JPH06309720A - Recording and reproducing method for optical recording - Google Patents

Abstract

PURPOSE:To execute many-valued recording and ultra-highdensity recording by recording the information marks varying in the width in the radial direction, reproducing the information marks of the different widths and contrasting the amplitude value thereof and the information of many values. CONSTITUTION:A disk drive is composed of the recording medium 101, an optical head 102 for realizing recording and reproducing and a processing system for converting the reproduced signal obtd. from the head to the information. The head 102 converges the light emitted from a laser 108 onto the medium 101. The recording code trains generate recording pulse trains in the pulse parts of the recording code trains by a recording waveform forming device 105. The recording pulse trains consist of such recording pulse trains that the influence of the heat from other pulse trains near the final falling position of the pulse at the min. changing length of the marks in the pulse length of the top pulse and the second and subsequent pulse trains is negligible. The information marks having the mark widths meeting the information patterns are formed by applying the high-accuracy mark length control, and the recording and reproducing are executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording in which at least a laser beam is used for recording, reproducing, or erasing, and more particularly, a recording / reproducing method suitable for ultrahigh density optical recording utilizing multilevel recording. Regarding

[0002]

2. Description of the Related Art With the progress of the advanced information society in recent years, there is an increasing need for a high-density and large-capacity file memory. Optical recording is attracting attention as a memory to meet this demand. In particular, recently, rewritable magneto-optical recording has been put into practical use. At present, research and development is being pursued with the aim of achieving higher performance discs.
As one method for realizing high-density recording, there is a method for performing multivalued and multiplex recording.

As an example of using a magneto-optical recording medium in conventional multi-value recording, there is an example shown in JJAP 28 p343 (1989). This changes the intensity of an externally applied magnetic field while irradiating a laser beam on a film obtained by laminating three layers of magneto-optical recording films having different magnetic properties via silicon oxide. In this way, multi-value recording is realized by forming a difference in magneto-optical effect. In addition, as another publicly known example of realizing multi-valued recording using an organic material, Optical Memory Symposium 92 Proceedings p45 (199
As shown in 2), there has been proposed a method of recording using a multi-layer recording film by using the difference in absorbance at different wavelengths.

[0004]

In the above-mentioned prior art,
Multi-valued recording on a perpendicular magnetic film provided on a magneto-optical recording medium has problems such as a complicated disk structure and difficulty in controlling magnetic characteristics in manufacturing the disk. Further, no consideration has been given to problems in the device configuration, such as difficulty in controlling the magnetic field strength by the levitation magnetic head and inability to obtain a sufficient margin against fluctuations in the device. In particular, in order to perform optical recording at high density, it is necessary to form desired information marks stably and accurately, and it is necessary to solve such problems for practical use.

An object of the present invention is to realize a multi-valued recording by improving the recording control of a conventionally used optical information recording / reproducing apparatus, and to provide an optical recording medium and an apparatus having a low cost and a super high density. To do.

[0006]

In order to achieve the above object, the present invention irradiates a recording medium with light emitted from a light source to record information marks having different widths in the radial direction of the recording medium. The information mark is reproduced and the amplitude value and the multivalued information are associated with each other.

[0007]

In order to control the shape of the magnetic domain, it is important to control the heat flow flowing in the recording medium. For that purpose, devise a method of giving heat to the medium from the drive device side of the disk,
On the disk side, the desired magnetic domain shape can be obtained by devising the laminated structure of the medium and the material used. In the magneto-optical recording, the reproduction signal strength is such that if the Kerr rotation angle of the recording film is constant, the size of the magnetic domain (especially if it is the same length in the track direction of the disk within the range of the effective spot system of light). , Magnetic domain width), and in the case of optical recording, it changes according to the size of information pits (hereinafter, the magnetic domains and pits having information on the recording medium are referred to as information marks). By the way, this magnetic domain width is formed by a recording pulse waveform determined in consideration of heat flow in the medium.
What is important here is that the medium and the device are compatible. This requires a medium structure that matches the pulse waveform coming out of the device, and at the same time, it is necessary to use a recording pulse waveform that matches the medium structure. Particularly, based on the multi-pulse, a preheat portion is provided before the recording waveform and a heat flow control portion is provided at the rear portion of the recording waveform to balance the heat, whereby the shape of the magnetic domain to be formed can be controlled with high accuracy. By using this high precision magnetic domain shape precision control technology, the domain width control performance is ± 0.02 μm or less, and a domain shape of any size in both width and length can be obtained.

