JPH03152748A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To always appropriately control laser power against a variation of optimum recording power of a medium due to a temp. change and to improve an error rate by disposing a temp. sensor inside or in the vicinity of a bias magnetic field generating device close to a recording layer. CONSTITUTION:The temp. sensor 13 is provided inside or in the vicinity of the bias magnetic field generating device 12 to be driven by a driver 11, monitoring temp. in the vicinity of the recording layer of a magneto-optical disk 1. An output signal of this temp. sensor 13 is inputted via a sensor processing circuit 14 to a laser power controller 7 and a CPU 15. The optimum laser power is obtained by the laser power controller 7 based on output signals of a monitor diode 6, the CPU 15 and the sensor processing circuit 14, and a laser driver 8 is driven in accordance with this value. By this method, the optimum control on the laser power can be preformed by correcting a variation of the optimum recording power in response to the temp. of a recording medium, and the recording medium and the device itself can be protected by stopping a recording/erasing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording/reproducing device that records, reproduces, or erases information on an optical recording medium using magneto-optical effect.

[Conventional technology]

As an optical information recording/reproducing device using magneto-optical effect,
As optical recording media, there are known ones that use disk-shaped magneto-optical disks and those that use card-type optical cards. Information recording will be described below using an optical disc as an example.

A magneto-optical disk has a substrate formed thereon with a magnetic thin film having an axis of easy magnetization perpendicular to the film surface, and information is recorded by changing the magnetization direction of this magnetic thin film.

For this recording, two methods are generally known: a method of recording by modulating a laser beam, and a method of recording by modulating a bias magnetic field. To explain the method for recording by modulating laser light, first, for initialization, a laser diode emits a direct current laser beam and irradiates it onto the recording medium, and the temperature of the area irradiated with the laser beam is changed to Curie. Raise it to near the point and keep it in a state where the holding force is reduced.
In this state, by applying a bias magnetic field in a predetermined direction, the magnetization direction of the magnetic thin film is aligned in one direction in advance. Next, for recording, the recording medium is irradiated with a laser beam that is digitally modulated according to the information signal while applying a bias magnetic field in a direction opposite to the magnetization direction. As a result, the temperature of the part irradiated with the laser beam rises to near the Curie point, the coercive force decreases, and the bias magnetic field causes the part to be magnetized in the opposite direction to the surroundings, causing the part to respond to the information. A magnetized pattern is formed.

On the other hand, the method of recording by modulating the bias magnetic field is to emit direct current laser light from a laser diode and irradiate it onto the recording medium. , a magnetization pattern corresponding to information is formed by applying a bias magnetic field that is digitally modulated according to the information signal. The information recorded in this way can be read out (reproduced) using the magneto-optic effect from the returned light by irradiating the recording medium with a laser beam that is emitted in direct current at a lower output than during recording. Can be done.

By the way, this type of information recording method is performed by heating the recording medium by irradiating laser light, so if the laser power deviates from the optimum laser power C for recording (hereinafter referred to as the optimum laser power), the recording state may deteriorate. may not be good.

Therefore, if the laser power deviates from the optimum laser power by more than a certain degree, the eye pattern deteriorates, leading to a deterioration of the error rate of the reproduced signal. One of the reasons why the above laser power deviates from the optimum laser power is due to temperature changes, and these can be roughly divided into those caused by fluctuations in laser emission output, and those caused by fluctuations in the optimal recording power of the recording medium. There are some causes. Fluctuations in laser output are caused by changes in the characteristics of the input terminal of the laser diode and the output of the laser diode due to changes in ambient temperature. There is a method in which a temperature sensor is provided near the diode to detect the temperature, and the laser power is controlled based on the obtained laser output light or temperature. Regarding fluctuations in the optimal recording power of a recording medium, since this optimal recording power is determined by the type and temperature of the recording medium, a temperature sensor is installed near the objective lens of the optical pickup to detect the ambient temperature. A method of installing a temperature sensor near the cartridge to detect and correct the temperature, and a method of installing a non-contact temperature sensor to directly detect and correct the temperature of the recording medium have been proposed. (One of the conventional methods described above, in which a temperature sensor is provided near the objective lens of an optical pickup, is shown in FIG. 10).

[Problem to be solved by the invention]

ISO standard 3.5-inch magneto-optical disks are single-sided disks, and as shown in Figure 11, there is a side of the magneto-optical disk that faces the laser beam irradiation side (hereinafter referred to as the pickup side). extremely thin (e.g. 1~40μ)
+*) Recording layer lb (for example, 0.05
~0.3 μm), and the ambient temperature on that side and the temperature of the recording layer are relatively close to each other. On the other hand, on the backup side, a substrate 1c of about 1.2 m+ of polycarbonate, glass, etc. is interposed between the recording layer, and since polycarbonate and glass have quite low thermal conductivity (high heat insulation properties), there is a There is a large temperature gradient.

