JPH0636382A - Photomagnetic recording device - Google Patents

Abstract

(57) [Summary] [Object] To accurately detect the temperature of a magneto-optical recording medium without using a temperature sensor, and to set the recording light beam to an optimum recording power accurately. In a magneto-optical recording device for recording information by irradiating a magneto-optical recording medium with a light beam and applying a magnetic field, a signal of a predetermined frequency is applied to a predetermined recording area of the magneto-optical recording medium. First recording means for recording, second recording means for recording a new signal on the recorded information, and reflected light of the light beam irradiated on the recording medium at the same time as the recording of the information. Level detection means for reproducing the recorded information based on the original information and detecting the reproduced signal amplitude level of the old information component recorded by the first recording means in the obtained reproduced signal, and the detected amplitude level. A control means for detecting an information signal corresponding to the temperature of the recording medium and controlling the recording power of the recording light beam based on the obtained information signal corresponding to the temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording device for recording information by interaction between light and magnetism.

[0002]

2. Description of the Related Art FIG. 11 is a diagram showing a relationship between a laser power and a carrier-to-noise ratio C / N and a carrier-to-noise ratio C ₂ / N ₂ of a second harmonic when information is recorded on a magneto-optical disk. Is. The recording conditions at this time were 3.5 inches for a magneto-optical disk and 300 rpm.
The recording frequency is 0 rpm, the recording frequency is 4.8 MHz, the recording position is a radial position of 24 mm on the disk, and the temperature is room temperature. Figure 11
As is clear from the above, the carrier-to-noise ratio C / N does not change so much when the laser power is 4 mW or more, but the second harmonic C ₂ / N ₂ has a laser power of about 4.
It becomes the minimum value at 5 mW, and tends to increase both below and above it. Generally, the laser power at which the second harmonic has a minimum value is the optimum recording power,
It is said that information can be recorded with the fewest errors. Further, it is known that the optimum laser power depends on the temperature of the magneto-optical disk and has a proportional relationship with the disk temperature, as shown in FIG.

Therefore, in order to perform optimum recording, it is necessary to change the laser power according to the temperature of the magneto-optical disk. For that purpose, it is necessary to detect the temperature of the magneto-optical disk and control the laser power. Therefore, in general, a temperature sensor is provided in the magneto-optical recording / reproducing device,
Alternatively, a temperature sensor is directly attached to the disk cartridge to detect the temperature, and the laser power is controlled according to the result.

[0004]

However, in the prior art, when the temperature of the magneto-optical disk is detected, the temperature inside the apparatus or the temperature of the disk cartridge is detected, so that the magneto-optical disk is detected. It is difficult to say that the temperature of the laser is accurately detected, and it is difficult to accurately control the laser power to the optimum power. More specifically, when a temperature sensor is installed in the device, the ambient temperature inside the device is detected, so the temperature varies depending on the direction and movement amount of air in the device, and even within the device the temperature varies depending on the position. There is a difference. Therefore, it is extremely difficult to accurately detect the temperature of the magneto-optical disk. In particular, since the magneto-optical disk is attached to and detached from the device, if the magneto-optical disk is mounted on a device whose internal temperature has already risen, there is a large temperature difference between the temperature detected by the temperature sensor and the actual temperature of the magneto-optical disk. Will occur. Therefore, for a while after the mounting of the magneto-optical disk, the recording is performed with the laser power which is different from the optimum laser power, which may cause a recording error. Even when detecting the temperature of the disc cartridge, there is a temperature difference between the surface temperature of the cartridge and the temperature of the magneto-optical disc due to the difference in heat capacity and thermal conductivity between the disc and the cartridge. It was difficult to detect, and it was difficult to accurately control the laser power to the optimum power.

