JPH08227542A - Magneto-optical recording and reproducing device - Google Patents

Abstract

PURPOSE: To suppress the generation of heat and to control the magnetic field generated from an electromagnet at a high speed by arranging this electromagnet on the side of a recording disk opposite to its light incident side and lessening the restriction on the position of an optical system on the light incident side fo this recording disk. CONSTITUTION: An intensity change is applied to a laser beam by the optical modulator 4 according to the information to be recorded and this laser beam is converged by a converging lens 11. A recording track 23 is irradiated with this beam as a spot of about 1μm diameter. Curie point recording or coercive force recording is executed on the recording track 23 according to the intensity change of the laser beam. At this time, a magnetic field is generated by a coil 24 from the rear surface of the recording disk 12 and this magnetic field is impressed on the recording tack 23. The laser beam polarized to linearly polarized light is passed through Faraday glass 6 by a polarizing prism 5, by which an azimuth angle is rotated 45 deg. in the case reproduction of information is executed. The loss of the light quantity is minimized when the transmission axis of the next polarizing prism 7 is aligned to the azimuth angle of the polarized light after passing through the Faraday glass 6.

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 / reproducing device for reproducing information recorded on a perpendicular magnetization film by using a laser beam.

In recent years, an optical memory device has been widely studied as a memory device capable of high density, large capacity, and high speed access. When roughly classified, the following three types can be considered.

A device that can only reproduce information recorded in a storage element.

Those capable of reproduction and additional recording of information.

Not only reproduction / additional recording but also erasing unnecessary information and re-recording.

Of these, the devices of and have already reached the stage of practical application, but the device of is at the stage of research and development, and there is nothing that can be put to practical use.

The present invention is based on Ar laser, HeCd laser, H
Information is recorded and erased thermomagnetically by using a laser beam such as an eNe laser and a semiconductor laser, and information is reproduced by utilizing a magneto-optical effect. The present invention relates to an optical recording / reproducing device.

[0008]

2. Description of the Related Art Very few conventional systems have been reported as practical systems for magneto-optical recording / reproducing devices.

As one close to practical use, there is the Denpa Newspaper Magnetic Memory Special Electronic Technology (published on September 18, 1980).

In this article, writing is performed by heating a magnetic thin film of an amorphous alloy containing iron as a main component to the Curie point with the heat of a laser to magnetize the magnetic thin film in the direction of the bias magnetic field, while linearly polarized light is obtained. When the reflected laser beam is incident on the magnetic thin film and when it is reflected, the polarization plane of the light rotates depending on the direction of magnetization, and the rotation state is measured through an analyzer. A device for reproducing information is shown.

The structure of the writing means of this device will be briefly described. An optical system such as a laser light source and a lens for guiding light emitted from the laser light source to a magneto-optical disk and forming a light spot on the magneto-optical disk. And a coil for applying a bias magnetic field from the outside to the magnetic thin film of the magneto-optical disk in the middle of the magneto-optical disk and the focusing lens for forming a light spot included in the optical system on the magneto-optical disk.

[0012]

However, the structure for writing in the magneto-optical recording / reproducing apparatus shown in this article has the following problems.

That is, when a coil is arranged between the focusing lens and the magneto-optical disk, the distance between the focusing lens and the magneto-optical disk cannot be shortened because the coil needs a certain thickness.

On the contrary, in order to set the distance between the focusing lens and the magneto-optical disk to an appropriate value, the thickness of the coil must be made extremely thin, and in that case, the number of turns of the coil cannot be taken sufficiently.

Further, when an electric current is passed through the coil to generate a magnetic field, it is difficult to obtain a sufficient strength of the generated magnetic field as compared with the case where a permanent magnet is used.

Therefore, it is necessary to increase the current and the number of turns of the coil. However, increasing the current is not preferable because it causes heat generation and raises the temperature in the device, and increasing the number of coil turns slows down the response change of the magnetic field due to the increase in the inductance, and There is a problem that high-speed switching of the magnetic field supplied to the disk becomes difficult.

