JPH087376A - Magnetic field modulation type magneto-optical recording device - Google Patents

Abstract

PURPOSE:To facilitate the overwriting recording without remaining previous record and, further, control the size of a recording magnetic domain precisely to realize high density recording by a method wherein a bias magnetic field applying means is provided in addition to a magnetic head separately. CONSTITUTION:A bias magnetic field applying means 52 is provided in addition to a magnetic head 16 separately. The intensities of magnetic fields generated by a light condensing means 33, the scanning means of an optical head 62, a motor 321, etc., are measured beforehand as the leakage of a bias magnetic field and the intensity of a magnetic field which is to be applied by the means 52 for offset correction is stored in a memory 54. The intensity of the leakage magnetic field is varied in accordance with the position of the optical head 62, i.e., the radial position on a disc. Therefore, the table of the intensities of the magnetic fields to be applied are stored in the memory 54 in terms of the respective positions on the disc. Then, in the actual recording/reproducing operations, a main control means 55 refers to the applicable magnetic field table stored in the memory 54 to control the bias magnetic field.

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, and more particularly to a magnetic field modulation type magneto-optical recording device.

[0002]

2. Description of the Related Art FIG. 4 shows a configuration example of a conventional magnetic field modulation type magneto-optical recording. It shows one configuration example of the overwrite method. In FIG. 4, the laser light emitted from the laser 13 is collimated by the lens 91, passes through the beam splitter 10, and is further condensed by the lens 92 to form a light spot on the magneto-optical recording medium 8. The laser light is irradiated onto the magneto-optical recording medium 8 continuously or repeatedly at a constant period in a pulsed manner, and is heated to near the Curie temperature by the laser light to a part of the magneto-optical recording medium 8 whose coercive force is small, A magnetic field that has been modulated at high speed according to the recorded information is applied from the floating magnetic head 16 having a high magnetic permeability core 18.

The floating magnetic head 16 includes a support spring 1
It is connected to the optical head 62 by means of 7 and is adjusted so that it is always positioned directly above the light spot. In this way, the magnetization of the magneto-optical recording medium 8 is aligned in the direction of the applied magnetic field to form a recording magnetic domain. That is, when the applied magnetic field is upward, magnetic domains having upward magnetization are formed, and when the applied magnetic field is downward, magnetic domains having downward magnetization are formed. As the recording frequency at this time, high-speed modulation of 10 to 20 MHz is possible, and since the laser light is applied continuously or repeatedly in pulse form, a recording magnetic domain is formed regardless of previously recorded information, and high-speed recording is possible. Overwrite can be realized.
Here, the floating magnetic head 16 is used for the magneto-optical recording medium 8
The buoyancy due to the air flow generated by the rotation of the and the force of the support spring (gimbal) 17 are balanced and held stably. This method is described, for example, in JP-A-63-21754.
8 are proposed.

[0004]

However, in the above-mentioned conventional example, when there is a magnetic field leak 65 from the outside of the device or from the inside of the device, the magnetic field is amplified by the high magnetic permeability core 18 of the magnetic head 16 and the magnetic field on the medium is increased. The applied magnetic field 66 is greatly offset (FIG. 5). When the magnitude of the upward applied magnetic field and the magnitude of the downward applied magnetic field are different due to such an offset, the magnitudes of the upward magnetic domain 411 and the downward magnetic domain 412 are different as shown in FIG. Magnetic domain 411 with upward magnetization and magnetic domain 4 with downward magnetization
When the sizes of 12 are different, when the smaller magnetic domain is overwritten (overwritten) on the larger magnetic domain, the larger magnetic domain disappears and remains a problem. In addition, at the time of high density recording, it is necessary to precisely control the formation of the recording magnetic domain near the limit of the optical resolution, but it is in terms of signal quality that the size of the magnetic domain varies due to the above offset. It was a problem. That is, high density recording was difficult.

Actually, from the viewpoint of miniaturization of the device, it was difficult to completely shield the magnetic field by leaking in the magnetic field from the outside or the inside. Therefore, it is difficult to perform overwriting without erasing and to perform high density recording.

An object of the present invention is to solve the above-mentioned problems, perform overwriting without erasing, and precisely control the size of the recording magnetic domain to realize high density recording. To provide a device.

[0007]

In order to achieve the above object, the present invention uses the following means.