The present invention has been made to solve the above problems, and its purpose is to accurately detect the temperature of a magneto-optical recording medium without using a temperature sensor, and to accurately record a recording light beam. An object of the present invention is to provide a magneto-optical recording device that can be controlled to an optimum recording power.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magneto-optical recording device for recording information by irradiating a magneto-optical recording medium with a light beam and applying a magnetic field to the magneto-optical recording medium. A first recording means for recording a signal having a predetermined frequency in a predetermined recording area, a second recording means for recording a new signal on the recorded information, and at the same time as recording this information. To reproduce the recorded information based on the reflected light of the light beam applied to the recording medium and to detect the reproduced signal amplitude level of the old information component recorded by the first recording means in the obtained reproduced signal. And a level detecting means for detecting an information signal corresponding to the temperature of the recording medium from the detected amplitude level, and controlling the recording power of the recording light beam based on the information signal corresponding to the obtained temperature. for It is achieved by a magneto-optical recording apparatus characterized by comprising a control means.

Another object of the present invention is to write new information on top of old information in a magneto-optical recording apparatus for recording information by irradiating a magneto-optical recording medium with a light beam and applying a magnetic field. In this case, the level detection means for detecting the reproduction signal amplitude level of the old information component, and the recording light beam is changed by changing the recording light beam so that the amplitude level of the level detection means maintains a predetermined level. And a control means for controlling to an optimum recording power.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the magneto-optical recording apparatus of the present invention. In FIG. 1, reference numeral 1 denotes a magneto-optical disk having a thin film magneto-optical recording layer 2 as a magnetic layer formed on a transparent substrate. The center of the magneto-optical disk 1 is supported by the rotating shaft of the spindle motor 3 and is rotated at a constant speed by driving the spindle motor 3. An optical head 4 for irradiating the magneto-optical disk 1 with a recording / reproducing light beam and for detecting reflected light of the reproducing light beam to reproduce information is provided on the lower surface of the magneto-optical disk 1. There is. The optical head 4 includes a semiconductor laser 5 as a light source for recording and reproduction, a collimator lens 6 for collimating the divergent laser light flux thereof, and a polarization beam splitter 7 for separating an incident light flux and a reflected light flux on the magneto-optical disk 1. , An objective lens 8 for condensing a light beam to form a minute light spot on the recording layer 2, a sensor lens 9 for condensing reflected light from the magneto-optical recording layer 2, and a lens for collecting the light with the sensor lens 9. It is composed of an optical sensor 10 for detecting the emitted light.

An optical head 4 is provided on the upper surface of the magneto-optical disk 1.
A magnetic head 11 for generating a recording bias magnetic field is provided so as to face the magnetic head. The magnetic head 11 generates a magnetic field modulated according to an information signal to be recorded by driving the magnetic head drive circuit 12, and applies the magnetic field to the magneto-optical recording layer 2 of the magneto-optical disk 1. At the time of information recording, the optical head 4 irradiates the magneto-optical recording layer 2 with a light beam having a constant intensity, and a modulation magnetic field of the magnetic head 11 is applied to the irradiated portion to correspond to the information signal on the recording layer 2. Information pits of the magnetization direction are recorded. Reference numeral 13 is a reproduction signal amplifier circuit for photoelectrically converting and amplifying the detection signal of the optical sensor 10.
At the time of reproducing information, a reproducing light beam is emitted from the optical head 4 onto the magneto-optical recording layer 2, and the reflected light is detected by an optical sensor 10 in the optical head 4. The reproduction signal amplifier 13 photoelectrically converts and amplifies the detection signal of the optical sensor 10 to generate a reproduction signal. Reference numeral 14 is a filter circuit for detecting only a predetermined frequency component from the reproduction signal of the reproduction signal amplifier 13, and reference numeral 15 is a reproduction signal level detection circuit for detecting the amplitude level of the reproduction signal output from the filter circuit 14. Is. Reference numeral 16 denotes a control circuit for detecting the temperature of the magneto-optical disk 1 from the obtained amplitude level and controlling the laser power of the semiconductor laser 5 to the optimum recording power based on the result.