Therefore, the ambient temperature on the pickup side and the temperature of the recording layer may have considerably different values. Therefore, it is difficult to accurately detect the temperature of the recording layer with a configuration in which a temperature sensor is provided on the optical pickup on the pickup side, as disclosed in FIG. 2 of JP-A-1-179224. It is necessary to perform temperature detection near the recording medium on the side opposite to the recording medium.

Furthermore, since a protective layer of, for example, 1 to 40 tIIm is only formed on the recording layer on the side facing the pickup of a single-sided disk, a bias magnetic field is applied to that side, which is generally adopted in the case of magneto-optical disks. In the case of a configuration in which a generator is provided, if the bias magnetic field generator and the recording layer are placed very close to each other, heat will not be blocked because there is no substrate like the pickup side, and the bias magnetic field generator will be an electromagnet. In this case, the recording medium is greatly affected by the heat generated by the electromagnet. In the case where the bias magnetic field generating device is a permanent magnet, the same applies as in the case of an electromagnet as long as the magnetic field reversal mechanism is one that generates heat. The effect of this heat generation is due to the presence of a substrate or cartridge with low thermal conductivity in the method of detecting it on the pickup side as in JP-A-1-179224 or the method of detecting it in the cartridge as in JP-A-1-191325. Accurate detection is not possible and there is a delay in detection. Therefore, in order to quickly and accurately detect the influence of this heat generation, it is necessary to detect the temperature near the recording medium on the side facing the pickup.

By the way, magneto-optical disks, both double-sided and single-sided, are generally configured so that the bias magnetic field generator faces the pickup with the recording medium in between, so if the bias magnetic field generator generates abnormal heat, the above characteristics will not occur. If temperature is detected on the pickup side as in Patent Publication No. 1-179224, there will be a detection delay due to the intervening substrate, which may cause damage to the medium (particularly in the case of single-sided disks, the bias magnetic field generator will be closer to the recording layer and heat will be generated). Since there is no board intervening to interrupt the flow, the risk of medium destruction is greater, and in that case, the abnormal heat generation described above may lead to destruction of the device itself). Furthermore, even with the method of detecting temperature using a cartridge as in JP-A-1-191325, there is a time lag until the medium temperature and car IJ temperature become equal when the abnormal heat generation occurs, and during this time, the recording medium and device itself There is a risk of destroying it. Therefore, the temperature sensor needs to be provided inside or near the bias magnetic field generator.

Considering the above, it is clear that the method of directly detecting the temperature of the recording medium is the most desirable method. When using a sensor,
This sensor is expensive because it utilizes the pyroelectric effect of some dielectric materials such as ceramics and polymer compounds, which causes spontaneous polarization and induces electric charges when exposed to infrared rays. Depending on the sensor installation location, there is a risk of malfunction due to stray light from the laser beam or ambient light, and accurate temperature detection is difficult unless a separate temperature sensor is installed to compensate for variations in infrared emissivity from the medium. However, placing the sensor in a position where it receives direct infrared radiation from the medium poses problems such as space and layout difficulties, making it quite difficult to incorporate into actual equipment and increasing costs. I also invite you.

The present invention has been made to solve these conventional problems, and it is possible to accurately detect the temperature of the recording layer of a recording medium and control the laser diode to the optimum laser power for recording/reproducing. An object of the present invention is to provide an inexpensive device that can protect a recording medium and the device itself when a bias magnetic field generating device generates abnormal heat.

[Means and operations for solving the problems] In order to achieve the above object, the present invention provides an optical information recording/reproducing device using a magneto-optical effect, in which a temperature sensor is disposed inside or near a bias magnetic field generating device.

Based on the detected value of the temperature sensor, for example, it is possible to perform control to optimize the laser power by correcting changes in the optimum recording power depending on the temperature of the recording medium, or to stop the recording/erasing operation and control the recording medium or device itself. can be protected.

