JPH0850742A - Optical disk reproducer and reproducing method - Google Patents

Abstract

PURPOSE:To control the effective spot shape of a scanning spot at the time or reproducing by providing preheating means for forming a preheating area prior to the spot. CONSTITUTION:An optical head 1, a magneto-optic disk 2, and a motor 3 are provided, and a preheating head 4 is provided at the head 1. The head 1 is so regulated as to form a preheating spot adjacent to the scanning spot formed on the disk 2. Further, LD drivers 4, 8, a reproducing amplifier 6, an A/D converter 23, a modulator 9, a motor controller 7 and a microcomputer 10 are provided. The preheating spot is formed by the head 4 prior to the scanning spot, and at the time of reproducing, the effective spot shape of the scanning spot is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus and reproducing method.

[0002]

2. Description of the Related Art Magneto-optical disks, which are rewritable optical disks, have already been put to practical use. However, the existing magneto-optical disk has a drawback that the data transfer speed is slow because it is necessary to erase old information and then record new information when rewriting information. In order to overcome this drawback, an overwrite method has been proposed. A conventional magnetic field modulation method is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-214447, in which the direction of the magnetic field is reversed corresponding to the data to be recorded while continuously irradiating the laser beam.

A conventional magnetic field modulation recording method will be described below with reference to the drawings. FIG. 15 is a schematic diagram showing the basic configuration of a conventional magnetic field modulation recording system. In the figure, 1
Reference numeral 21 is a magneto-optical disk, 122 is a laser beam, and 123 is a magnetic field modulation head.

The magnetic field modulation recording method is used for the magneto-optical disk 12
Recording is performed by continuously irradiating the laser beam 122 on the first magnetic field and inverting the direction of the external magnetic field according to the signal. The recording magnetic layer is heated to the Curie temperature or higher by irradiating the region to be recorded on the magneto-optical disk 121 with the laser beam 122. At this time, the direction of the current flowing through the magnetic field modulation head 123, which is provided on the opposite side of the optical pickup with the magneto-optical disk 121 sandwiched, is reversed depending on whether the data to be recorded is "1" or "0". , "N" or "S" magnetic field is generated.

Laser light 122 on the magneto-optical disk 121
The region heated by is separated from the irradiation position of the laser beam 122 as the magneto-optical disk 121 rotates. Accordingly, the temperature of this region decreases, and when it decreases to below the Curie temperature of the recording magnetic layer, the data "1" or "0"
The magnetic field of "N" or "S" corresponding to is recorded. In this method, since the rewrite signal is recorded regardless of the magnetization direction before recording, overwriting is possible.

As described above, basically, the value that can be represented by the recording pit itself is binary information of "0" or "1", and in order to improve the recording density, the pit length and the pit interval are reduced. By doing so, it is possible to increase the density to some extent in the line direction, but in this case, since the reproducible pit length and pit interval depend on the spot diameter of the laser light, there is a limit to the increase in reproduction density. Will be done.

This will be described in detail with reference to FIG.
FIG. 16 shows an MTF (Modul in an optical system without aberration).
FIG. 3 is a diagram showing an Application Transfer Function). Generally, the frequency characteristic in recording / reproducing is represented by MTF which is a transfer function of an optical system. The MTF in the optical system of an optical pickup having no aberration is as shown in FIG. 16 when the horizontal axis represents the spatial frequency. When the wavelength is λ and the numerical aperture NA of the objective lens is, the spatial frequency at MTF = 0 is represented by 2NA / λ, which is called a cutoff frequency.

The pit length at the cutoff frequency indicates the limit value at which the signal can be reproduced, and pits smaller than this cannot be read as information. Usually, half of the cutoff frequency is selected as a guide for stable reproduction, and the pit length required from this is the shortest pit length.

Therefore, when high density recording is performed in the magnetic field modulation recording system, high density can be achieved by high-speed modulating the applied magnetic field during recording, but regarding reproduction, the pit length that can be read during reproduction is as described above. M
Since it is determined by the TF characteristic, there is a limit to high density recording. Therefore, the following super-resolution reproduction method has been proposed.