When detecting the temperature of the magneto-optical disk 1,
Two signals with different frequencies are applied to a predetermined area of the magneto-optical disk 1.
The temperature is indirectly detected from the amplitude level of the reproduction signal obtained by double recording and reproducing the same. The temperature detecting operation will be described later in detail. A semiconductor laser drive circuit 17 drives the semiconductor laser 5 based on an instruction from the control circuit 16. Although not shown in FIG. 1, the magneto-optical recording apparatus of the present embodiment has an autofocus control circuit for focusing a recording or reproducing optical spot on the magneto-optical recording layer 2 and those optical spots. There is provided an auto-tracking control circuit for scanning the track following the information track or a seek control circuit for seeking the optical head 4 to the target information track.

FIG. 2 shows the magneto-optical recording layer 2 of the magneto-optical disk 1.
FIG. 6 is a diagram showing changes in the magnetization state of the recording layer when a light beam and a magnetic field are applied to the recording layer. Here, the magneto-optical recording layer 2 is composed of two magnetic layers, a recording layer 20 and a reproducing layer 21, which are exchange-coupled to each other. As shown in FIG. 3, the recording layer 20 has a coercive force larger than that of the reproducing layer 21 at room temperature and a Curie temperature T _c1 lower than the Curie temperature T _c2 of the reproducing layer 21. When such a magneto-optical recording layer is irradiated with a light spot, the temperatures of both the recording layer 20 and the reproducing layer 21 rise, and the temperature distribution becomes as shown in FIG. As a result, the Curie temperature T _{c1 of the} recording layer 20 indicated by hatching in the figure
The magnetization disappears in the region beyond the above region, and the reproducing layer 21 facing the region where the magnetization disappears is oriented in the direction of the magnetic field of the magnetic head. Since the upward magnetic field is applied here, the magnetization of the reproducing layer 21 is oriented upward as shown in the figure. When the magneto-optical disk 1 rotates and the light spot passes by, the recording layer 21 is cooled and the magnetization of the reproducing layer 21 is transferred. In this way, the old information on the recording layer is erased, and at the same time, new magnetization corresponding to the information signal is recorded as an information pit on the recording layer. In this case, since the Curie temperature T _c2 of the reproducing layer 21 is higher than the temperature rise due to the irradiation of the recording light beam, even if the recording light beam is irradiated, the reproduction signal can be obtained from the reflected light. This area is shown as D in FIG. However, in the area E where the temperature of the recording area 20 is the Curie temperature T _c1 or less and the light spot is irradiated, the old information in the recording layer 21 is not erased, and the reproducing layer 2 is exchange-coupled.
From this area E of 1, the old information component is reproduced.

Next, the specific operation of this embodiment will be described with reference to FIG. First, when the magneto-optical disk 1 is mounted on the device, the control circuit 16 controls each part to record a signal of a constant frequency in a predetermined recording area of the magneto-optical disk 1.
For example, a 3.5-inch magneto-optical disk 1 is used and rotated at 2400 rpm, and a signal with a frequency of 1.5 MHz is recorded at a position with a radius of 24 mm. At this time, the control circuit 16 outputs a control signal to the semiconductor laser drive circuit 17 to set the laser power of the semiconductor laser 5 to a predetermined recording power. Further, the control circuit 16 outputs a 1.5 MHz drive signal to the magnetic head drive circuit 12 to drive the magnetic head 11 at 1.5 MHz. As a result, the information track is irradiated with a light beam having a constant intensity, and at the same time, a modulation magnetic field of 1.5 MHz is applied as shown by 18 in FIG. Reference numerals 22 and 23 shown in FIG. 4 are information pits thus recorded. The information pits 22 have upward magnetization because the magnetic field has a positive polarity, and the information pits 23 have downward magnetization because they have a negative polarity. The length of the information pits 22 and 23 is about 2 because the frequency is 1.5 MHz.
μm. Since the information pit is recorded by the magnetic field modulation method, it has an arrow blade shape as shown in the figure. It should be noted that it is desirable to predetermine the area in which the above recording is performed, such as an area that is not used for recording information.

