JPH0863865A - Magnetooptical recording apparatus - Google Patents

Abstract

PURPOSE: To increase a repeated reproducing number of times and use an apparatus stably for a long time. CONSTITUTION: An auxiliary magnetic field generating part 21 is arranged at an upper side of a magnetooptical disc 11 and a permanent magnet 23 is rotatably fitted inside the generating part 21 by a bearing 24. The permanent magnet 23 is rotated by a magnetic field generated by a coil 25 and controlled so as to face a magnetic pole S or a magnetic pole N to the magnetooptical disc 11. At a still reproduction mode, similar to a recording mode, the S pole of the permanent magnet 23 is opposed to the magnetooptical disc 11. Therefore, an auxiliary magnetic field is in the same direction both in the still reproduction mode and in the recording mode. If the auxiliary magnetic field is directed in the same direction as in the recording mode, a repeated reproducing number of times grows ten times in comparison with when the auxiliary magnetic field is directed in the same direction as in an erasure mode. Accordingly, this magnetooptical disc apparatus 1 enjoys an improved repeated reproducing number of times as compared with the prior art not controlling the direction of the auxiliary 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 suitable for application to a magneto-optical disk device or the like.

[0002]

2. Description of the Related Art The reliability of a recording medium such as a magneto-optical (MO) disk is evaluated by its storage life and repeated life. The storage life of a magneto-optical disk is said to be 10 to 15 years under normal use. On the other hand, the repeat life is the number of repeated recordings (Write-Stability:
Stability) and the number of repeated playbacks (Read-Stabilit
y: Read stability).

The number of times of repetitive recording indicates the number of times recording can be performed on the same track, and in the case of a magneto-optical disk, it is said to be about 10 ⁶ times under normal use. Also,
The number of times of repetitive reproduction indicates the number of times of reproducible from the same track, and means the number of times of reproduction when the C / N of the write data signal is lowered by 3 dB from the initial value. It is said to be about 10 ⁹ times.

[0004]

In the still playback mode, the same track is repeatedly played back. Therefore, in the case of a usage state where the still playback mode is frequently performed, the life depends on the number of repeated playbacks. Is determined. Now, the rotation speed of the magneto-optical disk is 18
When still reproduction is continuously performed at 00 rpm,
The life of the magneto-optical disk is 33 msec x 10 ⁹ times = 92
59 hours = 385 days. That is, the life of the magneto-optical disk is exhausted in about one year. This makes it difficult to use the magneto-optical disk stably for a long period of time, and it becomes impossible to perform still reproduction at high frequency.

If the reproducing power is lowered, the deterioration can be reduced. However, the laser noise level and the like relatively increase, the CNR deteriorates, and the error rate deteriorates. In addition, if the laser wavelength becomes shorter and the beam spot diameter becomes smaller due to the higher density, it is possible to reduce the MO even with the same reproducing power.
The power per unit area of the film is increased. That is, a short wavelength laser is used substantially. The shorter the wavelength, the higher the reproduction power and the more easily the magneto-optical disk deteriorates. There is also a method of lowering the recording sensitivity of the MO film and increasing the recording and erasing power, but if the disk diameter increases due to the increase in capacity and the rotation speed increases due to the higher transfer rate, the laser diode emission power increases. There is a risk that the data cannot be erased due to a shortage.

On the other hand, there is also a method of generating an external magnetic field by an electromagnet, but if the disk diameter is large, an electromagnet having the same length as this is required. The problem of occurs. Further, when a cartridge type disc is used, it is difficult to arrange the magnetic field generating means close to the disc. In this case, the use of electromagnets results in much larger dimensions than permanent magnets, and at the same time the current must be increased. Also in this case, there arises a problem that the amount of heat generation increases.

In order to avoid such a problem, the applicant of the present invention has proposed an optical recording medium in which the optical pickup is retracted to a track different from the track for still reproduction in the still reproduction mode. (Japanese Patent Application No. 6-49577). In this optical recording medium, for example, a retract area is provided on one or both of the innermost circumference and the outermost circumference of the magneto-optical disk, and the optical pickup is retracted to this retract area in the still reproduction mode.
Since only the address information needs to be reproduced normally in the save area, there is no problem even if the C / N drops below 3 dB. Therefore, the number of repeated reproductions in the save area is significantly larger than that in the data area. Further, at this time, since the data area is not irradiated with the laser beam, the number of times of repetitive reproduction is increased.

The present invention has solved the above-mentioned problems by a method different from the previously proposed optical recording medium, and is an optical system capable of improving the number of repetitive reproduction with a simple structure. A magnetic recording device is proposed.