FIG. 17 is a schematic sectional view of a conventional magneto-optical recording medium disclosed in Japanese Patent Laid-Open No. 5-73977. In the figure, a first magnetic layer 103 having a relatively low coercive force on a transparent substrate 101, and a coercive force higher than the first magnetic layer 103 and exchange-coupled with the first magnetic layer 103. A second magnetic layer 105 is provided, and the Curie temperature of the first magnetic layer 103 and the Curie temperature lower than the Curie temperature of the second magnetic layer 105 are provided between the first magnetic layer 103 and the second magnetic layer 105. A third magnetic body 104 having a temperature is provided.

FIG. 18 is a diagram showing a state during reproduction on the medium of FIG. FIG. 18A is a schematic view of the vicinity of the light spot of the medium as seen from the optical head side, and shows the temperature distribution of the light spot and the portion heated by the light spot. Also,
FIG. 18B is a schematic view of the vicinity of the light spot of the medium as seen from a cross section parallel to the scanning direction of the light spot, and shows the magnetization state of each magnetic layer. 18C is a schematic diagram showing the light intensity distribution of the light spot and its effective range.

In the figure, at the time of reproducing information, the magnetization of the third magnetic layer 104 is extinguished in a high temperature region which is a part of the region irradiated with the light beam to perform a masking action as a super-resolution film. Orient the magnetization of the magnetic layer 103 in one direction,
Prevent the information in the mask area from being detected by the light beam. In this way, by masking a part of the light spot to prevent unnecessary information from entering, it becomes possible to read information with a spatial frequency higher than the cutoff frequency of the optical system, which is called the super-resolution reproduction method. Has been. Also,
In such a method in which the mask region is generated in the high temperature portion heated by the light beam, the high temperature portion is generated in the backward direction with respect to the traveling direction of the light beam. Such a super-resolution reproduction method is called an erasing method.

Further, according to Japanese Patent Laid-Open No. 5-101472, at least the reproducing layer 111 as shown in FIG.
Information is transferred to the magneto-optical recording medium 115 having the memory layer 112 and the recording layer 113, and the reproducing layer 111 and the memory layer 112 are irradiated by an external recording magnetic field with high light intensity irradiation.
As shown in FIG. 20, the information recorded in the memory layer is reproduced only in the high temperature region due to the temperature distribution in the reproduction light spot as shown in FIG. The data is read while being transferred to 111. In this case, the reproducing layer 111 acts as a super-resolution film, and conversely to the case of JP-A-5-73977, the outside of the high temperature portion is masked. In such a method in which the mask disappears in the high temperature portion heated by the light beam, a high temperature portion is generated in the rear direction with respect to the traveling direction of the light beam, so that the effective opening of the light spot has a spindle shape. Such a super-resolution reproduction method is called an initializing method.

As described above, there are a magnetic field modulation recording method capable of high density recording and a magnetic super resolution method capable of high density reproduction. , And the effective opening in the anti-fog method is a crescent, so as shown in the schematic diagram of FIG.
When reproducing as it is, the adjacent pit will enter the optical spot, so even if both magnetic field modulation recording and magnetic super-resolution recording are combined, the reproduction limit pit will be It was difficult to make the length smaller. For example, FIG. 22A shows an aperture occupation focusing on a specific pit when a pattern obtained when high density recording by magnetic field modulation recording is attempted to be read by a crescent-shaped effective aperture using a super-resolution phenomenon. It is a calculated rate.
In this example, the pit width and the read beam width are ⅙ of the laser beam diameter, the horizontal axis is the read position normalized by the laser beam diameter, and the vertical axis is the ratio of the focused pit in the effective opening of the read beam. Is shown. This is the case corresponding to FIG.
In this example, the occupancy ratio of the focused pit is 5 at maximum.
It does not reach 0%, and it is understood that the information of the focused pit cannot be read correctly because the information of the pits adjacent in the scanning direction is mixed in the remaining portion. On the contrary, it can be seen that the information of the focused pit appears over several times the pit width and is mixed in the reproduction information of the adjacent pit. Such interference of information between the pits causes a reduction in reproduction signal and unnecessary reproduction jitter.