When the above signal recording is completed, the control circuit 1
6 controls to overwrite a new signal on the recorded information pit. Here, the recording frequency is 3
MHz and the laser power is left unchanged. Therefore,
The control circuit 16 outputs a drive signal of 3 MHz to the magnetic head drive circuit 12, and outputs a control signal to the semiconductor laser drive circuit 17 to drive the semiconductor laser 5 with the same optical power as the previous time. As a result, the light beam spot 24 having a constant intensity is scanned in the direction of the arrow on the information track as shown in FIG. 4, and the 3 MHz modulation magnetic field indicated by 19 is applied. The light is written. Reference numerals 28 and 29 are information pits just recorded in this way, and since the recording frequency is 3 MHz, each has a pit length of about 1 μm. Also, information pit 28
Is the downward magnetization, and the information pit 29 is the upward magnetization, and the downward and upward magnetization information pits are alternately recorded.
In this case, the region 26 in which the recording layer 20 is raised to the Curie temperature T _c1 or higher by the irradiation of the light beam spot 24 is shown. At this time, the average temperature of the magneto-optical disk 1 before the irradiation of the light beam spot 24 is set to 30
℃.

On the other hand, the reflected light of the light beam spot 24 is detected by the optical sensor 10 in the optical head 4, and the detection signal is photoelectrically converted and amplified by the reproduction signal amplifier 13, so that the recorded information is recorded at the same time as the overwrite. Is played. Here, in FIG. 4, the reflected light of the light beam spot 24 is detected by the optical sensor 10. However, in the area 26 within the spot 24, the temperature of the recording layer 20 becomes _{equal to} or higher than the Curie temperature T _{c1 as described} above. Because it is rising, 1.
The old information component of 5MHz is erased and the new information of 3MH
The z signal is recorded. Also, the light beam spot 2
The crescent-shaped region other than the region 26 in 4 is below the Curie temperature, so that the 1.5-MHz signal component of the old information remains. Therefore, the components of the old information and the new information are mixedly contained in the obtained reproduced signal.

FIG. 5A is a signal waveform of the reproduced signal thus obtained, and FIG. 5B is a diagram showing the spectrum distribution of the reproduced signal. Since the reproduced signal contains the components of the old information and the new information as described above, it has a signal waveform as shown in the figure. Also, the small peaks shown in the spectral distribution are the 1.5 MHz components of the old information, and the large peaks are the 3 MHz of the new information.
The signal component of 1.5 MHz, which is the component of z and is the old information component, is slightly included. The reproduction signal reproduced by the reproduction signal amplifier 13 is output to the filter circuit 14, and only the old information component is extracted. That is, the filter circuit 14 is composed of a bandpass filter centering on 1.5 MHz as shown in FIG.
The Hz signal component is cut, and only the 1.5 MHz signal component of the old information is output to the reproduction signal level detection circuit 15 in the next stage. FIG. 5C shows the signal waveform of the 1.5 MHz component extracted by the filter circuit 14. Filter circuit 14
The amplitude level of the output signal is detected by the reproduction signal level detection circuit 15 and is sent to the control circuit 16. In FIG. 5C, the amplitude level is b.

