JP2000215542A - Optical disc playback method - Google Patents

Abstract

(57) [Problem] To provide an optical disk reproducing method capable of easily reproducing a fine recording mark having an optical resolution or less with good quality. An optical disc has a reproducing layer and an information recording layer. A plurality of light beams are radiated close to the reproduction layer of the same information track of the optical disc 10. In the light spots 1 and 2, mask regions 3 and 4, which are portions whose temperature has been increased by irradiation, are formed. The mask areas 3 and 4 hide the recording marks 5 and reproduce the recording marks 5 using areas other than the mask areas 3 and 4 in the light spots 1 and 2 as detection areas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the use of a plurality of light beams to reproduce high-quality (ultra-high-quality) minute recording marks having a resolution lower than the resolution of a reproduction optical system recorded on an optical information medium (also referred to as an optical disk). The present invention relates to an optical disk reproducing method that enables (resolution reproduction).

[0002]

2. Description of the Related Art In order to record information on an optical disk, for example, a magneto-optical recording medium, information is recorded as a magnetic domain pattern on a magnetic film having perpendicular magnetic anisotropy by a thermomagnetic recording method using a laser beam. The recording mark pattern can be formed by setting the state to downward magnetization and forming a recording mark composed of an upward magnetization region in this state. At the time of reproduction, the magnetization direction of the magnetic film is converted into an electric signal and detected by a magneto-optical effect called the Kerr effect.

In order to meet the recent demand for a higher recording density of a magneto-optical recording medium, a technique for reproducing a very fine recording mark exceeding the optical resolution in a reproducing optical system and a reproducing light wavelength has been developed. A magnetic super-resolution reproduction method is known as a method developed and achieved by devising a recording medium. In this method, by forming a mask region magnetically aligned in one direction in a reproduction spot in a magnetic multilayer film, a recording mark transferred only in a detection region narrowed by the mask region as compared with the related art is detected. Therefore, the signal detection area is substantially limited, and reproduction exceeding the resolution of the optical system can be performed.

[0004] As the magnetic super-resolution reproducing method, there have been proposed several methods having different forms of a mask region and a detection region. A FAD method (Front A) in which a mask area is formed in a high-temperature area behind a reproduction spot and a front area is a detection area.
RAD system (Redetection) in which the high-temperature area behind the reproduction spot is a detection area.
ar Aperture Detection).

[0005] In this specification, the term "recording mark" means a magnetic domain magnetized in a direction opposite to that of the surroundings. The description is made on the assumption that the surroundings have downward magnetization and the recording marks have upward magnetization. However, the same holds true for the case where the periphery is upward and the recording mark is downward.

On an optical disk such as a phase change recording medium, the information is recorded on the recording information layer in a crystalline or amorphous state, and is reproduced as a change in each reflectance. In a phase change recording medium, for example, super-resolution reproduction is possible by using a mask layer whose transmittance decreases in a high-temperature region. It is possible to reproduce recorded marks.

FIG. 7 is an explanatory view showing the state of the reproducing layer of the magneto-optical disk, the temperature profile indicating the temperature distribution of the optical disk, and the magnetization state of the optical disk in association with the reproduction of the conventional magneto-optical disk of the FAD system. 5 is a recording mark, 7 is a light spot, 8 is a mask area, 11 is a first magnetic layer, 12 is a second magnetic layer, and 13 is a third magnetic layer.
A magnetic layer, and the magneto-optical disk comprises first, second, and third
This is an exchange-coupled three-layer medium composed of a magnetic layer, and 14 is an external auxiliary magnetic field. In other words, the portion where the exchange coupling force from the third magnetic layer 13 to the first magnetic layer 11 is reduced by raising the temperature to near or above the Curie temperature of the second magnetic layer 12 by the irradiation of the laser beam, By applying an external auxiliary magnetic field 14 having a switching magnetic field strength equal to or higher than the switching magnetic field strength of one magnetic layer 11,
A mask region 8 having a uniform magnetization state can be formed. By reproducing information only in the area (detection area) excluding the mask area 8 from the light spot area 7, the effective detection area is limited and magnetic super-resolution reproduction can be realized.

