JPH11296926A - Magneto-optical record medium recording device and recording method therefor and magneto-optical record medium reproducing device and reproducing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the capacity of a magneto-optical record medium large and also to make the density of the medium high and to realize the correct recording and reproduction of information. SOLUTION: This device is provided with a magneto-optical record medium 1 that a first magnetic layer 4 is formed on the surface of one side of a substrate 2 and a second magnet layer 7 is formed on the surface of other side of the substrate 2, a first light source 10 irradiating the second layer 7 via the first magnetic layer 4 with a light beam, a first magnetic field generating means 15 orienting the magnetic polarity of the part on which the light beam from the light source 10 is to be focused of the second magnetic layer 7, a second light source 20 irradiating the first magnetic layer 4 via the second magnetic layer 7 with a light beam and a second magnetic field generating means 25 orienting the magnetic polarity of the part on which the light beam from the light source 20 is to be focused of the first magnetic layer 4, and an information signal is recorded on the second magnetic layer 7 by the light beam from the first light source 10 and the first magnetic field generating means 15 and an information signal is recorded on the first magnetic layer 4 by the light beam from the first light source 20 and the second magnetic field generating means 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus and method for recording information on a magneto-optical recording medium having magnetic recording layers on both surfaces of a substrate, and a reproducing apparatus for reproducing information recorded on the magneto-optical recording medium. And a method of reproducing the same.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium capable of recording and reproducing information, a magneto-optical recording medium which records or reproduces an information signal by irradiating a light beam to the magnetic recording medium has been used.

In this magneto-optical recording medium, a magnetic recording layer, a dielectric layer or a reflective layer for recording or reproducing information signals is laminated on one surface of a transparent substrate made of synthetic resin such as glass or polycarbonate resin. ing.

In order to record an information signal on the magneto-optical recording medium, first, a light beam is focused on the magneto-optical recording medium and partially heated to a temperature above the Curie point. The coercive force of Then, by applying a recording magnetic field from outside using a magnetic field generating means such as a magnetic field head to the portion where the coercive force of the magneto-optical recording medium is reduced, the magnetization direction is oriented to the magnetic field direction of the recording magnetic field. Signal recording is performed, and so-called recording pits, which are magnetic domain units to be oriented, are formed.

On the other hand, to reproduce an information signal recorded on a magneto-optical recording medium, a light beam is focused on the magneto-optical recording medium, and the light beam reflected from the magneto-optical recording medium is reflected by a photodetector. By the detection, the information signal recorded on the magneto-optical recording medium is reproduced.

Here, the information contained in the reflected light reflected from the magneto-optical recording medium includes the Kerr rotation angle and the Kerr ellipticity.
The information signal is reproduced by either a change in the Kerr rotation angle or a change in the Kerr ellipticity of the light beam irradiated on the magneto-optical recording medium and reflected from the magneto-optical recording medium.

[0007]

In the magneto-optical recording medium, the areal recording density is determined mainly by the S / N, which is the ratio between the signal and the noise at the time of reproduction. Also,
The signal amount at the time of reproduction is represented by the period f of the pit row as a magnetic domain unit of the recorded signal and the wavelength λ of the light beam of the reproduction optical system.
It is also known that it largely depends on the numerical aperture NA of an objective lens for focusing a light beam on a magneto-optical recording medium. That is, in the conventional reproducing method of the magneto-optical recording medium,
If the wavelength of the light beam emitted from the light source of the reproduction optical system is λ, the numerical aperture of the objective lens is NA, and the period of the detectable pit is f, then f = λ / 2NA. Therefore, as a method of increasing the density of the magneto-optical recording medium, there are a method of shortening the wavelength λ of the light beam and a method of increasing the numerical aperture NA of the objective lens.

However, there is a limit to shortening the wavelength of a light beam used for recording and reproduction on a magneto-optical recording medium and increasing the numerical aperture of an objective lens.