Next, a reproduction signal when the average temperature of the magneto-optical disk 1 before the light beam spot irradiation is 0 ° C. and 60 ° C. will be described. First, the reproduced signal at 60 ° C. will be described. When the disk temperature becomes high and the recording laser power is the same, the temperature of the recording layer 20 becomes higher than that at the temperature of 30 ° C., and the Curie temperature T is naturally increased.
The temperature range above _c1 also becomes wider. In FIG. 4, the region above the Curie temperature at 60 ° C. is indicated by 27. In this case, the ratio of the old information remaining area in the light beam spot 24 becomes small as shown in FIG. 4, and the old information component contained in the reproduction signal also becomes small. FIG. 7A is a signal waveform of a reproduction signal when the disc temperature is 60 ° C., and FIG. 7B is a diagram showing its spectrum distribution. Further, FIG. 7C shows an output signal of the filter circuit 14, and as described above, the amplitude level c becomes smaller as the remaining area of the old information in the light beam spot 24 becomes narrower. This amplitude level is detected by the level detection circuit 15 and sent to the control circuit 16.

On the other hand, when the disk temperature is 0 ° C., the temperature range above the Curie temperature T _c1 of the recording layer 20 is narrowed contrary to the above. In FIG. 4, the region above the Curie temperature at this time is shown by 25. Therefore, in this case, the ratio of the remaining area of the old information component in the light beam spot 24 becomes large, and the component of the old information included in the reproduction signal also becomes large. FIG. 8A shows a reproduced signal at this time, and FIG.
8B shows the spectrum distribution, and FIG. 8C shows the output signal of the filter circuit 14. The amplitude level a of the output signal of the filter circuit 14 is larger than that when the disk temperature is 30 ° C., because the remaining area of the old information component is wide as described above. This amplitude level is detected by the reproduction signal level detection circuit 15 and sent to the control circuit 16.

As described above, the amplitude level of the output signal of the filter circuit 14 changes according to the temperature of the magneto-optical disk 1, and there is a temperature dependence that the amplitude level decreases as the disk temperature increases. FIG. 9 is a diagram showing the correlation between the disk temperature and the amplitude level. Here, the change in the amplitude level with respect to temperature when the recording laser power is 6 mW and the linear velocity of the magneto-optical disk 1 is 7.5 m / s is shown. Note that a, b, and c shown in FIG. 9 are output amplitude levels of the filter circuit 14 when the disk temperature is 0 ° C., 30 ° C., and 60 ° C., as described above. From the above, if the amplitude level of the output signal of the filter circuit 14 is measured,
The actual temperature of the magneto-optical disk 1 can be accurately detected, and the laser power of the semiconductor laser 5 can be controlled to the optimum recording power based on the detected temperature obtained.

A memory is provided inside the control circuit 16, and a conversion table for converting the amplitude level into the disk temperature from the correlation shown in FIG. 9 is provided in the memory, as shown in FIG. A conversion table is provided for converting the disc temperature into the optimum laser power based on the relationship between the temperature and the laser power. As described above, the control circuit 16 has two conversion tables, and first converts the amplitude level obtained by the reproduction signal level detection circuit 15 into a disk temperature by the conversion table. Then, the control circuit 1
Reference numeral 6 converts the obtained disk temperature into an optimum laser power using a conversion table. Then, the control circuit 16 outputs a laser power setting signal for driving the semiconductor laser driving circuit 17 with the optimum power to set the laser power of the semiconductor laser 5 to the optimum power. As described above, a series of laser power adjustment processing after the magneto-optical disk 1 is mounted is completed, and information can be recorded.

As described above, in this embodiment, the temperature of the magneto-optical disk is detected by utilizing the fact that the ratio of the remaining area of the old information in the light beam spot changes depending on the temperature. As described above, the temperature of the magneto-optical disk can be accurately detected without using a temperature sensor and in a non-contact manner. Therefore, since the detected temperature is accurate, it is possible to accurately set the laser power of the semiconductor laser to the optimum power, which allows information recording with a low error rate. Although the above laser power adjustment is performed when the magneto-optical disk is mounted, it is desirable to perform readjustment at any time thereafter, for example, at regular time intervals. In addition, the first recording frequency is 1.5 MHz and the second recording frequency is 3M.
However, the frequency is not limited to this. Further, although the recording frequencies of the first time and the second time may be the same, if the phase is the same, the old information component cannot be reproduced, and therefore, it is necessary to shift the phase at this time.