FIG. 8 shows a reproduction waveform b showing a reproduction signal by a conventional reproduction method without forming a mask region (hereinafter referred to as a maskless reproduction method) and a reproduction signal obtained by magnetic super-resolution reproduction by the conventional FAD method. FIG. 9 is an explanatory diagram showing a comparison between reproduced waveforms f. As shown in FIG.
The reproduction waveform f by the method shows the same rise as the reproduction waveform b by the maskless reproduction method, but the fall at which the recording mark end (edge) falls from the detection area in the light spot to the mask area sharply decreases compared to the reproduction waveform b. I do.

Similarly, in the magnetic super-resolution reproduction of the RAD system, a reproduced signal which changes sharply when moving from the mask region to the detection region is obtained. This sharp change in the reproduction signal provides good reproduction quality in mark edge recording where information is recorded according to the position of the recording mark end.

In the above-mentioned conventional FAD system and RAD system, since there is only one mask area, a steep reproduction signal can be obtained only at either the rear edge or the front edge of the recording mark, and the reproduction is equal to the reproduction without mask. Sufficient signal quality cannot be obtained at edges that become signals.

Japanese Patent Application Laid-Open No. 4-255946 discloses that in order to form a mask region in front of a low-temperature region of a light spot, the reproducing layer is magnetized in one direction in advance by using an initialization magnetic field. A double-mask RAD type magnetic super-resolution reproducing method in which the front and rear sides are formed before and after is disclosed.

Japanese Patent Application Laid-Open No. 8-77626 discloses that
There is disclosed a double-mask method in which an initialization magnetic field is unnecessary, and a reproduction magnetic field is reduced by using a nonmagnetic intermediate layer that blocks an exchange coupling force between a reproduction layer and a recording layer. That is, a mask in which the magnetization of the reproducing layer holds the initialization magnetic field direction is formed in the low-temperature region within the reproducing beam spot, and a mask in which the magnetization of the reproducing layer is aligned in the reproducing magnetic field direction is formed in the high-temperature region. In the intermediate temperature region of the mask, the magnetization of the recording layer causes the recording mark to be transferred by the magnetostatic coupling force.

Further, a multi-beam optical head and a reproducing method for recording or reproducing information on an optical disk by generating a plurality of laser beams from one optical head have been proposed, and information can be simultaneously recorded from a plurality of information tracks on the optical disk. It performs recording or reproduction, and is considered promising as a measure for increasing the data transfer rate. For example, JP-A-9
Japanese Patent Publication No. 312035 proposes a multi-beam optical head capable of rotating the polarization planes of a plurality of light beams by a predetermined angle and separating and receiving reflected light reflected from an optical disk according to the polarization plane angle. As a method of separating and receiving a plurality of light beams irradiated on an optical disk, a method using light beams of different wavelengths is also possible in addition to the method of changing the polarization plane.

[0014]

However, in the magnetic super-resolution reproduction of the double mask RAD method, an initializing magnetic field is required, or a magnetostatic coupling force sufficient for transferring under the reproducing magnetic field is not sufficient. There is a problem that it is difficult to control the composition, film thickness, and the like of the obtained magnetic layer, and a sufficient manufacturing margin cannot be obtained.

Further, in the above-mentioned multi-beam optical head and reproducing method, recording or reproduction can be simultaneously performed on a plurality of tracks of an optical disk, but it is not possible to reproduce fine recording marks having an optical resolution or less with good quality. was there.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide an optical disk reproducing method capable of easily reproducing a fine recording mark having an optical resolution or less with high quality. is there.

[0017]

According to a first optical disk reproducing method of the present invention, an optical disk having at least a reproducing layer and an information recording layer has a light spot of one light beam on the reproducing layer on the same track. At least two light beams are radiated in close proximity to each other so that the light spot of the other light beam includes a mask area that has risen to a specific temperature or higher, and an area other than the mask area in the light spot is set as a detection area. This is a method for reproducing the information recorded on the information recording layer.

In a second optical disk reproducing method according to the present invention, an optical disk having at least a reproducing layer and an information recording layer is a magneto-optical disk, and one optical beam is provided on the reproducing layer on the same track of the disk. At least two light beams are radiated in proximity to each other so that the light spot of the other light beam includes the mask region heated to a specific temperature or higher by the light spot, and the mask region of the reproducing layer is magnetized by an external auxiliary magnetic field. In this method, the recording or reading of the information recording layer is performed by using a region other than the mask region in the light spot as a detection region in which the magnetization reverses or disappears.

According to a third optical disk reproducing method of the present invention, in the above-mentioned second optical disk reproducing method, one of the adjacent light beams is FAD (Front Apart).
ureDetection), the rear edge information of the recording mark is used, and the other is the RAD method (Rear Apart).
This is a method of reproducing the leading edge information of the recording mark by using “Detection”.

A fourth optical disk reproducing method according to the present invention is a method according to the second or third optical disk reproducing method, wherein an external auxiliary magnetic field is applied in a direction in which the sublattice magnetization direction of the reproducing layer becomes the erasing direction. .

According to a fifth optical disk reproducing method of the present invention, in any one of the first to fourth optical disk reproducing methods, a reproduced signal by one of the light beams is transmitted within a time period during which the other light beam is extinguished. How to get.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is an explanatory diagram for explaining an optical disk reproducing method according to a first embodiment of the present invention. In the figure, reference numeral 10 denotes an optical disk having at least a reproducing layer and an information recording layer, and 6 denotes a moving direction of the optical disk 10. It is. Reference numerals 1 and 2 denote light spots formed by two light beams that are radiated close to the reproduction layer of the same track of the optical disk 10. In FIG. 1, the two light beams are based on the moving direction 6. Assuming that a light beam in front of the optical disk is a first light beam and a rear light beam is a second light beam, 1 is a first light spot by the first light beam, and 2 is a second light spot by the second light beam. The light spot 3 is a first mask region formed by raising the first light spot 1 above a specific temperature, and the second light spot 4 is formed by raising the second light spot 2 above a specific temperature. As shown in FIG. 1, at least two first and second light beams pass through the first mask region 3 raised to a specific temperature or higher by the first light spot 1 to the second light spot. Illuminated in close proximity to include That. A detection area for reproducing information recorded on the information recording layer of the optical disc is an area other than the mask area in the light spot.

For example, as the above-mentioned optical disk, a reproducing layer is a magnetic layer having a magnetic property that makes it difficult to maintain a small magnetic domain in a specific temperature range of room temperature or higher. Some of the optical disks have a layer that changes as a reproducing layer. Such an optical disk can achieve the effects of the present invention without using an external auxiliary magnetic field during reproduction, as described below.

In the optical disk reproducing method according to the first embodiment of the present invention, the recording mark formed by the first light beam and entering the first mask area 3 is not detected as a reproduction signal. Thereafter, the temperature of the disk is lowered by the temperature decreasing process, and the recording mark 5 that has exited the first mask area 3 appears in the second light spot 2 by the second light beam and is detected as a reproduction signal intensity. Again, the recording mark 5 enters the second mask area 4 formed by the second light beam, so that the reproduction signal intensity decreases. As described above, a steep reproduction signal is obtained at the two edges of the recording mark smaller than the resolution of the reproduction optical system due to the two boundaries from the mask region to the detection region and from the detection region to the mask region.

Embodiment 2 The optical disk reproducing method according to the second embodiment of the present invention uses a magneto-optical disk having at least a reproducing layer and an information recording layer as the optical disk according to the first embodiment, and performs a magnetic super-resolution reproducing method. It is a method of doing. The material of the magnetic layer of the magneto-optical disk capable of magnetic super-resolution reproduction will be described later, but a transition metal alloy or a rare earth-transition metal alloy can be used. In the transition metal alloy, the magnetization of the transition metal is the magnetization of the alloy. The rare earth-transition metal alloy is a ferrimagnet in which the sublattice magnetization of the rare earth metal and the sublattice magnetization of the transition metal are coupled in opposite directions, and the subtraction magnetization of both is observed as external magnetization. . In a multilayer magnetic film such as a magneto-optical disk used in the present invention, an exchange force acts so as to align the direction of the same type of sublattice magnetization between adjacent magnetic layers in the same direction. This magnetic coupling between adjacent layers is called exchange coupling. In the present specification, the direction of the magnetization shall be represented by the direction of the transition metal magnetization or the direction of the transition metal sublattice magnetization, and unless otherwise specified, the magnetization shall mean the transition metal magnetization or the transition metal sublattice magnetization, "Total magnetization" is used to express the subtraction magnetization observed externally.
I will call it. The application direction of the reproducing magnetic field Hr in the specification generally corresponds to the recording magnetic field direction with the upward direction being the + (plus) direction, and the-(minus) direction is used as the erasing magnetic field direction.

FIG. 2 is a configuration diagram showing the configuration of a magneto-optical disk according to a reproducing method according to a second embodiment of the present invention.
1 is a first magnetic layer serving as a reproducing layer, 12 is a second magnetic layer, 13
Denotes a third magnetic layer serving as an information recording layer, which is formed on a transparent substrate 30 by a first dielectric layer 31, three-layered magnetic layers of first to third magnetic layers, and a second dielectric layer 32. . Usually the second
A protective layer such as a UV resin is provided on the dielectric layer 32.

The first magnetic layer 11 is preferably made of a material having a perpendicular magnetic anisotropy and a large magneto-optical effect.
Fe, GdFeCo, GdNdFeCo or GdDy
A material containing Fe or the like as a main component can be used. In addition, a material having a small perpendicular magnetic anisotropy is desirable so that the magnetization state of the mask region can be easily reversed or eliminated in the portion heated by the laser beam irradiation.

The second magnetic layer is made of a material capable of adjusting the Curie temperature Tc ₂ to a relatively low temperature, for example, DyFe,
DyFeCo, TbFe, TbFeCo, TbDyFe
Alternatively, a material containing TbDyFeCo or a material obtained by adding Gd or Ni to them as a main component can be used. The thickness of the second magnetic layer depends on its Curie temperature T
In order to sufficiently cut the exchange coupling between the first magnetic layer and the third magnetic layer at c ₂ or more and to perform a stable reproducing operation, 3n
m to 80 nm is desirable. The Curie temperature Tc ₂ of the second magnetic layer is required to be lower than the Curie temperature Tc ₃ Curie temperature Tc ₁ and the third magnetic layer of the first magnetic layer, in order to perform a stable reproducing operation 60 ° C. or higher 250 C or lower is desirable.

The third magnetic layer is desirably a perpendicular magnetic film having a large perpendicular magnetic anisotropy in order to stably hold recorded information.
Materials include, for example, DyFe, DyFeCo, TbF
e, TbFeCo, TbDyFe or TbDyFeC
A material containing o as a main component can be used. Third
The thickness of the magnetic layer is desirably from 10 nm to 250 nm in order to stably retain recorded information even when the first magnetic layer and the second magnetic layer change in domain wall motion, magnetization disappearance, and the like. It is necessary that the Curie temperature Tc ₃ of the third magnetic layer does not disappear due to temperature rise during reproduction, and has a practical recording sensitivity.
In order to perform a stable reproduction operation, the temperature is desirably 200 ° C. or more and 360 ° C. or less. Switching field H ₃ of the third magnetic layer must reproducing magnetic field H _r or applied during reproduction.

The information is recorded and held as the direction of the magnetization of the third magnetic layer.
The temperature T _{1 at} which the exchange coupling force applied from the magnetic layer to the first magnetic layer via the second magnetic layer exceeds the coercive force energy of the first magnetic layer is changed from the ambient temperature to the Curie temperature Tc ₂ of the second magnetic layer. Exists in the temperature range between By passing through this temperature during the temperature raising / lowering operation, the magnetization direction of the first magnetic layer is aligned with the magnetization directions of the second magnetic layer and the third magnetic layer. Further, in the temperature range higher than the temperature T _1, the reversal magnetic field H ₁ of the first magnetic layer than the reproducing magnetic field H _r is applied by an external auxiliary magnetic field the temperature T ₀ is present decreases during reproduction. The temperature T ₀ or more temperature range, the mask area magnetization is aligned in one direction of the first magnetic layer is formed by the reproducing magnetic field H _r.

FIG. 3 shows a relation between the state of the reproducing layer of the magneto-optical disk during reproduction, the temperature profile indicating the temperature distribution of the optical disk, and the magnetization state of the optical disk in the optical disk reproducing method according to the second embodiment of the present invention. FIG. Arrows in the magnetic layer indicate transition metal sublattice magnetization. Since the optical disk is moving, the peak in the temperature profile is located behind the center of the light spot.
For example, when the temperature is increased by a laser beam, the region of the second magnetic layer 12 having a Curie temperature Tc ₂ or higher and the first magnetic layer 11
Regions whose magnetization direction aligned switching field H ₁ is an external auxiliary magnetic field 14 by the reproducing magnetic field H _r becomes smaller than the temperature T in the reproducing magnetic field direction at ₀ over the first magnetic layer 11, that is, the mask region is formed of. Since the first magnetic layer 11 is dominant transition metal sublattice magnetization at temperature T _0, the magnetization direction is parallel to the reproducing magnetic field H _r. Reproducing magnetic field H _r in FIG. 3 are applied to the erasing direction. The first light spot 1 formed by the first light beam and the first mask area 3 formed thereby are replaced by the second light spot 2 formed by the second light beam and the second mask area formed thereby. 4 are formed.

In the optical disk reproducing method according to the second embodiment of the present invention, when the recording mark enters the first mask area 3 formed by the first light spot 1, the reproducing magnetic field from the external auxiliary magnetic field 14 the first magnetic layer 11 by H _r is the magnetization reversal. Thereafter, the temperature of the optical disc is decreased by the temperature decreasing process such that the exchange coupling force exerted from the third magnetic layer 13 to the first magnetic layer 11 via the second magnetic layer 12 exceeds the coercive force energy of the first magnetic layer 11. When the temperature becomes equal to or lower than T _1, the magnetization direction of the first magnetic layer 11 appears so as to be aligned with the third magnetic layer 13 again. By setting the second light spot in the temperature region where the temperature is equal to or lower than T _1, a steep reproduction signal change due to the magnetization reversal of the first magnetic layer 11 can be obtained.
Furthermore, when the transferred recording mark 5 reaches the second mask area 4 formed by the temperature rise by the second light spot 2, it disappears again due to the magnetization reversal of the first magnetic layer 11. Due to the magnetization reversal of the first magnetic layer 11 at the time of the magnetization disappearance, a steep reproduction signal change can be obtained.

As described above, by forming a mask region with two light beams, a reproduced signal of the second light beam can obtain a steep reproduced signal at both rise and fall.

Embodiment 3 FIG. 5 is an explanatory diagram showing, in association with the optical disc reproducing method according to the third embodiment of the present invention, the state of the reproducing layer of the magneto-optical disc during reproduction, the temperature profile indicating the temperature distribution of the optical disc, and the magnetization state of the optical disc. FIGS. 6A and 6B show a reproduction waveform b obtained by a conventional maskless reproduction method and an FAD method using a first light beam by an optical disk reproduction method according to a third embodiment of the present invention. FIG. 9 is an explanatory diagram showing a comparison between a reproduced waveform af of Example 1 and a reproduced waveform ar of the RAD method using a second light beam.

In the optical disk reproducing method according to the third embodiment of the present invention, when the recording mark 5 enters the first mask area 3 formed by the first light spot 1, the recording mark 5 The first magnetic layer 1 is _generated by the reproducing magnetic field _Hr .
1 reverses the magnetization. Due to the magnetization reversal of the first magnetic layer 11 at the time of the magnetization disappearance, a steep reproduction signal change can be obtained. Thereafter, the temperature of the optical disc is reduced to a third
The first magnetic layer 11 from the magnetic layer 13 via the second magnetic layer 12
When the exchange coupling force exerted on the first magnetic layer 11 becomes equal to or lower than the temperature T ₁ that exceeds the coercive force energy of the first magnetic layer 11, the magnetization direction of the first magnetic layer 11 appears so as to be aligned with the third magnetic layer 13 again. By setting the second light spot 2 in the temperature region where the temperature is equal to or lower than T _1, it is possible to obtain a sharp change in the reproduction signal due to the magnetization reversal of the first magnetic layer 11.

As described above, in the present embodiment, as shown in FIG. 6, the reproduced waveform a of the first light beam has a sharp fall due to the magnetic super-resolution reproduction of the FAD system.
f, With the second light beam, a reproduced waveform ar having a steep rise is obtained by the magnetic super-resolution reproduction of the RAD method. As described above, the first light beam and the second light beam can detect the rear edge and front edge position information of the recording mark with better signal quality than normal reproduction. Note that, in the optical disk reproducing method of the present embodiment, it is not always necessary to form the mask region with the second light beam. In addition, the first for forming a mask region
Magnetization reversal of the magnetic layer, the reproducing magnetic field H _r is as long reversal magnetic field H ₁ or more of the first magnetic layer, thus may be a Tc ₂ temperatures below not affect the effect of the present invention.

