JP2000036115A - Optical recording method - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide an ultra-high-density optical recording method that suppresses a change in recording mark shape due to a change in recording sensitivity and controls the recording mark shape with high accuracy. is there. According to the present invention, test recording is performed prior to recording user information by using a multi-pulse as a recording waveform in consideration of the flow of heat in a recording medium. Has a mechanism.
Then, a mechanism for controlling the pulse width for controlling the pulse width of the recording waveform using the result of the test recording is provided. According to the present invention, recording on a disk is always performed under optimum conditions even when the use environment conditions of the recording / reproducing device and the recording medium fluctuate or the laminated structure of the disk is different.
(Domains of the same shape can be formed with high precision).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical recording in which recording, reproduction, or erasing is performed using at least a laser beam, and more particularly to a recording method suitable for ultra-high-density optical recording.

[0002]

2. Description of the Related Art With the recent development of a highly information-oriented society, the need for a high-density and large-capacity file memory is increasing. In order to respond to this, optical recording has attracted attention, and many research institutions are conducting research and development. Of these, rewritable magneto-optical disks have recently been put to practical use and used for document files, image files, and the like.
By the way, since the first generation magneto-optical disk was put to practical use, studies have been made for higher performance, and the third generation write-once optical recording is also being studied for higher performance.

One of high performance techniques is to increase the recording capacity. In order to increase the recording capacity,
1) narrow track pitch, 2) record mark length,
Methods of 3) reducing the bit pitch, 4) devising a modulation method, 5) using a laser beam with a short wavelength, and 6) using the MCAV method have been proposed. Recording using these methods /
What is important when reproducing / erasing is that a recording domain having the same shape is always obtained under any recording conditions. Japanese Patent Application Laid-Open No. 3-22223 can be cited as a known example that has examined this point. In this known example,
The recording code sequence of the recording mark is pulsed to form a series of pulse sequences corresponding to the length of the recording code sequence, and the length and amplitude of the pulse sequence are set to the opposite phase length of the recording code sequence immediately before the recording code sequence. According to this method, recording is performed by dividing the pulse train into three parts and changing the pulse width of each pulse.

[0004]

In the above prior art, in the mark length recording method, a change in recording sensitivity to a recording medium due to a change in film thickness of each layer of a recording medium of a disc or a change in environmental temperature, an edge shift based on the change, or a servo system. It is not always the case that sufficient consideration is given to the occurrence of edge shift due to fluctuation. For example, there has been a case where a highly accurate recording mark shape required for ultra-high-density optical recording cannot be controlled.

Accordingly, a first object of the present invention is to provide a highly accurate recording mark shape control method which minimizes the fluctuation of the recording mark shape and the edge shift due to the fluctuation of the recording sensitivity, and provides a highly accurate recording mark shape control method. It is to provide high density optical recording. It is another object of the present invention to improve the consistency between a recording / reproducing device and a recording medium, and to suppress fluctuation in recording sensitivity and edge shift by the recording / reproducing device. Another object of the present invention is to improve the reliability, storage capacity, and information transfer rate of a recording / reproducing apparatus.

[0006]

In order to achieve the above object, it is necessary to improve the consistency between the recording / reproducing apparatus and the recording medium. In particular, since the optical disk is a replaceable medium, it may be an obstacle in securing compatibility due to variations in the recording / reproducing device, variations in the recording medium, and the like. In particular, when realizing high-density recording, it is necessary to minimize these variations, but there is a limit to this. Therefore, in order to absorb this variation, before recording user data, test recording is performed at a fixed position on the disc, and a reproduction signal obtained by the test recording is compared with test recording pattern data. After the difference falls below a certain value, the user data is recorded. The purpose of performing this test recording is to change the recording sensitivity of the recording medium due to the fluctuation of the thickness of each layer of the recording medium of the disc or the fluctuation of the environmental temperature in the mark length recording method, or the fluctuation of the laser power of the recording / reproducing apparatus. It is to detect an edge shift based on the edge shift or an edge shift caused by a change in the servo system, and to suppress it. Here, the fluctuation of the servo system is a fluctuation of a focus, a deviation of a track position, or the like, thereby causing an edge shift. In addition, considering that an optical disk is a replaceable medium, an edge shift also occurs due to an aberration generated during an assembly process of an optical head. In consideration of compatibility between the recording and reproducing devices, the aberration must be suppressed to a certain amount or less. At the same time, using an equalizer,
The correction can be made by setting the slope of the waveform of the reproduced signal at the front edge portion or the rear edge portion to a constant value without depending on the recorded pattern.

