor laser. An optical information recording / reproducing method, characterized in that the superposition of the high frequencies is stopped. 3. Information is recorded by modulating laser light from a semiconductor laser according to the information to be recorded and irradiating the recording medium, and irradiating the medium on which the information is recorded with the laser light from the semiconductor laser. In the optical information recording / reproducing method for reproducing the information from the returning light, a high frequency is applied to the semiconductor laser only when reproducing the information. 4. A laser beam from a semiconductor laser is irradiated onto a medium on which information is recorded at a first predetermined level and the information is reproduced from the returning light, and the laser beam from the semiconductor laser is converted into the first beam. In an optical information recording / reproducing method of irradiating a recording medium at a second level higher than the level to record or erase information, when the semiconductor laser is driven at the first level, An optical information recording / reproducing method, characterized in that a drive signal is applied and when the drive is performed at the second level, the application of the drive signal is stopped.