JPH05250752A - Magneto-optical recorder/reproducer - Google Patents

Abstract

PURPOSE:To set recording light power accurately at an optimal level by detecting temperature distribution at a light beam irradiating part of a magneto- optical recording medium indirectly and then setting a recording light power based on detection result. CONSTITUTION:Predetermined recording test area on a magneto-optical disc 1 is brought into erased state and an LD driver 18 is commanded to record a pit row in predetermined pattern with recording laser power. The recording light beam is reflected on a magnetic layer 3 and introduced to a reproducing optical system where it is detected through photosensors 13a, 13b. Thus detected signals are then subjected to differential detection through a differential amplifier 14 and reproduced as a magneto-optical signal while optical bits recorded for the purpose of test are reproduced simultaneously with recording. Thus obtained magneto-optical signal is then fed to a signal processing circuit 15 where the amplitude of signal is detected. A controller 17 takes in thus detected value and controls the LD driver 18 to vary the recording laser power in step thus detecting each magneto-optical signal with its laser power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field modulation type magneto-optical recording / reproducing apparatus for recording information by irradiating a light beam and applying a modulation magnetic field.

[0002]

2. Description of the Related Art FIG. 7 is a schematic block diagram showing a laser power control device for a semiconductor laser used in a magnetic field modulation type information recording device. In the figure, reference numeral 32 is a semiconductor laser unit in which a semiconductor laser 32a that emits a light beam by laser oscillation and a photosensor 32b provided in the vicinity thereof for detecting the amount of laser light are integrated. Further, 33 is a current-voltage conversion circuit (IV conversion circuit) for converting the photocurrent of the photosensor 32b into a voltage signal, and 34 is a temperature sensor provided near the optical head in the apparatus. Further, 35 is the output of the IV converter 33,
This is a controller that controls the LD driver 36 by calculating the laser power from the output of the temperature sensor 34, the disk rotation speed obtained as system information, and its radial position.

In the above laser power control device, when setting the recording laser power, first, the semiconductor laser 32a is driven by a predetermined first drive current designated by the controller 35 in the recording laser power area (APC area).
At this time, the light amount of the semiconductor laser 32a is determined by the photo sensor 3
It is monitored by 2b and converted into a voltage signal by the IV converter 33. The controller 35 calculates the output laser power from the relationship between the laser power output input in advance and the monitor output from the photo sensor 32b. Next, the controller 35 instructs the LD driver 36 to drive the semiconductor laser 32a with a predetermined second drive current, and determines the output laser power from the monitor output by the photosensor 32b obtained at this time and the value input in advance. calculate. The controller 35 obtains the correlation between the driving current of the semiconductor laser 32a and the laser power from the relation between the output laser power thus obtained and the two driving currents, and determines the driving current for outputting the desired laser power from this relation. To control the LD driver 36. Here, the desired laser power is the optimum laser power of the magneto-optical recording medium under these environments, which is determined by the rotational speed of the magneto-optical disk, the linear velocity determined by the radial position, and the ambient temperature inside the device. ..

[0004]

However, in the conventional laser power control device, when the recording laser power of the magneto-optical recording medium is set, the sensitivity varies between the recording media and the accuracy of the thermistor used as a temperature sensor. It is difficult to accurately set the recording laser power to the optimum value because there is a limit to the accuracy of measuring the ambient temperature in the device by the method. In addition, since the temperature characteristics of the photosensor that monitors the light intensity of the semiconductor laser and the reduction of the laser power output on the surface of the magneto-optical recording medium due to the dirt of the lens group of the optical system, etc. The accuracy was lowered, and it was difficult to accurately control the laser power to a desired power.

The present invention has been made to solve such a problem, and its purpose is to accurately set the power of the light beam to the optimum value regardless of factors such as sensitivity variations among recording media. An object of the present invention is to provide a magneto-optical recording / reproducing device that can be used.

[0006]

It is an object of the present invention to exchange-couple with a first magnetic layer and the first magnetic layer, and
Of the second magnetic layer, which has a higher coercive force and a lower Curie temperature than that of the magnetic layer of FIG. In a magneto-optical recording / reproducing apparatus for recording information by applying a voltage, means for erasing a predetermined area of the recording medium to record pits of a predetermined test pattern, and at the same time as the recording of the test pattern And means for detecting the amplitude of the magneto-optical signal reproduced from the reflected light of the recording optical beam, and the power of the light beam is adjusted so that the detected magneto-optical signal amplitude value is within a predetermined level. This is achieved by a magneto-optical recording / reproducing device characterized by controlling.

