JPH0512780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a magneto-optical recording and reproducing device that reproduces information recorded on a perpendicularly magnetized film using a laser beam.

In recent years, optical memory devices have been widely studied as high-density, large-capacity, and high-speed access memory devices, and the following three types can be considered.

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

Something that can be played back and additionally recorded.

In addition to playback and additional recording, it is also possible to erase unnecessary information and re-record.

Of these, the devices in . have already reached the stage of practical use, but the devices in .

The present invention records and erases information thermomagnetically using a laser beam such as an Ar laser, HeCd laser, HeNe laser, or semiconductor laser, and reproduces the information using the magneto-optic effect. The present invention relates to a magneto-optical recording/reproducing device which aims to put the device into practical use.

<Prior Art> Until now, very few practical systems of magneto-optical recording and reproducing devices have been reported.

An example of something close to practical use is the Dempa Shimbun Magnetic Memory Special Feature on Electronic Technology (published on September 18, 1980).

In this article, writing is performed by heating a magnetic thin film made of an amorphous alloy mainly composed of iron to the Curie point using laser heat, and magnetizing it in the direction of a bias magnetic field. A beam is incident on a magnetic thin film, and when it is reflected, the plane of polarization of the light rotates depending on the direction of magnetization. Information is reproduced by measuring the state of rotation using an analyzer. The device that does this is shown.

The structure of the writing means of this device will be briefly explained: a laser light source, an optical system such as a lens that guides the light emitted from the laser light source to the magneto-optical disk and forms a light spot on the magneto-optical disk, and the above-mentioned optical system. It consists of a coil that is located between the magneto-optical disk and a focusing lens that forms an optical spot included in the optical system on the magneto-optical disk, and applies a bias magnetic field from the outside to the magnetic thin film of the magneto-optical disk.

<Problems to be Solved by the Invention> However, the following problems arose in the configuration for writing in the magneto-optical recording/reproducing device shown in this article.

That is, when a coil is placed 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 must be thick to some extent.

Conversely, 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 very thin, and in this case, the number of turns of the coil cannot be sufficient.

Furthermore, when a magnetic field is generated by passing a current through a coil, it is difficult to obtain a sufficient strength of the generated magnetic field compared to when using a Hikyu magnet.

Therefore, it is necessary to increase the current or increase the number of turns of the coil. However, increasing the current is undesirable because it generates heat, which increases the temperature inside the device, and increasing the number of turns in the coil increases the inductance, which slows down the response change of the magnetic field and magneto-optically. There is a problem in that it becomes difficult to quickly switch the magnetic field supplied to the disk.

<Means for Solving the Problems> The present invention solves these conventional problems, and includes: a laser light source; a recording disk formed by forming a perpendicularly magnetized film on a transparent substrate; an optical means for spot-irradiating the emitted light onto the perpendicularly magnetized film through the transparent substrate; and a light incident side of the recording disk is a reflective side,
An electromagnet formed by winding a coil around a magnetic material is provided to supply a magnetic field to the perpendicularly magnetized film during information recording, and information is recorded using the laser beam emitted from the laser beam and the magnetic field provided by the electromagnet. It is characterized by this.

<Example> Hereinafter, an example according to the present invention will be described in detail using the drawings.

FIG. 1 is a diagram showing a simplified configuration of an embodiment of a magneto-optical storage/reproduction device according to the present invention.

A case will be described in which a gas laser is used as the laser light source.

In the figure, 3 is a laser light source, an optical modulator 4 that is emitted from the laser light source 3 and transmits an information signal to be recorded into the light, a polarizing prism 5 that passes only linearly polarized light, and a Faraday effect that rotates the plane of polarization. Light that has passed through the element 6, the polarizing prism 7 that allows only linearly polarized light to pass through, the beam splitter 8, the optical path changing mirror 9, the λ/4 plate 10, and the aperture lens 11 is incident on the magneto-optic storage disk 12. The returning light from this disk 12 is transmitted through the aperture lens 11,
The light passes through a λ/4 plate 10 and a mirror 9, has its optical path changed by a beam splitter 8, passes through a λ/4 plate 13 and an analyzer 14, and enters a light receiving element 15. or,
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/
Reproduction will be described later.

Next, the recording disk 12 has a structure as shown in the sectional view of FIG. 2, for example. That is, on a transparent glass or resin substrate 16 with a thickness of about 0.5 mm to 2 mm.
Perpendicular magnetization film 17 of amorphous ferrimagnetic material made of rare earth metals such as GdTbFe and TbFe and transition metals
is formed on the amorphous film 17.
A dielectric film 18 such as SiO ₂ is formed, and the dielectric film 1
A reflective film 19 made of Al, Au, Ag, etc. is formed on 8, and a support disk 20 made of glass, ceramic, metal, resin, etc. is pasted together with an adhesive 21. The magnetic film 17 has a guide track 22 formed in advance by crystallization and a recording track 23 for performing magnetic recording. This recording disk 12 is rotated by a motor 28 at a predetermined speed.