Next, another embodiment of the present invention will be described. First, a magneto-optical recording apparatus of a magnetic field modulation recording system using a usual magneto-optical disk having one magnetic layer instead of a magneto-optical disk having two magnetic layers will be described as a second embodiment. In the second embodiment, first, a predetermined area of the magneto-optical disk is erased, and a signal of, for example, 1.5 MHz is recorded from above. When erasing, a light beam for erasing is applied while applying a magnetic field in a fixed direction. Then, the previously recorded area is irradiated again with the erasing magnetic field and the light beam, and at the same time as the erasing, reproduction is performed based on the reflected light of the light beam to detect the amplitude level of the reproduction signal. The amplitude level obtained here becomes the amplitude level of the reproduction signal of the old information component, as in the above embodiment. Therefore, the disk temperature can be detected from the obtained amplitude level, and the laser power can be set to the optimum power based on this temperature. In this embodiment, when a signal is erased, the magnetization disappears in the region where the temperature of the recording layer exceeds the Curie temperature, and the erasing signal component (DC component) does not appear, so a filter circuit is not necessary. .

As a third embodiment, an example of a magneto-optical recording apparatus for recording information by an optical modulation method using a magneto-optical disk having two magnetic layers as described above will be described. In this embodiment, first, an erasing light beam and a magnetic field are applied to a predetermined area of the magneto-optical disk to perform erasing, and then a signal having a frequency of 1.5 MHz, for example, is recorded in the erased area. When recording a signal, of course, the recording is performed by an optical modulation method in which a light beam whose intensity is modulated according to an information signal is emitted while applying a magnetic field in a fixed direction for recording. Next, the erasing magnetic field and the light beam are applied again to the area just recorded, and at the same time as the erasing, a signal is reproduced based on the reflected light of the light beam to detect the amplitude level of the reproduced signal. The obtained amplitude level is likewise the amplitude level of the old information component.
Therefore, the disk temperature can be detected from this amplitude level,
Moreover, the optimum laser power can be set based on this temperature. It should be noted that no filter circuit is required in this embodiment either.

As a fourth embodiment, an example of an optical modulation type magneto-optical recording apparatus using a magneto-optical disk having one magnetic layer will be given. In this embodiment, erasing, recording and erasing are performed in the same manner as in the second and third embodiments, and at the same time as this erasing, the signal is reproduced and the amplitude level is detected. Therefore, the disk temperature can be detected from the obtained amplitude level, and the optimum laser power can be set based on this temperature.

Next, a fifth embodiment of the present invention will be described. When the number of rotations of the magneto-optical disk is constant, the disk linear velocity varies depending on the recording radial position, and the optimum recording power also varies depending on the recording radial position. FIG. 10 shows the relationship between the disk linear velocity and the optimum laser power. In this case, according to an experiment conducted by the inventor of the present application, when the information was recorded by changing the optimum laser power according to the disk linear velocity as shown in FIG. 10, the reproduction signal amplitude level of the old information was almost constant. I was able to confirm that there is. This means that at the time of optimum recording, the ratio of the remaining area of the old information component in the light beam spot 24 is always constant regardless of the disc linear velocity. In this case, the optimum laser power depends on the disc temperature and the disc linear velocity as described above. Therefore, in this embodiment, the laser power is controlled so that the amplitude level of the reproduction signal of the old information is always constant regardless of the disc temperature and the disc linear velocity. Specifically, the control circuit 16 shown in FIG. 1 monitors the reproduction signal amplitude level of the old information obtained by the reproduction signal level detection circuit 15, and the amplitude level is, for example, c (disk temperature of 30 ° C. in FIG. 10). The semiconductor laser drive circuit 17 is controlled so that the amplitude level at the time is set. As a result, the laser power of the semiconductor laser 5 can always be controlled to the optimum laser power, and information can be recorded with the optimum laser power regardless of the disk temperature and the disk linear velocity.