Further, the information mark width corresponding to the information pattern is formed by using the high-precision magnetic domain width control technique based on the recording waveform. As a result, since the signal amplitude changes according to the information mark width, by demodulating the obtained signal, multivalued information of 0, 1, 2, 3, ... Is obtained according to the amplitude value. More specifically, the information mark is pre-test recorded on the recording medium, and the output of the laser light source is set to a desired output according to the magnitude of the reproduction signal amplitude obtained from the test-recorded information mark. Multivalued information can be recorded according to the shape. In that case, the width of the information mark and the multivalued information can be associated with each other.
In order to obtain a constant information mark width with high accuracy, when controlling the laser light source using a multi-pulse formed from an aggregate of minute pulses, the pulse width of each pulse, the interval between adjacent pulses, etc. are controlled. When this method is used, the pulse width and the gap length can be controlled with high accuracy, so that the magnetic domain shape can be controlled with high accuracy.

In this way, the recording pulse shape is controlled so that the information mark width in the radial direction of the disc (that is, the direction in which the light spot for recording information is perpendicular) corresponds to the multi-value of information. Therefore, it is possible to easily perform large-capacity recording using the conventional optical recording medium.

[0010]

EXAMPLES The details of the present invention will be described below with reference to Examples 1 and 2.

(Embodiment 1) FIG. 1 is a schematic view showing the sectional structure of a magneto-optical disk used in this embodiment. For the disc, a silicon nitride layer having a thickness of 60 nm was formed as a heat flow resistance layer (2) on a glass or plastic disc substrate (1) having an uneven guide groove. A sputtering method was used for forming the film, and a reactive sputtering method using Si as a target was used. Next, a TbFeCoNb film was formed as an information recording film (3) by a sputtering method. Sputtering method is used for film formation,
TbFeCoNb alloy was used as the target. The magnetic properties of this film are a Curie temperature of 210 ° C and a compensation temperature of 80 ± 20 ° C. In this way, the difference between the Curie temperature and the compensation temperature (the point where the magnetization of the iron group element and the magnetization of the rare earth element are equal) is set at 150 ° C.
It is the following. Then, again, a silicon nitride layer was formed to a thickness of 15 nm as a heat flow resistance layer (4). And finally, an Al ₉₈ Ti ₂ film was formed to a film thickness of 50 nm as the thermal diffusion layer (5).
The entire recording medium thus prepared was protectively coated with the ultraviolet curable resin (6). In addition to the protective function, this layer also serves as a heat flow control layer.