On the other hand, to increase the capacity of a magneto-optical recording medium 1
As one method, a magnetic recording layer is formed on both sides of the substrate, a light beam is irradiated from the surface close to the magnetic recording layer, and the direction of magnetization of the part irradiated with this light beam and heated above the Curie point is determined by the magnetic field generation means 2. Description of the Related Art A double-sided recording type magneto-optical recording medium capable of recording an information signal by orienting by an applied magnetic field has been proposed.

[0010] By using such a magneto-optical recording medium, information can be recorded on the magnetic recording layers provided on both sides of the substrate. Is twice as large as that of a single-sided magneto-optical recording medium provided with.

In the conventional method using a double-sided recording type magneto-optical recording medium, an objective lens that focuses a light beam emitted from a light source on the magneto-optical recording medium and a magnetic lens provided on the magneto-optical recording medium are used. Since the magnetic field generating means is disposed between the magnetic recording layer and the recording layer, the distance between the objective lens and the magnetic recording layer increases, making it difficult to increase the numerical aperture NA of the objective lens. Further, since the objective lens and the magnetic field generating means are arranged on the light source side, the configuration of the optical head becomes complicated.

Also, a so-called dual-type, in which, for example, two magnetic recording layers are formed on one surface side of the substrate, and each of the magnetic recording layers is irradiated with a light beam to record and / or reproduce information signals. Layer discs have been proposed. When recording information on this dual-layer disc by magneto-optical recording, an optical head is arranged on the substrate side to irradiate a light beam on the magneto-optical recording medium, and a magnetic field generating means is arranged on the magnetic recording layer side to set an external magnetic field. However, since the distances from the magnetic field generating means to the first and second magnetic recording layers are different from each other, the intensity of the magnetic field applied to each of the first and second magnetic recording layers is different. Must be different, the configuration and control of the magnetic field generating means are complicated, and the recording apparatus itself has a complicated configuration.

Accordingly, the present invention has been proposed in view of the above-mentioned circumstances, and aims at increasing the recording capacity of a magneto-optical recording medium and using a simple configuration to transmit an information signal to the magneto-optical recording medium. An object of the present invention is to provide a magneto-optical recording device and a method thereof, and a magneto-optical reproducing device and a reproducing method thereof capable of performing recording and reproducing an information signal recorded on the magneto-optical recording medium.

[0014]

The present invention proposed to achieve the above-mentioned object has a first magnetic layer formed on one surface of a substrate and a second magnetic layer formed on the other surface of the substrate. A magneto-optical recording medium on which a magnetic layer is formed, and a second magnetic layer via a first magnetic layer;
A first light source for irradiating the magnetic layer with a light beam; a first magnetic field generating means for orienting a magnetic pole of a portion where the light beam from the first light source of the second magnetic layer is focused; A second light source for irradiating the first magnetic layer with a light beam through the magnetic layer; and a second light source for orienting a magnetic pole of a portion of the first magnetic layer where the light beam from the second light source is focused. Magnetic field generating means,
The light beam from the light source and the first magnetic field generating means
The information signal is recorded on the first magnetic layer by the light beam from the second light source and the second magnetic field generating means.

According to the present invention proposed to achieve the above object, a first magnetic layer is formed on one surface of a substrate, and a second magnetic layer is formed on the other surface of the substrate. And a method of reproducing a magneto-optical recording medium for reproducing an information signal recorded on a magneto-optical recording medium, comprising: means for detecting reflected light from a first magnetic layer through a second magnetic layer; Means for detecting reflected light from the second magnetic layer through the first magnetic layer, and reproduces information individually from the two independent magnetic layers.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical recording medium recording apparatus and a recording method thereof, and a magneto-optical recording medium reproducing apparatus and a reproducing method according to the present invention will be described below with reference to the drawings.

