JPH08203148A - Magneto-optical recording medium reproducing device - Google Patents

Abstract

PURPOSE: To make a light beam incident diagonally on a magneto-optical disk and to impart a coma aberration thereto by inclining this magneto-optical disk so that the angle of inclination becomes a prescribed acute angle while rotating the disk by means of an actuator at the time of reproducing the magneto-optical disk on which information has been recorded by narrowing the spacings between information tracks. CONSTITUTION: This magneto-optical recording medium reproducing device S has a semiconductor laser 5 for emitting a light beam B for recording and reproducing, a beam splitter 6 for reflecting the light beam B and allowing the transmission of the reflected light from the disk 1 and an objective lens 4 for condensing the light beam B onto the recording surface of the disk 1. Further, the device has also a spindle motor 2 for rotating the disk 1, the actuator 3 as a coma aberration forming means for rotating the disk 1 by inclining the disk at prescribed acute angle α, a polarization separator 7 for separating the reflected light of the light beam B transmitted through the beam splitter 6 according to the difference in the planes of polarization thereof, a photodetector 8 for receiving one of the separated and reflected light beams and outputting a photodetection signal and a photodetector 9 for receiving the other of the separated and reflected light beams and outputting a photodetection signal.

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 medium reproducing apparatus, and more specifically, it reproduces information recorded by a recording mark smaller than the optical diffraction limit of a light beam for reproducing information. The present invention relates to a magneto-optical recording medium reproducing apparatus capable of resolution reproduction.

[0002]

2. Description of the Related Art Magneto-optical recording media such as so-called optical discs are widely used today as recording media for recording video and computer data because they can record information at high density on their information recording surfaces. ing.

In recent years, attempts have been made to record high-definition television signals on this magneto-optical recording medium. However, the above-mentioned high-definition television signals are recorded on magneto-optical recording media having conventional recording densities. When I try to record
The amount of information that can be recorded on a single magneto-optical recording medium is only about 10 minutes as a reproduction time. Therefore, it is required to improve the recording density of information in the magneto-optical recording medium.

As a method of improving the recording density of information, there are a method of improving the recording density in the time axis direction (the traveling direction of the magneto-optical recording medium) and a track pitch of an information track composed of recording marks corresponding to the information. It is possible to improve the recording density in the direction (the direction orthogonal to the time axis direction, and in the case of a disc-shaped magneto-optical recording medium, the radial direction).

Here, as the former method (in the case of improving the recording density in the time axis direction), the MSR (Magn
So-called super-resolution reproduction such as etically induced Super Resolution) has been proposed.

Here, an outline of the MSR will be described. It has been conventionally known in the world of microscopes that resolution is improved by providing an optical mask such as a pinhole at the position of an object to be observed. So M
SR does not provide a physical mask on the recording surface of the magneto-optical recording medium, but utilizes the temperature distribution on the medium including the recording surface to create an effective mask in the medium, and to effectively reproduce the reproduction limit. The spatial frequency is increased, and the recording density can be improved by about 1.5 to 3 times (For more details, see "Super-Resolution Magneto-Optical Disk", The Japan Society for Applied Magnetics, Vol1.15, No.5. , 1991 etc.).

Various magneto-optical recording media to which such MSR is applied have been proposed, and an example thereof is shown in FIG. In FIG. 7, a magneto-optical disk 1 as a magneto-optical recording medium.
As shown in FIG. 7A, P is a substrate B ′ transparent to a light beam such as a laser beam, a reproducing layer P ′ having a small coercive force, a large coercive force, and a perpendicular magnetization state. A recording layer R'on which information is recorded and a switch layer S'for controlling the exchange coupling force between the reproducing layer P'and the recording layer R'are provided. At this time, between the Curie temperature T _CR ′ of the recording layer R ′, the Curie temperature T _CP ′ of the reproducing layer P ′, and the Curie temperature T _CS ′ of the switch layer S ′, T _CR ′> T _CS ′ and T The composition of the reproducing layer P ′, the recording layer R ′, and the switch layer S ′ is determined so that the relation of _CP ′> _TCS ′ (1) is established.

Next, the operation of recording information on the magneto-optical disk 1P will be described. At the time of recording information, the output power of the light beam, which is the recording light, has a maximum temperature in the irradiation range of the light beam on the magneto-optical disk (hereinafter referred to as a light spot), which is the Curie temperature T of the recording layer R ′.
It is set to be _CR 'or higher. Then, the recording layer R '
Since the coercive force of the reproducing layer P ′ disappears, if the external magnetic field corresponding to the information to be recorded is given from the outside at this time, the temperature of the recording layer R ′ and the reproducing layer P ′ is moved by the movement of the magneto-optical disk. The recording layer R ′ and the reproducing layer P ′ are magnetized in the direction of the external magnetic field as a result, and information is recorded.