FIG. 2 is a schematic diagram showing the basic structure of the disk drive used. This device is a type of drive to which a test recording circuit is added. This drive includes a recording medium 101 for recording information, an optical head 102 for realizing recording / reproduction, and a processing system for converting a reproduction signal obtained from the optical head 102 into information. The optical head 102 narrows the light emitted from the laser 108 onto the recording medium 101. When recording information, the input data bit string (information) is input to the encoder 104, the recording code string 120 output from the encoder 104 is guided to the recording waveform generator 105, and the recording obtained by the recording waveform generator 105. Waveform is APC
The light intensity corresponding to the recorded code string is input to the laser 106.
It is output from 108. At the time of reproducing information, the light reflected from the recording medium 101 is guided to the light receiver 109 and converted into an electric signal. The signal is input to the reproduction amplifier 110. The input switch 112 receives the output of the reproduction amplifier and the output of the waveform equalizer to which the output of the reproduction amplifier is input. Further, a trial writing command signal is input to the input switch, and the output signals of the reproduction amplifier 110 and the waveform equalizer 111 are selectively output to the shaper 113 according to the trial writing command signal. The shaper 113 converts the signal from the input switcher into a pulse signal indicating the presence / absence of a signal. The pulse signal is
It is guided to the discriminator 115 and the PLL 114. Sync signal output from PLL 114 (signal synchronized with the basic cycle of pulse signal)
Is input to the discriminator 115. The discriminator 115 is the shaper 113.
The detection code string is generated based on the pulse signal from the sync signal from the PLL 114, and the decoder 117 outputs the data bit string (information). The detection code string obtained by the discriminator 115 is also output to the comparison / determination unit 116. The comparator / discriminator 116 outputs the trial writing data from the trial writing device 103 which operates according to the trial writing command signal to the encoder 104, and the input switching device which operates according to the trial writing command signal.
112 switches the output of the reproduction amplifier 110 to be output to the shaper 113, and the recording code string from the encoder 104 and the discriminator 115.
Output the control signal that controls the APC 106 that controls the laser driver 107 that drives the laser 108 so as to cancel the difference in the reproduction code sequence from the symbol code sequence. The difference from the reproduction code sequence of is reduced to some extent, and the trial writing end signal is output within the allowable range. After the trial writing end signal is output, the input switch 112 switches the output of the waveform equalizer 111 to the shaper 113, and starts a normal recording / reproducing operation. Even after the normal recording / reproducing operation is started, the comparison / determination unit 11
In step 6, check that the difference between the recorded code string and the reproduced code string is within the allowable range. If not, start the test write operation described above, and once the test write end signal is output, restart the record operation. Continue. Further, when the difference between the reproduced code string and the recorded code string is confirmed by the comparison discriminator 116, it can be detected more accurately if the output of the input switch 112 is operated so that the signal of the reproduction amplifier 110 is output. In the above operation, the same operation can be realized without using the input switch 112. In order to detect the difference in the reproduced code string from the recorded code string in the comparison discriminator 116 with high accuracy, it is better not to use the waveform equalizer 111.

FIG. 3 illustrates the relationship between an embodiment of the recording method for recording on the recording medium of the present invention and the recorded recording marks. The output from the encoder 104 described in FIG. 2 is the recording code string 120. The recording code string 120 is the recording waveform generator 10
5, the recording pulse train 12 is added to the pulse portion of the recording code train 120.
Raises 1. In the recording pulse train 121, the influence of heat from other pulse trains near the final falling position of the pulse when the pulse lengths of the first pulse train and the second and subsequent pulse trains are the minimum change length of the recording mark can be almost ignored. Or a recording pulse train that allows a constant heat inflow. The recording auxiliary pulse 122a is generated in the gap portion (rest period portion other than the pulse portion) of the recording code string 120. The recording auxiliary pulse 122a is provided with a constant gap portion from the trailing edge of the recording code train 120 so that the heat from the last trailing edge of the recording pulse train hardly changes the temperature of the leading leading edge of the next recording pulse train. It is important to make the cooling speed and the temperature rising speed equal without depending on the length of the mark.

Data was recorded on the disk having the structure shown in FIG. 1 by using the recording waveform shown in FIG. Here, four levels of 0, 1, 2, and 3 were formed. The first level is an unrecorded state. The second level is the case where a magnetic domain having a width of 0.35 μm is formed. The third level is the case where a magnetic domain having a width of 0.55 μm is formed. The fourth level formed a magnetic domain with a width of 0.75 μm. FIG. 5 shows a schematic diagram of the reproduced waveform and the recording magnetic domain formed when recording is performed in this manner. 0 to 3 of 4
Even if two levels were recorded continuously, it had a good magnetic domain shape, and the reproduced signal waveform was also good reflecting that, and the original signal could be demodulated by the slice level provided.
This means that the length of the disc in the direction of travel is 0.75.
It is μm long. In the present embodiment, the wavelength of the laser light used is 780 nm, but the effect of the present invention does not change depending on the wavelength. However, when the wavelength of light is shortened and the energy is increased when the light is narrowed down by a lens, the temperature of the recording film in a minute area can be raised, so that a minute recording magnetic domain can be easily formed. Is effective in improving.

