JPS6032149A - Photomagnetic recorder - Google Patents

Abstract

PURPOSE:To increase the quantity of information per bit and to perform recording with high density in the shifting direction of a magnetic recording medium as well as in the direction vertical said moving direction with a photomagnetic recorder which records information by means of laser light and a magnetic field, by changing the irradiating time and interval of the laser light. CONSTITUTION:A magnetic disk 1 contains a magnetic layer 3 and a reflection preventing film 4 formed on a circular transparent substrate 2. This disk 1 is attached to a rotary shaft 6 of a drive motor 5 with the side of the layer 3 turned upward. A photomagnetic head 10 is moved in the radius direction of the disk 1 at a fixed speed. Laser light generators 11 and 12 produce laser light, and a modulator 13 varies the irradiating time an interval of the laser light in response to the recorded information. A polarized beam splitter 14 connects both laser beams orthogonal to each other so that they are irradiated in the same direction. A magnetic field control circuit 17 controls the current which is applied to an electromagnet 16. Thus the form of a writing bit to the layer 3 is charged to increase the quantity of information per bit, and the recording is possible with high density in both shifting direction of a magnetic recording medium and the direction vertical to said shifting direction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for recording information using light and a magnetic field.

BACKGROUND ART For conventional write-once optical discs, as shown in FIG. 1, a method has been proposed in which information is recorded by forming bits (holes) B on a plastic disc A using a laser beam or the like. This method has the disadvantage that it cannot be rewritten because digital information is formed by opening bits B in the plastic thin film. Therefore, to eliminate this drawback, users can record freely.

A magneto-optical recording method has been proposed in which digital information corresponding to information such as documents, audio, two images, etc. is recorded on a rewritable recording medium that can be reproduced and erased.

This magneto-optical recording method uses, for example, Tb-Fe.

T b −F e −G o , G d −T b
-F e , G d -C.

A magnetic recording medium having a recording layer made of an amorphous magnetic film having perpendicular anisotropy.

A laser beam modulated based on the information to be recorded is irradiated, and the laser beam irradiated area of the recording layer is heated to approximately one Curie temperature to generate a stray magnetic field or a forcibly generated forced magnetic field around the recording layer. Accordingly, magnetic recording is performed by reversing the magnetization of the magnetic domain in the irradiated area.

In such a magneto-optical recording device, the inventor discovered the following.

(1) When recording is performed while rotating the magnetic recording medium and increasing the irradiation time of the recording laser beam, as shown in Figure 2,
The shape of the recorded bit is initially circular, then becomes elliptical, and finally the length in the radial direction of rotation is a constant width and the length in the circumferential direction is proportional to the irradiation time of the recording laser beam. become.

(2) When recording is performed while changing the external magnetic field, the length of the recorded bit in the radial direction increases in proportion to the increase in the external magnetic field, as shown in FIG.

(3) When reproducing recorded bits, if the recorded bit is larger than the spot diameter of the reproducing laser beam, a reproducing wave is obtained according to the length of the recorded bit in the circumferential direction. On the other hand, if the recording bit has a size comparable to the spot diameter of the reproduction laser beam, a reproduction wave can be obtained depending on the length of the recording bit in the rotation radius direction.

Note that FIG. 2 shows a moving magnetic recording medium (G
d-Co magnetic layer), the X-axis is the recording laser beam irradiation time (pulse width; μS).
) The Y axis is the size of recording pitch 1 (μrn)', v is the magnetic recording medium moving speed (V=0°65 m/s), a is the recording bit size in the magnetic recording medium moving direction (μm), and b is This is the size (μm) of a recording bit in the direction perpendicular to the direction of movement of the magnetic recording medium.

FIG. 3 is a diagram showing that the size of a recorded bit changes depending on the strength of the applied magnetic field, where the X axis represents the strength of the applied magnetic field (Oe), the Y axis represents the bit diameter (μm), and P5. P6.
P8 is the power of the recording laser beam (mW), G d-C
o is the magnetic layer of the magnetic recording medium.