Next, the reproducing operation of the information recorded by the above method will be described. When playing back information,
As the first condition of the output power of the light beam that is the reproduction light,
The maximum temperature T _H in the light spot is set so that T _H <T _CR '. When the magneto-optical disk 1P is irradiated with the light beam whose output power is set in this way from the reproducing layer P ′ side, as the magneto-optical disk 1P moves, as shown in FIG. A region having a higher temperature than the surroundings (hereinafter referred to as a high temperature region) is formed in the rear part of the spot.

The temperature of this high temperature region is equal to or higher than the Curie point of the switch layer S ', and the temperature of other regions within the light spot (hereinafter referred to as low temperature region) is the switch layer S'.
The output power of the laser beam is set under the second condition that it is equal to or lower than the Curie point. At this time, the output power of the light beam is set so that the shape of the low temperature region becomes substantially crescent as shown in FIG. 7B, and the shape of the high temperature region becomes substantially elliptical.

Then, the temperature of the high temperature region is the switch layer S '.
Above the Curie point, the magnetic domain of the switch layer S ′ disappears, that is, the coercive force becomes zero and the exchange coupling force between the reproducing layer P ′ and the recording layer R ′ becomes weak. When a reproducing magnetic field H _r is applied from the outside at the same time, a reproducing layer P ′ having a small coercive force is applied.
The magnetization direction of is aligned with the direction of the reproducing magnetic field H _r .

Therefore, the high temperature region serves as a mask region in which the recording information of the recording layer R'cannot be read, and the recording information of the recording layer R'can only be read from the crescent-shaped low temperature region in the light spot. Even at this time, since the temperature in the light spot does not exceed the Curie temperature T _CR ′ of the recording layer R ′, the information recorded on the recording layer R ′ is not erased.

Due to the functions of the low temperature region and the high temperature region described above, the reproduction of information on the recording layer R'can only be performed from the low temperature region within the light spot. That is, since the low temperature region functions as a window region for information reproduction, the size of the light spot can be substantially reduced, and information having a spatial frequency higher than the physical spatial frequency of the light spot is reproduced. be able to. That is, super-resolution reproduction in the time axis direction of the magneto-optical disk can be performed.

[0014]

However, in the reproducing operation of the above-mentioned conventional magneto-optical disk, the operation shown in FIG.
As shown in (b), the mask area is the high temperature area, and the information is reproduced only from the low temperature area of the crescent moon. Therefore, the recording density can be improved in the time axis direction of the magneto-optical disk. Although it is possible, the recording density cannot be improved in the track pitch direction.

Therefore, if the information recorded by narrowing the track pitch is reproduced by using the above super-resolution reproduction method, the information on the information track adjacent to the information track to be reproduced is also reproduced at the same time. As a result, there is a first problem that crosstalk occurs and accurate information reproduction cannot be performed.

As a method for solving the first problem, for example, the method disclosed in Japanese Patent Laid-Open No. 5-225643 has been proposed. According to this method
As shown in FIG. 8, three light spots a to c are formed on the magneto-optical disk 1P by using a grating.
Then, the respective light spots are track TR _{1 to} T
By irradiating R ₃ individually and reading the information from the track TR ₁ , the information on the tracks TR ₂ and TR ₃ is masked by the same method as the above super-resolution reproducing method, thereby recording density in the track pitch direction. The information is read from the magneto-optical disk having improved optical characteristics.

By using this method, super-resolution reproduction can be performed also in the track pitch direction, but since three light beams are used, the grating is removed to form one beam at the time of recording, or Since it is necessary to perform recording and reproduction by different devices, there is a second problem that the recording device and the reproduction device cannot be shared. Furthermore, since the grating is used, the structure of the apparatus itself (particularly the pickup section for detecting the reproduction signal) becomes complicated, and there is a third problem that the conventional reproduction apparatus cannot be used.

Therefore, the present invention has been made in view of the above problems, and a first object thereof is a magneto-optical recording of information by increasing the recording density in the track pitch direction with a simple structure. It is an object of the present invention to provide a magneto-optical recording medium reproducing device capable of super-resolution reproducing information on a recording medium. A second object is to obtain a magneto-optical recording medium reproducing device capable of super-resolution reproduction by using the same optical system as the recording device.