Therefore, at least in optical recording in which recording, reproduction, or erasure is performed using a laser beam, the laser power is set to a constant value for performing test recording prior to recording user data. Perform test recording by increasing / decreasing the pulse width of the test recording centering on the reference set value, play back the results, perform statistical processing, and set the user data recording conditions based on the obtained results. I just need. By performing recording by changing the pulse width of a minute pulse constituting a recording waveform used for test recording or user data recording at a fixed time interval around a standard set value in test recording, the recording medium can be used. It is possible to determine an optimum recording condition that is matched with the recording / reproducing device. The recording waveform used for this test recording and user data recording is composed of a collection of minute pulses, the width of the first pulse is set wider than the width of the other pulses, and the width of the subsequent pulses and the pulses and pulses It is preferable to record on an optical disk with a recording waveform having the same interval. Further, in the recording waveform used for the test recording and the recording of the user data,
The set power level comprises at least four power levels, the lowest one of the levels is the read level, the next one is the preheat level, and
The remaining two levels are recording levels, and each power level has a role. The read level is for reproducing recorded information and verifying the recorded information, and the preheat level is for supplying power to balance heat so that the temperature of the recording medium between pulses is constant. The recording level is used as a level for recording information on a disc. In the setting of the two recording levels in the recording waveform used for the test recording and the recording of the user data, the first pulse and the subsequent pulses are balanced in heat, and the temperature of the recording film becomes constant independently of the pattern. Set as follows.
In the case of controlling the heat balance, it is more effective to control the pulse width (time) than to control with the laser power, since the influence on the controllability is significantly larger than the control with the laser power. In a recording waveform used for test recording and recording of user data, the first recording level or the second recording level is used.
The ratio between the recording level and the preheat level and the ratio between the first recording level and the second recording level are set by changing depending on the laminated structure of the disks or the material used as the recording medium. Therefore, it goes without saying that the first recording level and the second recording level may be set equal. This is because the flow of heat flowing through the medium differs depending on the structure of the medium and the material used. In the recording waveform used for the test recording and the recording of the user data, after irradiating the recording pulse, after passing the read level for a certain period, it shifts to the preheat level for a certain period, and again enters the recording area, so that the recording pattern is Thermal interference can be eliminated. In the recording waveform used for test recording and recording of user data, the read level and the preheat level for a certain period after the irradiation of the recording pulse are periods synchronized with the write clock. This is because a high-precision clock can be generated and the device is easy to manufacture. In the test recording, a certain pattern is recorded on the test track, reproduced, and the result is statistically processed, so that the fluctuation of laser power,
A change in recording conditions such as a focus change, a track position shift, or an environmental temperature change is detected, and based on the detection result, recording is performed by changing the pulse width of each minute pulse in a recording waveform composed of minute pulses. Thus, control may be performed so that a recording domain having the same shape can always be recorded on the optical disk irrespective of a change in recording conditions. In recording information, it is particularly effective to record information by a so-called mark length recording method of recording information at an edge portion of a formed mark. In test recording, a modulation method is used in which a fixed pattern is recorded on a test track at a fixed rate around a reference pulse width without changing the set power, and then reproduced and reproduced as a pattern to be used. By alternately recording the shortest pattern and the repetition of the pulse interval and the longest pattern and the repetition of the shortest pulse interval, and detecting the voltage difference at the center position of the signal amplitude of both patterns when it is reproduced. By detecting a change in the recording condition and detecting a pulse width at which the potential difference becomes zero, a domain having the same shape can be obtained without depending on the recording condition. By the way, it is needless to say that this test recording is required to be performed before recording, but since it is a test recording for detecting the optimum recording condition, it is not known when a recording or erasing command comes. Performing it at each time interval is efficient in terms of time. By the way, a so-called ZCAV system in which one optical disc is divided into a plurality of zones under an optimum recording condition detected by the test recording, and recording is performed so that the recording density becomes equal at least at any position of each zone. Preferably, it is used. Then, in order to perform test recording for detecting optimum recording conditions, one disk is divided into a plurality of zones, and user information is recorded after performing test recording in a certain area of each zone. This test area must be set in advance.

It has been effective to use a test recording method in combination with a recording method for improving the controllability of recording magnetic domain shape control using a recording waveform using a multi-pulse. Furthermore, when this method is used, not only can precision control be carried out with respect to fluctuations in use environment conditions, but also, besides, differences in recording sensitivity depending on positions such as the inner circumference and outer circumference of the disk, sensitivity variations between disks, or The present invention also functions effectively for ensuring compatibility between disks having different stacked structures. In particular, subtle magnetic domain shape control is required to achieve ultra-high density recording.
The control of the pulse width according to the present invention greatly contributes to the improvement of the controllability even when the recording condition is controlled by changing the laser power. Particularly in magneto-optical recording which is sensitive to temperature, it is necessary to perform particularly precise control, and the present invention is particularly effective for achieving the purpose.