(1) Light irradiating means for irradiating the magneto-optical recording medium with light, and high-frequency magnetic field applying means for applying a modulating magnetic field according to information to be recorded in a region irradiated with light by the light irradiating means. In the magneto-optical recording apparatus including at least reproducing means for reproducing recorded information, a bias magnetic field applying means is provided separately from the modulating magnetic field applying means.

As a result, it is possible to easily compensate for the leakage magnetic field, which has been a problem in the prior art, without affecting the drive of the magnetic head.

(2) The intensity of the magnetic field applied by the bias magnetic field applying means is controlled according to the type of the recording medium, the recording portion on the recording medium, the intensity of the magnetic field applied from the outside of the magneto-optical recording device, and the like. A bias magnetic field strength control means is provided.

As a result, even when the strength of the leaked magnetic field differs depending on the recording portion, it is possible to easily compensate for it.

(3) The bias magnetic field strength control means comprises:
Recording is performed by irradiating light by the light irradiating means and applying a modulation magnetic field by the modulation magnetic field applying means to form a recording mark on a magneto-optical recording medium, and then reproducing information of the recording mark portion by the reproduction. Means for controlling the intensity of the magnetic field applied by the bias magnetic field applying means on the basis of the reproduction information.

Thus, it is possible to reproduce the recorded information to accurately grasp the offset amount of the applied magnetic field, and to correct the intensity of the magnetic field to be applied by the bias magnetic field applying means using the offset information. Therefore, even a minute recording mark can be recorded with high accuracy and high density recording can be performed.

(4) A magnetic field strength detecting means for detecting the strength of the magnetic field applied on the optical recording medium is provided. This makes it possible to accurately grasp the strength of the leaking magnetic field and easily compensate for the leaking magnetic field from outside the device.

[0015]

In the present invention, the bias magnetic field applying means is provided separately from the magnetic head 16. As described above, the magnetic head 16
Has a high-permeability core 18, and has an action of amplifying a magnetic field from the outside. In the present invention, this is reversed. That is, by applying a small bias magnetic field (compensation magnetic field) by the bias magnetic field applying means, the magnetic field on the magneto-optical recording medium 8 becomes large due to the amplifying action of the high magnetic permeability core 18. As a result, the leak magnetic field can be corrected with a small bias magnetic field. Further, since the leakage magnetic field can be compensated without changing the driving current of the magnetic head 16 at all, there is no influence on the characteristics for high-speed modulation of the magnetic field, and unnecessary current does not flow to the magnetic head. The head design is easy.

[0016]

【Example】

Example 1 A configuration example of a magneto-optical recording device according to the present invention is shown in FIG.
Shown in In this embodiment, the light generating means 31 has a wavelength of 68.
A 0 nm semiconductor laser was used. The intensity of the semiconductor laser is controlled by the light intensity control means 36 having an automatic light intensity control function. The light 22 emitted from the light generating means 31 is
The light is condensed on the magneto-optical recording medium 12 by the light collecting means 33. The light collecting means 33 is composed of at least one lens.
In this example, the objective lens 3 that focuses on the optical recording medium 12
The aperture ratio of 31 was 0.55. Therefore, the diameter of the light spot 21 on the optical recording medium 12 is 1.1 μm. The light spot can be moved to an arbitrary position (track 43) on the optical recording medium 12 by the scanning means 32. In this embodiment, the scanning means 32 is a motor 321 for rotating the disk-shaped magneto-optical recording medium 12, and an automatic position control means 32 having functions of automatic focus control and automatic tracking.
At least 2. The automatic position controller 322 uses the reflected light 23 from the magneto-optical recording medium 12 to perform feedback control. In this example, the reflected light from the light spot 21 is guided to the light detection means 34 by the polarization beam splitter included in the light collection means 33. The light detecting means 34 includes a polarization analyzing means such as a polarizer and a light detecting element that changes light into an electric signal. The reproduction signal converted into the electric signal by the light detecting means is the demodulation circuit 3
The recording information is demodulated by being guided to the reproducing means 37 composed of 7 or the like.

