JPS6043246A - Photo magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain such a device with good optical effect that only one head is employed with a light source having a relatively low output and the size of the head is reduced by using a polarizing prism and a Faraday effect element on an optical path in combination. CONSTITUTION:Light polarized by the polarizing prism 22 is transmitted with the plane of polarization rotated by a specific angle theta through the Faraday effect element 23, and converged on the recording layer of a magnetic recording medium 26 through an objective lens 24. The part of the recording layer irradiated with the light rises in temperature, and when the temperature rises almost up to the Curie point, the coercive force decreases to cause magnetism inversion by a magnetic field produced by an electromagnet 25. In this case, the magnetic field established by the electromagnet 25 is set smaller than the coercive force of said recording layer at room temperature, and consequently the recording layer is not magnetized except where the layer is not irradiated with the light. For the purposed, the radiation of the light source 20 is controlled according to a signal of information to be recorded to record the information on the magnetic recording medium 26.

Description

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

:'LD layer of magnetic recording medium is, for example, T b -F e
.

It is composed of a magneto-optical recording magnetic film having perpendicular anisotropy, such as a G d -1' b -F c amorphous film. A laser beam modulated based on the information to be recorded in this recording layer is irradiated, and the laser irradiated area of this recording layer is heated to approximately one Curie temperature, and the stray magnetic field or forced magnetic field around the recording layer is heated. A magneto-optical recording method has been proposed in which magnetic recording is performed by reversing the magnetization of the magnetic domain in the irradiated area using a forced magnetic field generated by the magnetic field.

Figure 1 shows the schematic configuration of the optical system of a conventional device for performing magneto-optical recording, reproduction, and erasing. Collimator lens to obtain.

3 is a polarizer, 4 is a half mirror, 15 is an objective lens,
6 is an electromagnet, 7 is a magnetic recording medium, 8 is an analyzer, and 9 is a photodiode 1.

However, in such conventional bag FT, 1 to F+.

Since the half mirror 4 is used to separate the laser beam from the chemical laser 1 and the reflected light from the magnetic recording medium 7, there is a loss of light. For example, if a half mirror 4 with a transmittance of 50% is used, 50% of the laser light will be ineffective light that does not reach the magnetic recording medium 7. In the above optical system, when the collimator lens 2 is made of Na.0.25, the efficiency of removing the half mirror 4 is about 50%, and multiplying this by the transmittance of the half mirror 4 is the magnetic Efficiency of light actually used for recording (0.5 x 0.5 =
0.25; 25%).

Currently, the maximum rated output of semiconductor lasers used in optical disks, etc. is about 5 milliwatts (mW), and when a half mirror with a transmittance of 50% is used, the maximum output power is 1.2 watts.
Only 5 milliwatts reaches the surface of the magnetic recording medium. The power of this laser beam is not necessarily sufficient as the laser beam power of about 1 to 10 milliwatts, which is necessary for magneto-optical recording or erasing. In order to compensate for this, a light source such as a high-output semiconductor laser or a laser beam can be used, or, as shown in Figure 2, two heads, the recording/erasing head (I) and the reproducing head (11), can be used. It is necessary to use a magneto-optical recording device. Half mirror for recording/erasing head (1)
efficiency is increased by not using In FIG. 2, IO is a polarizing prism, 11 is a quarter wavelength plate, and the same parts as in FIG. 1 are given the same reference numerals, and repeated explanations will be omitted. 1) Polarizing prism lO and quarter wave plate 11
is provided to prevent the reflected light from the magnetic recording medium 7 from returning to the V conductor laser 1 and to detect focus errors, 1-rack errors, etc. The reduction in optical power efficiency due to the provision of the polarizing prism 10 and quarter wavelength plate 11 is considered to be within 10%.

As can be seen from the above, both the method of using a high-output light source such as a conductor laser or gas laser, and the method of using two heads have the drawback of increasing the size and cost of the equipment. Ta.

It is an object of the present invention to provide a magneto-optical recording/reproducing device which has a simple structure, uses a relatively low-output light source, and has a single head, and has a miniaturized head and high optical efficiency. There is a particular thing. .

The above and other LI-related and novel features of the present invention! l! J characteristics will become clear from the description of this specification and the accompanying drawings.

The structure of the present invention will be explained below along with examples.

FIG. 3 is a diagram showing a schematic configuration of an optical system according to an embodiment of the present invention.

In FIG. 3, 20 is a light source, for example, a semiconductor laser, a gas laser, etc. are used. A collimator lens 21 converts the light emitted from the light source 20 into parallel light. Reference numeral 22 denotes a polarizing prism, which has a configuration as shown in FIG. 4, for example. That is, perpendicular (90°) to the reflective surfaces R and F of the polarizing prism 22.
Only the component (hereinafter referred to as the 1) component) becomes linearly polarized light, and only the component parallel to the reflecting surface RF (hereinafter referred to as the S component) is reflected, or the opposite component is transmitted and reflected by a polarizing prism. be. For example, Grand 1 ~ Musomburi 1%
, Nicol Priz 11, etc. can be used.

Reference numeral 23 denotes a Faraday effect element, which rotates the polarization direction in the same direction even when the traveling direction of the light is reversed. That is, it is a magnetic optical rotation element, and unlike the case of natural optical rotation, the rotation angle is the same even if the traveling direction of the light is iφ, so when the light is reflected in a medium, the rotation angle is doubled. The strength of the magnetic field is I+.

Assuming that the distance through which light passes through the substance is 0 and the proportionality constant is 2, the rotation angle O of the plane of polarization by the Faraday effect element 23 is as follows: 0 = V ) - I L . For a ferromagnetic metal thin film, if the magnetization M is substituted for the magnetic field 11, the proportional relationship with 0 will be j:(i).

24 is an objective lens, and 25 is an electromagnet. 26 is a magnetic recording medium such as a magneto-optical disk, for example, T b −
Fe, Gd-Tb-FC! A magnetic recording layer (hereinafter referred to as BM) having perpendicular anisotropy, such as an amorphous film, is formed on a synthetic resin or glass substrate by vapor deposition, sputtering (IN, etc.).

The temperature of the portion of the recording layer irradiated with light increases, and as the temperature increases to near the Curie point, the coercive force decreases.
It is magnetized in the direction of rdlW. 27 is a light receiving element such as a photodiode.

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

(1) When performing recording Light emitted from the light source 20 is converted into parallel light by the collimator lens 21 and irradiated onto the polarizing prism 22 . The irradiated parallel light is reflected by the reflective surface R of the polarizing prism 22.
For example, with respect to F, only the P component light is linearly polarized and transmitted.

Here, if a semiconductor laser or the like is used as the light source 20, the emitted laser light has a certain degree of polarization characteristics, so this polarization direction should be set to the direction of P polarization (linear polarization) of the polarizing prism 22. For example, most of the laser light passes through the polarizing prism 22, with little loss of light.

The light polarized by the polarizing prism 22 passes through the Faraday effect element 23 with its plane of polarization rotated by a predetermined angle of 0, and is focused by the objective lens 24 onto the recording layer of the magnetic recording medium 26 . The temperature of the portion of the recording layer irradiated with light increases, and when the temperature rises to near the Curie point, the coercive force decreases and the magnetization is reversed by the magnetic field created by the electromagnet 25. If the magnetic field created by the electromagnet 25 is made smaller than the coercive force of the recording layer at room temperature, the portion that is not irradiated with light will not be magnetized in the direction of the magnetic field.

Therefore, information is recorded on the magnetic recording medium 26 by controlling the radiation of the light source 20 according to the signal of the information desired to be recorded.

(2) When performing erasing The operation of erasing information recorded on the recording layer of the magnetic recording medium 26 is almost the same as the recording operation, but the light source 20 continuously emits light and the electromagnetic By passing a current opposite to that of the recording operation through the magnetic recording medium 25 and reversing the magnetic field applied to the magnetic recording medium 26, the magnetic recording medium 26 is
The recording layer is magnetized in the opposite direction to the recorded information. In other words, the recorded information is erased.

(3) When reproducing information When reproducing information recorded on the recording layer of the magnetic recording medium 26, the light source 20
The optical power emitted from the magnetic recording medium 26 is also set to such a level that the magnetization of the recording layer of the magnetic recording medium 26 is not reversed.

The light emitted from the light source 20 undergoes BP conversion by the collimator lens 21 and enters the polarizing prism 22 .

In the parallel light incident on the polarizing prism 22, only its P component is linearly polarized and transmitted through the reflecting surface RF of the polarizing prism 22. The plane of polarization of this polarized light is rotated by a predetermined angle φ by the Faraday effect element 23, focused by the objective lens 24, and irradiated onto the recording layer of the magnetic recording medium 26. This irradiated light is reflected by the recording M.

At the time of this reflection, the polarization direction of the reflected light is rotated to the left or right by an angle ek depending on the magnetization direction of the recording layer.

The light reflected by the recording layer of the magnetic recording medium 26 is turned into parallel light again by the objective lens 24, and the plane of polarization is further rotated by a predetermined angle φ by the Faraday effect element 23.
The light is incident on the polarization prism 1122. Regarding the polarization direction of the light at this time, only the S component is reflected by the reflecting surface RF of the polarizing prism 22. The amount of light of this reflected polarized beam is the incident light multiplied by sjn'' (2φ±ek).

The signs of r-4-J and r-J for ±θ in this equation change depending on the magnetization direction of the portion of the recording layer of the magnetic recording medium 26 that is irradiated with light. That is, recorded information is detected based on the magnetization direction of the recording layer irradiated with the light. Here, the Faraday effect element 23 plays the same role as the analyzer 8 in the conventional device.

The light reflected by the polarizing prism 22 is incident on a light receiving element 27 made of a fort diode or the like. This change in the intensity of the incident light causes the magnetic recording medium 26 to
information recorded on the recording layer of the device can be read.

Although it is effective if the rotational power of the Faraday effect element 23 is even small, it is desirable that the rotational power is less than the angle (-) k. However, 22.5° or more is not necessary.

Further, when an avalanche effect first diode is used as the light receiving element 27, the rotational power of the Faraday effect element 23 may be relatively small.

As explained above, according to the technical means disclosed in the description of this specification and the accompanying drawings, by using a polarizing prism and a Faraday effect element together on the optical path,
Conventional equipment polarizer, half mirror, analyzer, 4
Since the half-wave plate and the like can be omitted, the device can be made smaller. Furthermore, a single head can be achieved using a relatively low output light source. For example, if a collimator lens with Na 0.25 is used, approximately 50% of the light emitted from the light source (approximately twice as much as before) can reach the magnetic recording medium, so it can be used as a collimator lens for low-power light sources. Even one head can sufficiently supply the optical power necessary for recording and erasing.

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 drawings]

1 and 2 are diagrams showing a schematic configuration of an optical system of a conventional magnetic recording/reproducing device. FIG. 3 is a diagram showing a schematic configuration of an optical system of an embodiment of the present invention. , is a diagram showing an example of a polarizing prism. 20...Light source, 21...Collimator lens, 22
...Polarizing prism, 23...Faraday effect element, 24...Objective lens, 25...Electromagnet, 26...
Magnetic recording medium, 27... Light receiving element. Agent Patent Attorney Shuki Akita Figure 2 Figure 3 (II) ■

Claims (1)

[Claims] In an apparatus for recording and reproducing information using light and magnetism, a polarizing prism provided in an optical path "2" between a light source and a magnetic recording medium; and a polarizing prism provided in an optical path "2" between the polarizing prism and the magnetic recording medium. What is claimed is: 1. A magneto-optical recording and reproducing apparatus comprising: a Faraday effect element that rotates a plane of polarized light by a predetermined angle; and a light receiving element that receives reflected light from the polarizing prism and converts it into electricity.