[0037]

[Embodiment 1] The following thin films are sequentially formed by a sputtering method on a glass 2P transparent substrate having a spiral guide groove on a disk-shaped surface having a thickness of 1.2 mm and a diameter of 13 cm and having a track pitch of 1.1 μm. A magneto-optical disk having the configuration shown in FIG. 2 was prepared, and a UV-curable resin layer was formed on the second dielectric layer for mechanical protection. <Layer><Material><Filmthickness><Curietemperature> First dielectric layer SiN _x 60 nm First magnetic layer GdFeCo 50 nm Tc ₁ > 300 ° C. Second magnetic layer DyFeCo 25 nm Tc ₂ = 150 ° C. Third magnetic layer TbFeCo 50 nm Tc ₃ = 240 ° C. Second dielectric layer SiN _x 90 nm Protective layer UV resin

The measured compensation temperature of the first magnetic layer was about 50 ° C. The second and third magnetic layers have compensation temperatures near room temperature. A reproduction experiment was performed using this magneto-optical disk.

Recording Conditions A light beam is tracked on an information track at a linear velocity of 7.5 m / s, and the laser power during recording is increased to 1.5 mW and 6.7 mW while an external magnetic field of 300 Oe is applied upward.
Irradiated with intensity modulated. As a result, only the portion irradiated at 6.7 mW becomes a recording mark of upward magnetization, and a recording mark having a length of about 0.30 μm is recorded.

Reproduction The reproduction in the erasing direction is performed by using an optical head designed so that the distance between the centers of the first and second light spots formed by the first light beam and the second light beam is about 3.0 μm. Magnetic field 3
00 Oe was applied, and reproduction was performed by the optical disk reproduction method according to the second embodiment of the present invention. That is, after the recording mark passes through the first mask area formed by the first light spot, the first mark is formed in the light spot by the second light beam.
Since the signal appears again by being transferred to the magnetic layer, the reproduced signal sharply increases. Further, when a recording mark enters the second mask area formed by the second light spot, the recording mark on the reproduction layer disappears, and the reproduction signal sharply decreases. FIG. 4 shows a reproduced waveform a of the second light beam obtained by using the reproducing method of the magneto-optical disk according to the second embodiment of the present invention and a reproduced waveform b obtained by the conventional maskless reproducing method. It is explanatory drawing which shows and compares. As shown in FIG.
With the mask region formed by the first and second light spots, the reproduction resolution is remarkably improved, and a reproduction waveform a having both steep rising and falling is obtained, and the second embodiment of the present invention is achieved. It was confirmed that the reproduction quality was improved by the optical disk reproduction method using the two-beam method. On the other hand, as shown by the reproduction waveform b in FIG. 4, in the reproduction without a mask, the reproduction signal appears and gradually increases due to the recording mark entering the light spot, and the reproduction signal gradually increases at the central part of the light spot where the light intensity is strong. , And the reproduced signal thereafter gradually decreases.

Embodiment 2 FIG. A magneto-optical disk recorded in the same manner as in Example 1 using the same magneto-optical disk as in Example 1 was reproduced by the optical disk reproducing method according to the third embodiment of the present invention. That is, as shown in FIGS. 5 and 6, magnetic super-resolution reproduction is performed by the FAD method using the first light beam, and a reproduced waveform af having a sharp fall is obtained, and magnetic reproduction is performed by the RAD method using the second light beam. Super-resolution reproduction was performed, and a reproduction waveform ar having a sharp rise was obtained. As described above, the first light beam and the second light beam can detect the rear edge and front edge position information of the recording mark with better signal quality than the reproduction without mask.

In the above embodiment, when the external auxiliary magnetic field applied in the erasing direction for forming the mask area is the recording direction, the magnetization direction of the mask area formed is the same as that of the recording mark. Even in the external auxiliary magnetic field in the recording direction, a mask region is formed by each light beam, and reproduction of a minute magnetic domain having an optical resolution or less is possible. However, since the magnetization direction of the mask area is the same as the recording mark direction, the signal from the mask area in the light spot is added to the reproduction signal, and the change in the shape and size of the mask area causes a rise in noise level. Become. The sub-lattice magnetization direction of the first magnetic layer in the mask region is desirably antiparallel to the recording mark so that the shape of the mask region is not affected by the quality of the reproduction signal. Therefore, the external auxiliary magnetic field is applied to the first auxiliary magnetic field in the mask region.
It is preferable that the magnetic layer be applied in a direction in which the sublattice magnetization direction is the erasing direction.