When recording is carried out by the apparatus of this embodiment, the recording light 22 whose intensity is controlled by the light intensity control means 36 is irradiated onto the magneto-optical recording medium 12 to form a light spot 21. At this time, the light intensity of the light spot 21 is controlled on the magneto-optical recording medium 22 so that the temperature of the region where the recording magnetic domain 41 is desired to be formed is near the Curie temperature of the magneto-optical recording medium 12. In this example, the size of the recording magnetic domain 41 is aimed at a width of about 0.6 μm. Further, in this example, the magneto-optical recording medium 12 having the TbFeCo recording film was used. The Curie temperature of this medium 12 was about 200 ° C. Therefore, as the light intensity, the temperature of the region of about 0.6 μm width on the magneto-optical recording medium 12 is 200 ° C.
The strength was controlled to exceed. The light intensity at this time is 6.5 mW
Met. In this way, when the temperature of the area of about 0.6 μm width on the magneto-optical recording medium 12 exceeds the Curie temperature, the flying magnetic head 16 applies the modulation magnetic field to the vicinity of the area. As a result, the magnetization of the region of about 0.6 μm width is aligned in the direction of the modulation magnetic field. At this time, strictly speaking, the region aligned in the direction of the modulation magnetic field is the magneto-optical recording medium 12
Is a region in which the coercive force of is smaller than the magnitude of the modulation magnetic field.
Therefore, the larger the modulation magnetic field, the larger the size of the recording magnetic domain formed. Therefore, when the effective magnetic field applied to the medium is offset by the leakage magnetic field from the outside as shown in FIG. 5 and the magnitudes of the upward magnetic field and the downward magnetic field are different, the size of the recording magnetic domain is increased. Is different between the upward and downward parts. This is a problem because, when the smaller magnetic domain is overwritten (overwritten) on the larger magnetic domain as described above, the larger magnetic domain disappears and remains. Further, at the time of high density recording, it is necessary to precisely control and form a recording magnetic domain near the limit of optical resolution, but it is a problem in terms of signal quality that the size of the magnetic domain varies due to the above offset. It was.

Therefore, in order to solve these problems, in the present invention, the bias magnetic field applying means 52 is used as the magnetic head 16.
It was set up separately from. In this embodiment, as the leakage of the bias magnetic field, the amount of the magnetic field generated from the condensing means 33, the scanning means of the optical head, the motor 321 and the like should be measured in advance and applied by the bias magnetic field applying means for offset correction. The amount of magnetic field was recorded in the memory 54. The amount of the leaked magnetic field differs depending on the position of the optical head 62, that is, the radial position on the disk. For this reason,
On the memory 54, the amount of the magnetic field to be applied is recorded as a table corresponding to each position of the disk. In this example,
The recording on the memory 54 was performed at the adjustment stage before shipment.

In actual recording / reproducing, the main control means 55 controls the bias magnetic field by referring to the applied magnetic field table recorded in the memory 54.

FIG. 6 shows an example of the effect of this embodiment. That is, in this example, the scanning means of the optical head and the motor 32
Due to the magnetic field generated from No. 1, the size of the leak magnetic field differs depending on the disk radial position. For this reason,
In the conventional example, in the portion where the amount of leaked magnetic field is not 0, the unerased portion occurs when overwriting is performed, and in this example, the erase ratio (ratio of the unerased amount and the signal amount) is −25 dB at maximum. It's getting worse to the extent. On the other hand, as shown in the present embodiment, when the bias magnetic field is applied to correct the leakage magnetic field by referring to the applied magnetic field table recorded in the memory 54, the erasing ratio depends on the disk radial position. However, −45 dB can be secured.

<Embodiment 2> FIG. 2 shows another configuration example of the information reproducing apparatus. In this embodiment, a semiconductor laser having a wavelength of 680 nm is used as the light generating means 31, and the optical recording medium 12 is used.
The aperture ratio of the objective lens 331 that collects the light above is set to 0.55. Therefore, the diameter of the light spot 21 on the optical recording medium 12 is about 1.1 μm. The light spot is moved to an arbitrary position (track 43) on the optical recording medium 12 by the scanning means 32.
Can be moved to. Also in this embodiment, the feedback control is performed using the reflected light 23 as in the first embodiment. The reflected light from the light spot 21 is, in this example,
It is guided to the light detection means 34 by the polarization beam splitter included in the light collection means 33. The reproduction signal is the demodulation circuit 3
The recording information is demodulated by being guided to the reproducing means 37 composed of 7 or the like.