〔Example〕

Hereinafter, each embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention, and the same parts as in the conventional example shown in FIG. 10 are given the same reference numerals. This example shows a case where the present invention is applied to a magneto-optical disk device.
The disk surface is irradiated with laser light as shown below. This laser light is emitted from the laser diode 3, and a part of it is transmitted through the collimator lens 4,
The signal is guided through the beam splitter 5 to a monitor diode 6 provided in front, and the output signal of the monitor diode 6 is fed back to the laser power controller 7, which controls the light emission output of the laser diode 3 via the laser driver 8. Most of the remaining laser light passes through an optical system consisting of a collimator lens 4, a beam splitter 5, and an objective lens 9, and is irradiated toward the magneto-optical disk 1, and the laser light reflected by the magneto-optical disk 1 is also irradiated with the same optical system. The beam returns to the system, passes through the objective lens 9, enters the beam splitter 5, and is guided there to the photodetection system 10. On the other hand, on the side facing the optical pickup across the magneto-optical disk 1, a temperature sensor 13 is provided in or near the bias magnetic field generator 12 driven by the driver 11. The temperature near the recording layer is monitored. There are no particular restrictions on the temperature sensor used.
Cheap and space-saving sensors such as thermistors can also be used.

The output signal of this temperature sensor 13 is input to the laser power controller 7 and CPU 15 via the sensor processing circuit 14. The output signal of the monitor diode 6 and the output signal of the CPU 15 are also input to the laser power controller 7, and the laser power controller 7 adjusts the optimum laser power based on the output signal of the monitor diode 6, the output signal of the CPU 15, and the output signal of the sensor processing circuit 14. seek,
The laser driver 8 is driven according to the value. At this time, the output signal of the monitor diode 6 is specifically used to determine the relationship between the current applied to the laser diode 3 and the amount of emitted light, and to compensate for fluctuations in the amount of emitted light due to variations in the laser device or deterioration over time. belongs to. Further, the output signal of the sensor processing circuit 14 is transmitted to the laser beam so that the recording power of the recording medium becomes the optimum recording power according to the temperature (ambient temperature) near the recording layer of the magneto-optical disk 1 detected by the temperature sensor 13. It is used to correct the laser power of the diode 3 and thus the amount of emitted light.

The optimum recording power of the recording medium mentioned above can be determined by, for example, storing the relationship between the medium temperature and the optimum recording power in a ROM (not shown) in the apparatus, and reading this as necessary. That's fine. The characteristics showing the relationship between the medium temperature and the optimum recording power are such that, as illustrated in FIG. 7, the optimum recording power generally decreases as the detected temperature increases. When this characteristic is incorporated into a device, it may be set to the average value of values obtained for various recording media, or it may be determined by the type of recording medium and switched to the one appropriate for that recording medium. Unless the rotational speed of the magnetic disk is controlled to a constant linear velocity (CLV), if the rotational speed is constant, the linear velocity will be greater on the outer circumference of the disk, so the optimum recording power will depend on the radial position on the disk. (Figure 8 shows an example of the relationship between the radial position and the optimum recording power during constant angular velocity control), so the optimum recording power may be determined from two parameters: medium temperature and track resistance. (In this case, the optimum recording power will be higher for the outer track).

Furthermore, in this example, when the detected medium temperature exceeds a preset limit temperature, the sensor processing circuit 14
The abnormality is communicated to U15 to take measures such as stopping the recording/erasing operation.

Note that the operation may be stopped by hardware without going through the CPU 15, and the CPU 15 constantly monitors the output from the sensor processing circuit 14 to determine whether or not there is an abnormality.
The PU 15 may perform the processing. Also, instead of setting a limit temperature, a new temperature sensor is installed in a different location,
It may be determined that there is an abnormality when the difference with the output of the temperature sensor exceeds a predetermined value.

In this way, the temperature of the recording medium is accurately detected using an inexpensive and space-saving temperature sensor such as a thermistor, and the device is always operated at the optimum recording power based on the detected medium temperature, and the bias magnetic field generator When abnormal heat generation occurs, the recording/erasing operation can be stopped to protect the recording medium and the device itself.

FIGS. 2(a) and 2(b) and FIGS. 3 to 5 are diagrams showing the specific arrangement of the temperature sensor 13 in the first embodiment, respectively. That is, FIG. 2(a) is a perspective view when an electromagnet field system is used as the bias magnetic field generating device 12, and as shown in FIG. 2(b), which is a longitudinal cross-sectional view, the temperature sensor 13 is The coil 12a is fixed to the lower surface of the yoke 12b, which supports the coil 12a, with a heat insulating material 16 interposed therebetween.

Moreover, FIG. 3 is a cross-sectional view of the electromagnet seen from a direction perpendicular to FIG.
The structure is such that the height direction dimension H is suppressed so that the field system and temperature sensor can be as close to the magneto-optical disk as possible. In addition, in the above two cases, the yoke 12
Although the heat insulating material 16 is interposed so as not to directly detect the temperature of b, an adhesive having a heat insulating effect may be used instead.