Another object of the present invention is to record information by applying a magnetic field modulated according to recorded information while irradiating a magneto-optical recording medium with a light beam having a constant intensity. A means for recording pits of a predetermined pattern in a predetermined area of the magneto-optical recording medium, and scanning with a recording light beam while applying a magnetic field in a predetermined direction onto the pits of the predetermined pattern, and Means for detecting the amplitude of the magneto-optical signal of information, and controlling the power of the light beam so that the detected signal amplitude value falls within a predetermined level. To be achieved.

[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 a magneto-optical recording / reproducing apparatus of the present invention. In FIG. 1, 1
Is a magneto-optical disk which is an information recording medium,
It rotates at a constant speed by driving a spindle motor (not shown). In the magneto-optical disk 1, a magnetic layer 3 is formed on a transparent substrate 2 such as glass or plastic, and a protective film 4 is further formed on the surface thereof. The magnetic layer 3 is composed of two magnetic layers, the structure and characteristics of which will be described later in detail. Reference numerals 5 to 12 are individual parts of an optical head for irradiating the magneto-optical disk 1 with laser light and obtaining information from reflected light. Specifically, 5 is an actuator, 6 is a semiconductor laser, 7 is a condenser lens, 8 is a beam shaping lens, 9 is a beam splitter, 10 is a λ / 2 plate, and 1 is a 1
Reference numeral 1 is a polarization beam splitter, and 13a and 13b are photosensors. The laser light emitted from the semiconductor laser 6 is applied to the magneto-optical disk 1 via the beam shaping lens 8, the beam splitter 9, and the condenser lens 7. At this time, the condenser lens 7 is controlled by the actuator 5 so as to move in the focusing direction and the tracking direction so that the laser light is focused on the magnetic layer 3. Further, the laser light is subjected to tracking control so as to scan along the guide groove formed on the magneto-optical disk 1.

On the other hand, the laser beam reflected by the magneto-optical disk 1 has its optical path changed by the beam splitter 9 toward the polarization beam splitter 11, and enters the λ / 2 plate 10 and the polarization beam splitter 11. The polarized beam splitter 11 collects the light on the sensor 13a or 13b by the lens 12 depending on the direction of magnetization on the magnetic layer. The outputs of the respective sensors 13a and 13b are differentially amplified by the differential amplifier 14 to generate a magneto-optical signal. Reference numeral 15 denotes a signal processing circuit which operates when the recording laser power is irradiated, and is a circuit for detecting the signal amplitude of the magneto-optical signal reproduced by the recording laser power. Controller 17
Controls the LD driver 18 for driving the semiconductor laser 6 with the output of the temperature sensor 16, the output of the signal processing circuit 15, the rotational speed of the magneto-optical disk 1 and its recording radial position as input information. Reference numeral 19 is a magneto-optical disk 1 at the time of recording operation.
Is a floating magnetic head for applying a modulation magnetic field to the laser irradiation part of the laser beam, and the condensing lens 7 sandwiches the magneto-optical disk 1.
It is arranged to face. The floating magnetic head 19 generates a magnetic field having different polarities in response to a recording signal by a magnetic field modulation driver 20. In addition, the flying magnetic head 19
Moves in the radial direction of the magneto-optical disk 1 in conjunction with the optical head, and information is recorded by sequentially applying a magnetic field to the laser irradiation portion of the magnetic layer 3 during recording.

FIG. 2 is a sectional view showing the structure of the magneto-optical disk 1 in detail. The magnetic layer 3 is composed of two layers, a recording layer 3a and a reproducing layer 3b exchange-coupled to the recording layer 3a. The characteristics of the recording layer 3a and the reproducing layer 3b are as shown in FIG.
a has a higher coercive force at room temperature than the reproducing layer 3b, and the reproducing layer 3b has a higher Curie temperature than the recording layer 3a. That is, the recording layer 3a has a high coercive force and a low Curie temperature, and the reproducing layer 3b has a low coercive force and a high Curie temperature.

FIG. 4 is a diagram showing the laser beam spot on the magnetic layer 3 during the recording operation and the temperature distribution increased by the irradiation of this spot. In addition, in FIG.
Is a guide groove for tracking control, 22
Is an information track (land) for recording information pits provided therebetween. The laser beam spot is assumed to be traveling in the direction of the arrow in the figure. When the recording laser beam spot 23 is irradiated onto the land as shown in FIG. 4, the recording layer 3a of the magnetic layer 3 first reaches the Curie temperature. On the other hand, the reproducing layer 3b does not reach the Curie temperature and retains the magnetized state, but since it has a small coercive force, it is oriented in the direction of the external magnetic field applied from the levitation magnetic head 19. In this case, since it takes a certain amount of time for the temperature of the magnetic layer 3 to rise, the temperature region of the recording layer 3a which has reached the Curie point is displaced to the rear position with respect to the laser beam spot. Therefore, a region below the Curie point and a region above the Curie point coexist in the laser beam spot, so when an attempt is made to obtain a reproduced signal from the reflected light of this beam spot, the reproduced magneto-optical signal does not overlap. Old information before writing and new information currently recorded are mixed.

