JPH03256234A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To satisfactorily guarantee the quality of a data against deterioration of a signal under high temp. and residual erasure under low temp. and to promote the reliability of the regenerative data by controlling an output of a semiconductor laser at the time of erasing or recording in accordance with an output of a detecting circuit. CONSTITUTION:An ambient temp. of a recording medium 29 is detected by a temp. sensor 19, and a temp. change is detected by a temp. detecting circuit 30, and is converted into a voltage and sent to a superimposing power control circuit 25, where superimposing power is controlled in order to keep the temp. on a recording film constant. Since the temp. sensor itself cannot be disposed on the recording film, it is multiplied by a fixed conversion coefft. and fed back to the control circuit 25. Then, the detecting circuit 30 is capable of detecting simultaneously also a using guarantee temp. of the recording medium, detecting an abnormal temp. owing to the stop of a fan, etc., and an alarm signal is sent to a microprocessor 31 for a processing control on an optical disk device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording/reproducing device, and particularly to a semiconductor laser decommissioning control circuit used in this device.

[Conventional technology]

In a conventional rewritable optical disk device, for example, a magneto-optical disk device, as shown in FIG. It is recorded by the difference in the direction (either facing up or down). In this case, laser light is used as a heat source and is irradiated onto the film in pulses to locally raise the temperature. As is well known, when a recording film is heated to near the Curie temperature, the coercive force of the film decreases and the magnetization is reversed by the oriented magnetic field generated by an external electromagnetic coil. For erasing, magnetization can be returned to its original direction by applying a magnetic field in the opposite direction to that during recording and continuously irradiating it.

To reproduce information from an optical disc, as shown in Figure 2,
When the laser beam 4 is irradiated onto the disk surface on which information is recorded in the form of a domain array, and the Kerr effect occurs, i.e., when linearly polarized laser light is incident on the perpendicularly magnetized film, the polarization plane of the reflected light changes to the left according to the direction of magnetization. Alternatively, this can be done by detecting the rotation angle due to the phenomenon of slight rotation to the right.

As shown in the cross-sectional view of FIG. 2(a) and the plan view of FIG.
), there are overlapping parts.

In addition, the information track on the optical disk is divided into multiple areas (called sectors) as shown in Figure 3, and each area contains the track number, sector number, and other information necessary for recording and reproduction. It consists of a part where information is recorded (usually this part is called an ID) and a data part in which user data is recorded by additional recording.

For example, to record data in sectors on an optical disk, first magnetize a magnet coil that applies an external magnetic field in the direction of the recording magnetic field, recognize the ID on the track, and then adjust the emission power of the semiconductor laser according to the recording data pattern. In a controlled manner, only when the recorded data is LL I I+, the superimposed power to be superimposed is added to the reproduced power, and when the recorded data is 0'', only the reproduced power is used), and the temperature at the position on the recording film to be recorded is locally adjusted. Data is recorded by increasing the temperature.

Therefore, in magneto-optical recording, the emission power of the semiconductor laser during recording and erasing becomes heat on the recording film as described above.
Contribute to regeneration. Therefore, in order to stabilize the recording/erasing characteristics, it is necessary to stabilize the magnitude of the external magnetic field and to stabilize the recording film.
It is necessary to stabilize the temperature at 2.

As a conventional control method for the semiconductor laser in such an optical disk device, as proposed in JP-A-61-165835 and JP-A-63-74131, the power of the reproduced light is monitored by a light receiving element, and the reproduced light is detected. There is a method in which the optical power is controlled to be constant during both reproduction and recording, and the optical power is superimposed on the reproduction level during recording. However, these methods all keep the light emitting power constant during recording and erasing, but do not keep the temperature on the recording film constant.

For this reason, temperature changes on the recording film due to changes in environmental temperature cannot be controlled, and the recording domain may become too large or too small depending on the environmental temperature, resulting in a problem of lowering reliability during reproduction. Additionally, when the equipment is operating at abnormally high temperatures, the media may be destroyed if some protection is not provided.

[Problem to be solved by the invention]

, 3. .