[0019]

In order to solve the above-mentioned first problem, the invention according to claim 1 relates to a magneto-optical recording such as a magneto-optical disk in which information is recorded on an information track by a recording mark or the like. Within the irradiation range of a light beam for reproducing information such as a laser that irradiates the medium, a window region having a predetermined reproduction temperature or lower and a mask region having a predetermined reproduction temperature or higher are formed, and within the window region. In a magneto-optical recording medium reproducing apparatus for super-resolution reproducing the information existing in the above, the reproducing information track is the information track to be reproduced, the adjacent information track adjacent to the reproducing information track, and the reproducing information track. And a side portion thereof on the adjacent information track, and a leg opening direction thereof is opposite to a moving direction of information on the reproduction information track. A coma aberration generating means for giving the light beam a coma aberration forming the mask area having a letter shape, the area sandwiched between the respective side portions of the mask area, the area on the reproduction information track being the window; Area.

In order to solve the first to third problems, the invention according to claim 2 is the magneto-optical recording medium reproducing apparatus according to claim 1, wherein the coma aberration generating means is The inclination of the magneto-optical recording medium or the irradiation of the light beam such that the angle formed by the irradiation direction of the light beam with respect to the magneto-optical recording medium and the moving direction of the information on the reproduction information track is a predetermined acute angle. It is configured to be a control means for controlling the direction.

Further, in order to solve the first problem, the invention according to claim 3 is the magneto-optical recording medium reproducing apparatus according to claim 1, wherein the coma aberration generating means is
It is configured to be an optical coma aberration generating means arranged on the optical path between the light beam emitting means for emitting the light beam and the recording surface of the magneto-optical recording medium.

[0022]

According to the invention described in claim 1, the coma aberration generating means has the bent portion on the reproduction information track on the reproduction information track and the adjacent information track, and the side portion on the adjacent information track. The light beam is provided with a coma aberration that forms a substantially V-shaped mask area having a portion and the opening direction thereof is opposite to the moving direction of information on the reproduction information track.

The area sandwiched between the sides of the mask area and located on the reproduction information track serves as a window area. Therefore, the window area is formed on the reproduction information track sandwiched between the adjacent information tracks, and the mask area is formed on the adjacent information track adjacent to the window area. In the magnetic recording medium, the information on the reproduction information track can be read without being affected by the adjacent information tracks.

According to the invention of claim 2, claim 1
In addition to the effect of the invention described in (1), the control means as the coma aberration generating means makes an angle between the irradiation direction of the light beam with respect to the magneto-optical recording medium and the moving direction of the information on the reproduction information track to be a predetermined acute angle. Thus, the tilt of the magneto-optical recording medium or the irradiation direction of the light beam is controlled.

Therefore, even when super-resolution reproduction is performed by using the optical system of the recording apparatus, the structure of the optical system is affected only by controlling the inclination of the magneto-optical recording medium or the irradiation direction of the light beam. It is possible to super-reproduce information on a magneto-optical recording medium having a high recording density in the information track pitch direction by giving coma aberration to the light beam without affecting the information.

According to the invention described in claim 3, the optical coma aberration generating means is arranged on the optical path between the light beam emitting means for emitting the light beam and the recording surface of the magneto-optical recording medium. The coma aberration that forms a substantially V-shaped mask region similar to that of the invention of Item 1 is given to the light beam.

The area sandwiched between the sides of the mask area and located on the reproduction information track is used as the window area. Therefore, the window area is formed on the reproduction information track sandwiched between the adjacent information tracks, and the mask area is formed on the adjacent information track adjacent to the window area. In the magnetic recording medium, the information on the reproduction information track can be read without being affected by the adjacent information tracks.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. (1) First Embodiment First, a first embodiment corresponding to the invention described in claim 1 or 2 will be described with reference to FIGS. 1 to 5.

First, the structure of the magneto-optical recording medium reproducing apparatus in the embodiment will be described with reference to FIG. As shown in FIG. 1A, the magneto-optical recording medium reproducing apparatus S according to the embodiment.
Is a semiconductor laser 5 that emits a light beam B for recording and reproduction.
And a beam splitter 6 which reflects the emitted light beam B and transmits the reflected light from the magneto-optical disk 1 as a magneto-optical recording medium, and the reflected light beam B on the recording surface of the magneto-optical disk 1. A magneto-optical disk 1 as a magneto-optical recording medium having an objective lens 4 for condensing, a recording layer R'on which information is recorded, a reproducing layer P ', and a switch layer S'as in the prior art, and a magneto-optical disk 1. A spindle motor 2 for rotating the optical disk, an actuator 3 as a coma aberration generating means (control means) for rotating the magneto-optical disk 1 at a predetermined angle, and a reflected light of the light beam B transmitted through the beam splitter 6. A polarization separator 7 such as a polarization beam splitter for separating light according to the difference in the polarization plane thereof, and a photodetector 8 for receiving one of the separated reflected lights and outputting a light reception signal. A photodetector 9 which outputs a light receiving signal by receiving the other of the separated reflected light, the reproducing magnetic field H _r
And a reproducing magnetic field magnet MG for applying the magnetic field.