In the above embodiment, the distance between the first light beam and the second light beam irradiated on the same track is set at the end of the mask area by the first light spot formed by the first light beam. Is included in the light spot by the second light beam (that is, the recording mark appears in the second light spot), and the distance between the centers of the first and second light spots is about 3.0 μm. Thus, the optical head is designed and adjusted. However, in practice, the mask area by the first light spot formed by the first light beam, in particular, the end portion fluctuates due to the variation of the optical disk and the linear velocity at the time of reproduction, so that the light intensity of the first light beam is changed. In addition, the reproduction is performed by controlling the reproduction magnetic field intensity by the external auxiliary magnetic field so that an appropriate area is obtained. Therefore, as in the present embodiment, the value of the interval of 3.0 μm is not always an optimum value, and the variation of the optical disk to be used or the linear velocity or the ambient temperature, which is the condition at the time of reproduction, is not affected by the first light beam. The beam interval may be set according to the intensity and the reproducing magnetic field intensity by the external auxiliary magnetic field.

Embodiment 3 FIG. In the first and second embodiments, when the optical disc is irradiated with at least two light beams to obtain a reproduction signal, the reproduction signal from the second light beam, which is the corresponding beam to the light receiving unit, is converted to the first light beam. Was obtained within the time during which the light was quenched, thereby obtaining a reproduced signal free from influences other than from the second light beam. In particular, the first and second
Of the present invention in which both light beams are used for reproducing information.
In the optical disk reproducing method according to the embodiment, it is necessary to separate and detect a reproduced signal by each light beam. First
The reproduced signals of both the second light beam and the second light beam are pass-emitted so that the reproduced signals can be obtained by the same detection system, thereby enabling separation of the reproduced signals. That is, when the first beam emits light with a predetermined power, the second beam is quenched or emitted with low power, so that the reproduction signal in the detection system becomes a reproduction signal by the first beam which is not affected by the second beam. Conversely, by emitting the second beam at a predetermined power while the first beam is quenched or emitted with low power,
A reproduction signal by the second beam is obtained. As mentioned above,
By causing the light beams to emit pulses, the reproduced signal from each beam could be separated.

Further, in the above embodiment, the case where the optical disk reproducing method of the present invention is performed using two light beams has been described. However, a mask region is formed by more light beams to limit the detection region. As a result, it is possible to reproduce a fine recording mark having an optical resolution or less with high quality. In addition, by irradiating a signal from an adjacent track, that is, a light beam to an adjacent track in order to suppress crosstalk, it is possible to reproduce an optical disk having a higher recording density.

Although the present invention has been described with respect to the recording method using the light intensity modulation recording method, the same applies to the case where the same recording pattern is recorded even when the recording method is the magnetic field modulation recording method, and the effect of the present invention is not changed. Absent.

Although the optical disk reproducing method of the present invention has been described with respect to the case where light is incident from the transparent substrate side, if the order of laminating each dielectric layer and magnetic layer is reversed, the optical disk reproducing method can be realized. The recording and reproduction may be performed from the opposite side. Further, in the optical disk reproducing method of the present invention, test recording and test reproduction for optimally adjusting the recording power, the reproducing power, and the magnitude of the reproducing magnetic field by the external auxiliary magnetic field are used immediately before recording or reproducing on the optical disk. It goes without saying that it can be done.

As a recording method, there are a mark position recording method in which information is carried at a position where a recording mark exists, and a mark edge recording method in which information is carried at a front end and a rear end of a recording mark. Is particularly effective for the mark edge recording method, but can also be used for the mark position recording method, and reproduction with the same high resolution is possible.

[0049]

According to the first optical disk reproducing method of the present invention,
On the reproduction layer of the same track of the optical disc having at least the reproduction layer and the information recording layer, such that the light spot of the other light beam includes a mask region that has been raised to a specific temperature or higher by the light spot of one light beam, A method of irradiating at least two light beams in close proximity to each other and reproducing the recorded information on the information recording layer by using an area other than the mask area in the light spot as a detection area. Can be reproduced with good quality.

According to the second optical disk reproducing method of the present invention, an optical disk having at least a reproducing layer and an information recording layer is a magneto-optical disk, and the light of one light beam is placed on the reproducing layer on the same track of the disk. At least two light beams are radiated in proximity to each other so that the light spot of the other light beam includes the mask area raised to a specific temperature or higher by the spot, and the mask area of the reproducing layer is magnetization-reversed by an external auxiliary magnetic field. Alternatively, magnetization is lost, and a method of reproducing the recording of the information recording layer using a region other than the mask region in the light spot as a detection region can easily reproduce a fine recording mark having an optical resolution or less with good quality. This has the effect.