If the magnetization of the magnetic layer 3 is set in one direction before recording, the signal component detected as old information is DC.
Since it is only a component, only new information due to the magnetization of the reproducing layer 3b recorded by the currently applied external magnetic field appears as a component of the magneto-optical signal and can be detected as a new recording signal. Further, when the recording laser power changes, the Curie point reaching temperature region changes as shown by a, b, and c in FIG. 4, and further, the change of the reflected light amount due to the change of the recording laser power and the magneto-optical effect Along with the change, the amplitude of the magneto-optical signal due to the new recording signal changes as shown in FIG. Therefore, the width of the Curie point reaching temperature region on the magnetic layer 3 can be detected indirectly by detecting the amplitude of the magneto-optical signal by the new recording signal, and this is used for recording. The laser power can be determined. In this case, the information obtained from the amplitude of the magneto-optical signal is the sensitivity variation between the magneto-optical recording media,
Information that can be obtained directly from the media in a form that includes all information such as the ambient temperature in the device, the reduction of laser power due to dirt on the condenser lens, the rotational speed of the magneto-optical disk, the linear velocity determined by the radial position, etc. Therefore, the recording laser power can be set after absorbing all the influences. Therefore, for example, as shown in FIG. 5, in the relationship between the recording laser power and the jitter when the data recorded with the power is reproduced by the reproducing laser power, the recording laser power that gives the best jitter characteristics is considered as the optimum recording power P _0. By controlling the recording laser power so that the magneto-optical signal amplitude becomes the optimum magneto-optical signal amplitude V ₀ during recording at the optimum recording power P ₀ , it is possible to set the laser power with higher accuracy.

Therefore, based on the above concept,
The operation of this embodiment will be described. First, the controller 17 sets the recording laser power based on the ambient temperature in the apparatus detected by the temperature sensor 16 and the linear velocity determined by the rotational speed and the radial position of the magneto-optical disk 1 sent from the main controller (not shown). Determine the initial value of. In addition, a predetermined recording test area of the magneto-optical disk 1 is set in the erased state, and the LD driver 18 is instructed to record the recording pit row of the predetermined pattern with the recording laser power determined as described above. At this time, the reproducing layer 3b of the magnetic layer 3 does not reach the Curie point temperature and has magnetization, but the coercive force of the reproducing layer 3b is sufficiently inverted by the modulation magnetic field strength, so that the magnetization is changed according to the modulation magnetic field. Are aligned, and a recording pit string having a predetermined pattern is recorded on the information track in the recording test area.
At the same time, this recording light beam is reflected by the magnetic layer 3 and guided to the reproducing optical system, and is detected by the photosensors 13a and 13b. Then, these detection signals are differentially detected by the differential amplifier 14 and reproduced as magneto-optical signals, and the pits recorded for testing are reproduced simultaneously with recording. The obtained magneto-optical signal is sent to the signal processing circuit 15, and the signal amplitude is detected. The controller 17 fetches the detected value and controls the LD driver 18 to change the recording laser power stepwise, and detects the amplitude of the magneto-optical signal with each laser power. The controller 17 changes the recording laser power in this way to detect the magneto-optical signal amplitude, finds the recording laser power P ₀ at which the signal amplitude becomes V ₀ as shown in FIG. The output power of the laser 6 is set as the optimum laser power. As described above, the laser power can be set with higher accuracy. The laser power setting is
It may be performed before recording the information, or may be determined arbitrarily such as periodically.

Next, another embodiment of the present invention will be described. In the above-mentioned embodiment, the recording laser power is set by detecting the amplitude of the magneto-optical signal. In this embodiment, the old information is read as a crosstalk magneto-optical signal and the recording laser power is set based on the level. .. In this embodiment, the magneto-optical disk is not a two-layered magneto-optical disk but an ordinary one-layered magneto-optical disk. As shown in FIG. 4, in the laser beam spot 23, there is a region which has not reached the Curie temperature represented by the diagonal line,
In this area, there is an old recording pit before overwriting. Therefore, it is possible to read the old information as a crosstalk magneto-optical signal from the reflected light of the laser beam spot 23. Further, when the recording laser power changes, the width of the Curie point temperature reaching region changes, and further, the change in the reflected light amount accompanying the change in the recording laser power changes the amplitude of the crosstalk magneto-optical signal as shown in FIG. Change. Therefore, by detecting the amplitude of this crosstalk magneto-optical signal, it is possible to indirectly detect the width of the region where the Curie point temperature reaches on the magnetic layer 3. In this case, since the information obtained from the crosstalk magneto-optical signal is information including all the fluctuation factors as described above, it is possible to set the recording laser power after absorbing all the influences thereof. Therefore, for example, as shown in FIG. 6, in the relationship between the recording laser power and the jitter characteristic when the data recorded by the recording laser power is reproduced by the reproducing laser power, the recording laser power that gives the best jitter characteristic is the optimum recording power P ₀ . Considering this, by controlling the recording laser power so that the crosstalk magneto-optical signal amplitude at this time becomes V ₀ , it is possible to set the laser power with higher accuracy.