[0015]

In the conventional optical disk reproducing apparatus and reproducing method, when the recording pit shape and the reproducing spot shape do not match with each other as described above, interference occurs between adjacent pits in the reproduced signal, and There are problems such as inter-interference, occurrence of jitter, and decrease in C / N.
The problem was how to match the shape of the recording pit and the shape of the reproduction spot.

The present invention has been made in order to solve the above-mentioned problems, and at the time of reproduction, a preheating region is formed by preheating means prior to the scanning spot so that the reproduction spot shape matches the recording pit shape. An object of the present invention is to obtain an optical disc reproducing apparatus and a reproducing method capable of realizing an optimum super-resolution phenomenon and performing higher density recording and reproducing.

[0017]

An optical disk reproducing apparatus according to a first aspect of the present invention is an optical disk reproducing apparatus provided with preheating means for forming a preheating area prior to a scanning spot.

Further, the optical disk reproducing apparatus according to the second aspect of the present invention uses the optical disk reproducing apparatus which has a preheating means for forming a preheating area prior to the scanning spot and which cannot be read in the high temperature area. It is a thing.

According to a third aspect of the present invention, there is provided an optical disc reproducing apparatus which is provided with a preheating means for forming a preheating area prior to the scanning spot, and which is capable of reading in a high temperature area. Used.

An optical disk reproducing apparatus according to a fourth aspect of the present invention is an optical disk reproducing apparatus using two lasers having different wavelengths.

An optical disk reproducing apparatus according to a fifth aspect of the present invention uses an electro-optical element or an acousto-optical element in the optical disk reproducing apparatus.

Further, in the optical disk reproducing method according to the sixth aspect of the present invention, the preheating area is formed by the preheating means prior to the scanning spot. Information is read by the scanning spot controlled by the preheating area. The read signal is processed in synchronization with the irradiation of the scanning spot, the operation of the preheating means, or both operations.

[0023]

In the optical disk reproducing apparatus according to the first aspect of the present invention, the temperature distribution within the scanning spot is controlled by forming the preheating area to control the effective spot shape.

In the optical disk reproducing apparatus according to the second aspect of the present invention, the effective spot shape of the scanning spot is controlled by controlling the preheating area.

Further, in the optical disk reproducing apparatus according to the third aspect of the present invention, the effective spot shape of the scanning spot is controlled by controlling the preheating area.

Further, in the optical disk reproducing apparatus according to the fourth aspect of the present invention, the scanning beam and the preheating beam are respectively produced by using two lasers having different wavelengths.

Further, in the optical disk reproducing apparatus according to the fifth aspect of the present invention, the scanning beam and the preheating beam are produced by using the electro-optical element or the acousto-optical element.

Further, in the optical disk reproducing method according to the sixth aspect of the present invention, the preheating area is formed by the preheating means prior to the scanning spot. Information is read by the scanning spot controlled by the preheating area. The read signal is processed in synchronization with the irradiation of the scanning spot, the operation of the preheating means, or both operations.

[0029]

【Example】

Example 1. 1 is a block diagram showing an optical disk device according to a first embodiment of the present invention. In the drawing, 1 is an optical head, 2 is a magneto-optical disk, and 3 is a motor. Reference numeral 4 denotes a preheating head attached to the optical head 1, which is adjusted so as to form a spot adjacent to a spot formed on the optical disk by the optical head 1. 5 and 8 are LD drivers, 6 is a reproduction amplifier, 23 is an A / D converter, 9 is a demodulation circuit,
Reference numeral 7 is a motor control circuit, and 10 is a microcomputer.