Further, analyzing the cause of the fluctuation of the recording domain size in the write-once optical disc, the main cause is the fluctuation of the laser power. This is because the temperature of the recording film at the time of recording is extremely high at 400 to 500 ° C., so that the influence of the temperature rise of the recording film at the time of recording due to the fluctuation of the room temperature on the recording domain size can be ignored. Therefore, in recording on a write-once optical disc, a change in the size of the recording domain can be suppressed by incorporating an operation for detecting a change in the laser power when the disc is loaded or the apparatus is started. More specifically, at least in optical recording in which recording or reproduction is performed using a laser beam, at the time of disc loading or immediately before recording information on the disc, test recording is performed on the disc using a certain pattern, and the test recording is performed. Reproduce the recorded data, perform statistical processing on the results, and control the power of the laser light source using the results to form a recording domain of the same size without being affected by fluctuations in recording conditions. can do. Alternatively, at least in optical recording in which recording or reproduction is performed using a laser beam, a signal of a fixed pattern as a reference is previously recorded in a fixed area of the disc, and at the time of disc loading or immediately before recording information on the disc, Perform test recording on the disc using a certain pattern, reproduce the test recorded data, perform statistical processing on the result, compare the result with the pre-recorded signal to determine the optimum power, Recording domains of the same size can always be formed without being affected by such fluctuations. By the way, it is necessary that the width or length of a recording domain to be formed is different as a signal of a certain pattern which is a reference to be previously recorded in a certain area of the disc. It is preferable to use a mark length recording method to record a fixed pattern of information on a disc. A write-once optical disc on which a user can record information only once is used as a disc for recording information. Here, when recording information, recording is performed so that the recording density of the information is equal at any position on the disk, and more advantageously, the disk is divided into a plurality of zones, and the recording conditions are set for each zone. It is desirable to record by setting. Further, when performing test recording on a disc, a test area is provided for each zone, a test area in at least one of the zones is used, and the result is analyzed to detect laser power. Needless to say, the recording conditions may be optimized. Here, it is preferable to perform statistical processing as a result analysis method. To perform test recording to disk,
This may be performed at least when the disk drive is started or when the disk is loaded into the drive. here,
In the recording domain formed for recording on the disk, the length of the domain to be formed in the radial direction of the disk may be set to a constant length without depending on the length of the domain in the rotation direction of the disk. Here, a write-once type optical disk is used as the disk to be used. The information is recorded by using the change in the reflectance of the recording layer. Rate change, change in light absorption rate at the wavelength of light used for reproduction,
Recording may be performed using a method of performing recording using at least one method selected from the formation of an alloy portion, the formation of a layer that diffusely reflects light, or the formation of a lost portion of a recording layer. As a recording pattern used for performing test recording on a disk, a pattern including at least the longest pattern and the shortest pattern in the modulation method used may be used. Here, the purpose is not to detect thermal interference between recording domains, but to detect fluctuation in domain size. In addition, as a recording pattern used for performing test recording on a disc, a pattern including at least a longest pattern and a shortest pattern in a modulation system to be used is used, and more preferably, the pattern is recorded using different laser powers. Thus, the optimum laser power may be detected. As the recording power used to perform test recording on the disc, increase or decrease the recording power or pulse width compared to the standard conditions, focusing on the standard recording conditions recorded on the disk or the memory of the disk drive. What is necessary is just to record according to the conditions made. Here, the recording power at which a fixed reproduction signal output can be obtained may be obtained. Test recording is performed on a disc to detect fluctuations in laser power, by detecting at least the difference between the center values of the signal amplitudes of the longest pattern and the shortest pattern in the modulation method used, and determining the optimum recording power. The shape of the recording domain may be controlled by controlling the recording power so as to minimize the deviation of the center value. Here, in order to demodulate the recorded information, the information recorded on the disk is reproduced as a digital electric signal, and the obtained reproduced signal is binarized by slicing it at a constant level. The signal is demodulated by obtaining and reproducing the center value of the amplitude of the signal whose level has been obtained.

Normally, in write-once optical recording, rewriting cannot be performed, so that if test recording is performed, the recording area is reduced accordingly. However, the number of bytes used can be saved by devising a pattern to be used for the test recording, such as recording all the patterns recorded by changing the power in a test recording area within one sector. Also, it is not necessary to perform the test recording every time before recording,
It may be performed only at the time of starting the disk drive or at the time of loading of the disk where the fluctuation of the laser beam is considered. Number of bytes required for the normal test recording is about 50 bytes, the number of times of performing the test recording onto the disk is considered as about 10 ⁵ times, capacity required it is 70MB, the capacity that can be recorded by the present invention It is 1% or less at 7 to 10GB, which is a sufficiently acceptable value.