The magneto-optical recording medium 1 used in the present invention comprises:
As shown in FIG. 1, a substrate 2 having optical transparency is provided.
The substrate 2 is formed of, for example, transparent glass or a synthetic resin such as a polycarbonate resin. On a first surface, which is one surface of the substrate 1, a first dielectric layer 3, a first magnetic layer 4, and a second dielectric layer 5 are sequentially laminated. A third dielectric layer 6, a second magnetic layer 7, and a fourth dielectric layer 8 are sequentially stacked on a second surface, which is the other surface of the substrate 1.

Information is recorded on the first and second magnetic layers 4 and 7 formed on the first and second surfaces of the substrate 2 by changing the magnetization direction, and the Kerr rotation of incident light is performed. Information is read by changing the corner or the Kerr ellipticity. Then, the first and second magnetic layers 4 and 7
Is composed of a perpendicular magnetization film, for example, Tb, Fe,
It is made of a Co alloy, and each thickness is selected to be a thickness that allows transmission of a light beam.

In FIG. 1, Rf ₁ and Rf ₂ are incident on the magneto-optical recording medium 1, and the first and second magnetic layers 4, 4
7 and FIG. 4 to be described later.
5 and FIG. 5, the reflectance is measured as the reflectance extracted from the magneto-optical recording medium 1 based on the reflected light from the first and second magnetic layers 4 and 7.

As shown in FIG. 2, a recording / reproducing apparatus for recording / reproducing an information signal on / from a magneto-optical recording medium 1 according to the present invention includes a first optical disc on one surface of the magneto-optical recording medium 1. A first light source 10 that emits a beam L1, and a first light source 10
A collimator lens 11 that converts the first light beam L1 emitted as divergent light from the light into parallel light, and a first wave plate 12
And the first bending of the optical path of the first light beam L1 by 90 degrees.
And a first objective lens 14 for converging the first light beam L1 and focusing on the second magnetic layer 7 formed on the other surface of the magneto-optical recording medium 1. I have.
The first light beam L1 emitted from the first light source 10 is
After being converted into parallel light by the collimator lens 11 and transmitted through the first wavelength plate 12, the optical path is bent by 90 degrees by the first half mirror 13 and is incident on the first objective lens 14. The first light beam L1 incident on the first objective lens 14 is converged by the first objective lens 14, is incident from one surface of the magneto-optical recording medium 1, and is formed on the other surface. The second magnetic layer 7 is focused, and the focused part of the second magnetic layer 7 is heated to a temperature equal to or higher than the Curie point.

As shown in FIG. 2, the first magnetic field generating means 15 is located on the other surface side of the magneto-optical recording medium 1.
Is provided. The first magnetic field generating means 15 is provided so as to approach the second magnetic layer 7 on which the first light beam L1 is focused by the first objective lens 14. First
The first magnetic field generating means 15 is applied to the second magnetic layer 7 where the light beam L1 is focused and heated to a temperature equal to or higher than the Curie point.
The information is recorded by applying a magnetic field from above and arranging the magnetization direction of the second magnetic layer 7 according to the information signal.
Here, the distance between the first magnetic field generating means 15 and the fourth dielectric layer 8 provided on the other surface side of the magneto-optical recording medium 1 is:
It is set to about 100 μm.

The first light beam L1 incident on the magneto-optical recording medium from one side of the magneto-optical recording medium 1
Is also applied to the first magnetic layer 4 formed on one surface side of the substrate 2, but the first magnetic layer 4 is irradiated with the first light beam L 1 converged by the first objective lens 14. Are not heated to the Curie point.