(Embodiment 2) FIG. 6 is a schematic view showing the sectional structure of the magneto-optical disk used in this embodiment. For the disc, a silicon nitride layer having a thickness of 60 nm was formed as a heat flow resistance layer (2) on a glass or plastic disc substrate (1) having an uneven guide groove. A sputtering method was used for forming the film, and a reactive sputtering method using Si as a target was used. Next, the information recording film (3) is composed of three layers. The first layer is the recording layer (3-1), which is a TbFeCo film. Film thickness is 40nm
And the Curie temperature is 210 ℃, the compensation temperature is 80 ± 20 ℃,
The coercive force is 12 kOe. Here, the maximum difference between the Curie temperature and the compensation temperature was 150 ° C. The second layer is the middle layer (3-2)
Then, this is a layer for controlling the exchange coupling force between the recording layer and the initialization layer (3-3), and a GdFeCo alloy was used. The film thickness at that time is 12 nm. Then, as the initialization layer (3-3), TbDyFeC
o An alloy film was formed. The magnetic properties of this layer are a Curie temperature of 300 ° C. and a coercive force of 3 kOe. Next, again, a silicon nitride layer was formed in a thickness of 100 nm as a heat flow resistance layer (4). The entire recording medium thus prepared was protectively coated with the ultraviolet curable resin (6). In addition to the protective function, this layer also serves as a heat flow control layer.

The disk manufactured in this way is shown in FIG.
Recording was performed using the recording waveform shown in. Where 0,1,2,3
Recorded four levels of. In addition to this, information was recorded in addition to the change in signal amplitude by changing the magnetic domain length. When information is given to the magnetic domain length, both (2,
7) The modulation method was used. However, the effect of the present invention does not depend on the modulation method. The first level is the unrecorded state.
The second level is the case where a magnetic domain having a width of 0.35 μm is formed. The third level is the case of forming a magnetic domain with a width of 0.55 μm. The fourth level then formed a 0.75 μm wide magnetic domain. In this case, it is necessary to pay attention to the thermal crosstalk and the self-sharpening effect. But,
These problems can be solved by the presence of the ultraviolet curable resin layer and recording by multi-pulse. 0 to 3
Even if the four levels were recorded continuously, it had a good magnetic domain shape, and the reproduced signal waveform was also good reflecting that, and the original signal could be demodulated by the slice level provided. further,
In this embodiment, a medium that can be overwritten by light intensity modulation is used as the recording medium, and the data transfer rate can be improved.

(Embodiment 3) FIG. 8 shows another configuration diagram of the optical recording / reproducing apparatus of the present invention. The recording information input from the information input / output unit 801 is encoded by the encoder 807, passes through the recording control unit 802, forms an optical spot by the optical head 803, and is recorded on the optical recording medium 804. Further, the optical signal obtained from the optical head for reproduction is subjected to signal processing by the reproduction means 805, demodulated by the decoder 808 and output. In the present invention, since the multi-valued information corresponds to the width of the information mark on the recording medium, the information mark shape is controlled with high accuracy. Therefore, the relationship between the laser output when information is recorded on the optical recording medium 804 and the information mark width is obtained in advance. In addition to the information input / output means 801, the encoder 807 includes test pattern shape control means.
806 is connected. Test pattern shape control means 806
Is a laser that compares the test pattern storage means 809 recorded on the optical recording medium 804, the signal 812 reproduced from the test pattern recorded on the optical recording medium 804, and the signal 813 encoded from the test pattern. It has a comparison / determination unit 810 that outputs a signal 814 that controls the output, and control means 811 for them. Here, the comparison / determination unit 810 compares the uncoded signal 812 before decoding with the coded test pattern signal 813, but if the signals to be compared are signals of the same form. Well, for example, it may be an uncoded signal.

An example of the comparison discriminator 810 is shown in FIG.