According to the present invention, a test recording is performed prior to recording of user information, a fluctuation of a recording magnetic domain to be formed is detected, a fluctuation of a recording condition is found, and the fluctuation is corrected. Recording domains having the same shape can be formed. This is because the deviation from the standard recording condition can be detected by performing the test recording according to the present invention under any use environment conditions and using different recording / reproducing devices and recording media. By controlling the conditions, it is possible to suppress changes in edge shift and jitter due to changes in recording sensitivity due to differences in environmental conditions, devices, and media in which the system is placed.

According to the above method, before recording user information, test recording is performed when a disk drive is started or when a disk is loaded, so that recording can be performed with an optimum laser power. Since a recording domain can be formed, high-density recording can be realized. Here, the recording area of the write-once optical disc is reduced each time test recording is performed. However, test recording is performed only when the disc drive is started or when the disc is loaded. Since the area is small, it is small compared to the entire recording capacity.

[0013]

(Embodiment 1) Details of the present invention will be described with reference to an embodiment. First, FIG. 1 is a schematic diagram showing a cross-sectional structure of a used magneto-optical disk. On a plastic or glass substrate (1) with uneven guide grooves on the surface,
A silicon nitride film (2) was formed by a sputtering method. The film thickness at that time is 75 nm. Next, a magneto-optical recording film (3) was formed continuously without breaking vacuum. The thickness is 25 nm. Then, a silicon nitride film (4) was formed again by the sputtering method. The film thickness at that time is 25 nm. Finally, A
l ₉₈ Ti ₂ metal film (5) was formed by sputtering. The film thickness at that time is 50 nm. The surface of the recording medium was protectively coated with an ultraviolet curable resin (6). The discs thus produced were bonded together with two single discs so that the surfaces on which the recording media were formed faced each other.

Signals were recorded on the disk thus manufactured. FIG. 2 schematically shows the recording / reproducing apparatus used. The recording / reproducing apparatus includes a recording medium (101) for storing information, an optical head (102) for realizing recording / reproduction, and an optical head.
It comprises a processing system for converting the reproduction signal obtained from (102) into information. The optical head (102) focuses the light emitted from the laser (108) on the recording medium (101). When recording information, an input data bit sequence (information) is input to an encoder (104), and a recording code sequence output from the encoder (104) is guided to a recording waveform generator (105), and the recording waveform generator The recording waveform obtained by (105) is APC (auto power controller) (1
06), and the light intensity corresponding to the recording code string is
Output from 8). At the time of reproducing information, 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) and output to the waveform equalizer (111) and the input switch (112). The input switch (112) is converted into a pulse signal indicating the presence or absence of a reproduction signal of either the reproduction amplifier (110) or the waveform equalizer (111) according to the test writing command signal. The pulse signal is discriminator
(115) and a PLL (phase locked loop) (114). PLL (1
The synchronization signal (signal synchronized with the basic period of the pulse signal) output from 14) is input to the discriminator (115). Discriminator (11
In 5), a detection code sequence is generated from the pulse signal and the synchronization signal, and a decoder (117) outputs a data pit sequence (information). The detection code string of the discriminator (115) is a comparison discriminator.
Output to (116). The comparison discriminator (116) outputs test writing data from the test writing device (103) operated by the test writing command signal to the encoder (104), and further, the input switching device (112) operated by the test writing command signal. ) Is a playback amplifier
Switch the output of (110) to output to the shaper (113),
The symbol code string from the encoder (104) is compared with the reproduced code string from the discriminator (115), and the difference between the reproduced code strings from the symbol code string is reduced to some extent. Is output. After the test writing end signal is output, the input switch (112) switches the output of the waveform equalizer (111) to output to the shaper (113), and starts a normal recording / reproducing operation. Even after starting the normal recording operation, the comparison discriminator (116) confirms that the difference between the reproduction code string from the recording code string is within an allowable range. Is started, and when the test writing end signal is output, the normal recording operation is continued again. In addition, when the difference between the recorded code sequence and the reproduced code sequence is checked by the comparison / determination device (116), it is preferable that the output of the input switch (112) is operated so as to output the signal of the reproduction amplifier (110). Can be accurately detected. In these operations,
A similar operation can be realized without using the input switch (112). In order for the comparison discriminator (116) to accurately detect the difference between the reproduced code string and the recorded code string, the waveform equalizer (11
It is better not to use 1).