1. The present invention was made by utilizing the above-mentioned findings, and its purpose is to increase the amount of information per bit, and to increase the amount of information in the moving direction (rotating circumferential direction) and the moving direction of the magnetic recording medium. The object of the present invention is to provide a magneto-optical recording device that can perform high-density recording in the perpendicular direction (radial direction).

The above and other objects and novel features of the present invention are as follows.

It will become clear from the description of this specification and the accompanying drawings.

The principle of the present invention is that when recording on a magnetic recording medium, the characteristics shown in Figures 2 and 3 are used to adjust the irradiation time of the recording laser beam or the applied magnetic field to the information to be recorded. If the settings are made accordingly, bits with the corresponding shape will be recorded. This allows high-density recording not only in the direction of the rotational circumference (direction of movement) of the magnetic recording medium, but also in the radial direction of rotation (direction perpendicular to the direction of movement).

Further, during reproduction, it is possible to obtain reproduction waves according to the shape of the recorded bits. In this case, if a change in the duty ratio (ratio of bit length to bit pitch) is also added to the recording conditions,
The amount of information per bit further increases.

Vehicle Bottom The structure of the present invention will be described below along with one embodiment.

FIG. 4 is a diagram showing a schematic configuration of an embodiment of the present invention.

In FIG. 4, reference numeral 1 is a magnetic disk, and a magnetic layer 3 is formed on a circular transparent substrate 2 made of a transparent synthetic resin material or transparent glass by a vapor deposition method, an ivy method, etc. Reflection flJ+ on 3, 1-II ratio A 10 purchase/, -71 urn soil, t11 riuchisu own cost - size next door 3
Alloys of heavy rare earths and transition metals, such as Tb-Fe.

Tb-Fe-Go, Gd-Tb-Fe, Gd-C.

etc. can be used as an amorphous medium, MnCuB+ as a polycrystalline medium, hexagonal,
Fe of barium ferrite, [BaAlxFt2 with some of the children replaced with AI
2-XOl 9 etc. are used. This magnetic layer 3 is
It is preferable to have a relatively low Curie temperature (about 250° C.) and a large coercive force (1KOe or more).

The magnetic disk 1 is attached at its center to the rotating shaft 6 of the drive motor 5 so that the surface on the magnetic M3 side faces upward and is horizontal.

lO is a magneto-optical head, as shown by the arrow.

A moving mechanism (not shown) moves the magnetic disk 1 in the radial direction at a predetermined speed.

11 and 12 are laser light generating devices such as semiconductor laser devices that emit laser light. Reference numeral 13 denotes a modulator that controls the laser beam irradiation time and its interval in accordance with the information to be recorded. 14 indicates both the laser beam generators 11 and 1.
This is a polarizing beam splitter for combining mutually perpendicular laser beams emitted from the two beams so that they are projected in the same direction.

This polarizing beam splitter 14 linearly polarizes only the component perpendicular (90°) to its reflecting surface (hereinafter referred to as the P component), and only the component parallel to the reflecting surface (hereinafter referred to as the S component) is reflected. It is a polarizing prism. For example, polarizing prisms such as Grand Thompson prisms and Nicol prisms can also be used. 15 and 18 are objective lenses;
16 is an electromagnet, and 17 is a magnetic field control circuit that controls the current value and application time applied to the electromagnet. 19 is an analyzer, 2
0 is a photodetector, and Q is a laser beam irradiation point.

Although not shown, the magnetic field control circuit 17 is provided with means for synchronizing the recording laser beam irradiation time and the magnetic field application time.

Next, the operation of this embodiment will be explained with reference to FIG.