FIG. 2 is a schematic diagram of a magneto-optical disk. The magneto-optical disk 2 is composed of a transparent substrate 24, a super-resolution film 25 formed on the surface thereof, a magneto-optical recording film 26, and a protective layer 27. FIG. 3 is a schematic diagram of recording pits when recording is performed on the magneto-optical disk by magnetic field modulation recording. FIG. 4 is a schematic diagram showing the heat distribution and the effective spot shape during reproduction. FIG. 5 is a diagram showing an example of the calculation result of the aperture occupancy when the effective spot shape is controlled by preheating an optical disk having an erasing-type super-resolution film. FIG. 6 is a diagram showing an example of experimental results of signal output during forward rotation reproduction and reverse rotation reproduction. FIG. 7 is a diagram showing an example of the experimental results of the recording frequency and the signal output at the time of forward rotation / reverse rotation reproduction.

Next, the operation of the embodiment will be described with reference to the drawings. On the magneto-optical disk 2, as shown in FIG.
It is assumed that a crescent-shaped recording pit as recorded by magnetic field modulation recording is written. This magneto-optical disk 2 is reproduced by the device having the preheating head 4 shown in FIG. At the time of reproduction, by the preheating spot created by the preheating head 4,
Preheating is performed prior to the reproduction spot. As shown in FIG. 4, the temperature on the magneto-optical disk 2 rises due to preheating, and when the temperature exceeds a certain temperature, the information in that area cannot be read.
It becomes a masking area. When the preheating spot moves in accordance with the scanning of the spot, and the preheating spot deviates from the area, the preheating spot is cooled by the effect of heat diffusion and the information can be read again. Therefore, by irradiating the reproducing spot on the location where the masking area disappears, a crescent-shaped effective spot lacking in the traveling direction of the reproducing spot can be obtained. This is a crescent moon with the opposite side to the effective spot (Fig. 3 (b)) obtained by normal super resolution reproduction without a preheating spot, and is written by magnetic field modulation recording as shown in Fig. 3 (c). The orientation matches the crescent shape created by the recorded pattern. By matching the recording pattern and the reproduction spot shape in this way, it is possible to prevent the information of the pits adjacent in the line direction from being mixed in the reproduction signal and accurately reproduce the signal recorded at high linear density. become.

FIG. 5 shows that writing is performed so that the writing pit length becomes 1/6 of the laser beam diameter.
The reproduction spot width during reproduction is still 1 of the laser beam diameter.
This is an example of calculating the aperture occupancy rate when super-resolution reproduction is performed so as to be / 6. FIG. 5A shows the case without preheating and corresponds to FIG. 3B, and FIG. 5B shows the case where preheating is performed and the effective spot shape matches the recording pattern.
An opening occupancy ratio focusing on a specific pit in the case of (c) is shown. In the case of no preheating, the aperture occupancy rate does not reach 50% at maximum in this example, whereas in the case of preheating, the maximum aperture occupancy rate is 100%, which reduces the mixing of information of adjacent pits. You can see that you can.

Next, in order to compare the effects of the case where preheating is not carried out and the case where preheating is carried out and the effective spot shape is matched with the recording pattern, a normal optical disk reproducing apparatus having no preheating means is rotated forward during reproduction. The experiment was performed by rotating the reverse direction and changing the direction of the effective spot. An example of the experimental result of the reproduced signal in this case will be shown. FIG. 6 shows an example of a reproduction signal, FIG. 6A shows an experimental result during forward rotation, and FIG. 6B shows an experimental result during reverse rotation reproduction. It can be seen that a higher quality reproduction signal is obtained by the reverse rotation reproduction than by the reproduction signal. Further, FIG. 7 is an example of an experimental result showing the relationship between the recording frequency and the C / N of the reproduced signal. The cutoff of this experimental system (the frequency at which reproduction cannot be performed due to the limitation of the optical spatial frequency) is near the recording pit frequency of 4 MHz. It can be seen that a higher C / N is obtained by the reverse rotation reproduction.

As described above, by matching the reproduction spot shape with the recording pit pattern during reproduction, it becomes possible to reproduce high density recorded information.