Recording / reproducing was performed on a disk using the recording / reproducing apparatus and the recording medium described above. The disk rotation speed of the equipment used is 3000 rpm, and the laser wavelength is 780 n
m, and (1,7) RLL was used as the modulation method. here,
Recording was performed so that the recording density was equal at any position on the disk. FIG. 3 shows a recording waveform used for recording on this disk. The laser power used was a read level (Pr) of 1.5 mW and a preheat level (Pas)
3.5mW, the first recording level (Pw1) to 5.8mW, and the second
The recording level (Pw2) was set to 6.1mW. Here, the value of each power varies depending on the laminated structure of the disk and the material used. However, the greatest effect of suppressing jitter and edge shift caused by thermal interference between recording domains to a certain value or less is the laminated structure of the disk except for the material used. When this is evaluated using the parameters of the recording / reproducing apparatus, Pw1 / Pas, Pw2 / Pas, Pw1 /
It is necessary that the ratio of Pw2 is within a certain range. When this value is measured for many disks, 1.5 <Pw1
For discs in the range of /Pas<1.7, 1.6 <Pw2 / Pas <1.8, 0.9 <Pw1 / Pw2 <1.1, when performing mark length recording,
The length and width of the formed recording domain could be precisely controlled. The control accuracy at that time was such that the domain length (in the track direction of the disk) was ± 0.02 μm or less, and the domain length direction (in the radial direction of the disk) was ± 0.05 μm or less. This accuracy is a value obtained from both the measurement of jitter and edge shift at the time of reproduction and the measurement by MFM (scanning magnetic force microscope). Then, recording / playback was attempted in the innermost zone of the 5.25 ″ disk.
C), a random pattern was recorded using the (1,7) RLL method at the previously set power. FIG. 4 shows the jitter distribution at that time. This is a result measured without applying a PLL. According to this, the ratio to the window width was 39%. Also,
When the edge shift amount was measured, it could be suppressed to ± 2 ns or less. When the recording / reproducing apparatus and the medium were left in an environment of 50 ° C., the jitter increased to 50% in a window width ratio.
Also, the shift increased greatly to ± 10 ns. In this state,
Test recording was performed on this magneto-optical disk. The test pattern used is a repetition of 2 Tw and 8 Tw. here,
Pulse width is uniform ± 3% ± 6% for test recording
The change in the difference between the center values of the signal amplitudes of the longest pattern and the shortest pattern when the recording was performed while changing to ± 10% was examined. FIG. 5 shows the result of detecting the potential difference (ΔV) between the patterns. From this figure, the pulse width at which ΔV = 0 was obtained. Under this condition, the pulse width was 5% smaller than at room temperature. Therefore, when recording under the condition of reducing the pulse width uniformly by 5%,
The jitter was 39% with respect to the window width ratio. Further, when the edge shift amount was measured, it could be suppressed to ± 2 ns or less, which was the same as that in the case of recording under the standard recording conditions and standard environment. Conversely, the recording / reproducing apparatus and the recording medium were left at 0 ° C. When recording was performed under the recording conditions set in the apparatus without performing test recording, the jitter increased to 65% in the window width ratio. Also, the shift greatly increased to ± 15 ns.

In this state, test recording was performed on the magneto-optical disk. The test pattern used is a repetition of 2 Tw and 8 Tw. Here, a change in the difference between the center values of the signal amplitudes of the longest pattern and the shortest pattern when the test recording was performed while changing the pulse width uniformly to ± 3% ± 6% ± 10% was examined. FIG. 6 shows the result of detecting the potential difference (ΔV) between the patterns. From this figure, the pulse width at which ΔV = 0 was obtained. Under this condition, the pulse width was 7% larger than at room temperature. Then, when a random pattern was recorded assuming the form of user information under the condition that the pulse width was uniformly increased by 7%, the jitter was 39% in terms of window width ratio. When the edge shift amount was measured, it was ± 2n
s or less, which is the same as when recording under the standard recording conditions and standard environment.

Further, another embodiment will be described. In this example, the laminated structure of the disks is different. The magneto-optical disks used are the disk I having the structure shown in FIG. 1 and the disk II having the structure shown in FIG. Disk I
Is as described above. Disc II
A silicon nitride film (2) was formed by a sputtering method on a plastic or glass substrate (1) having an uneven guide groove on the surface. The film thickness at that time is 75 nm. next,
A magneto-optical recording film (3) was formed continuously without breaking vacuum. The thickness is 100 nm. Then, a silicon nitride film (4) was formed again by the sputtering method. The film thickness at that time is 200
nm. The surface of the recording medium was protectively coated with an ultraviolet curable resin (6). The disc manufactured in this manner is placed in such a manner that the surfaces on which the recording media are formed face each other.
Two disk veneers were laminated.