Further, as shown in FIG. 2, the recording / reproducing apparatus according to the present invention comprises a second light source 20 for emitting a second light beam L2 on the other surface side of the magneto-optical recording medium 1; Second light beam L emitted as divergent light from the second light source 20
2, a collimator lens 21 that makes 2 parallel light, a second wave plate 22, a second half mirror 23 that bends the optical path of the second light beam L2 by 90 degrees, and a light that converges the second light beam L2. A first recording medium formed on one surface side of the magnetic recording medium 1
A second objective lens 24 for focusing on the magnetic layer 4 is disposed. Second light beam L emitted from second light source 20
The light 2 is converted into parallel light by the collimator lens 21 and transmitted through the second wave plate 22, then the optical path is bent by 90 degrees by the second half mirror 23 and is incident on the second objective lens 24. The light beam L2 incident on the second objective lens 24 is converged by the second objective lens 24, is incident on the other surface side of the magneto-optical recording medium 1, and is formed on one surface side. The portion focused on the magnetic layer 4 and focused on the second light beam L2 of the first magnetic layer 4 is heated to a temperature equal to or higher than the Curie point.

As shown in FIG. 2, the second magnetic field generating means 25 is located on one side of the magneto-optical recording medium 1.
Is provided. The second magnetic field generating means 25 is provided so as to approach the first magnetic layer 4 where the second light beam L2 is focused by the second objective lens 24. Second
Is focused on the first magnetic layer 4 heated to a temperature equal to or higher than the Curie point.
The information is recorded by applying a magnetic field from above and arranging the magnetization direction of the first magnetic layer 4 according to the information signal.
Here, the distance between the second magnetic field generating means 25 and the second dielectric layer 5 provided on one surface side of the magneto-optical recording medium 1 is:
It is set to about 100 μm.

The second light beam L2 incident on the magneto-optical recording medium from the other surface side of the magneto-optical recording medium 1
Is also applied to the second magnetic layer 7 formed on the other surface side of the substrate 2, but the second magnetic layer 7 is irradiated with the second light beam L 2 converged by the second objective lens 25. Are not heated to the Curie point.

It is desirable to use a laser light source such as a semiconductor laser that emits laser light as the first and second light sources 10 and 20 described above, but the present invention is not limited to this.

In the recording / reproducing apparatus according to the present invention, the first light beam L 1 applied to the magneto-optical recording medium 1 from the first light source 10 is combined with the second magnetic layer 7 by the first objective lens 14. A magnetic field modulated by an information signal to be recorded from the first magnetic field generating means 15 is applied to a portion of the second magnetic layer 7 which has been heated to a temperature equal to or higher than the Curie point of the second magnetic layer 7, and Information is recorded by arranging the magnetization directions of the second magnetic layer 7 by the applied magnetic field.

Similarly, the second light beam L2 applied to the magneto-optical recording medium 1 from the second light source 20 is focused on the first magnetic layer 4 by the second objective lens 24, and the first magnetic layer A magnetic field modulated by an information signal to be recorded from the second magnetic field generating means 25 is applied to a portion of the layer 4 heated to a temperature equal to or higher than the Curie point, and the first magnetic field is modulated by the modulated magnetic field. Information is recorded by arranging the magnetization directions of the layer 4.

Next, in the magneto-optical recording medium 1 used in the present invention, a state in which reflected light from a predetermined magnetic layer is led out of the magneto-optical recording medium 1 will be described.

Here, the first dielectric layer 3 and the third dielectric layer 6 of the magneto-optical recording medium 1 are formed of SiN, and each has a thickness D ₁ of 60 nm. At this time, the refractive index (n) of the first and third dielectric layers 3 and 6 is 2.0.
Also, a second dielectric layer 5 of the fourth dielectric layer 8 is formed by SiN, each of the thickness D ₂ and 75 nm. At this time, the refractive index (n) of the second and fourth dielectric layers 5, 8
Is 2.0. Then, the wavelengths of the first and second light beams L1 and L2 applied to the magneto-optical recording medium 1 are set to 680n.
m, the thickness D ₃ of the first and second magnetic layers 4 and 7 is set to 1
from 100 nm to 100 nm, as shown in FIG.
When illuminating the first light beam L1 from the one surface side of the magneto-optical recording medium 1, the reflectance of the reflected light Rf ₁ reflected from the first magnetic layer 4, as shown in FIG. 3 R1 3 and the reflectance from the second magnetic layer 7 shows the characteristic indicated by R2 in FIG. The first and second magnetic layers 4, 7
Is 2.5 + 3.0i, and the substrate 2
Has a refractive index of 1.6.