In the above conventional technology, the recording/erasing power of the semiconductor laser is always constant even when the temperature changes on the recording medium, so the temperature on the recording medium cannot be guaranteed sufficiently, resulting in the following problems. There was a point.

(1) In recording at high temperatures, the domain diameter increases, resulting in degraded resolution and reduced reliability during reproduction.

(2) When erasing at low temperatures, the domain diameter becomes smaller, so domains recorded at high temperatures remain unerased and S/N
decreases.

(3) Since the temperature is not controlled, the life of the medium is accelerated when the temperature becomes abnormal.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an optical recording/reproducing device having a highly reliable information reproducing circuit.

[Means to solve the problem]

In order to achieve the above objective, a temperature detection means is installed near a recording medium such as an optical disk, and the temperature near the recording medium is detected and the information signal is transmitted to the semiconductor laser (4) meza power control circuit or write pulse during recording. This is fed back to the width control circuit and controls the power of the semiconductor laser to provide the most optimal laser power for the temperature at the time of detection.

[Effect]

The light emitting power of a semiconductor laser during erasing or recording is normally switched only by track address information. By adding information about the temperature detection means to this function, it is possible to easily control the light emission power with respect to temperature. The temperature detection means can be easily constructed by using a commercially available resistor with a large temperature coefficient. Since the resistance value of the temperature detection means changes linearly with temperature change, it can be easily controlled by detecting the change in resistance value as the change in voltage value.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a recording medium 10 is a magneto-optical disk, which is rotated by a spindle motor 11. As shown in FIG. A light beam 13 emitted from a semiconductor laser 12 passes through an optical system and reaches a galvano mirror 14. The light beam deflected by the galvano mirror 14 is focused by an objective lens 15 to a small spora 1 to a diameter, and reaches a recording film 16. There is a magnetic coil 17 above the recording medium 10, which generates an external magnetic field during recording and erasing. Reference numeral 18 indicates a circuit component mounting board for controlling the optical disk device. The temperature sensor 19 is arranged at a position where it can detect the temperature near the recording medium. Further, in FIG. 1, in order to simplify the explanation, parts not directly related to the invention are omitted. The light reflected by the recording film 16 is separated from the incident light by a beam splitter 20 and reaches a photodetector 21 . During reproduction, the output of the semiconductor laser 12 is controlled by the following method to keep the emission power constant. The output of the monitor paired with the laser is amplified by the amplifier 22, and the difference from the reference voltage - is determined by the subtraction circuit 24 to obtain an error voltage for generating the laser opening current. Since optical disk devices have recording, playback, and erasing modes, the power is controlled using the above method during playback, but when recording and erasing, the error voltage during playback is held by the sample hold circuit 23, and the error voltage during playback is held during recording and erasing. The superimposed power is generated by a superimposed power control circuit 25, and the current is added to the laser rotation current 26 during reproduction to obtain the recording/erasing power. Further, 27 determines the response characteristics of the power control circuit.

A laser ablation circuit that generates a laser ablation current from P, F (Low Pa5s Filter) and an error voltage is shown. Since the superimposing power is added to the reproducing power at a certain constant value, the light emitting power during recording and erasing is constant at the light emitting surface 28 of the laser. This emitted light power is converted into heat on the recording film 16, but it is not constant on the recording film 16 depending on the state of the ambient temperature.

Therefore, the temperature sensor 19 detects the temperature near the recording medium 29, and the temperature detection circuit 30 shown in FIG. Control the superimposition power so that Since the temperature sensor itself is not placed on the recording film, it is multiplied by a certain conversion coefficient and fed back to the superimposed power control circuit 25.

Furthermore, the temperature detection circuit 30 is designed to be able to simultaneously detect the guaranteed operating temperature of the recording medium, and detects abnormal temperatures due to fan stoppage, etc., and sends an alarm signal to the microprocessor 31 that controls the processing of the optical disk device. This is to protect the recording medium by forcibly turning off the laser power supply 32 (currently, if the recording medium is used outside the guaranteed temperature range, its lifespan will be shortened).