Reproduced signal 812 of the test pattern before decoding
And the encoded test pattern recording signal 813 is output to the comparator 9
At 01, the corresponding bits are compared. In order to compare the code signals, for example, a shift register is used to compare bits of a certain length, and signals showing different numbers of bits are output. The comparison / determination means 810 is provided with means 902 for holding in advance a control amount of laser power according to an error between a recording signal and a reproduction signal of the same pattern. The output of the comparator 901 is input to the means 902, and the control amount 814 corresponding to the output of the comparator 901 is output to the APC (automatic output control means) 806.

When the control amount of the laser power is 0, that is, when it is not necessary to control the laser power, a signal for stopping the recording of the test pattern is output from the means 902 to the control means 811. The control unit 811 informs a higher-order control unit (not shown) that the laser power control has been completed by recording the test pattern, and thereafter shifts to normal recording and reproducing operations.

Although not shown, information input / output means 801,
The recording control means 802, the optical head 803 reproducing means 805, and the like are also mutually controlled by a higher-order control means.

Next, FIG. 10 shows an information mark shape recorded by using the present invention and a corresponding reproduction waveform. Figure 10
(a) shows information marks (402, 403, 404) recorded along the track center 401. The reproduced waveforms of these information marks are shown in FIG. The reproduction signal level rises and falls depending on the width.

FIG. 11 shows the relationship between the information mark width and the reproduction signal. This is a waveform 7 of the information mark recorded on the medium.
This is a reproduced signal when reproduced with a laser beam of 80 nm.

Further, the reproduction signal for the information mark width is
If the information mark for multi-valued recording is accurately recorded using only the increasing range, multi-valued information can be easily recorded and reproduced.

The following points may be considered in common with the above embodiments. That is, in order to record a multi-value information mark, a high-precision mark width control technique based on a recording waveform is used. Regarding high precision mark length control, Japanese Patent Application No. 4-26511 and Japanese Patent Application No. 4-2382 previously filed by the present inventors.
No. 76, Japanese Patent Application No. 4-338240, Japanese Patent Application No. 5-234.
There are No. 3 etc. In the present invention, since multi-valued recording is associated with the width of the mark, highly precise control of the mark width is required. Therefore, the above-described high precision mark length control is applied to form an information mark having a mark width according to the information pattern. As a result, the signal amplitude changes according to the mark width. The signal amplitude controlled in this way can be demodulated by slicing at a fixed position. When demodulating the signal, values 0, 1, 2, 3 ... Are obtained depending on the amplitude value. This corresponds to the fact that multivalued information can be recorded using this principle. More specifically, in optical recording for recording, reproducing, or erasing using at least a laser beam, a multi-valued signal corresponding to the magnitude of a reproduced signal amplitude generated based on a mark recorded on a recording medium is used. Just record the information. In that case, it is effective to record multi-valued information by controlling the width of the mark recorded on the recording medium to obtain a desired reproduction signal amplitude. Here, in order to obtain a recording mark with a constant width, it is effective to drive the laser using multi-pulses formed from an aggregate of minute pulses. Particularly, in that case, it is particularly effective that the pulse width or the laser power of the leading pulse of the pulse composed of the aggregate of minute pulses is different from that of other minute pulses. By the way, in a recording pulse composed of a minute pulse used to form a recording mark, at least one selected from the pulse width of the leading pulse, the interval between the leading pulse and the following pulse, the interval between minute pulses, and the laser power. It is important to control one type of value according to the flow of heat in the medium. By the way, in the recording pulse composed of the minute pulses, the pulse width of each minute pulse and the interval between the minute pulses may be an integral multiple of the write clock or a fraction of an integer. When this method is used, the pulse width and the gap length can be controlled with high precision, so that the mark shape can be controlled with high precision. Here, for example, in the case of magneto-optical recording as a recording medium to be used, recording is performed by giving information in the direction of the easy axis of magnetization. Recording is performed using a material having Further, this material uses an alloy thin film of a rare earth element and an iron group element as a material having an easy axis of magnetization in a direction perpendicular to a substrate used as a recording medium, and more advantageously, the thin film is amorphous. Membranes are preferred. Of course, there is no problem even if a superstructure film in which rare earth elements and iron group elements are alternately laminated is used. More specifically, the recording film is an alloy thin film composed of at least one element selected from Tb, Dy, Ho, and Gd as a rare earth element and two elements of Fe and Co as an iron group element. It is desirable to use as. In particular, the Tb-Fe-Co system is the best in terms of magnetic characteristics and disk characteristics. By the way, the magnetic film composed of the rare earth element and the iron group element is a ferrimagnetic material, and in this alloy thin film, the magnetization of the rare earth element is It is preferable to use a recording film in which the temperature at which the magnitude of the magnetization of the rare earth element and the magnitude of the magnetization of the iron group element are equal to each other is higher than 60 ° C. and lower than 100 ° C. In this region, the magnetic domain shape can be precisely controlled in consideration of the influence of the demagnetizing field. Further, in a ferrimagnetic alloy thin film composed of a rare earth element and an iron group element, a recording film in which the difference between the Curie temperature and the compensation temperature is higher than 70 ° C. and lower than 150 ° C. may be used. In particular, in the region having this magnetic property, the fine magnetic domain can be easily and stably formed. Here, in order to realize precise control of the shape of the magnetic domain, in addition to the correspondence on the device side, correspondence on the disk side is important, and it is important to match the device and the disk. Therefore, in order to control the heat flow flowing in the recording film when the recording film is irradiated with laser light, the recording film is covered with a heat resistance layer, and a thermal diffusion layer is provided on the side opposite to the light incident side. It is effective to use a disk having