Next, a case where information is recorded using the apparatus shown in FIG. 1 will be explained.

To record information using the storage device, the optical modulator 4 changes the intensity of the laser beam according to the information to be recorded, and the laser beam is focused through the aperture lens 11.
The recording track 23 is irradiated with a spot of approximately 1 μmφ. Curling point recording or coercive force recording is then performed on the recording track 23 in response to changes in the intensity of the laser beam. At this time, the recording disk 12
A magnetic field is generated by a coil 24 from the back side of the recording track 23, and this magnetic field is applied to the recording track 23.

The coil 24 is wound around a magnetic material 25 such as permalloy to form an electromagnet.

By the above method, information is recorded on the recording track 23 as magnetic domains pointing vertically upward or vertically downward to the recording surface.

Next, the case of reproducing information will be explained.

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

To explain with reference to FIG. 1, the laser beam, which has been linearly polarized by a polarizing prism 5 such as a Gram-Thompson prism, is transmitted through a Faraday glass 6 such as FR-5.
By passing through, the azimuth is rotated by 45°.
By aligning the transmission axis of the next polarizing prism 7 with the azimuth of the polarized light after passing through the Faraday glass 6, the loss of light amount can be minimized. The light that has passed through the polarizing prism 7 is incident on the recording track 23, is reflected as the polarization state and light amount changes, and is guided to the light receiver 15 by the beam splitter 8. At this time, the transmission axis of the analyzer 14 and the azimuth angle of the λ/4 plate 13 are appropriately changed to adjust the signal-to-noise ratio (S/N) corresponding to the recording state to be the largest. λ/
The four plates 10 are also rotated appropriately and used to maximize the S/N ratio.

The reflected light is generally elliptically polarized light, but the elliptical component is removed by the polarizer 7 and enters the Faraday glass 6. The polarized light whose azimuth angle has been advanced by 45 degrees by the Faraday glass 6 makes an azimuth angle of 90 degrees with the passage axis of the polarizing prism 5, so it is not returned to the direction of the laser light source 3 but is reflected in the direction C.

The Faraday glass 6 is placed inside a ring-shaped magnet 26, and a coil 27 is placed outside the magnet 26.
Create a rolled configuration. 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 degrees. Therefore, depending on the type of Faraday effect element, only the magnet 26 or only the coil 27 may be sufficient.

In the above explanation, FIG. 1 is a simplified diagram,
Optical systems necessary for servo such as focus tracks and lens systems necessary to optimally focus the laser beam are omitted.

Furthermore, although the above description of recording and reproducing has been made with respect to a gas laser, recording and reproducing when a semiconductor laser is used is performed in exactly the same way except that the modulator 4 is not required.

Furthermore, although a disk was used as the recording medium in the above explanation, 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 that has magnetization perpendicular to the film surface. , instead of a disk, the present invention can be applied to a tape-shaped, drum-shaped, sheet-shaped memory element, etc.

<Effects> According to the present invention described above, the light emitted from the laser light source is spot irradiated onto the perpendicularly magnetized film of the recording disk through the transparent substrate, and the perpendicularly magnetized film of the recording disk is spot-irradiated on the side opposite to the light incident side of the recording disk. Since it is equipped with an electromagnet formed by winding a coil around a magnetic material, there are fewer positional constraints on the optical system on the light incident side of the recording disk, so the focusing lens for spot irradiating the perpendicularly magnetized film can be placed perpendicularly. It can be brought sufficiently close to the magnetized film. Furthermore, since the electromagnet has a coil wound around a magnetic material, it is possible to generate a strong magnetic field with a small amount of current, which can suppress the generation of heat.Also, because the reactance can be reduced, the direction of the magnetic field generated by the electromagnet can be switched at high speed. It is possible to switch the magnetic field to

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of an embodiment of a magneto-optical recording/reproducing apparatus according to the present invention, and FIG. 2 is a partially enlarged side sectional view showing an example of a magneto-optic storage disk. In the figure, 3: laser light source, 5, 7: polarizing prism, 6: Faraday effect element, 12: magneto-optic storage disk.

Claims (1)

[Claims] 1. A laser light source, a recording disk formed by forming a perpendicularly magnetized film on a transparent substrate, and spot irradiation of light emitted from the laser light source onto the perpendicularly magnetized film via the transparent substrate. an optical means for causing the recording disk, and the light incident side of the recording disk is on the reflective side,
An electromagnet formed by winding a coil around a magnetic material is provided for supplying a magnetic field to the perpendicularly magnetized film during information recording, and information is recorded using a laser beam emitted from a laser light source and a magnetic field provided by the electromagnet. A magneto-optical recording and reproducing device characterized by: