JP3517727B2 - Information recording method and information recording device for optical recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk,
Optical recording media such as magneto-optical tape and magneto-optical card, especially magnetic super-resolution (MSR, Magnetically Induced Super Resolution)
ion) reproducing information recording method and magneto-optical recording device.

[0002]

2. Description of the Related Art In recent years, along with the progress of the information society, there is an increasing demand for further increase in recording capacity of media. In order to increase the recording capacity of the magneto-optical disk, that is, to increase the recording density, it is necessary to reduce the recording marks (bits) and the recording mark intervals in the track direction.

In order to realize such high density recording, magnetic super resolution reproduction (MSR (Magnetically Induced S
upper resolution (reproduction) method is disclosed in Japanese Patent Laid-Open Nos. 1-143041 and 4-271039, Jpn. J. Appl. Phys. 31 (19).
92) 568 etc. With this recording / playback system,
By using a recording medium in which a plurality of magnetic layers having different magnetic characteristics depending on the temperature are stacked and the temperature distribution of the recording medium formed in the beam spot is used, the same effect as when the beam spot is narrowed is produced. This makes it possible to reliably read a recording mark having a diameter smaller than the size determined by the beam spot.

An edge recording method is another method for realizing high density recording in the track direction. The edge recording method is a method in which the edge portion of the recording mark corresponds to "1" and the other portions correspond to "0", and the position recording in which the presence or absence of the recording mark corresponds to "0" or "1" is performed. Information can be recorded at high density. FIG. 7 is a diagram showing a recording mark and its temperature distribution by a conventional recording method. Figure 7
7A shows the pattern of data to be recorded, FIG. 7B shows the emission waveform of the laser beam, FIG. 7D shows the shape of the recording mark recorded corresponding to the recording data, and FIG. ) Indicates the temperature distribution of the recording mark. A recording mark is formed by the rectangular waveform emission of the laser light. The hatched portion of the recording mark shows an ideal shape.

As shown in FIG. 7D, the longer the length of the recording mark in the track direction is, the more it is affected by heat accumulation, and the rear edge of the recording mark is formed in a teardrop shape that swells radially and backward. It Further, as the length of the space due to the pattern of the recording data is shorter, the front edge shifts forward due to thermal interference from the previous recording mark. The precision of the reproduced signal is lowered due to the shift of the edge of the recording mark. As described above, in order to obtain an accurate reproduction signal in the edge recording method, it is necessary to form the recording mark without shifting the edge position, and it is difficult to precisely control the position.

As a method of solving this edge shift,
The applicant of the present application has proposed, in Japanese Patent Laid-Open No. 3-22223, a multi-pulse type optical recording method in which laser light is pulsed and irradiated. Further, Japanese Patent Laid-Open No. 5-290437 proposes an optical recording method in which a laser beam is pulsed according to the state of a recording mark that is written by trial. FIG. 8 is a diagram showing a conventional multi-pulse recording mark and its temperature distribution. Laser light is pulsed and irradiated with four power values Pw1, Pw2, Pa and Pb. When forming a recording mark, first, a laser beam having a power value Pw1 is irradiated as a first pulse for a certain period to form a front edge, and then a power value Pw2 and a power value Pa are used as a second pulse.
The laser beam is alternately irradiated by the number of pulses corresponding to the length of the recording mark. After that, the power value Pb is set as the third pulse.
To form a rear edge. After forming the recording mark in this manner, laser light having a power value Pa is irradiated for a period corresponding to the recording data to form a space.

With such a multi-pulse system, it is possible to suppress the accumulation of heat during the formation of recording marks and prevent the shift of the rear edge. Further, the heat shield region is provided by irradiating the laser beam having the power value Pb immediately before the space corresponding to the recording data, and the laser beam having the power value Pa is irradiated between the spaces to heat the recording mark in the preceding stage. The temperature change due to the interference and the temperature rise due to the preheating in the Pa emission are balanced, and thereby the temperature distribution between the spaces is made constant. Since the temperature distribution of the space is constant, the shift of the front edge of the recording mark can be prevented. In this multi-pulse system, the two power values Pw1 and Pw2 are used.
This is because Pw2 corrects the difference in heat storage due to the length of the recording mark.

As another method for solving the edge shift, there is disclosed an optical disk recording apparatus for adjusting the irradiation time and irradiation power of the beam light according to the length of the recording mark.
-53722 is proposed. In this device, since the recording mark is formed by the rectangular wave emission of the light beam, it is difficult to suppress the thermal interference depending on the recording mark length, and a specific method therefor is not presented.

[0009]

It is possible to further increase the density of information recording by combining the method for realizing the high density of information as described above, that is, by combining the MSR reproducing method and the edge recording method. It is necessary to form minute recording marks on the MSR medium compatible with the MSR reproducing method, and the spot of the beam light is irradiated with a small aperture. For this reason, the heat distribution of the recording marks greatly differs depending on the pattern of the recording data. FIG. 9 is a diagram showing a reproduced waveform with respect to a pattern of recorded data on the MSR medium. As shown in the figure, when the space interval is large, it is almost the same as the above-described recording mark shown in FIG. 8, but the recording mark is formed with high appearance frequency, long recording mark is formed, or the space interval is short. After such a pattern, even if the multi-pulse method shown in FIG. 8 is used, the thermal interference cannot be suppressed, and there is a problem that the front edge of the recording mark shifts to the front side.

The present invention has been made in view of the above circumstances, and changes the power value of the light beam according to the formed recording pattern, and irradiates the light beam with the changed power value to obtain a light beam. An object of the present invention is to provide an information recording method and an information recording device capable of preventing the shift of the front edge of a recording mark recorded at high density on a recording medium.

[0011]

In an information recording method according to the present invention, a recording pattern is formed in a recording mark corresponding to information to be recorded and a space between the recording marks by irradiating an optical recording medium with a beam of light. In the method of recording the information on an optical recording medium, a step of irradiating the beam light with a predetermined power value to form a recording pattern, a step of calculating an evaluation parameter of the formed recording pattern, and an operation Where the values of the evaluated parameters are obtained in advance
Compared with the fixed value, the evaluation parameter exceeds the specified value.
When it is determined that the effect of heat accumulation is large, the power value of the light beam is set lower than the predetermined power value.
It is characterized by including a step of changing to a value and a step of irradiating the beam light with the changed power value to form a next recording pattern.

The information recording apparatus according to the present invention irradiates an optical recording medium with a beam of light to form a recording pattern at a recording mark and a space between recording marks corresponding to information to be recorded, and the information is recorded. In an apparatus for recording on an optical recording medium, a light source that emits the light beam, a calculation unit that inputs information to be recorded and calculates an evaluation parameter of a formed recording pattern, and a value of the calculated evaluation parameter and a predetermined value. determination means for determining the magnitude of the value, the
Heat accumulation because the value of the evaluation parameter is larger than the specified value
And a means for changing the power value of the light beam to a lower value when it is determined that the influence of is large .

In the present invention, the degree of the effect of heat accumulation on the recording mark by the formed recording pattern is evaluated by the evaluation parameter. The evaluation parameters are cumulatively calculated within a predetermined period, and when it is determined that the effect of heat accumulation is large according to the calculated value, the power value of the beam light is changed to a low value to form the next recording pattern. For example, in the case of a recording pattern in which recording marks are formed with a high appearance frequency, long recording marks are formed, or short space intervals are formed, it is determined that the influence of heat accumulation is large, and the beam light The power value is changed. This can prevent the front edge of the recording mark from shifting forward.