As is apparent from the reflectance characteristic diagram shown in FIG. 3, for example, the thickness D _{3 of} the first and second magnetic layers 4 and 7 is set.
Is set to about 10 nm, the reflectance R1 from the first magnetic layer 4 is substantially 0%, that is, the first
There is no reflected light from the magnetic layer 4, and reflected light Rf ₂ only from the second magnetic layer 7 appears outside the magneto-optical recording medium 1.
Incidentally, when the thickness D ₃ of the first magnetic layer 4 and the second magnetic layer 7 selected from 5nm in the range of 13 nm, the reflectance R2 of the reflected light Rf ₂ which are reflected from the second magnetic layer 7 is first since relative reflectance R1 of Rf ₁ reflected from the first magnetic layer 4 there is a difference of 2% or more, the reflected light Rf _1, Rf ₂ is reflected from the first and second magnetic layers 4 and 7 Detected by the detector,
By electrically processing the detected reflected lights Rf ₁ and Rf ₂ , the reflected light Rf ₂ reflected from the second magnetic layer 7 can be extracted.

Further, the second dielectric layer 5 and the fourth dielectric layer 8 of the magneto-optical recording medium 1 are formed of SiN, and each has a thickness D ₂ of 75 nm. At this time, the refractive index (n) of the second and fourth dielectric layers 5, 8 is 2.0. The thickness D ₃ of the first and second magnetic layers 4 and 7 is set to 10 n.
m, and the wavelengths of the first and second light beams L1 and L2 applied to the magneto-optical recording medium 1 are 680 nm. Here, the thickness D1 of the first dielectric layer 3 and the third dielectric layer 6 formed of SiN and having a refractive index (n) of 2.0 was changed from ₁ nm to 100 nm, as shown in FIG. When the first light beam L1 is incident on one side of the magneto-optical recording medium 1, the reflected light Rf ₁ reflected from the first magnetic layer 4
Shows a characteristic as shown by R1 in FIG.
The reflectance of the reflected light Rf ₂ which are reflected from the magnetic layer 7, shows a characteristic as shown in Figure 4 in R2. Note that the first and second
The value of the complex refractive index of the magnetic layers 4 and 7 is 2.5 + 3.0i.
And the refractive index of the substrate 2 is 1.6.

As is apparent from the reflectance characteristic diagram shown in FIG. 4, for example, by selecting the thickness D ₁ of the first dielectric layer 3 and the third dielectric layer 6 to be approximately 60 nm. ,
Reflectance R of reflected light Rf ₁ reflected from first magnetic layer 4
1 is substantially 0%, that is, there is no reflected light from the first magnetic layer 4, and reflected light Rf ₂ only from the second magnetic layer 7 appears outside the magneto-optical recording medium 1. Incidentally, if the thickness D ₁ of the first dielectric layer 3 and the third dielectric layer 6 1 nm or more, the reflectance R2 of the reflected light Rf ₂ which are reflected from the second magnetic layer 7 first of the reflectance R1 of the reflected light Rf ₁ reflected from the magnetic layer 4 to a difference of 2% or more, the reflected light Rf _1, Rf ₂ is reflected from the first and second magnetic layers 4 and 7 The reflected light Rf ₁ ,
Rf ₂ can be taken out reflected light Rf ₂ which are reflected from the second magnetic layer 7 by electrical processing.