In this embodiment, the controller 17 first determines the initial value for setting the recording laser power according to the ambient temperature in the apparatus and the linear velocity of the magneto-optical disk 1 as in the above embodiments. Next, the controller 17 controls the LD driver 18 to set a pit string of recording pits having a length equal to or more than the shaded portion shown in FIG. 4 in a predetermined recording test area of the magneto-optical disk 1 with the laser power of the initial value. Record with. Of course, at the time of recording, a pit for test is recorded by applying a modulation magnetic field while irradiating a recording light beam. Next, the recorded pit row is scanned with the recording laser power, the obtained magneto-optical signal due to crosstalk is processed by the signal processing circuit 15, and the signal amplitude is detected. At this time, in order to stabilize the direction of magnetization in the vicinity of the Curie point temperature reaching region of the magnetic layer 3, a recording magnetic field in a fixed direction is applied from the flying magnetic head 19 to erase the test recording pits and a crosstalk magneto-optical signal. Read out. The controller 17 controls the LD driver 18 to change the recording laser power and repeat the signal amplitude detection operation as in the above-described embodiment. Then, the output of the semiconductor laser 6 is finally set to the optimum recording laser power P _{0 at} which the amplitude of the crosstalk magneto-optical signal shown in FIG. 6 becomes V ₀ . As described above, the laser power can be set with higher accuracy as in the embodiment of FIG. The laser power may be set before the recording operation, or may be set arbitrarily such as periodically.

[0016]

As described above, the present invention indirectly detects the temperature distribution of the light beam irradiation portion of the magneto-optical recording medium,
By setting the recording light power based on the detection result, it will not be affected by variations in sensitivity between magneto-optical recording media, variations in measured value of ambient temperature, etc. The effect is that it can be set.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing a layer structure of a magneto-optical disk used in the embodiment of FIG.

FIG. 3 is a diagram showing characteristics of a recording layer and a reproducing layer of the magneto-optical disk.

FIG. 4 is a diagram showing a positional relationship between a light beam spot applied to a magneto-optical disk and a Curie temperature reaching region due to the spot irradiation.

FIG. 5 is a diagram showing the relationship between the recording laser power, the magneto-optical signal amplitude during recording, and the magneto-optical signal jitter during reproduction.

FIG. 6 is a diagram showing the relationship between the recording laser power, the amplitude of the old data signal during recording, and the magneto-optical signal jitter during reproduction.

FIG. 7 is a schematic block diagram showing a conventional laser power control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 3 Magnetic layer 6 Semiconductor lasers 13a, 13b Photo sensor 15 Signal processing circuit 16 Temperature sensor 17 Controller 18 LD driver 19 Flying magnetic head

Claims (2)

[Claims] 1. A first magnetic layer, which is exchange-coupled to the first magnetic layer and has a high coercive force as compared with the first magnetic layer,
Light for recording information by applying a magnetic field modulated according to recorded information to a magneto-optical recording medium formed by laminating a second magnetic layer having a low Curie temperature while irradiating a light beam having a constant intensity. In a magnetic recording / reproducing apparatus, means for erasing a predetermined area of the recording medium to record a pit of a predetermined test pattern, and at the same time as this recording, reproduction from reflected light of a recording light beam at the time of recording the test pattern. And means for detecting the amplitude of the magneto-optical signal, and controlling the power of the light beam so that the detected magneto-optical signal amplitude value is within a predetermined level. apparatus. 2. A magneto-optical recording / reproducing apparatus for recording information by applying a magnetic field modulated according to recorded information while irradiating a magneto-optical recording medium with a light beam having a constant intensity. Means for recording pits of a predetermined pattern in a predetermined area of the medium, and a magneto-optical signal amplitude of old information due to crosstalk by scanning the pits of the predetermined pattern with a recording light beam while applying a magnetic field in a constant direction. And a means for detecting, and controlling the power of the light beam so that the detected signal amplitude value falls within a predetermined level.