FIG. 5 shows the configuration of the temperature sensor 19 and the temperature detection circuit 30. It is composed of a resistor (temperature sensor) with a large temperature coefficient, a resistor R with a small temperature coefficient, R2, R3, and a comparator 33. When the ambient temperature of the temperature sensor 19 rises, the resistance value of the temperature sensor 9 increases, the potential of the power control signal increases, and when the temperature exceeds the abnormal temperature detection level V□, a temperature abnormality detection signal is generated. Further, the power control signal is connected to the superimposed power control circuit so as to reduce the superimposed power by a certain ratio when the potential becomes high. That is, the power control signal is sent to the superimposed power control circuit 25 and connected to the semiconductor laser 12 via the circuit configuration shown in FIG. As the temperature around the recording film increases, the resistance value of the temperature sensor 19 of the temperature detection circuit 30 increases. As a result, the emitter potential of the transistor 34 of the superimposed power control circuit 25 increases and operates to reduce the superimposed current added to the semiconductor laser, thereby reducing the recording power relative to the normal temperature. For this reason, heat on the recording film due to the recording power of the semiconductor laser
Since the 1 rise decreases by the amount of rise in ambient temperature, the temperature on the recording film is kept constant. Similarly, when the ambient temperature drops, the superimposed current operates to be larger than that at room temperature, so the temperature on the film can be kept constant in the same way as when the temperature rises. By changing the power during recording and erasing in accordance with changes in the ambient temperature in this way, the temperature on the recording film during recording and erasing can be kept constant, and the recording and erasing characteristics can be stabilized.

In other words, if the optimum temperature on the recording film for recording is T (°C), and the recording power required to raise the temperature to that temperature at an ambient temperature of 25°C is P2□mW, then the thermal conversion efficiency of the semiconductor laser is Hani=(T-25)/Pzs (℃/ml11
). Here, the optimum emission power of the semiconductor laser when the ambient temperature changes to 50 DEG C. is R5(1=(T'be)50)/(T-25)XP25(n+W). In addition, the optimum light emission power at an ambient temperature of 0°C is Po
” T/ (T-25) It operates as described above to keep the temperature on the recording film constant.

Although one embodiment of the present invention has been described above, the present invention is applicable not only to magneto-optical disk devices but also to write-once optical disk devices.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to sufficiently guarantee data quality such as signal deterioration at high temperatures and unerased data at low temperatures, and is therefore effective in improving the reliability of reproduced data.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a semiconductor laser drive circuit in a rewritable optical disc device according to an embodiment of the present invention, FIG. 2 is a diagram showing an optical disc playback operation, FIG. 3 is a diagram showing the format of an optical disc, and FIG. 5 is a diagram showing an example of an optical disc, FIG. 5 is a diagram showing an example of a temperature detection circuit, and FIG. 6 is a diagram showing a superimposition power control circuit. 1. Optical disc, 2. Track, 3. Domain,
4. Laser beam, 10. Recording medium, 1 spindle motor, 12. Semiconductor laser, 13. Light beam, 14. Galvanometer mirror 115. Objective lens,
16. Recording film, ■7. Magnetic coil, (8. Base plate, 19. Temperature sensor, 20. Beam splitter,
21... Photodetector, 22... Amplifier. 23... Sample hold circuit, 24... Subtraction circuit, 25... Superimposition power control circuit, 26... Laser perturbation current during reproduction, 27. L, P, F and laser driving circuit,
28... Emission power at the semiconductor laser emission surface, 29.
...Recording medium, 30...Temperature detection circuit, 31...Microprocessor, 32...Laser power source, 33.
- Comparator, 34...transistor.

Claims (1)

[Claims] 1. Equipped with a semiconductor laser serving as a light source, a control circuit that controls the output power of the semiconductor laser, a temperature detection means installed near the recording medium, and a detection circuit that detects the temperature from the temperature detection means, An optical recording/reproducing device characterized in that the output from a semiconductor laser during erasing or recording is controlled in accordance with the output of the detection circuit.