In addition to the members shown in FIG. 1, the magneto-optical recording medium reproducing apparatus S in the embodiment signal-processes the received light signal and outputs the signal as an output signal to the outside, and the input signal from the outside as a signal. A signal processing unit for processing and converting into a recording signal, and a servo control unit for performing servo control such as tracking servo, focus servo, and spindle servo are included, but for simplification of description, these members are shown in FIG. Not shown in.

Further, in the actuator 3, the inclination angle α formed by the irradiation direction V _B of the light beam B and the rotation direction V _T of the magneto-optical disk 1 at the irradiation position of the light beam B is shown in FIG.
The magneto-optical disk 1 is tilted while being rotated so as to form an acute angle as shown in FIG.

Here, as the configuration of the magneto-optical disk 1, the above-mentioned Curie temperature conditions in the reproducing layer P ', the recording layer R'and the switch layer S' (see the equation (1) or the equation (2)) are used. In order to satisfy the above, the composition of the reproducing layer P ′ is, for example, Gd _x (Fe _100-y Co _y ) _100-x (15 <x <30 (particularly 23 <x <25 is preferable), 10 <y <30) And the thickness is 10 to 60 nm. (Here, in the above composition formula, the ratio of each element is atomic% (at%)
Indicated by The same applies to the following.) The composition of the switch layer S ′ is, for example, Tb _x (Fe _100-y Co _y ) _100-x (15 <x <30, 0 <y <5) and has a thickness of 5 To 50 nm (in particular, 8 nm to 20 nm is preferable).

In addition to this, as the switch layer S ′, Dy is used.
A substance such as FeCo or TbDyFe may be used. Further, the composition of the recording layer R ′ is, for example, Tb _x (Fe _100-y Co _y ) _100-x (15 <x <25 (particularly 18 <x <24 is preferable) or 27 <x <3
2, 5 <y <30, and the thickness is 20 to 60 nm.

In addition to this, as the recording layer R ', NdDy is used.
A substance such as FeCo, TbDyFeCo, GdTbFeCo may be used. The reproduction layer P ′ and the switch layer S ′ described above.
In the case of the composition of the recording layer R ′, the temperature of the high temperature region A _H is 130 ° C. or higher.

As another construction of the magneto-optical disk 1, a dielectric protection for protecting the magneto-optical layers (reproducing layer P ', switch layer S'and recording layer R') in order from the substrate B'side. ZnS (thickness 70 nm) as a layer, Gd ₂₃ (Fe ₉₀ Co ₁₀ ) ₇₇ (thickness 35 nm) as a reproduction layer P ′, Tb ₂₂ Fe ₇₈ (thickness 10 nm) as a switch layer S ′, and a recording layer R As Tb ₂₃ (Fe ₉₀ Co ₁₀ ) ₇₈ (40 n thick
It is also possible to use a magneto-optical disk 1 having a structure of m), ZnS (thickness 70 nm) as a dielectric protection layer, and an overcoat layer (2P (Photo Polymer) coating) for protecting the magneto-optical disk 1. Also in this composition, the temperature of the high temperature region A _H is set to 130 ° C. or higher.

Further, the information recorded on the recording surface R'of the magneto-optical disk 1 is recorded with a narrower information track interval than that of the conventional technique. Next, the operation of the magneto-optical recording medium reproducing apparatus in the first embodiment will be described separately for reproduction and recording. (I) During Reproduction First, the operation during reproduction will be described with reference to FIGS. 1 to 4.

When reproducing the magneto-optical disk 1 in which information is recorded by narrowing the intervals between the information tracks as compared with the prior art, the magneto-optical disk 1 is rotated by the actuator 3 as shown in FIG. As shown, the inclination angle α is inclined so as to have a predetermined acute angle.

As a result, the light beam B is obliquely incident on the magneto-optical disk 1, and a coma aberration is given on the irradiation surface of the magneto-optical disk 1. At this time, the intensity distribution of the light beam B given the coma aberration on the irradiation surface becomes substantially V-shaped as shown in FIG.

Here, the horizontal axis of FIG. 2 indicates the length in the magneto-optical disk 1 in units of aR, a is the radius of the objective lens 4, R is the coordinate on the image plane ρ, and the objective lens 4 is Is b and the wavelength of the light beam B is λ, R = (2π / λ) ρ. Further, the vertical axis also indicates the length in the unit of aR in the magneto-optical disk 1 as with the horizontal axis. Further, the tree-shaped tree is an isointensity line connecting points of the same irradiation intensity of the light beam B, and the denser the isointensity line is, the higher the irradiation intensity is. Furthermore, when the inclination angle α in FIG. 1B is set to an acute angle, the rotation direction of the magneto-optical disk 1 in FIG.
It will face downward as shown in.

Further, the size of the angle β formed by one side of the substantially V-shape in FIG. 2 and the rotating direction of the magneto-optical disk 1 is determined by the numerical aperture of the objective lens 4, the wavelength of the light beam B and the magneto-optical disk. It is possible to set by the inclination angle α of.

More specifically, letting W be the coma aberration,

[0042]

[Equation 1] It is expressed as Here, t is the substrate B ′ of the magneto-optical disk 1.
, NA is the numerical aperture of the objective lens 4, α is the tilt angle of the magneto-optical disk 1 (see reference numeral α in FIG. 1B), n is the refractive index of the substrate B ′ with respect to the light beam B, and λ is the light beam. B wavelength. For example, α is 84.6 °, NA is 0.5, t
Is 1.2 mm, n is 1.5, and λ is 0.78 μm,
The coma aberration W is 6.4λ. And this coma aberration W
Becomes larger than a predetermined value, the intensity distribution of the light beam B on the irradiation surface becomes a substantially V-shaped distribution as shown in FIG.

As is clear from FIG. 2, when a coma aberration is given to the light beam B, its intensity distribution on the irradiation surface on the magneto-optical disk 1 is strong near each side of the substantially V-shape. Become. In other words, the high temperature region A _H is formed in this region by the strong irradiation of the light beam near each side of the substantially V-shape. As compared with the high temperature region A _H , the intensity of the irradiated light beam B becomes weaker inside the substantially V-shaped side portions, so that a low temperature region A _L having a lower temperature than the high temperature region A _H is formed. Become.

Further, FIG. 2 also shows the light spot L by the light beam B when no coma aberration is given.
As is clear from this, the low temperature region A _L is smaller than the light spot L in both width and length.

Next, during reproduction, the light beam B that gave the adjacent information tracks TR _2, TR ₃ and coma which information to be reproduced is adjacent to the recording reproduction information track TR ₁ and reproducing the information track TR ₁ The relationship with the intensity distribution on the irradiation surface will be described with reference to FIG.

As shown in FIG. 3A, during reproduction, the intensity distribution on the irradiation surface of the light beam B is such that the reproduction information track TR ₁ passes through the low temperature region A _L and high temperature region A _H in FIG. The numerical aperture of the objective lens 4, the wavelength of the light beam B, and the inclination angle α of the magneto-optical disk 1 are set so that the information tracks TR ₂ and TR ₃ have a distribution that passes only the high temperature region, and the information tracks TR ₂ and TR ₃ are substantially V-shaped. An angle β between one side and the rotation direction of the magneto-optical disk 1 is set.

Next, FIG. 3 (b) shows the temperature distribution of the AA 'cross section in FIG. 3 (a). During playback, Fig. 3
As shown in (b), the temperature of the low temperature region A _L becomes equal to or lower than the Curie temperature T _CS ′ of the switch layer S ′, and the temperature of the high temperature region A _H through which the adjacent information tracks TR ₂ and TR ₃ pass is the switch layer S ′. The output power of the light beam B is set such that the Curie temperature T _CS ′ is equal to or higher than the Curie temperature T _CS ′ of the recording layer R ′ and the temperature of the entire irradiation surface does not exceed the Curie temperature T _CR ′ of the recording layer R ′.

The output power of the light beam B is set as described above.
Playback information track TR ₁High temperature area
Area A_HThe adjacent information track is located near
Click TR₂And TR₃High temperature area A through which_HStronger
Since the intense light beam B is emitted (see FIG. 2),
High temperature region A_HTemperature (near the bending point of V-shape)
Is the adjacent information track TR₂And TR₃The high temperature that passes through
Area A_HSince the temperature becomes higher, the high temperature area A_HThe entire
As the Curie temperature T of the switch layer S '_CS’And above
It Therefore, this high temperature region A_HBecomes the mask area,
Information is regenerated in the low temperature region A_LOnly from.

Therefore, since the width and length of the low temperature area A _L are smaller than the light spot of the light beam B when no coma aberration is applied, the light on which information is recorded with a narrower track pitch than in the prior art. Even with the magnetic disk 1, super-resolution reproduction can be realized simultaneously in the time axis direction and the track pitch direction.

Here, in FIG. 4, the magneto-optical disk 1 on which information is recorded by narrowing the intervals of the information tracks as compared with the prior art is irradiated with the light beam B having the coma aberration of this embodiment. Relationship between each information track and the temperature distribution on the irradiation surface (FIG. 4A), and the light beam in a state where no coma aberration is applied (the light beam B is incident almost perpendicularly to the magneto-optical disk 1) The relationship between each information track and the temperature distribution of the irradiation surface when B is irradiated is shown (FIG. 4B).

As shown in FIG. 4A, when the coma aberration is given to the light beam B, the Curie temperature T _CS ′ of the switch layer S ′ is higher than the Curie temperature T _CS ′ of the recording layer R ′. Inside the substantially V-shaped high temperature region A _H below _CR ′, a low temperature region A _L below the Curie temperature T _CS ′ of the switch layer S ′ is formed. Since the high temperature area A _H operates as a mask area as described above, the information of the adjacent information tracks TR ₂ and TR ₃ is not read out, and the super resolution reproduction in the track pitch direction is realized. Further, since the magneto-optical disk 1 rotates from top to bottom in FIG.
Since the high temperature region A _H also functions as a mask region in the time axis direction of the reproduction information track TR ₁ , super resolution reproduction is possible in the time axis direction.

On the other hand, as shown in FIG.
Light spot L by irradiating light beam B that does not give coma aberration
In the case of forming the film, super-resolution reproduction is possible in the time axis direction because the high temperature region A _H functions as a mask region as shown in the prior art, but in the track pitch direction, a high resolution region A _H to become a low-temperature region a _L comes to take on the adjacent information track TR ₂ and TR ₃ becomes crescent, information of the adjacent information tracks TR ₂ and TR ₃ will be read out, the super-resolution reproduction is not realized.

Incidentally, when the above-mentioned information is reproduced, if the tilt angle α of the magneto-optical disk 1 is reduced, coma and astigmatism may occur. In this case, the amount of astigmatism will increase in proportion to the square of the numerical aperture NA of the objective lens 5. Therefore, when the objective lens 5 having a relatively small numerical aperture NA is used, this astigmatism amount cannot be ignored. In this case, the astigmatism is removed by inserting a cylindrical lens for correcting astigmatism or an optical wedge on the optical path of the light beam B between the objective lens 5 and the magneto-optical disk 1. be able to. (II) During Recording Next, the operation during recording will be described with reference to FIGS. 1 and 5.

In the magneto-optical recording medium reproducing apparatus of this embodiment, it is possible to form a recording mark having a frequency exceeding the spatial frequency of the light beam B without changing the structure of the optical system.

When information is recorded using the magneto-optical recording medium reproducing apparatus of the present embodiment, the tilt angle α (see FIG. 1B) of the optical disk is 90 degrees due to the operation of the actuator 3 shown in FIG. Then, the coma aberration of the light beam B is set to zero (that is, the light beam B enters the magneto-optical disk 1 at a right angle). At this time, the light spot L formed on the magneto-optical disk 1 has a circular shape without coma as shown in FIG. At this time, the temperature distribution on the irradiation surface on the magneto-optical disk 1 has a mountain shape with the highest central portion, as shown in FIG. Therefore, the output power of the light beam B (light beam for recording) and the recording layer are adjusted so that the Curie temperature T _CR ′ of the recording layer R ′ is higher than the temperature of the peripheral portion of the light spot L and lower than the temperature of the central portion thereof. When the Curie temperature of R'is set, the magnetization of the recording layer R'in the range smaller than the range of the light spot L disappears. Therefore, if an external magnetic field corresponding to the information to be recorded is applied to the area where the magnetization has disappeared, the area where the magnetization has disappeared is magnetized in the direction of the external magnetic field, as shown in FIG. As shown in a), the recording mark M corresponding to the information to be recorded and smaller than the light spot L (that is, the frequency exceeding the spatial frequency of the light beam B) is formed.

As described above, according to the magneto-optical recording medium reproducing apparatus of the first embodiment, the coma aberration is given to the light beam B with which the magneto-optical disk 1 is irradiated, so that the structure is simple. Thus, super-resolution reproduction can be realized not only in the time axis direction of the magneto-optical disk 1 but also in the track pitch direction.