When recording is performed by the apparatus of this embodiment, the recording light 22 whose intensity is controlled by the light intensity control means 36 is irradiated onto the magneto-optical recording medium 12 to form a light spot 21. In this example, in order to stably record a smaller magnetic domain, the recording light is repeatedly applied in pulses in synchronization with the recording clock. As a result, only a smaller area on the recording medium can be heated. At this time, in order to synchronize the position of the recording magnetic domain, a sample servo method was used as a tracking method. At this time, the light intensity of the light spot 21 on the magneto-optical recording medium 22 is 4
The strength is controlled so that the temperature of the region where 1 is desired to be formed is near the Curie temperature of the magneto-optical recording medium 12. In this example,
As a size of the recording magnetic domain 41, a width of about 0.4 μm is aimed at. Further, in this example, the magneto-optical recording medium 12 having the TbFeCo recording film was used. The Curie temperature of this medium 12 was about 200 ° C. Therefore, the light intensity was controlled so that the temperature of the region of about 0.4 μm width on the magneto-optical recording medium 12 exceeded 200 ° C. The light intensity at this time was 7.0 mW (linear velocity 15 m / s, irradiation pulse period 15 ns, pulse duty 50%). In this way, when the temperature of the area of about 0.4 μm width on the magneto-optical recording medium 12 exceeds the Curie temperature, the flying magnetic head 16 applies a modulating magnetic field to the vicinity of the area. As a result, the magnetization of the region of about 0.4 μm width (the region where the coercive force is smaller than the magnitude of the modulating magnetic field) is aligned in the direction of the modulating magnetic field. At this time, if the effective magnetic field applied to the medium is offset due to a magnetic field leaking from the outside as shown in FIG. 5, the smaller magnetic domain is overwritten (overwrite) on the larger magnetic domain as described above. ), The larger domain disappears and remains a problem. Further, at the time of high density recording, it is necessary to precisely control and form a recording magnetic domain near the limit of optical resolution, but it is a problem in terms of signal quality that the size of the magnetic domain varies due to the above offset. It was.

Therefore, in the embodiment, the Hall element is used as the magnetic field detecting means provided with the magnetic field detecting means for detecting the effective magnetic field (leakage magnetic field + bias magnetic field) applied on the medium.

When recording / reproducing is actually performed, the main control means 55 controls the applied amount of the bias magnetic field so that the amount of the magnetic field detected by the leak magnetic field detecting means becomes zero.

Also in this embodiment, substantially the same effect as that of the first embodiment shown in FIG. 6 was obtained. That is, the erasing ratio can secure -45 dB regardless of the disk radial position.

<Third Embodiment> FIG. 3 shows another configuration example of the information reproducing apparatus. The present embodiment is the same as the second embodiment except that the trial writing control is performed without using the magnetic field detecting means to determine the magnitude of the bias magnetic field to be applied. The method of trial writing control will be described below.

In this embodiment, at least two control means, a trial writing control means and a recording / reproducing control means, are provided as main control means, and these are selectively controlled by the central control means.

During normal recording, first, the trial writing control means first changes the bias magnetic field in an appropriate region (in the trial writing region) on the recording medium 12,
Record the magnetic domain of constant wavelength (duty 50%),
The recorded information is reproduced, sliced at the median of the amplitude of the reproduced signal to be binarized, the duty ratio of the binarized signal is investigated, and the bias magnetic field at which the duty of the binarized signal is exactly 50%. (Bias magnetic field drive current)
Is recorded in the memory 54.

The trial writing procedure after this is performed in several areas on the medium when the medium is mounted.

After that, the recording / reproducing control means applies a modulating magnetic field in accordance with the recording information to the area to be recorded to perform recording. At this time, referring to the memory 54,
This is done by setting the bias magnetic field to be applied.

The method of this embodiment is suitable for high-density recording because the optimum bias magnetic field is always set even when the characteristics of the recording medium are changed.

FIG. 6 shows the effect of reducing the remaining loss in this embodiment. The effect of using the method of the invention is shown. Unlike the first and second embodiments, in this embodiment, since the optimum bias magnetic field can be set according to the characteristics of the magneto-optical recording medium, a good erasing characteristic of −50 dB or less is obtained regardless of the recording position. .

<Embodiment 4> The configuration of one embodiment of the present invention is shown in FIG. In the present invention, two light spots are radiated on the medium in the same manner. Recording is performed with the first light spot in the same manner as in the above-described three embodiments, and the recorded information is immediately reproduced with the second light spot.

According to the present invention, since the recorded information can be immediately reproduced, it is possible to correct the temporal fluctuation of the bias magnetic field.

