JPS613343A - Optical reproducing head of magnetooptic system - Google Patents

Abstract

PURPOSE:To read out information form plural areas with a single reproducing head by deforming the sectional shape of a radiated reading optical beam to project this beam to plural areas on a magnetic recording medium and receiving the reflected or transmitted light through an analyzer. CONSTITUTION:The reading optical beam radiated from a light source 1 is converged by a cylindrical lens 4 and an object lens 9 after passing through a polarizer 2 and a half mirror 3 and is projected onto a magnetic transfer medium 5. Information magnetically recorded on plural tracks of a magnetic recording medium 10 which is run in the direction of an arrow while being a gap apart from the lower face of the medium 5 are transferred from individual tracks simultaneously as the variance of magnetization in the thickness direction of the medium 5. The optical beam which passed through the medium 5 and is reflected on a reflecting film formed on the rear face and is discharged is reflected on the mirror 3 and is inputted to an analyzer 7 through a concave lens 6. The output of the analyzer 7 is inputted to a multidivision sensor 8 to reproduce information recorded on plural tracks of the medium 10, and thus, information in plural areas is read out by the single reproducing head.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention Industrial Field of Application The present invention relates to a magneto-optical reproduction method that uses magneto-optic effects to read information such as video signals magnetically recorded on a magnetic recording medium. It is related to the head.

In conventional magneto-optic reproducing heads, the diameter of the readout light beam is considerably larger than the realizable magnetic recording wavelength, so the shortening of the magnetic recording wavelength is difficult.

This cannot be said to be an effective means for increasing the read speed. Therefore, conventionally, in order to increase the read speed.

The relative speed (linear velocity) between the recording medium and the playback head was increased, and a multi-track system was adopted.

Problems to be Solved by the Invention However, the method of increasing the linear velocity has its own limitations, taking into account constraints on the control mechanism, the strength and wear resistance of the material, etc.

Furthermore, the multi-track system requires as many playback heads as the number of tracks, making the entire playback device expensive and complicating the control mechanism and assembly work.

Structure of the Invention Means for Solving the Problems The magneto-optical reproducing head of the present invention which solves the problems of the prior art described above has a light source that emits a readout light beam and a cross-sectional shape of the emitted readout light beam. A light beam cross-sectional shape changing means for transforming and projecting a light beam onto a plurality of tracks on a magnetic recording medium or a plurality of magnetic transfer areas formed above the plurality of tracks; The light receiving element is configured to include a light receiving element that receives the light beam through an analyzer.

The effects of the present invention will be explained below based on two examples.

Embodiment FIG. 1 is a sectional view showing the structure of an embodiment of a magneto-optical reproducing head according to the present invention together with a 5MI optical recording medium. The magneto-optical reproducing head of this embodiment is implemented as a magnetic transfer type. In this magnetic transfer type reproducing head, 1 is a light source, 2 is a polarizer, 3 is a half mirror, 24 is a cylindrical lens, 5 is a magnetic transfer medium, 6 is a concave lens, 7 is an analyzer, 8 is a multi-segment sensor, and 9 is a It is an objective lens.

This magnetic transfer type optical reciprocating head simultaneously reads information recorded as horizontal magnetization in a plurality of tracks on a magnetic recording medium 10 using a magnetic recording head (not shown).

The light source 1 is composed of a semiconductor laser or the like, and a reading light beam emitted from the light source 1 is linearly polarized by a polarizer 2. The linearly polarized reading light beam passes through a half mirror 3, is converged by a cylindrical lens 4 and an objective lens, and is projected onto a magnetic transfer medium 5.

The magnetic transfer medium 5 is made of a Bi-substituted magnetic garnet film or the like having a thickness of, for example, about 10 μm and having an axis of easy magnetization in the thickness direction. This magnetic transfer medium 5 transfers information magnetically recorded in a plurality of tracks on a magnetic recording medium 10 running in the direction of the arrow in the figure while maintaining a gap with the lower surface thereof, by magnetizing it in the thickness direction of the magnetic transfer medium 5. are transferred simultaneously from each track as a change in . On the magnetic recording medium 10, a recording area (horizontal signal magnetic domain) with a width of about 100 μm and a recording wavelength of several μm is formed in a multi-track format using a general-purpose ring-shaped write head or the like.

Each signal magnetic domain in each track is transferred to the magnetic transfer medium 5 as vertical magnetization due to leakage magnetic flux when passing under the magnetic transfer medium.

The reading light beam focused by the cylindrical lens 4 and the objective lens 9 and projected onto the magnetic transfer medium 5 passes through the magnetic transfer medium 5 and is then reflected by a reflective film formed on the back surface thereof.

It passes through the magnetic transfer medium 5 again and is ejected upward.