Example 2. FIG. 8 is a diagram showing a second embodiment of the present invention, which is an example in the case of using an optical disc having a so-called anti-blur type magnetic super-resolution film that cannot be read in a high temperature region. By creating a high-temperature region by the preheating means, the effective spot shape can be controlled by controlling the number and position of preheating spots for forming the mask region, as well as the irradiation power of the preheating spot and the reproduction spot. FIG. 8A shows a crescent-shaped reproduction spot formed in the opposite direction by one preheating spot. In FIG. 8B, the irradiation power of the reproduction spot is increased to form a dumbbell shape with front and rear parts cut off.
Further, FIG. 8C shows a case where two preheating spots are used and the effective spot is narrowed down in both length and width. Thus, the effective spot shape of the reproducing spot can be controlled by combining the anti-blur type magnetic super-resolution and the preheating means.

Example 3. FIG. 9 is a diagram showing a third embodiment of the present invention, which is an example of using an optical disc having a so-called start-out type magnetic super-resolution film capable of reading in a high temperature region. By creating a high temperature area by the preheating means, the effective spot shape can be controlled by controlling the number and position of the preheating spots and the irradiation power of the preheating spots and the reproduction spots to form the readable area. FIG. 9A shows 1
One preheating spot realizes a reproduction spot effective opening in which two spindles are arranged in front and back. In addition, FIG.
In (b), by shifting the preheating spot from the scanning line, a super-resolution reproduction spot shape elongated in the scanning direction is realized. As described above, the effective spot shape of the reproduction spot can be controlled by combining the start-up type magnetic super-resolution and the preheating means.

Embodiment 4 FIG. FIG. 10 is a diagram showing a fourth embodiment of the present invention and shows an example in which the preheating means is incorporated in the optical head. In the figure, 11 is an objective lens, 1
Reference numeral 2 is a polarizer, 13 is a dichroic mirror, 14 is a laser diode, 15 is a photodetector, 16 is a laser diode for preheating, 17 is a wavelength filter, and 18 is a polarizer.

Next, the operation will be described. The laser diode 14 and the laser diode 16 for preheating oscillate different wavelengths, and the laser diode 14 has a shorter wavelength than the laser diode 16 for preheating. Here, the oscillation wavelength of the laser diode 14 is λ1, and the oscillation wavelength of the preheating laser diode 16 is λ2. The light emitted from the laser diode 14 and the laser diode 16 for preheating are combined substantially coaxially with each other by the dichroic mirror 13 which is designed to reflect λ1 and transmit λ2. The combined light passes through the polarizer 12 and is condensed on the recording surface of the optical disc 2 by the objective lens 11. The spots formed by the light from the laser diode 14 and the light from the laser diode 16 for preheating when they are focused on the recording surface are slightly displaced from each other so that the preheating spot precedes the reproducing spot as shown in FIG. In other words, the masking area formed by the preheating spot masks a part of the reproduction spot, and is adjusted so as to form a crescent-shaped effective aperture lacking the scanning direction.

The light reflected on the disk surface is again transmitted through the objective lens 11 in a state where the reflected light from the preheating spot and the reflected light from the reproducing spot are mixed, and a part of the light is reflected by the polarizer 12. The wavelength filter 17 transmits λ1,
The wavelength filter 1 is designed not to transmit λ2.
7, only reflected light from the reproduction spot is selected and transmitted. The transmitted light is divided by a polarizer 18 into two components having orthogonal polarizations, and is converted into an electric signal by a photodetector 15 to be a reproduction signal. By using two laser diodes having different wavelengths in this way, it is possible to separate the reproduction spot and the preheating spot and reproduce using only the signal from the reproduction spot.

Example 5. 11 is a diagram showing a fifth embodiment of the present invention, in which 2 is an optical disc, 11 is an objective lens, 12 is a polarizer, 14 is a laser diode, and 1 is a laser diode.
Reference numeral 5 is a photodetector, and 19 is an electro-optical element (EO element). Next, the operation will be described. Laser diode 1
The light emitted from the laser light 4 passes through the EO element 19 and the polarizer 12, and is irradiated onto the recording surface of the optical disc 2 by the objective lens 11.
At this time, when a voltage is applied to the EO element 19, the optical path is bent and the focus position shifts. Therefore, as shown in FIG. 12, by utilizing the deviation of the optical path due to the EO element 19 and applying a time-varying voltage to the EO element 19, one laser diode 14 can generate both a preheating spot and a reproducing spot. You can get the effect.