By the way, in order to record multivalued information,
When forming marks on a recording medium, magnetic domains having different magnetic domain widths are formed and recorded without interruption. In that case, it is important to precisely control the domain width. Therefore, a recording mark is formed on a recording medium by using a multi-pulse formed from an assembly of minute pulses and controlling either the shape of the pulse, the pulse width, or the laser power. Thus, a desired magnetic domain width can be obtained. For that purpose, it is essential to use multi-pulses. By the way, in the case of using a multi-pulse formed from an assembly of minute pulses, in order to form a narrow magnetic domain width, it is necessary to set the pulse width to be narrow and the pulse width to be used short and to set the laser power high. Is preferred. By the way, when a mark is formed on a recording medium and multi-valued information is recorded, a recording pulse used in a recording pulse used in a recording pulse is changed to a next recording level after passing a read level from a recording level for a certain time. It is important to control the heat flow inside. Since multivalued information is converted into signal amplitude and recorded, it is important to precisely control the magnetic domain width. When a mark is formed on a recording medium and multi-valued information is recorded, the recording density is further improved by using a method of recording information at the edge portion of the formed mark as well as recording by the magnitude of the signal amplitude. Can be made. Then, in order to form marks on a recording medium and record multi-valued information, it is also important to record information at the same recording density in one round of the disc. On the other hand, when the environmental temperature fluctuates, the shape of the magnetic domain changes greatly, and the edge shift and jitter increase. To counter this, a test pattern may be recorded in a certain area of the disc, the domain may be reproduced, and statistical processing may be performed to find a recording condition that minimizes shift and jitter. As described above, by performing the test recording prior to the recording, the recording can always be performed under the same recording condition as seen from the disk, and thus the shape of the magnetic domain formed does not depend on the environmental condition.

Then, it is desirable to use an elliptical light spot for reproducing the recorded information and for reproducing the mark formed on the recording medium. And, more advantageously, it is preferable to match the longer diameter of the oval with the radial direction of the disk. This configuration is
No. 2 is described. To reproduce multi-valued information recorded on a recording medium, the obtained reproduced waveform may be sliced at different positions as it is and demodulated to the original information.

The magneto-optical disk has been described above, but the effect is not limited to the magneto-optical recording, and the write-once optical disk, the optical disk using the phase change, and the overwriting using the magnetic coupling are possible. It goes without saying that it can be applied to general optical discs such as various magneto-optical discs. In this case, what has to be changed is
It is the pulse width of minute pulses forming a multi-pulse, or the interval between pulses, or both. This is based on the difference in the thermal conductivity of the recording film and the structure of the disc. It is largely the structure of the disc and the materials used that must be considered here. This is because the optical disc has a great influence on the device performance in the optical disc system.