Further, the first dielectric layer 3 and the third dielectric layer 6 of the magneto-optical recording medium 1 are formed of SiN, and each has a thickness D ₁ of 70 nm. At this time, the refractive index (n) of the first and third dielectric layers 3 and 6 is 2.0.
The thickness D ₃ of the first and second magnetic layers 4 and 7 is set to 10
nm and the first and second
The wavelengths of the light beams L1 and L2 are 680 nm. Here, the thickness D ₂ of the second dielectric layer 5 having a refractive index is formed by SiN (n) of 2.0 the fourth dielectric layer 8 is changed from 1nm to 100 nm, as shown in FIG. 1 When the first light beam L1 is incident from one surface of the magneto-optical recording medium 1, the Rf of the reflected light reflected from the first magnetic layer 4
Reflectance of ₁ indicates the characteristic shown in Figure 5 in R1, the reflectance of the reflected light Rf ₂ which are reflected from the second magnetic layer 7,
A characteristic as shown by R2 in FIG. 5 is shown. The value of the complex refractive index of the first and second magnetic layers 4 and 7 is 2.5 + 3.0.
i, and the refractive index of the substrate 2 is 1.6.

As is apparent from the reflectance characteristic diagram shown in FIG. 5, for example, by selecting the thickness D ₂ of the second dielectric layer 5 and the fourth dielectric layer 8 to be around 75 nm. ,
Reflectance R of reflected light Rf ₁ reflected from first magnetic layer 4
1 is substantially 0%, that is, there is no reflected light from the first magnetic layer 4, and reflected light Rf ₂ only from the second magnetic layer 7 appears outside the magneto-optical recording medium 1. Note that the thickness D ₂ of the second dielectric layer 5 and the fourth dielectric layer 8 is changed from 70 nm to 90
nm, the reflected light R reflected from the second magnetic layer 7
the reflectance R2 of the f ₂ Whereas reflectance R1 of the reflected light Rf ₁ reflected from the first magnetic layer 4 there is a difference of 2% or more,
Reflected light Rf reflected from the first and second magnetic layers 4 and 7
₁ and Rf ₂ are detected by a photodetector, and the detected reflected light Rf ₁ and Rf ₂ are electrically processed to extract the reflected light Rf ₂ reflected from the second magnetic layer 7. .

In the above description, the light beam is incident from one surface of the magneto-optical recording medium 1 on which the first magnetic layer 4 is provided, and the light beams from the first and second magnetic layers 4 and 7 are irradiated. Has been described, but the characteristics shown in FIGS. 3, 4 and 5 can be obtained even when a light beam is incident from the other surface side on which the second magnetic layer 7 is provided. .

As described above, as is apparent from the characteristic diagrams of the reflectances R1 and R2 of the light beams L1 and L2 shown in FIGS. 3, 4 and 5, even if the light beam passes through the magnetic layer, Since it is possible to guide the reflected light from the predetermined magnetic layer to the outside of the magneto-optical recording medium, it is possible to reproduce the information signal recorded on the predetermined magnetic layer.

Therefore, a state in which information recorded on the magneto-optical recording medium 1 is reproduced using the recording / reproducing apparatus shown in FIG. 2 will be described. First, a state in which information recorded on the second magnetic layer 7 of the magneto-optical recording medium 1 is read will be described.

In order to reproduce the information recorded on the second magnetic layer 7, the first light source 10 is driven to emit the first light beam L1. At this time, the output of the first light source 10 is controlled such that the light beam L1 emitted from the first light source 10 does not heat the second magnetic layer 7 to a temperature higher than the Curie point.

The light beam L emitted from the first light source 10
1 is converted into parallel light by the collimator lens 11 and transmitted through the first wave plate 12 as in the case of recording the information signal described above, and then the optical path is bent by 90 degrees by the first half mirror 13. Incident on the first objective lens 14. The first light beam L1 incident on the first objective lens 14 is converged by the first objective lens 14, is incident from one surface of the magneto-optical recording medium 1, and is formed on the other surface. The light is focused on the second magnetic layer 7 and is reflected from the second magnetic layer 7. The reflected light reflected from the second magnetic layer 7 has its polarization plane rotated by + θk or −θk in accordance with the magnetization arrangement of the second magnetic layer 7. The reflected light whose polarization plane has been rotated is incident on the first half mirror 13 from the first objective lens 14, the optical path is bent by 90 degrees by the first half mirror 13, and is incident on the first polarizing plate 16. Then, the light passes through the first polarizing plate 16 and is incident on the first polarizing beam splitter 17, where the light is split into a P-polarized light component and an S-polarized light component. The P-polarized light component and the S-polarized light component of the reflected light split by the first polarizing beam splitter 17 are the first polarized light components, respectively.
And incident on the second photodetectors 18 and 19, and each detector 1
8 and 19 respectively. By differentially detecting the detection signals detected by the first and second photodetectors 18 and 19, the information signal recorded on the second magnetic layer 7 of the magneto-optical recording medium 1 is detected and reproduced. Is done.