[0017]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems by providing a laser light source, a recording disk formed by forming a perpendicular magnetization film on a transparent substrate, and emitting from the laser light source. Optical means for optically modulating the generated light according to the recorded information and spot-irradiating the perpendicularly magnetized film through the transparent substrate, and the light-modulated spot-irradiating laser light and an electromagnet provided. In a magneto-optical recording / reproducing apparatus for recording information by a magnetic field, an electromagnet formed by winding a coil around a magnetic body for supplying a magnetic field to the perpendicularly magnetized film at the time of recording the information is incident on the recording disc. It is characterized in that it is arranged on the side opposite to the side.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings.

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

A case where a gas laser is used as a laser light source will be described.

In FIG. 1, reference numeral 3 denotes a laser light source, which is an optical modulator 4 for transmitting an information signal to be recorded, which is emitted from the laser light source 3, a polarizing prism 5 for passing only linearly polarized light, and a polarization plane for rotation. Faraday effect element 6,
The light is incident on the magneto-optical recording disk 12 that has passed through a polarization prism 7, a beam splitter 8, an optical path changing mirror 9, a λ / 4 plate 10 and a diaphragm lens 11 that pass only linearly polarized light. The return light from the disc 12 is the diaphragm lens 1 described above.
1, the λ / 4 plate 10 and the mirror 9, and the optical path is changed by the beam splitter 8, and the λ / 4 plate 13 and the analyzer 14
And passes through to enter the light receiving element 15. The magnetic field applied to the recording element during recording and erasing is applied from the back surface of the recording disk 12. Recording / erasing / playback will be described later.

Next, the recording disc 12 is constructed as shown in the sectional view of FIG. 2, for example. Ie 0.5mm to 2m thick
GdTb on a transparent glass or resin substrate 16 of about m
A perpendicular magnetization film 17 of an amorphous ferrimagnetic material made of a transition metal and a rare earth metal such as Fe or TbFe is formed, and a dielectric film 18 such as SiO _{2 is} further formed on the amorphous film 17.
Is formed, a reflection film 19 of Al, Au, Ag, or the like is formed on the dielectric film 18, and a supporting disk 20 made of glass, ceramic, metal, resin, or the like is bonded with an adhesive 21. The magnetic film 17 has a guide track 22 previously formed by crystallization and a recording track 23 for magnetic recording. The recording disk 12 is rotated at a predetermined speed by a motor 28.

Next, the case of recording information using the apparatus shown in FIG. 1 will be described. In order to record information by the recording device, the optical modulator 4 according to the information to be recorded,
An intensity change is given to the laser light, and the laser light is stopped by the aperture lens 1
1, the recording track 23 is illuminated with a spot of about 1 μmφ. Curie point recording or coercive force recording is performed on the recording track 23 according to the change in the intensity of the laser beam. At this time, a magnetic field is generated from the back surface of the recording disk 12 by the coil 24, and this magnetic field is applied to the recording track 23.

The coil 24 is made of a magnetic material 2 such as permalloy.
It is wound around 5 to make an electromagnet.

By the above method, the information is recorded on the recording track 23 as a magnetic domain which is vertically upward or vertically downward on the recording surface.

Next, a case of reproducing information will be described.

The reproduction of the information recorded by the above method is carried out by utilizing the so-called magneto-optical effect, which is the change in the polarization state and the amount of reflected light of reflected light when polarized light is incident on the recorded track.