[0029]

According to the present invention, multi-valued information can be recorded and reproduced without significantly changing the disc structure. In particular, multivalued information can be recorded even if the conventional disc is used as it is. The recording density can be improved by further shortening the wavelength of the laser used. In this way, not only can the recording density of the disc be greatly improved,
It is possible to provide a low-cost high-performance optical disc.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a magneto-optical disk.

FIG. 2 is a diagram showing a basic configuration of an optical disc drive.

FIG. 3 is a diagram showing a process of generating a recording waveform.

FIG. 4 is a schematic diagram showing a recording waveform.

FIG. 5 shows the formed recording magnetic domain shape and reproduction waveform.

FIG. 6 is a schematic diagram showing a cross-sectional structure of a magneto-optical disk.

FIG. 7 is a schematic diagram showing a recording waveform.

FIG. 8 is a configuration diagram of a recording / reproducing apparatus of the present invention.

FIG. 9 is a configuration diagram of a comparison / determination unit of the present invention.

FIG. 10 is a diagram showing information mark shapes and corresponding reproduced waveforms.

FIG. 11 is a diagram showing a relationship between an information mark width and a reproduction signal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disk substrate, 2 ... Heat flow resistance layer, 3 ... Information recording layer, 3-1 ... Recording layer, 3-2 ... Intermediate layer, 3-3 ... Initialization layer, 4 ... Heat flow resistance layer, 5 ... Heat Diffusion layer, 6 ... UV curable resin, 101 ... Recording medium, 102 ... Optical head, 103
... trial writer, 104 ... encoder, 105 ... recording waveform generator, 106 ... APC, 107 ... laser driver, 108
… Laser, 109… Photo receiver, 110… Replay amplifier, 1
11 ... Waveform equalizer, 112 ... Input switcher, 113 ...
Shaper, 114 ... PLL, 115 ... Discriminator, 116 ... Comparison discriminator, 117 ... Decoder, 120 ... Recording code string, 12
1 ... Recording pulse train, 122a ... Recording auxiliary pulse, 123
... record mark, 124 ... reproduction signal, 125 ... reproduction code string.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Maeda 1-280 Higashi Koigokubo, Kokubunji City, Tokyo Metropolitan Research Laboratory, Hitachi, Ltd. (72) Fumio Kugiya 1-280 Higashi Koikeku Ku, Kokubunji, Tokyo Hitachi Ltd. Central Research Laboratory

Claims (19)