[0025]

As described above, according to the present invention, the temperature of the magneto-optical recording medium can be accurately detected without using a temperature sensor and in a non-contact manner. Therefore,
The recording laser power can be accurately set to the optimum recording power,
There is an effect that information can be recorded at a low error rate.
Further, when the new information is overwritten on the old information, by controlling the recording light beam so that the amplitude level of the old information component becomes a predetermined level, the recording medium temperature and the recording radius position of the recording medium are adjusted. Regardless of this, the recording light beam can always be controlled to the optimum recording power.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a magneto-optical recording apparatus of the present invention.

FIG. 2 is a diagram showing a principle of information recording of a magneto-optical disk used in the embodiment of FIG.

FIG. 3 is a characteristic diagram showing a relationship between temperature and coercive force of a recording layer and a reproducing layer of the magneto-optical disk.

FIG. 4 is a diagram showing a state in which an old information remaining area in a light beam spot changes according to a disc temperature when new information is overwritten on old information on an information track.

FIG. 5 is a diagram showing a reproduction signal at a disk temperature of 30 ° C., a spectrum distribution, and a reproduction signal of an old information component extracted by a filter circuit.

6 is a diagram showing frequency characteristics of the filter circuit of the embodiment of FIG.

FIG. 7 is a diagram showing a reproduction signal at a disk temperature of 60 ° C., a spectrum distribution, and a reproduction signal of an old information component extracted by a filter circuit.

FIG. 8 is a diagram showing a reproduction signal at a disk temperature of 0 ° C., a spectrum distribution, and a reproduction signal of an old information component extracted by a filter circuit.

FIG. 9 is a diagram showing the relationship between the disc temperature and the reproduction signal amplitude level of the old information component.

FIG. 10 is a diagram showing the relationship between the disc linear velocity, the optimum laser power, and the reproduction signal amplitude level of old information.

FIG. 11: Laser power and carrier-to-noise ratio and second
It is the figure which respectively showed the relationship of the carrier to noise ratio of a harmonic.

FIG. 12 is a diagram showing the relationship between the disk temperature and the optimum laser power.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 magneto-optical disk 4 optical head 5 semiconductor laser 10 optical sensor 11 magnetic head 12 magnetic head drive circuit 13 reproduction signal amplifier 14 filter circuit 15 reproduction signal level detection circuit 16 control circuit 17 semiconductor laser drive circuit 20 recording layer 21 reproduction layer

Claims (3)

[Claims] 1. In a magneto-optical recording apparatus for recording information by irradiating a magneto-optical recording medium with a light beam and applying a magnetic field, a predetermined recording area of the magneto-optical recording medium has a predetermined frequency. First recording means for recording a signal, second recording means for recording a new signal on the recorded information, and reflection of a light beam applied to a recording medium at the same time as recording this information Level detection means for reproducing the recorded information based on light and detecting the reproduced signal amplitude level of the old information component recorded by the first recording means in the obtained reproduced signal, and the detected level. Detecting an information signal corresponding to the temperature of the recording medium from the amplitude level,
And a control means for controlling the recording power of the recording light beam based on the obtained information signal corresponding to the temperature. 2. The second recording means applies a DC signal by applying a signal having a frequency different from the recording frequency of the first recording means, a signal having the same frequency but a different phase, or an erasing magnetic field and a light beam. The magneto-optical recording apparatus according to claim 1, wherein the recording is performed. 3. In a magneto-optical recording device for recording information by irradiating a magneto-optical recording medium with a light beam and applying a magnetic field, when old information is overwritten with new information, old information is overwritten. Level detection means for detecting the reproduction signal amplitude level of the component, and the recording light beam is varied to control the recording light beam to the optimum recording power so that the amplitude level of the level detection means maintains a predetermined level. And a control unit for controlling the magneto-optical recording device.