Further, without changing the configuration of the optical system,
The recording operation is also possible, and the reproducing operation and the recording operation can be executed using the same device. In the first embodiment described above, the coma aberration is given to the light beam B by tilting the magneto-optical disk 1, but the present invention is not limited to this, and the information of the magneto-optical disk 1 is not limited to this. The coma may be given by controlling the irradiation direction of the light beam B on the recording surface. (2) Second Embodiment Next, a second embodiment corresponding to the invention described in claim 3 will be described with reference to FIG.

In the above-described first embodiment, the coma aberration is given to the light beam B by inclining the magneto-optical disk 1, but the magneto-optical recording medium reproducing apparatus S'of the second embodiment is Instead of mechanically inclining the magneto-optical disk 1 as in the magneto-optical recording medium reproducing apparatus S of the first embodiment,
An optical coma aberration generator C is provided on the optical path of the light beam B between the semiconductor laser 5 and the beam splitter 6.

The rest of the configuration is the same as that of the magneto-optical recording medium reproducing apparatus S in the first embodiment, so the detailed description will be omitted. As shown in FIG. 6, the coma aberration generator C in the magneto-optical recording medium reproducing apparatus S ′ of the second embodiment is parallel to the parallel plate 10 arranged at a predetermined angle with respect to the optical axis of the light beam B. It is composed of a cylindrical lens 11 arranged perpendicularly to the light beam B passing through the flat plate 10.
Then, the light beam B emitted from the semiconductor laser 5 enters the parallel plate 10 to be given coma and astigmatism. The amount of coma at this time is determined by the refractive index of the light beam B on the parallel plate 10 and the parallel plate 10 and the light beam B.
Is determined by the angle formed by and the thickness of the parallel plate 10.

The light beam B given the coma aberration and the astigmatism by the parallel plate 10 has the astigmatism removed by the cylindrical lens 11 arranged perpendicularly to its optical axis, and the light beam B has only the coma aberration. The beam B is made incident on the magneto-optical disk 1 through the beam splitter 6 and the objective lens 4.

By the above operation of the coma aberration generating section C, the magneto-optical disk 1 is irradiated with the light beam B to which the coma aberration has been given, and its intensity distribution becomes a distribution as shown in FIG. Therefore, similarly to the first embodiment, super-resolution reproduction can be performed not only in the time axis direction but also in the track pitch direction.

The same effect can be obtained by using an optical wedge instead of the cylindrical lens 11. When recording information, the coma aberration generator C is removed or, for example, a tilted cylindrical lens (the tilt direction is opposite to the wedge).
If an optical component for removing the coma aberration as described above is inserted in the optical path of the light beam B, the light spot of the light beam B on the magneto-optical disk 1 becomes circular, which is the same as in the recording in the first embodiment. Information can be recorded by the recording mark M (see FIG. 5) smaller than the light spot L.

Further, the actuator 3 in the first embodiment and the coma aberration generating section C in the second embodiment so far.
It is also possible to use both and to generate coma for the light beam B.

Furthermore, in the above description,
Although the description has been made for a magneto-optical disk which is a disk-shaped magneto-optical recording medium, the present invention is not limited to this, and is applicable to so-called tape-shaped magneto-optical recording media such as an optical tape. It is possible.

[0065]

As described above, according to the invention described in claim 1 or 3, coma aberration is applied to the light beam to form a substantially V-shaped mask region, and each side of the mask region is formed. A window area is formed on the reproduction track sandwiched by adjacent information tracks by defining the area on the reproduction information track as a window area, and the adjacent information track adjacent to the window area is formed. Since the mask region is formed on the magneto-optical recording medium having a higher recording density in the information track pitch direction, the information on the reproduction information track can be read without being affected by the adjacent information tracks.

Therefore, the information density in the information track pitch direction in the magneto-optical recording medium can be increased, and the information amount of the entire magneto-optical recording medium can be improved. According to the invention described in claim 2, in addition to the effect of the invention described in claim 1 or 3, the direction of irradiation of the light beam to the magneto-optical recording medium and the direction of movement of information on the reproduction information track are controlled by the control means. Since the inclination of the magneto-optical recording medium or the irradiation direction of the light beam is controlled so that the angle formed by is a predetermined acute angle, even when super resolution reproduction is performed using the optical system of the recording device, A magneto-optical device that increases the recording density in the information track pitch direction by giving coma aberration to the light beam without affecting the structure of the optical system only by controlling the inclination of the magnetic recording medium or the irradiation direction of the light beam. Information on a recording medium can be reproduced with super resolution.