Referring to FIG. 1, the laser light linearly polarized by a polarizing prism 5 such as a Gram-Thomson prism passes through a Faraday glass 6 such as FR-5 to have an azimuth angle of 45 °. Rotate. When the transmission axis of the next polarizing prism 7 is adjusted to the azimuth angle of the polarized light after passing through the Faraday glass 6, the loss of the light quantity is suppressed to the minimum. The light that has passed through the polarization prism 7 is incident on the recording track 23, is reflected by the change in the polarization state and the light amount,
It is guided to the light receiver 15 by the beam splitter 8.
At that time, the transmission axis of the analyzer 14 and the azimuth angle of the λ / 4 plate 13 are appropriately changed, and the signal noise ratio (S / S) corresponding to the recording state is changed.
N) is adjusted to be the largest. The λ / 4 plate 10 is also used to appropriately rotate and maximize the S / N.

Although the reflected light is generally elliptically polarized light,
The elliptical component is removed by the polarizer 7 and enters the Faraday glass 6. And the azimuth is set to 4 by Faraday glass 6.
The polarized light advanced by 5 ° is 90 ° with the pass axis of the polarizing prism 5.
Since the azimuth angle of the laser light source 3 is formed,
Is reflected in the direction of.

The Faraday glass 6 is placed in a ring-shaped magnet 26, and a coil 27 is wound around the magnet 26. That is, the magnet 26 aligns the magnetization of the Faraday glass in the direction of the laser beam, and the coil 27 corrects the Faraday rotation angle to 45 °. Therefore, depending on the type of Faraday effect element, only the magnet 26 or the coil 27 may be sufficient.

In the above description, FIG. 1 is a simplified diagram, and the optical system necessary for servo of the focus track and the lens system necessary for optimally focusing the laser light are omitted.

Further, although the recording / reproducing has been described with respect to the gas laser, the recording / reproducing in the case of using the semiconductor laser is performed in exactly the same manner except that the modulator 4 is unnecessary.

Although a disk is used as the recording medium in the above description, reproduction is possible within the scope of the present invention as long as information can be recorded in the form of magnetic domains on a recording medium having a magnetization perpendicular to the film surface. This is also possible, and the present invention can also be applied to a tape-shaped, drum-shaped, sheet-shaped, or other storage element instead of a disc body.

[0034]

According to the present invention described above, a laser light source,
A recording disk formed by forming a perpendicular magnetic film on a transparent substrate, and light emitted from the laser light source is light-modulated according to recorded information, and the perpendicular magnetic film is spot-irradiated through the transparent substrate. In a magneto-optical recording / reproducing apparatus having optical means and recording information by the light-modulated spot irradiation laser light and a magnetic field given from an electromagnet, a magnetic field is supplied to the perpendicular magnetization film at the time of recording the information. Therefore, an electromagnet formed by winding a coil around a magnetic body is arranged on the light incident side of the recording disk and on the reflection side thereof, and there is a positional restriction of the optical system on the light incident side of the recording disk. Since the number is small, it is possible to bring the focusing lens for performing light modulation and spot irradiation on the perpendicular magnetic film sufficiently close to the perpendicular magnetic film. Furthermore, since the electromagnet has a coil wound around a magnetic body, it can generate a strong magnetic field with a small amount of current, suppress heat generation, and reduce reactance, so that the magnetic field generated from the electromagnet can be controlled at high speed. .

[Brief description of drawings]

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

FIG. 2 is a partially enlarged side sectional view showing an example of a magneto-optical recording disk.

[Explanation of symbols]

 3 Laser light source 5, 7 Polarizing prism 6 Faraday effect element 12 Magneto-optical storage disk

Claims (1)

[Claims] 1. A laser light source, a recording disk comprising a transparent substrate on which a perpendicularly magnetized film is formed, and light emitted from the laser light source is optically modulated in accordance with recording information, and is transmitted through the transparent substrate. An optical means for irradiating a spot on a perpendicularly magnetized film, and performing information recording by the magnetic field applied from the light-modulated spot irradiating laser light and an electromagnet. Magneto-optical recording / reproducing, characterized in that an electromagnet formed by winding a coil around a magnetic body for supplying a magnetic field to the perpendicularly magnetized film is arranged on the side opposite to the light incident side of the recording disk. apparatus.