At this time, the direction of the linearly polarized light beam is rotated 2 to 3 degrees to the left or right depending on the direction of magnetization transferred to the magnetic transfer medium 5 due to the Faraday effect. Here, as shown in FIG. 1, we define an orthogonal coordinate system (x, y, z) having an X axis perpendicular to the page, a y axis above the drawing, and two axes in the running direction of the magnetic recording medium 10. Suppose. half mirror
The reading light beam that has entered the cylindrical lens 4 via the cylindrical lens 3 is converged in two directions by the cylindrical lens 4, but not in the X direction.

Therefore, the cross-sectional shape of the reading light beam projected onto the magnetic transfer medium 5 is in the vertical direction (z
The width in the lateral direction (X-axis direction) is larger than the width in the axial direction. Cylindrical lens 4 and objective lens 9
The width of the reading light beam projected onto the magnetic transfer medium 5 in two axes is approximately equal to half the minimum recording wavelength (minimum recording section) on the magnetic recording medium, while the width in the X-axis direction The width of the track is set to be approximately equal to the track width of the number of tracks to be simultaneously read.

In the example of FIG. 2, the reading light beam is
The light beam is irradiated over five areas TI to T5 on the magnetic transfer medium 5 onto which five tracks of information on the magnetic transfer medium 5 are transferred, and the five tracks of information are simultaneously read out. Note that the horizontal lines in FIG. 2 indicate recording areas on the assumption that the minimum recording sections are continuous in each track on the magnetic recording medium 10.

The light beam emitted from the magnetic transfer medium 5 passes through the objective lens 9 and the cylindrical lens 4 again to the half mirror 3.
, and enters the concave lens 6. The reading light beam is diverged by the concave lens 6.

The light enters the analyzer 7. The analyzer 7 is configured to block the readout light beam in which the linearly polarized light is rotated in one direction, and to allow the readout light beam in which the linearly polarized light is rotated in the other direction to pass through.

As shown in FIG. 3, the multi-division sensor 8 includes five regions S1 electrically separated and formed on one silicon substrate.
Avalanche photodiodes (A
PD), etc.

This multi-segment sensor 8 is provided with a readout light beam with an amount of light corresponding to the direction of magnetization recorded in each of the five tracks of the magnetic recording medium 10, as shown by the shaded area in FIG. is incident as an elliptical light beam, and the information recorded as the direction of VA is reproduced as the magnitude of the amplitude of the electrical signal.

In the above, a structure in which the readout light beam is deformed by a cylindrical lens has been exemplified, but instead of this, readout can be performed by using an appropriate optical element such as a prism, a diffraction grating, a slit, or an asymmetrically deformed curved reflecting mirror. It is possible to have a configuration in which the optical beam for use is deformed.

Furthermore, although a configuration in which a multi-segment sensor is used as a light receiving element has been exemplified, a configuration in which a plurality of individual light receiving elements are used may be used.

Furthermore, by arranging the analyzer 7 and the light receiving element near the half mirror 3, the concave lens 6 can be omitted.

Furthermore, although a configuration using a magnetic transfer type optical reproducing head has been illustrated, the present invention can also be applied to a system in which information is perpendicularly recorded on a magnetic recording medium having a magneto-optical effect, and the information is directly read out by an optical reproducing head. You can also do that. In this case, it may be configured to receive transmitted light instead of receiving reflected light from the magnetic recording medium.

Effects of the Invention As described above in detail, the magneto-optical reproducing head of the present invention comprises a light beam cross-sectional shape changing means for transforming the cross-sectional shape of the emitted reading light beam and projecting it onto a plurality of tracks; Since it is configured to include a light receiving element that receives light beams reflected or transmitted from multiple tracks via an analyzer, information on multiple tracks can be read at once without using multiple playback heads. be able to.

Therefore, the reproduction head becomes inexpensive, and the entire reproduction apparatus can be made inexpensive.

Furthermore, since there is only one reproducing head, it is possible to read information at high speed using a drive system with a simple configuration.

5. Since the magneto-optical reproducing head of the present invention is configured to reproduce information by utilizing the rotation of the polarization direction due to the magneto-optic effect, it is possible to record/reproduce information using changes in the optical reflectance or optical transmittance of the recording medium. Unlike other methods, even if a single light source is used, there is almost no crosstalk problem due to interference from each track.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of a magneto-optical reproducing apparatus according to the present invention. 1. Light source, 2. Light beam splitting element, 3. Half mirror 14. Cylindrical lens. 5. Magnetic transfer medium, 6. Concave lens, 7. Analyzer,
8...Photoelectric conversion element, 9...Objective lens. 10...Magnetic recording medium, 'r1 to T5...5 tracks on the magnetic recording medium. Patent applicant: NEC Home Electronics Co., Ltd.

Claims (1)

[Claims] A light source that emits a readout light beam, and a cross-sectional shape of the emitted readout light beam that is modified to form a plurality of tracks on a magnetic recording medium or above the plurality of tracks. Magneto-optics characterized by comprising: means for changing the cross-sectional shape of a light beam projected onto a plurality of magnetic transfer areas; and a light receiving element that receives the light beam reflected or transmitted from the plurality of tracks or magnetic transfer areas via an analyzer. expression playback head.