Example 6. FIG. 13 is a diagram showing a sixth embodiment of the present invention, in which 20 is an EO driver, 21 is a clock signal generator, 22 is an analog gate circuit, and 23.
Is an A / D converter. Further, FIG. 14 is a diagram showing a state of the operation. In the device configured as shown in FIG. 11, if the reproduction signal is directly extracted, information from adjacent pits may be mixed during the preheating operation. Therefore, as shown in FIG. 13, an analog gate circuit 22 is provided so that the reproduction signal during the preheating operation is removed and only the signal during the reproduction operation is extracted from the reproduction signal. This operation will be described with reference to FIG. First, the clock signal is generated by the clock signal generator 21 according to the control signal from the microcomputer 10. The preheating operation and the reproducing operation are switched according to the clock signal. In this example, the preheating operation is performed when the clock signal is Hi, and the reproducing operation is performed when the clock signal is Lo.

During the preheating operation, the output of the laser diode 14 is switched for preheating by the clock signal and the signal from the microcomputer 10. The laser beam emitted from the laser diode 14 has its optical path bent by the EO element 19. The EO driver is controlled so that it can preheat a position slightly ahead of the reproduction position, and further, it can efficiently preheat the laser light by following the rotation of the disk. The laser light used for preheating operation does not need to be reproduced as a signal originally, but since the preheating position and the reproduction position are close to each other, most of the laser light used for preheating operation is almost the same as during reproduction. It reaches the photodetector 15 through the optical path of, is converted into an electric signal, is further amplified by the reproduction amplifier 6, and is taken out as a reproduction signal. If this is left as it is, unnecessary information will be mixed in the reproduced signal, and it will not be possible to read it out correctly as data. Therefore, the signal from the reproduction amplifier 6 is passed through the analog gate circuit 22, and the gate is closed during the preheating operation so that the reproduction signal is not output.

During the reproducing operation, the laser diode 14 is operated by the reproducing output according to the clock. The EO element 19 is also controlled so as to guide the beam to the reproducing position, and further guides the laser light by following the rotation of the disk so that the reproducing operation can be performed efficiently. The laser light reflected on the recording surface is guided to the photodetector 15 by the polarizer 12, converted into an electric signal, and further reproduced by the reproducing amplifier 6.
Is amplified by and extracted as a reproduction signal. This reproduction signal is passed through the analog gate circuit 22, but during reproduction operation, the gate is opened and the reproduction signal is output as it is. Next, the reproduction signal is converted into digital data by the A / D converter 23 and becomes reproduction data.

As described above, in the case where the preheating operation and the reproducing operation are divided in time, the correct reproducing signal can be taken out by processing the reproducing signal in synchronization with each operation.

[0045]

As described above, according to the optical disk reproducing apparatus of the first aspect of the present invention, the effective spot shape of the scanning spot can be controlled by controlling the preheating area.

Further, according to the optical disc reproducing apparatus of the second aspect of the present invention, the effective spot shape of the scanning spot is controlled by controlling the preheating area, and the crescent-shaped one having a string on the traveling direction side of the scanning spot. An effective spot shape can be obtained.

Further, according to the optical disk reproducing apparatus of the third aspect of the present invention, the effective spot shape of the scanning spot is controlled by controlling the preheating region, and the effective spot shape or the bell-bell shape in which two spindle shapes are arranged side by side. The effective spot shape can be obtained.

Further, according to the optical disc reproducing apparatus of the fourth aspect of the present invention, the effective spot shape of the scanning spot can be controlled by controlling the preheating region by the preheating beam.

Further, according to the optical disk reproducing apparatus of the fifth aspect of the present invention, the effective spot shape of the scanning spot can be controlled by controlling the preheating region by the preheating beam.