Recording was performed on these two types of discs under standard recording conditions and standard environments. Since the recording condition set in the recording / reproducing apparatus is a value matching the disc I, the jitter when recording under this condition is 39% in a window width ratio,
The edge shift amount was ± 2 ns or less. Next, when recording was performed on the disk II under these conditions, the jitter increased to 50% in a window width ratio. Also, the shift increased greatly to ± 10 ns. In this state, test recording was performed on the magneto-optical disk. The test pattern used is a repetition of 2 Tw and 8 Tw. Here, a change in the difference between the center values of the signal amplitudes of the longest pattern and the shortest pattern when the test recording was performed while changing the pulse width uniformly to ± 3% ± 6% ± 10% was examined. FIG. 8 shows the result of detecting the potential difference (ΔV) between the patterns. From this figure, the pulse width at which ΔV = 0 was obtained. Under this condition, the pulse width was 5% smaller than at room temperature. Therefore, when a random pattern was recorded on the assumption of the form of the user information under the condition of uniformly reducing the pulse width by 5%, the jitter was 39% in terms of the window width ratio. Also, when the edge shift amount was measured, it could be suppressed to ± 2 ns or less, which was the same as when recording on the disk I. As described above, by performing test recording even when the laminated structure of the disk is different, it is possible to always perform recording on the disk under optimum conditions (a magnetic domain having the same shape can be formed with high accuracy). At the same time as the laminated structure of the disk is different, even if the environment in which the recording / reproducing device and the recording medium are used is different, the recording is always performed on the disk under optimum conditions by performing the test recording. It goes without saying that you can do it. In this embodiment, the case where magneto-optical recording is used has been described. However, even when applied to a write-once type, magnetic domains having the same shape can be formed with high accuracy.

(Example 2) The disk used in the present invention had irregular guide grooves formed of an ultraviolet curable resin.
A nitrocellulose layer was formed on a 12-inch glass substrate. On top of that, a PbTeSe recording layer was formed and assembled so that the recording layer had a hollow structure inside.
(Air sandwich structure). This type of disc is a perforated write-once optical disc. Test recording was performed prior to recording user information on this disc. Fig. 9 shows the pattern used for test recording.
Shown in The recording temperature of this recording film is about 450 ° C. Here, a multi-pulse divided into minutely divided pulses was used to record one pattern. In this embodiment, a mark length recording method based on the (1,7) RLL method is used as a modulation method. The longest pattern is 8 Tw and the shortest pattern is 2 Tw. The rotation speed of the disk is 1200 rpm. After repeating the longest pattern 5 times, the cycle of 5 shortest patterns is defined as one cycle, and the power is ± 1 around the standard power.
A total of 5 points were recorded, shifted by 0%. Then, it was reproduced to obtain jitter and standard deviation, and a recording condition (mainly laser power) in which these values were equal to or less than a certain value was searched. A time interval analyzer was used for measuring the jitter and the standard deviation. As a result, the jitter was suppressed to ± 3 ns or less. By the way, when recording was performed under these optimal conditions, the median values of the amplitudes of the shortest pattern and the longest pattern matched. This means that finding the median of the amplitudes of the shortest and longest patterns has the same effect and controllability as the jitter and standard deviation. Using the recording method of the present invention, recording can always be performed under optimal conditions, and thus it was found that recording domains having the same shape were formed. This point was confirmed by observation with a scanning electron microscope and evaluation of electric signals, and it was found that a recording domain having a good shape was formed. The formed recording domain has the same width as both the longest domain and the shortest domain. In particular, in the longest domain, it is confirmed from the viewpoint of electric signals and domain observation that the domain width is stabilized. I was able to. From the aspect of the electric signal, it can be understood that the amplitude on the domain side is substantially constant. Although the type of the optical disk described here is taken as an example of a hole type, the effect of the present invention does not depend on the type of the optical disk, and any type of alloy type, phase change type, or bubble forming type is used. May be. The reason why the multi-pulse is used as the recording pulse is to control the heat flow in the recording medium. Thereby, the domain width can be made constant. Needless to say, the pulse width and the gap width may be changed depending on the thermal conductivity of the recording film.