In both of these cases, the effects of the first embodiment can be obtained.

Further, FIG. 4 is a sectional view showing an example of the arrangement of temperature sensors when a magnetic field modulation override magnetic head is used as the bias magnetic field generator 12. Here, the lead wire of the temperature sensor 13 is fixed to the side surface of the override magnetic head 12c. (glued). In the case of this arrangement, the effects of the first embodiment can be obtained, and since the override magnetic head 12c is always located above the trailing trunk of the disk during recording/erasing, the temperature of the recording layer near the trailing track can be measured more accurately. It also has the advantage of being detectable.

Furthermore, FIG. 5 is a sectional view showing an example of the arrangement of temperature sensors when a permanent magnet is used as a bias magnetic field generator.
7b, a coil 17c, and a substrate 17d, and a temperature sensor X3 is fixed to the lower surface of the substrate 17d.

Even with this arrangement, the effects of the first embodiment can be obtained.

FIG. 6 is a diagram showing the configuration of the main part of the second embodiment of the present invention, and in this example, there are a plurality of temperature sensors (three in this case).
The case of an electromagnet field system using temperature sensors 13a, 13b, and 13c is shown. In this case, temperature sensors 13a and 13b respectively correspond to the inner, middle, and outer circumferences of the disk in the radial direction of the disk.

13c, and a sensor switching circuit 18 that receives the output signals of the sensors 13a to 13c and signals related to track tracking and outputs a signal related to a desired detected temperature to the sensor processing circuit 14. The temperature sensor used is switched according to the temperature, the medium temperature is detected, and the laser power is controlled. Note that the angular velocity −
In the case of Ashikaga fil (CAV), the relationship between the radial position (track number) and the optimum recording power is as shown in Figure 8, so the inner track is followed as shown in Figure 9. When the laser power is controlled by pattern A based on the output of sensor 13a, in the middle part
The laser power may be controlled using pattern B based on the output of sensor 3b, and pattern C based on the output of number sensor 13c at the outer periphery.
In the case of a track between 13b and 13c, the sensor outputs on both sides of the track may be weighted and averaged depending on the track, without completely switching the sensor output.

The present invention is not limited to the above-mentioned examples, and various changes and modifications are possible. For example, the number and arrangement of temperature sensors to be used are not limited to the above-mentioned sides, and can be changed as desired.

Further, it goes without saying that a temperature sensor may be provided on the pickup side as long as the temperature on the side opposite to the pickup side is equal to the temperature on the pickup side.

〔Effect of the invention〕

As explained above, according to the present invention, since the temperature sensor is placed inside or near the bias magnetic field generator which is quite close to the recording layer of the recording medium, it is possible to accurately detect the temperature of the recording layer. In addition, it is possible to detect the effects of heat generated by the bias magnetic field generator without delay, and it is possible to improve the error rate of the device by constantly controlling the laser power appropriately in response to fluctuations in the medium's optimal recording power due to temperature changes. Furthermore, the recording/erasing operation can be stopped when the bias magnetic field generating device generates abnormal heat, thereby protecting the recording medium and the device itself.

Moreover, such a device can be realized at low cost.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the first embodiment of the present invention, and FIG. 2 (
a), (b), and FIGS. 3 to 5 are diagrams showing the specific arrangement of the temperature sensor in the first embodiment, respectively. FIG. 6 is a diagram showing the configuration of the main part of the second embodiment of the present invention. , Fig. 7 is a diagram showing the relationship between the temperature of the recording medium and the optimum recording power, Fig. 8 is a diagram showing the relationship between the radial position of the recording medium and the optimum recording power when controlling the angular velocity - Ashikaga, and Fig. 9 FIG. 10 is a diagram illustrating the configuration of a conventional example, and FIG. 11 is a sectional view showing the structure of a single-sided disk as a recording medium. DESCRIPTION OF SYMBOLS 1... Magneto-optical disk 3... Laser diode 7... Laser power controller 8... Laser driver 12... Bias magnetic field generator 13... Temperature sensor 14... Sensor processing circuit 15...・CPU Figure 2 Figure 3 Figure 4 Figure 1 Figure 5 Figure 7 Figure 8 Figure 9 Figure 11 Procedure amendment form

Claims (1)

[Scope of Claims] 1. An optical information recording and reproducing device using a magneto-optical effect, characterized in that a temperature sensor is disposed inside or near a bias magnetic field generating device.