According to a third optical disk reproducing method of the present invention, in the above-mentioned second optical disk reproducing method, one of the adjacent light beams is FAD (Front Architecture).
The information on the trailing edge of the recording mark is obtained by detection, and the other is RAD (Rear Apertur).
e Detection) is a method of reproducing the leading edge information of the recording mark by the method of reproducing the front edge information of the recording mark.

A fourth optical disk reproducing method according to the present invention is the method according to the second or third optical disk reproducing method, wherein an external auxiliary magnetic field is applied in a direction in which the sublattice magnetization direction of the reproducing layer is in the erasing direction. There is an effect that reproduction can be performed with higher quality.

According to a fifth optical disk reproducing method of the present invention, in any one of the first to fourth optical disk reproducing methods, a reproduced signal by one of the light beams is transmitted within a time period during which the other light beam is extinguished. There is an effect that reproduction can be performed with higher quality by the method of obtaining.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an optical disc reproducing method according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of a magneto-optical disk according to a reproducing method according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an optical disk reproducing method according to a second embodiment of the present invention in which the state of a reproducing layer of a magneto-optical disk during reproduction is associated with a temperature profile indicating a temperature distribution of the optical disk and a magnetization state of the optical disk. FIG.

FIG. 4 shows a reproduced waveform a of a second light beam obtained by using the reproducing method of the magneto-optical disk according to the second embodiment of the present invention and a reproduced waveform b obtained by the conventional maskless reproducing method. FIG. 4 is an explanatory diagram showing a comparison with FIG.

FIG. 5 is an explanatory view showing, in association with the optical disk reproducing method according to the third embodiment of the present invention, the state of the reproducing layer of the magneto-optical disk, the temperature profile indicating the temperature distribution of the optical disk, and the magnetization state of the optical disk in association with each other. FIG.

FIG. 6 shows a reproduction waveform b obtained by a conventional maskless reproduction method, a reproduction waveform af of a FAD method using a first light beam, and a second light by a first light beam by an optical disk reproduction method according to a third embodiment of the present invention. FIG. 6 is an explanatory diagram showing a comparison with a reproduced waveform ar of the RAD method using a beam.

FIG. 7 is an explanatory diagram showing the state of the reproducing layer of the magneto-optical disc, the temperature profile indicating the temperature distribution of the optical disc, and the magnetization state of the optical disc when reproducing the conventional FAD magneto-optical disc.

FIG. 8 is an explanatory diagram showing a comparison between a reproduction waveform b obtained by the conventional maskless reproduction method and a reproduction waveform f obtained by the conventional FAD method.

[Explanation of symbols]

1 first light spot, 2 second light spot, 3 first mask area, 4 second mask area, 5 recording mark, 10 optical disk, 11 first magnetic layer (reproducing layer),
12 second magnetic layer, 13 third magnetic layer (information recording layer),
14 External auxiliary magnetic field.

Claims (5)

[Claims] An optical disk having at least a reproducing layer and an information recording layer has a mask area raised to a specific temperature or higher by a light spot of one light beam on the reproducing layer of the same track. As includes
An optical disc reproducing method that irradiates at least two light beams in close proximity to each other and reproduces recording on the information recording layer using a region other than the mask region in the light spot as a detection region. 2. An optical disk having at least a reproducing layer and an information recording layer is a magneto-optical disk, and a mask whose temperature is raised to a specific temperature or higher by a light spot of one light beam on the reproducing layer on the same track of the disk. At least two light beams are radiated in proximity to each other so that the light spot of the other light beam includes the area, and the mask area of the reproducing layer is reversed or demagnetized by an external auxiliary magnetic field. An optical disk reproducing method for reproducing the information recorded on the information recording layer by using an area other than the mask area as a detection area. 3. One of the adjacent light beams is FAD (Front Aperture Detection).
n) indicates the trailing edge information of the recording mark, and the other indicates RA.
D method (Rear Aperture Detective)
3. The optical disk reproducing method according to claim 2, wherein the front edge information of the recording mark is reproduced according to (on). 4. The optical disk reproducing method according to claim 2, wherein an external auxiliary magnetic field is applied in a direction in which a sub-lattice magnetization direction of the reproducing layer becomes an erasing direction. 5. The optical disk reproducing method according to claim 1, wherein a reproduction signal by one of the light beams is obtained within a time period during which the other light beam is extinguished.