According to the optical disk reproducing method of the sixth aspect of the present invention, the signal is temporally processed by processing the reproduced signal in synchronization with the irradiation of the scanning spot, the operation of the preheating means, or both operations. It is possible to prevent unnecessary signals from being mixed by dividing into

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a magneto-optical disk.

FIG. 3 is a schematic diagram showing a recording pit pattern and a reproduction spot shape.

FIG. 4 is a schematic diagram showing a heat distribution during reproduction and an effective spot shape in the present invention.

FIG. 5 is a diagram showing an example of calculating an aperture occupancy rate focusing on a specific pit during reproduction according to the present invention.

FIG. 6 is a diagram showing an example of an experimental result of a reproduced signal during forward rotation and during reverse rotation.

FIG. 7 is a diagram showing an example of an experimental result of C / N of a recording frequency and a reproduction signal during forward rotation and reverse rotation.

FIG. 8 is a schematic diagram showing a second embodiment of the present invention.

FIG. 9 is a schematic diagram showing a third embodiment of the present invention.

FIG. 10 is a schematic diagram showing Example 4 of the present invention.

FIG. 11 is a schematic diagram showing a fifth embodiment of the present invention.

FIG. 12 is a diagram showing an operation in the fifth embodiment.

FIG. 13 is a schematic diagram showing Example 6 of the present invention.

FIG. 14 is a diagram showing an operation in the sixth embodiment.

FIG. 15 is a schematic diagram showing a basic configuration of a conventional magnetic field modulation recording method.

FIG. 16 is a diagram showing an MTF in an aberration-free optical system.

FIG. 17 is a diagram showing an example of a conventional magnetic super-resolution medium.

FIG. 18 is a schematic diagram showing a state of reproduction by a conventional magnetic super-resolution medium.

FIG. 19 is a diagram showing an example of a conventional magnetic super-resolution medium.

FIG. 20 is a schematic diagram showing a state of reproduction by a conventional magnetic super-resolution medium.

FIG. 21 is a schematic diagram showing a relationship between a recording pattern and a reproduction spot during forward rotation reproduction.

FIG. 22 is a diagram showing an example of calculating an aperture occupancy rate focusing on a specific pit at the time of forward rotation.

[Explanation of reference numerals] 1 optical head, 2,121 magneto-optical disk, 3 motor, 4 preheating head, 5 LD driver, 6 reproduction amplifier, 7 motor control circuit, 8 LD driver, 9 demodulation circuit, 10 microcomputer, 11 lens, 1
2,18 Polarizer, 13 Dichroic mirror, 14
Laser diode, 15 photodetector, 16 preheating laser diode, 17 wavelength filter, 19 electro-optical element, 20 EO driver, 21 clock signal generator, 22 analog gate circuit, 23 A / D converter, 24 transparent substrate, 25 super Resolution film, 26 magneto-optical recording film, 27 protective layer.

Claims (6)

[Claims] 1. An information surface is optically scanned by a scanning beam which forms a scanning spot by focusing on an optical disk substrate, and a region where information can be read and information cannot be read due to a temperature change in the scanning spot. An optical disk reproducing apparatus having an area and a preheating means for forming a preheating area prior to the scanning spot, and controlling the effective spot shape of the scanning spot during reproduction. 2. The optical disk reproducing apparatus according to claim 1, wherein an optical disk that cannot be read in a high temperature area is used. 3. The optical disk reproducing apparatus according to claim 1, wherein the optical disk is capable of being read in a high temperature region. 4. The optical disk reproducing apparatus according to claim 1, wherein two lasers having different wavelengths are used. 5. The optical disk reproducing apparatus according to claim 1, wherein an electro-optical element or an acousto-optical element is used. 6. An information surface is optically scanned by a scanning beam which forms a scanning spot by focusing on an optical disk substrate, and a region where information can be read and information cannot be read due to a temperature change in the scanning spot. An optical disk reproducing method for controlling the effective spot shape of the scanning spot by providing a preheating means for creating a preheating area prior to the scanning spot, and synchronizing with the irradiation of the scanning spot or the operation of the preheating means. A method for reproducing an optical disk, characterized by processing the reproduced signal.