[0009]

In order to solve the above-mentioned problems, the present invention controls the orientation of the permanent magnet for generating an auxiliary magnetic field for recording or erasing the recording medium and the magnetic pole of the permanent magnet with respect to the recording medium. In a magneto-optical recording device having magnetic field direction control means for controlling the direction of the auxiliary magnetic field and optical pickup means for irradiating the recording medium with light, the direction of the auxiliary magnetic field is the same as that at the time of recording during still reproduction of the recording medium. It is characterized in that

[0010]

As shown in FIGS. 1 to 3, the magneto-optical disk 11
An auxiliary magnetic field generating unit 21 is arranged on the upper side of, and a permanent magnet 23 is rotatably attached to the auxiliary magnetic field generating unit 21 by a bearing 24 therein.
The permanent magnet 23 is rotated by the magnetic field of the coil 25, and is controlled so that either the magnetic pole S or the magnetic pole N is arranged to face the magneto-optical disk 11. Then, as shown in FIG. 5, in the still reproduction mode, the S pole of the permanent magnet 23 is arranged facing the magneto-optical disk 11 as in the recording mode, and the directions of the auxiliary magnetic fields in the still reproduction mode and the recording mode are the same. Become. As shown in FIG. 7, when the direction of the auxiliary magnetic field is the same as that in the recording mode, the number of repetitive reproductions is 10 times that in the case of the same as in the erasing mode. Therefore, in this magneto-optical disk device 1, the number of times of repetitive reproduction is improved as compared with the conventional case where the direction of the auxiliary magnetic field is not managed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the magneto-optical recording apparatus according to the present invention applied to a magneto-optical disk device will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing the structure of a magneto-optical disk device 1 to which the magneto-optical recording device according to the present invention is applied. In this magneto-optical disk device 1, the magneto-optical disk 11 turns the recording surface 12 downward and the turntable 1
3 is chucked on and rotated by a spindle motor 14. The optical pickup 15 is arranged on the lower surface side of the magneto-optical disk 11 as shown in FIG. 2, and is attached so as to be movable along the radial direction of the magneto-optical disk 11. The fixed portion 16 is provided with a laser beam generating means (not shown), and the laser beam emitted from the fixed portion 16 is focused by the objective lens 18 of the movable portion 17 and applied to the recording surface 12 of the magneto-optical disk 11. And thus a beam spot is formed.

In the beam spot, the MO film (magneto-optical recording film) 28 (FIG. 5) is heated to the Curie temperature, and a magnetic field is applied to this to change the magnetic direction of the MO film 28 to record information. Alternatively, erasing is performed. Further, during reproduction, the laser light emitted to the recording surface 12 is reflected, and this is received by the light receiving element of the fixed portion 16 via the objective lens 18, converted into a servo signal and a reproduction signal, and output.

In order to make the objective lens 18 follow the magneto-optical disk 11 in the focus and tracking directions,
The movable portion 17 is provided with a biaxial direction moving device (not shown). Further, as shown in FIG. 1, the movable portion 17 is accessed in the radial direction of the magneto-optical disk 11 by a sled linear motor 19 and a linear guide 20. An auxiliary magnetic field generator 21 is arranged on the upper surface side of the magneto-optical disk 11. The above-mentioned parts are mounted on the chassis 10.

Now, as shown in FIG. 3, the auxiliary magnetic field generator 2
1, a long mounting plate 22 is provided along the radial direction of the magneto-optical disk 11, and a rod-shaped permanent magnet 23 having a rectangular cross section is rotatably mounted on a bearing 24 below the mounting plate 22.
The upper and lower sides of the center axis of the permanent magnet 23 are magnetized to have N poles and S poles, and recording or erasing of the magneto-optical disk 11 is performed by the auxiliary magnetic field generated here.

As shown in FIG. 4, one coil 25 is mounted on each side of the permanent magnet 23 on the upper side of the mounting plate 22. A substrate 26 is arranged on the lower side of the coil 25, and a yoke 27 is mounted on the upper side. Therefore, the permanent magnet 23, the coil 25, and the yoke 27 form a two-pole motor, and the rotation of the permanent magnet 23 can be controlled. That is, by controlling the direction of the current flowing through the coil 25, the directions of the magnetic poles N and S of the permanent magnet 23 facing the MO film 28 of the magneto-optical disk 11 can be set. A hall element 30 is arranged above the permanent magnet 23, and the direction of the magnetic poles N and S of the permanent magnet 23 is detected by the hall element 30.

In this magneto-optical disk device 1, as shown in FIG. 5, the permanent magnet 23 and the objective lens 1 of the optical pickup 15 are attached to the MO film 28 of the magneto-optical disk 11.
8 are arranged so as to face each other vertically. Then, in the recording mode, the S pole of the permanent magnet 23 is arranged so as to face the MO film 28 as shown in FIG. That is, the direction of the auxiliary magnetic field generated by the permanent magnet 23 is set to be the same as the irradiation direction of the laser light 29 emitted from the objective lens 18. In the erase mode, the permanent magnet 23 is reversed so that the N pole faces the MO film 28, as shown in FIG. In this case, the direction of the auxiliary magnetic field generated by the permanent magnet 23 is opposite to the irradiation direction of the laser light 29 irradiated from the objective lens 18.

In the reproducing mode, the auxiliary magnetic field is not required, but since the auxiliary magnetic field generator 21 is fixed, the auxiliary magnetic field always acts on the magneto-optical disk 11. Therefore, in the present invention, the number of repetitive reproductions of the magneto-optical disk 11 is improved by controlling the direction of the auxiliary magnetic field in the still reproduction mode as described below.