[0020]

According to the present invention, test recording is performed even when the use environment conditions of the recording / reproducing apparatus and the recording medium fluctuate, so that the recording is always performed on the disk under the optimum conditions.
(A magnetic domain of the same shape can be formed with high precision).
Even if the laminated structure of the disk is different (recording conditions of the disk are different), by performing test recording, it is possible to always perform recording on the disk under optimum conditions (a magnetic domain of the same shape can be formed with high precision). . In particular, by controlling the pulse width of the recording pulse to determine the optimum recording condition from the results of the test recording, fine adjustment becomes possible, and the control accuracy of the formed magnetic domain can be greatly improved. it can. As a result, fluctuations in the recording conditions due to fluctuations in the use environment and differences in the structure of the disk can be canceled, so that the minute magnetic domains can be stably recorded on the disk at the same size. Density write-once optical recording can be realized.

In a write-once optical disc, even if the recording conditions such as laser power fluctuate, the power can be detected and the power can be controlled based on the result by performing test recording and analyzing the results. Since recording domains of the same size can be formed, high-density optical recording was realized. Furthermore, the effects of the present invention are effective for write-once optical disks, and do not depend on the type of optical disk, and it goes without saying that any type of disk, such as alloy type, phase change type, or bubble forming type, may be used. .

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a configuration of a recording / reproducing device.

FIG. 3 is a diagram showing a waveform used for recording.

FIG. 4 is a diagram showing a jitter distribution.

FIG. 5 is a diagram showing a change amount of a pulse width and a difference between central values of signal amplitudes of a longest pattern and a shortest pattern.

FIG. 6 is a diagram illustrating a change amount between a difference between central values of signal amplitudes of a longest pattern and a shortest pattern and a pulse width.

FIG. 7 is a schematic diagram showing a cross-sectional structure of a magneto-optical disk.

FIG. 8 is a view showing a change amount between a difference between central values of signal amplitudes of a longest pattern and a shortest pattern and a pulse width.

FIG. 9 is a diagram showing a waveform used for recording.

[Description of Symbols] 1 ... disk substrate, 2 ... silicon nitride layer, 3 ... magneto-optical recording film, 4 ... silicon nitride layer, 5 ... metal film, 6 ... resin layer,
Reference numeral 101: recording medium, 102: optical head, 103: test writer, 104: encoder, 105: recording waveform generator, 10
6 APC, 107 laser driver, 108 laser, 109 light receiver, 110 reproduction amplifier, 111 waveform equalizer, 112 input switcher, 113 shaper, 11
4 PLL, 115 discriminator, 116 comparison discriminator, 1
17: decoder, 120: recording code sequence, 121: recording pulse sequence, 122: recording auxiliary pulse, 123: recording mark,
124: reproduced code, 125: reproduced code string.

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[Procedure amendment]

[Submission date] August 4, 1999 (1999.8.4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Ide 1-280 Higashi-Koikekubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory of Hitachi, Ltd. (72) Kuki Sugiyama 1-280 Higashi-Koikekubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory (72) Inventor Atsushi Saito 1-280 Higashi Koikekubo, Kokubunji City, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor Hiroyuki Tokunaga 1-1280 Higashi Koikekubo, Kokubunji City, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor Takeshi Maeda 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd.Central Research Laboratories

Claims (21)