(1) When recording, the laser beam irradiation time and interval of the laser beam generators 11 and 12 are controlled by the modulators 13A and 13B, and when the laser beam is emitted and enters the polarizing beam splitter 14, the action of the polarizing beam splitter 14 causes the laser beam to emit. The energies of both laser beams are combined in the same phase with almost no energy loss, and are focused and irradiated onto the magnetic layer 3 of the magnetic recording medium through the objective lens 15. As a result, when the temperature of the laser beam irradiation point Q of the magnetic layer 3 rises to near the Curie point, the coercive force of the magnetic layer 3 becomes weaker, and the magnetization is reversed by the magnetic field generated by the electromagnet.

The irradiation time and the irradiation interval of the laser beam are set such that the time when the size b shown in FIG. 2 becomes constant and the interval time when the magnetic disk 1 rotates by the length of the size a shown in FIG. It is set.

The size of the recording bits can also be changed by changing the power of the laser beams of the laser beam generators 11 and 12, but this is not necessary for recording.Since the power of the laser beams is predetermined, the above It is preferable to change the size of the recording bit by changing the strength of the external magnetic field.

(2) When performing reproduction, a laser beam of a predetermined intensity is emitted from the laser beam generator 1 and the photodetector 20 is turned on. At this time, the laser beam generator 12 and the electromagnet 16 are not operated.

A laser beam of a predetermined intensity emitted from the laser beam generator 11 is transmitted through a polarizing beam splitter 14, and the direct and linear laser beams transmitted through this polarizing beam splitter are transmitted through an objective lens 15. ^ The magnetic layer 3 of the magnetic disk 1 on which magnetic recording is performed is irradiated in the form of a spot. The laser beam at the laser beam irradiation point Q is rotated and polarized at a rotation angle α depending on the state of the magnetic layer 3, as known from the Faraday effect, and transmitted through the magnetic layer 3. This transmitted laser light is transmitted through the objective lens 18. The rotationally polarized component passes through the analyzer 19 and enters the photodetector 20, where information is reproduced.

A laser beam is reflected by the laser beam layer 3 and Kerr
) effect may be used for detection and reproduction.

(3) When erasing, the laser beam generators 11 and 12 continuously emit laser beams of a predetermined intensity, and the electromagnet 16 applies a magnetic field opposite to that for recording operation to the magnetic disk 1 for recording. Erase information.

As explained above, this embodiment can be applied as a rewritable optical audio device, optical video device, etc.

As explained above, according to the technical means disclosed in the description of this specification and the accompanying drawings, the following effects can be obtained.

(1) Since magneto-optical recording was performed, the information recorded on the magnetic recording medium can be rewritten.

(2) Since the shape of the recording bits is changed by changing the irradiation time and irradiation interval of the recording laser beam, it is possible to increase the amount of information per bit and increase the recording density per fixed medium. I can do it.

(3) Since the size of the recording bit is changed by changing the strength of the magnetic field generated by the electromagnet, the amount of information per bit can be increased, and the recording density per fixed medium can be increased.

(4) In particular, the recording density in the direction of the rotation radius (direction perpendicular to the direction of movement) can be increased in magnetic disks and the like.

It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without changing the gist thereof.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining an example of a conventional write-once optical disc. Figure 2 is a diagram showing the shape of a writing bit on a moving magnetic recording medium. Figure 3 is a diagram showing the strength of the applied magnetic field. FIG. 4 is a diagram showing a schematic configuration of an embodiment of the present invention. l...Magnetic disk, 2...Circular transparent substrate. 3... Magnetic layer, 4... Antireflection film, 5... Drive motor, 6... Rotating shaft, lO... Magneto-optical head. 11.12... Laser beam generator 13... Modulator, 14... Polarizing beam splitter 15.18... Objective lens, 16. Self-weight magnet, 17.
... Magnetic field control circuit, 19... Analyzer, 20... Photodetector. Agent: Patent Attorney Shuki Akita Figure 1 Figure 2. Laser"-16, #@Wr <ps> Fig. 3 c**n qtzsm to tnes) Fig. 4■

Claims (1)

[Claims] What is claimed is: 1. A magneto-optical recording device for recording information using a laser beam and a magnetic field, characterized by comprising means for changing the irradiation time and the irradiation interval of the laser beam for recording information.