FIG. 7 shows a 5.25 "magneto-optical disk 11.
Is used to show the number of times of repeated reproduction when the intensity of the auxiliary magnetic field and the reproduction power are changed in the still reproduction mode. The test conditions are as follows: wavelength of laser light is 780 nm, NA = 0.5
0, the radius of the track for still reproduction is 30 mm, the temperature of the magneto-optical disk 11 is 60 ° C., and the writing frequency of the data for still reproduction is 4.93 MHz.

FIG. 4A shows the number of times of repeated reproduction when the direction of the auxiliary magnetic field is the same as that at the time of recording, and FIG. 7B shows the number of times of repeated reproduction when the direction of the auxiliary magnetic field is the same as that at the time of erasing. Indicates. As can be seen from these figures, when the auxiliary magnetic field strength is the same, the smaller the reproduction power, the larger the number of times of repeated reproduction. Further, the weaker the strength of the auxiliary magnetic field, the larger the number of times of repeated reproduction.

Further, when the direction of the auxiliary magnetic field is the same as in the recording mode, the number of times of repeated reproduction is larger than that in the erasing mode. For example, if the auxiliary magnetic field strength is 400
When the reproducing power is Oe and the reproducing power is 2 mW, the number of repeated reproduction is 10 when the direction of the auxiliary magnetic field is the same as in the recording mode.
^{In the case of 12} times, the number of repeated reproductions in the case of the same as in the erase mode is 10 ¹¹ times, so that the number of times of the same in the case of the recording mode is 10 times. As a result, the magneto-optical disk device 1 of the present invention controls the direction of the auxiliary magnetic field in the still reproduction mode to be the same as that in the recording mode.

In this magneto-optical disk device 1, since the number of times of repetitive reproduction can be improved simply by controlling the rotational position of the permanent magnet 23, the MO film 28 is relatively formed.
The sensitivity of can be increased. Therefore, when the reproducing power is the same, the recording power and the erasing power can be reduced by the amount that the sensitivity of the MO film 28 is improved. If the erasing power can be reduced, the load on the laser diode can be reduced to prolong the life of the laser diode, thereby improving the reliability of the magneto-optical disk device 1.

Further, when the magneto-optical disk 11 having a large outer diameter is used, the auxiliary magnetic field generating section 21 can be made smaller than when an electromagnet is used, which occurs when heat is generated or a large current is used. Since there is no problem, the structure of the device can be simplified and the cost can be reduced. Further, the strength of the auxiliary magnetic field can be increased by the permanent magnet 23 having a relatively small size, and the magnetic field generation unit 21 can be arranged at a position relatively far from the magneto-optical disk 11. As a result, the degree of freedom in designing the cartridge of the magneto-optical disk 11 and the loader for loading / unloading the magneto-optical disk 11 is increased, so that the structure can be simplified and the cost can be reduced.

[0024]

As described above, the present invention controls the direction of the auxiliary magnetic field by controlling the orientation of the permanent magnet for generating the auxiliary magnetic field for recording or erasing the recording medium and the magnetic pole of the permanent magnet with respect to the recording medium. In a magneto-optical recording apparatus having a magnetic field direction control means for controlling the recording medium and an optical pickup means for irradiating the recording medium with light, the direction of the auxiliary magnetic field during the still reproduction of the recording medium is the same as that during the recording.

Therefore, according to the present invention, the number of repeated reproductions in the still reproduction mode is improved, and the magneto-optical recording apparatus can be stably used for a long period of time. Further, it becomes possible to reduce the recording power and the erasing power, which extends the life of the light generating means and improves the reliability of the magneto-optical recording device. Further, the auxiliary magnetic field generating section can be easily and miniaturized, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of a magneto-optical disk 1 to which a magneto-optical recording device according to the present invention is applied.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a cross-sectional view showing a configuration of an auxiliary magnetic field generator 21.

FIG. 4 is a view on arrow B of FIG.

FIG. 5 is a diagram showing directions of an auxiliary magnetic field during recording and still reproduction.

FIG. 6 is a diagram showing a direction of an auxiliary magnetic field at the time of erasing.

FIG. 7 is a diagram showing a relationship between the direction of an auxiliary magnetic field and the number of repeated reproductions.

[Explanation of symbols]

 1 Magneto-Optical Disk Device 11 Magneto-Optical Disk 15 Optical Pickup 21 Auxiliary Magnetic Field Generator 23 Permanent Magnet 28 MO Film

Claims (1)

[Claims] 1. A permanent magnet for generating an auxiliary magnetic field for recording or erasing a recording medium, and magnetic field direction control means for controlling the direction of the auxiliary magnetic field by controlling the direction of a magnetic pole of the permanent magnet with respect to the recording medium. In a magneto-optical recording apparatus having an optical pickup means for irradiating the recording medium with light, a magneto-optical recording apparatus is characterized in that a direction of an auxiliary magnetic field is made to be the same as in recording during still reproduction of the recording medium. .