Specifically, the length of the recording magnetic domain is compared between the information recorded at the first spot and the reproduction signal reproduced at the second spot, and recording is performed while correcting the bias magnetic field so that it is always the same. .

An example of the effect of this embodiment is shown in FIG. Since the length of the recording magnetic domain exactly matches the length of the information to be recorded, high density recording can be easily performed.

The effect of the present invention is not limited to the above embodiment.

[0038]

The leakage magnetic field, which has been a problem in the past,
It becomes possible to easily compensate without affecting the drive of the magnetic head, and it is possible to easily compensate even when the strength of the leakage magnetic field differs depending on the recording portion. As a result, it is possible to record with high accuracy even in a minute recording magnetic domain, and it is possible to perform good high density overwriting without erasure.

[Brief description of drawings]

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

FIG. 2 is a block diagram of an embodiment of a magneto-optical recording apparatus of the present invention.

FIG. 3 is a block diagram of an embodiment of a magneto-optical recording device of the present invention.

FIG. 4 is an explanatory diagram showing an example of a conventional magneto-optical recording apparatus.

FIG. 5 is an explanatory diagram showing a problem of a conventional magneto-optical recording device.

FIG. 6 is an explanatory diagram showing the effect of the magneto-optical recording method of the present invention.

FIG. 7 is a block diagram of an embodiment of a magneto-optical recording device of the present invention.

FIG. 8 is a graph showing the effect of the magneto-optical recording method of the present invention.

[Explanation of symbols]

8, 12 ... Magneto-optical recording medium, 91, 92 ... Lens, 10
... beam splitter, 13 ... laser, 16 ... magnetic head, 17 ... support spring, 18 ... core, 132 ... relevant track, 133 ... adjacent track, 14 ... reproducing layer, 15 ... recording layer, 16 ... substrate, 17 ... cutting layer , 21 ... light spot, 2
2 ... Reproduced light, 23 ... Reflected light, 31 ... Reproduced light generating means, 3
11 ... Diffraction grating, 32 ... Scanning means, 321 ... Disk rotating means, 322 ... Automatic position control means, 33 ... Focusing means,
331 ... Lens, 34 ... Photodetection means, 35 ... Reproducing means,
36 ... Light intensity control means, 37 ... Demodulation means, 38 ... Controller, 41 ... Recording domain, 43 ... Track, 51 ... Bias magnetic field, 52 ... Bias magnetic field applying means, 53 ... Bias magnetic field intensity control means, 61 ... Reproduction light detection Part, 62 ... Optical head, 65 ... Leakage, 66 ... Applied magnetic field.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Saito 1-280, Higashikoigokubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (5)

[Claims] 1. A light irradiating means for irradiating a magneto-optical recording medium with light, and a high frequency magnetic field applying means for applying a modulating magnetic field according to information to be recorded in a region irradiated with light by the light irradiating means. A magneto-optical recording apparatus comprising at least reproducing means for reproducing recorded information, wherein a bias magnetic field applying means is provided separately from the modulating magnetic field applying means. 2. The magneto-optical recording apparatus according to claim 1, wherein the bias magnetic field is determined according to the type of recording medium, the recording portion on the recording medium, the strength of a magnetic field applied from outside the magneto-optical recording apparatus, and the like. A magneto-optical recording apparatus comprising a bias magnetic field strength control means for controlling the strength of a magnetic field applied by the applying means. 3. The magneto-optical recording apparatus according to claim 2, wherein the bias magnetic field intensity control means irradiates light by the light irradiating means and applies a modulating magnetic field by the modulating magnetic field applying means to perform recording. Forming a recording mark on a magneto-optical recording medium, and then obtaining reproduction information of the recording mark portion by the reproducing means, and controlling the strength of the magnetic field applied by the bias magnetic field applying means based on the reproduction information. A magneto-optical recording apparatus having at least a trial writing control means. 4. The magneto-optical recording apparatus according to claim 2, further comprising magnetic field strength detecting means for detecting the strength of the magnetic field applied on the optical recording medium. . 5. The magneto-optical recording apparatus according to claim 2, further comprising a light irradiation means for forming at least two light spots on the magneto-optical recording medium, wherein information is recorded by the first light spot. Information is reproduced immediately after recording with 2 light spots,
A magneto-optical recording apparatus comprising a magnetic field strength control means for controlling the strength of a magnetic field applied to a magneto-optical recording medium based on comparison information of recorded information and reproduced information.