[Claims] 1. In optical recording in which recording, reproduction, or erasing is performed using at least a laser beam, a multi-value corresponding to the magnitude of a reproduction signal amplitude generated based on a mark width recorded on a recording medium. A recording / reproducing method of optical recording, characterized by recording and reproducing the information of 1. 2. In optical recording for recording, reproduction, or erasing using at least a laser beam, the reproduction signal amplitude obtained from a mark recorded on a recording medium is compared by a plurality of threshold values. A recording / reproducing method for optical recording, which comprises reproducing value information. 3. In optical recording for recording, reproducing, or erasing using at least a laser beam, an elliptical light spot is used for reproducing a mark formed on a recording medium, and more advantageously an elliptical spot. A recording / reproducing method for optical recording, characterized in that the longer diameter of the disk and the radial direction of the disk are matched. 4. A recording mark is formed on the recording medium according to claim 1, by using a multi-pulse formed from an assembly of minute pulses, A recording / reproducing method for optical recording, wherein the pulse width or laser power of the first pulse of the constituent pulses is different from that of other minute pulses. 5. A recording pulse composed of minute pulses used to form a recording mark on the recording medium according to claim 4, wherein the pulse width of the leading pulse, the interval between the leading pulse and the following pulse, and the minute pulse. A recording / reproducing method for optical recording, characterized in that at least one kind of value selected from among the intervals and the laser power is controlled according to the flow of heat in the medium. 6. A recording pulse composed of minute pulses according to claim 1, wherein the pulse width of each minute pulse and the interval between minute pulses are an integral multiple of the write clock, or A recording / reproducing method for optical recording, characterized in that it is divided by an integer. 7. Optical recording in which recording, reproduction, or erasing is performed by using at least a laser beam, recording is performed by giving information in the direction of the easy axis of magnetization as a recording medium to be used, and more advantageously, the medium. A recording / reproducing method for optical recording, wherein the recording is performed by using a material having an easy axis of magnetization in a direction perpendicular to the substrate. 8. An alloy thin film of a rare earth element and an iron group element is used as a material having an easy axis of magnetization in a direction perpendicular to a substrate used as the recording medium according to claim 7, and the thin film is predominantly non-magnetic. A recording / reproducing method for optical recording, characterized by being crystalline. 9. The rare earth element according to claim 7, which is at least one element selected from Tb, Dy, Ho, and Gd, and two iron group elements, Fe and Co. A recording / reproducing method for optical recording, characterized in that an alloy thin film composed of the element is used as a recording film. 10. In an alloy thin film of a ferrimagnetic material composed of a rare earth element and an iron group element according to claim 9, when the magnitude of magnetization of the rare earth element and the magnitude of magnetization of the iron group element are compared, the magnetization of the rare earth element is compared. Is more significant, and more advantageously, a recording film is used in which the temperature at which the magnitude of magnetization of the rare earth element and the magnitude of magnetization of the iron group element are equal is higher than 60 ° C. and lower than 100 ° C. Recording / reproducing method for optical recording. 11. An alloy thin film of a ferrimagnetic material composed of a rare earth element and an iron group element according to claim 9, wherein the difference between the Curie temperature and the compensation temperature is more than 70 ° C. and more than 150 ° C. A recording / reproducing method for optical recording, characterized by using a low recording film. 12. To control the heat flow flowing through the recording film when the recording film is irradiated with the laser beam according to claim 1, a thermal resistance layer covers the recording film, A recording / reproducing method for optical recording, wherein a disk having a structure in which a heat diffusion layer is provided on the side opposite to the incident side is used. 13. An optical recording in which recording, reproduction, or erasing is performed by using at least a laser beam, and in forming a mark on a recording medium, magnetic domains having different magnetic domain widths are formed without interruption. A method of recording and reproducing optical recording. 14. A recording mark is formed on the recording medium according to any one of claims 1 to 13 by using a multi-pulse formed from an aggregate of minute pulses, the shape of the pulse and the pulse. A recording / reproducing method for optical recording, wherein a desired magnetic domain width is obtained by controlling either the width or the laser power. 15. A recording mark having different magnetic domain widths is formed on the recording medium according to claim 14, by using a multi-pulse formed from an assembly of minute pulses to form a narrow magnetic domain width. A recording / reproducing method for optical recording, characterized in that the pulse width used becomes narrower as the width becomes narrower and the laser power is set higher. 16. A switching of magnetic domain width in a recording pulse used for forming a mark on a recording medium and recording multi-valued information in optical recording for recording, reproducing or erasing using at least a laser beam. A recording / reproducing method for optical recording, characterized in that the flow of heat in a recording medium is controlled by taking a next recording level after passing a read level from a recording level for a certain period of time. 17. In optical recording for recording, reproducing or erasing using at least a laser beam, in order to form a mark on a recording medium and record multi-valued information, recording is performed by the magnitude of signal amplitude. A recording / reproducing method for optical recording, characterized in that a method of recording information on the edge portion of the mark to be formed is also used. 18. In optical recording in which recording, reproduction, or erasing is performed at least by using a laser beam, a multi-valued information is formed by forming marks on a recording medium, and the same recording density is used for one round of the disk. A recording / reproducing method for optical recording, characterized in that information is recorded on the recording medium. 19. A reproduction waveform is sliced at different positions as it is to reproduce multi-valued information recorded on a recording medium in optical recording for recording, reproduction or erasing using at least a laser beam. And a method for recording and reproducing optical recording.