In order to reproduce the information recorded on the first magnetic layer 4, the second light source 20 is driven to emit the second light beam L2. Also in this case, the second light source 20
Means that the light beam L2 emitted from the first magnetic layer 4
Is controlled to an output that does not cause the temperature to be heated above the Curie point.

The light beam L emitted from the second light source 20
2 is converted into parallel light by the collimator lens 21 and transmitted through the second wave plate 22 as in the case of recording the information signal described above, and then the optical path is bent by 90 degrees by the second half mirror 23. Incident on the second objective lens 24. The second light beam L2 incident on the second objective lens 24 is converged by the second objective lens 24, is incident on the other surface of the magneto-optical recording medium 1, and is formed on one surface. The light is focused on the first magnetic layer 4 and is reflected from the first magnetic layer 4. The reflected light reflected from the first magnetic layer 4 has its polarization plane rotated by + θk or −θk in accordance with the magnetization arrangement of the first magnetic layer 4. The reflected light whose polarization plane has been rotated is incident on the second half mirror 23 from the second objective lens 24, the optical path is bent by 90 degrees by the second half mirror 23, and is incident on the second polarizing plate 26. Then, the light passes through the second polarizing plate 26 and enters the second polarizing beam splitter 27, where the light is split into a P-polarized light component and an S-polarized light component. The P-polarized light component and the S-polarized light component of the reflected light split by the second polarizing beam splitter 27
And incident on the fourth photodetectors 28 and 29, and each detector 2
8, 29 respectively. By differentially detecting the detection signals detected by the third and fourth photodetectors 28 and 29, the information signal recorded on the first magnetic layer 4 of the magneto-optical recording medium 1 is detected and reproduced. Is done.

The magneto-optical recording medium 1 used in the present invention can be used as a recording medium of a disk recording and / or reproducing apparatus by being formed as a disk. When configured as a disk, by setting the overall thickness to 1.2 mm, a disk recording and / or reproducing apparatus compatible with a conventionally used compact disk or digital video disk can be easily configured. .

[0044]

As described above, according to the present invention, information signals can be recorded on both sides of a magneto-optical recording medium, and a large amount of information can be stored on one recording medium.

Further, according to the present invention, the objective lens for converging the light beam on the magneto-optical recording medium and the magnetic field generating means for applying an external magnetic field to the magneto-optical recording medium are separately arranged with the magneto-optical recording medium interposed therebetween. Therefore, since the objective lens and the magnetic field generating means can be arranged very close to the magneto-optical recording medium, the magnetic field from the magnetic field generating means can be effectively applied to the magnetic layer, and not only high-density recording becomes possible, Record excellent frequency response.

Further, according to the present invention, since each surface of the magneto-optical recording medium is provided with optical means for reproducing information recorded on the recording medium, the magnetic layer which originally needs to be reproduced is provided. Crosstalk caused by information recorded on the other magnetic layers can be reduced by signal processing, and accurate information can be reproduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a magneto-optical recording medium used in an apparatus and a method according to the present invention.

FIG. 2 is a conceptual diagram of a magneto-optical recording / reproducing apparatus according to the present invention.

FIG. 3 is a characteristic diagram showing the reflectance of a light beam from each magnetic layer when the thickness of each magnetic layer provided on the magneto-optical recording medium is varied.