Therefore, the recording apparatus and the reproducing apparatus can be shared with respect to the optical system, and the magneto-optical recording medium reproducing apparatus capable of super-resolution reproduction in the information track pitch direction using the same optical system as the recording apparatus. Can be obtained.

[Brief description of drawings]

1A and 1B are configuration diagrams of a main portion of a magneto-optical recording medium reproducing apparatus according to a first embodiment, in which FIG. 1A is a main portion configuration diagram, and FIG. 1B is an irradiation direction of a light beam B and a rotation direction of a magneto-optical disk. It is a figure which shows the relationship of.

FIG. 2 is a diagram showing an intensity distribution of a light beam having a coma aberration on an irradiation surface.

FIG. 3 is a diagram showing a positional relationship between an intensity distribution and an information track on an irradiation surface of a light beam having a coma aberration,
(A) is a figure which shows the positional relationship of intensity distribution and an information track, (b) shows the temperature distribution in the AA 'cross section.

FIG. 4 is a diagram showing a comparison between a super-resolution in a track pitch direction by a light beam having a coma aberration and a conventional super-resolution reproduction, in which (a) is a track pitch by a light beam having a coma aberration. FIG. 3B is a diagram showing super-resolution in the direction, and FIG. 6B is a diagram showing conventional super-resolution reproduction.

FIG. 5 is a diagram showing a light spot during recording and a temperature distribution in the light spot.

FIG. 6 is a diagram showing a main configuration of a magneto-optical recording medium reproducing apparatus in a second embodiment.

FIG. 7 is a diagram showing super-resolution reproduction of a conventional technique, (a)
Shows a structure of a conventional super-resolution magneto-optical disk, (b)
FIG. 3 is a diagram showing a high temperature region and a low temperature region in a light spot and a relationship between these and a recording track.

FIG. 8 is a diagram showing super-resolution reproduction in the track pitch direction by three beams according to the related art.

[Explanation of symbols]

1, 1P ... Magneto-optical disk 2 ... Spindle motor 3 ... Actuator 4 ... Objective lens 5 ... Semiconductor laser 6 ... Beam splitter 7 ... Polarization separator 8, 9 ... Photodetector 10 ... Parallel plate 11 ... Cylindrical lens A _H ... High temperature area A _L ... low-temperature region B ... light beam B '... substrate C ... coma generator H _r ... reproducing magnetic field L ... light spot P' ... reproduction layer R '... recording layer M ... recording marks MG ... reproducing magnetic field magnet S , S '... Magneto-optical recording medium reproducing device TR ₁ ... reproduction information track (target track) TR ₂ , TR ₃ ... adjacent information track (adjacent track) T _CR ' ... Curie temperature of recording layer R 'T _CS ' ... switch layer Curie temperature of _{S'T COMP} ... compensation point temperature of the switch layer _{S'V B} ... irradiation direction V _T ... rotation direction α ... inclination angle β ... angle formed by one side of substantially V-shape and rotation direction

Claims (3)

[Claims] 1. A window region having a predetermined reproduction temperature or lower and a predetermined reproduction temperature within an irradiation range of a light beam for reproducing information that is irradiated onto a magneto-optical recording medium on which information is recorded on an information track. In a magneto-optical recording medium reproducing apparatus for forming a mask area as described above and reproducing the information existing in the window area by super-resolution reproduction, the reproduction information track is the information track to be reproduced and the reproduction information track. On the adjacent adjacent information track, the bent portion is formed on the reproduction information track, and the side portion is formed on the adjacent information track, and the leg opening direction is the moving direction of the information on the reproduction information track. A coma-aberration generating unit that gives the light beam a coma-aberration that forms the substantially V-shaped mask region that is in the opposite direction is provided, and the coma-aberration generating unit is sandwiched between the sides of the mask region. And a region, the magneto-optical recording medium reproducing apparatus characterized by the area on the reproduction information track to said window region. 2. The magneto-optical recording medium reproducing apparatus according to claim 1, wherein the coma aberration generating unit applies the light beam to the magneto-optical recording medium and a moving direction of the information on the reproduction information track. A magneto-optical recording medium reproducing apparatus, which is a control means for controlling the inclination of the magneto-optical recording medium or the irradiation direction of the light beam so that the angle formed by and becomes a predetermined acute angle. 3. The magneto-optical recording medium reproducing apparatus according to claim 1, wherein the coma aberration generating means emits light between a light beam emitting means for emitting the light beam and a recording surface of the magneto-optical recording medium. A magneto-optical recording medium reproducing apparatus, characterized in that it is an optical coma aberration generating means arranged on the road.