[Claims] At least in optical recording in which recording is performed by using a laser beam, prior to recording user data, test recording is performed by setting a constant laser power to a constant value. The test recording is performed by increasing or decreasing the width of the data centering on the reference setting value, the results are reproduced and statistical processing is performed, and recording conditions for recording user data are set based on the obtained results. A recording method for optical recording, characterized in that recording control by test recording is performed so that a recording domain of the same size is always formed even if there is a fluctuation of the apparatus or a variation in recording sensitivity of the disk. 2. A recording waveform for use in test recording and user data recording according to claim 1, comprising a set of minute pulses, wherein the width of the first pulse is set wider than the width of other pulses. A recording method for optical recording, wherein recording is performed on an optical disk by using a recording waveform in which the width of a subsequent pulse and the interval between pulses are equal. 3. A recording waveform used for test recording and user data recording according to claim 1, wherein the set power level comprises at least four power levels, and the lowest level among the levels is a read level. The next level is a preheat level, the remaining two levels are recording levels, and each power level has a role. The read level is used for reproducing recorded information and verifying the recorded information. The preheat level is a power for balancing the heat so that the temperature of the recording medium is constant between pulses, and the recording level is used as a level for recording information on a disc. Optical recording method. 4. A thermal balance between a leading pulse and a succeeding pulse at two recording levels in a recording waveform used for test recording and user data recording according to claim 3, thereby obtaining a maximum temperature of the recording film. Is set so as to be constant independently of the recording pattern. 5. A recording waveform used for test recording and user data recording according to claim 3 or 4, wherein a ratio between a first recording level or a second recording level and a preheat level, and a ratio between the first recording level and the preheating level. 2. A recording method for optical recording, wherein the ratio to the recording level is set by changing the ratio according to the laminated structure of the disks or the material used as the recording medium. 6. A recording waveform used for test recording and user data recording according to claim 1, wherein after irradiating a recording pulse, after passing a read level for a predetermined period, the recording mode is shifted to a preheat level for a predetermined period, and then again. A recording method for optical recording, wherein thermal interference between recording patterns is removed by entering a recording area. 7. A recording waveform used for test recording and user data recording according to claim 6, wherein the read level and the preheat level for a certain period after the irradiation of the recording pulse are periods synchronized with the write clock. A recording method for optical recording, comprising: 8. A recording waveform used for test recording and user data recording according to claim 1, wherein a pulse width of a recording pulse and a pulse-to-pulse interval under a reference recording condition are synchronized with a write clock. A recording method for optical recording, comprising: 9. The test record according to claim 1, wherein
By recording a certain pattern on the test track, playing it back, and statistically processing the result, the laser power fluctuation, focus fluctuation, track position shift, or
By detecting fluctuations in recording conditions such as environmental temperature fluctuations, and by changing the pulse width of each minute pulse in a recording waveform composed of minute pulses based on the results, recording is performed.
A recording method for optical recording, characterized in that a recording domain having the same shape is always recorded on an optical disk irrespective of a change in recording conditions. 10. A recording method for optical recording according to claim 1, wherein the recording is performed by a mark length recording method for recording information at an edge portion of a mark formed for recording information. 11. The test recording according to claim 1, wherein a fixed pattern is recorded on a test track by changing at a fixed rate around a reference pulse width without changing a set power, and reproduced. In the modulation method used for recording, the repetition of the shortest pattern and the pulse interval and the repetition of the longest pattern and the shortest pulse interval are alternately recorded as the pattern to be used, and the center of the signal amplitude of both patterns when the pattern is reproduced. Optical recording is characterized by obtaining a domain of the same shape by detecting a change in recording conditions by detecting a voltage difference at a position, and detecting a pulse width at which the potential difference becomes substantially zero. Method. 12. The test recording for detecting the optimum recording condition according to claim 1, wherein the information is recorded after performing the test recording at regular time intervals or after a recording command is issued. Optical recording method. 13. An optical disc is divided into a plurality of zones under an optimum recording condition detected by the test recording according to claim 1 and the recording density is at least at any position of each zone. A recording method for optical recording, wherein recording is performed so as to be equal. 14. A test recording for detecting an optimum recording condition according to claim 1, wherein test recording is performed after performing test recording in a fixed area of each zone on an optical disk divided into a plurality of zones. Optical recording method. 15. A recording method for optical recording, wherein the recording is performed using a magneto-optical disk by the recording method for optical recording according to claim 1. 16. An optical recording method according to claim 1, wherein the information is recorded on a write-once optical disc on which a user can record information only once. 17. In the write-once optical recording according to claim 15, test recording is performed on the disk using a fixed pattern before recording information on the disk at the time of loading the disk or at the time of starting the apparatus, and the test-recorded data is recorded. Optical recording characterized in that a recording domain of the same size is always formed by controlling the power emitted from a laser light source using the result to reproduce the data and perform statistical processing on the result. Recording method. 18. A write-once optical recording according to claim 15, wherein a signal of a fixed pattern serving as a reference is previously recorded in a fixed area of the disc, and information is recorded at the time of disc loading or on the disc. before,
Perform test recording on the disc using a certain pattern,
The test-recorded data is reproduced, the result is subjected to statistical processing, and the result is compared with a pre-recorded signal to determine the optimum power. The same power is always obtained without being affected by fluctuations in recording conditions and the like. A recording method for optical recording, wherein a recording domain having a size is formed. 19. An optical recording method according to claim 15, wherein the test recording on the disk is performed at least when the disk drive is started or when the disk is loaded into the drive. 20. The disk according to claim 15, wherein the disk is a write-once optical disk, and the information is recorded by using a change in the reflectance of a recording layer, and more advantageously, the change in the reflectance is recorded. Changes in the crystalline state of the layer, changes in the refractive index,
At least one selected from a change in light absorptance at a wavelength of light used for reproduction, a change in light reflectivity due to formation of an alloy portion, formation of a layer that diffusely reflects light, or formation of a disappearance portion of a recording layer. A recording method for optical recording, characterized by using a method. 21. In reproducing information recorded on a disk according to any one of claims 1 to 19 as a digital electric signal, the obtained reproduced signal is binarized by slicing it at a constant level. A recording method for optical recording, wherein the slice level is a center value of an amplitude of an obtained signal.