FIG. 4 is a characteristic diagram showing the reflectance of a light beam from each magnetic layer when the first and third dielectric layers provided on the magneto-optical recording medium are changed.

FIG. 5 is a characteristic diagram showing the reflectance of a light beam from each magnetic layer when the second and fourth dielectric layers provided on the magneto-optical recording medium are changed.

[Explanation of symbols]

Reference Signs List 1 magneto-optical recording medium, 2 substrate, 4 first magnetic layer, 7 second magnetic layer, 10 first light source, 14
A first objective lens, 15 first magnetic field generating means,
20 second light source, 24 second objective lens, 25
Second magnetic field generating means.

Claims (4)

[Claims] A first substrate is provided on one surface of a light-transmitting substrate.
A magneto-optical recording medium in which a second magnetic layer is formed on the other surface of the substrate; a first light source; and a light beam from the first light source. And a first objective disposed on one surface side of the substrate so as to heat a portion of the second magnetic layer where the light beam is converged to a Curie point or higher. A lens, a first magnetic field disposed in close proximity to the second magnetic layer heated above the Curie point, and orienting the magnetism in the second magnetic layer heated above the Curie point in accordance with an information signal; Generating means, a second light source, and a light beam from the second light source is converged on the first magnetic layer through the second magnetic layer, and the light beam on the first magnetic layer is converged. On one side of the substrate so that the part The second objective lens is arranged in close proximity to the first magnetic layer heated above the Curie point, and the magnetism of the first magnetic layer heated above the Curie point is changed according to an information signal. A recording device for a magneto-optical recording medium, comprising: a second magnetic field generating means for orienting. 2. A thin first magnetic layer is formed on one surface of a light-transmitting substrate, and a thin second magnetic layer is formed on the other surface of the substrate.
Of the magneto-optical recording medium having the above-described first and second magnetic layers formed thereon.
In the magneto-optical recording method of recording an information signal on each of the magnetic layers, a light beam from a first light source is converged on the second magnetic layer through the first magnetic layer. The portion where the light beam is converged is heated above the Curie point, and the magnetism of the portion heated above the Curie point of the second magnetic layer is changed to a first magnetic field disposed close to the second magnetic layer. It is oriented according to the information signal by the generating means, and the light beam from the second light source is made to converge on the first magnetic layer through the second magnetic layer, and the light beam on the first magnetic layer is converged. The portion of the first magnetic layer heated above the Curie point is magnetized by a second magnetic field generating means disposed close to the first magnetic layer. Magneto-optical, characterized by being oriented according to Recording method of the air recording medium. 3. A thin first magnetic layer is formed on one surface of a substrate having optical transparency, and a thin second magnetic layer is formed on the other surface of the substrate.
A first light source; and a light beam from the first light source being converged on the second magnetic layer through the first magnetic layer to form the second magnetic layer. A first lens for guiding a polarized reflected wave from the layer to first light detecting means; a second light source; and a light beam from the second light source passing through the second magnetic layer to the first magnetic layer. And a second lens that guides the polarized reflected wave from the first magnetic layer to the second photodetector, and the first and second photodetectors from the first and second photodetectors. Wherein the information recorded on the magnetic layer is independently taken out. 4. The first information is recorded on a thin first magnetic layer on one surface of a substrate having light transmittance, and the second information is recorded on a thin second magnetic layer on the other surface of the substrate. In a reproducing method of a magneto-optical recording medium for reproducing the first and second information from a recorded magneto-optical recording medium, a light beam from a first light source is transmitted through the first magnetic layer to the second magnetic layer. And converging the reflected light from the second magnetic layer to the first light detecting means, and converging the light beam from the second light source to the first magnetic layer through the second magnetic layer. Then, the polarized reflected wave from the first magnetic layer is guided to the second light detecting means, and the information recorded on the first and second magnetic layers is independent from the first and second light detecting means. A method for reproducing a magneto-optical recording medium, wherein