A DSV value or an integrated value can be used as the evaluation parameter. The DSV value shows the recording mark (+
1), the space between recording marks is (-1) and is a value accumulated in code units within a predetermined period, and it can be said that the heat accumulation increases as the DSV value increases. The integrated value is a value calculated by averaging the amplitude center value of the recorded data and calculating the area for each time with the upper (+) and the lower (-) above the standard, and the heat accumulation increases as the integrated value increases. Can be said to be large. Therefore, by lowering the power value of the beam light when the DSV value or the integrated value exceeds a predetermined value,
The front edge of the next recording mark is formed without being affected by excessive heat. As a result, by the edge recording method in which the edge of the recording mark corresponds to "1" of the information,
Even if the recording pattern is formed with high density on the MSR medium, it can be formed without shifting the front edge of the recording mark.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 1 is a block diagram showing the configuration of the magneto-optical recording / reproducing apparatus of the present invention. First, the structure of the information recording system will be described. Recording data to be recorded on the magneto-optical disk is input to the encoder 11 and code-modulated, and the modulated signal is output to the recording pulse generation circuit 12 and the control unit 13. The recording pulse generation circuit 12 generates pulse signals W1, W2, W3 based on the input modulation signal, and the pulse signals W1, W2, W3 are respectively first and second.
Also, the opening and closing of the third switches SW1, SW2 and SW3 are controlled.

On the other hand, the control unit 13 calculates a parameter for evaluating the recording pattern from the input modulated signal.
This parameter is a value for evaluating how much heat accumulation of a formed recording pattern affects a recording mark to be formed next, and for example, DSV (digital sum vari).
ation) value, integral value, etc. are used. Then, the signal corresponding to the calculated parameter value is output to the first, second, third and fourth digital / analog converters (DAC). The first DAC 14a is connected to the current source 15a and outputs a signal for setting the instructed current value to the current source 1a.
5a. In addition, the second DAC 14b is a current source 15b.
And supplies a signal for setting the instructed current value to the current source 15b. Similarly, the third DAC 14c and the fourth DAC 14d also give signals for setting the instructed current value to the current source 15c and the current source 15d, respectively.

The first, second and third current sources 15a, 15
b and 15c are connected to the LD driver 16 via the first, second and third switches, respectively, and the fourth current source 15d is an LD
It is directly connected to the driver 16. As a result, a signal corresponding to the current value from the fourth current source 15d is constantly given to the LD driver 16, and the first, second and third current sources 15 are supplied.
The signals corresponding to the current values of a, 15b, and 15c are provided to the LD driver 16 when the first, second, and third switches are turned on. Also the optical head 17
Has a laser diode LD and a photodiode PD. The LD driver 16 outputs a signal according to the given current value to the laser diode LD, and the laser diode LD emits laser light with a power value corresponding to the given signal.

Next, the structure of the information reproducing system of this apparatus will be described. Laser light for reproduction is emitted from the laser diode LD and irradiates the magneto-optical disk. The reflected light enters the photodiode PD and is converted into an electric signal. This electric signal is input to the reproduction amplifier 18, and the waveform equalizer 1
It is input to 9 and waveform processing is performed. And the waveform shaper 20
To the discriminator 21.
Is input to the PLL 22. The PLL 22 outputs a clock signal that is synchronized with the basic cycle of the pulse signal and is input to the discriminator 21. The discriminator 21 generates a detection code string from the pulse signal and the clock signal output from the waveform shaper 20, inputs it to the decoder 23, and outputs the reproduced data from the decoder 23.

A procedure for recording information using the magneto-optical recording / reproducing apparatus having the above-mentioned structure will be described below. M
A magneto-optical disk capable of SR reproduction is prepared. In a magneto-optical disk, a dielectric layer made of SiN, a reproducing layer made of GdFeCo, an intermediate layer made of GdFe, a recording layer made of TbFeCo, and a protective layer made of SiN are laminated in this order on a polycarbonate substrate. Composition of each layer,
The film forming conditions and the magnetization state of each layer at the time of MSR reproduction are disclosed in Japanese Patent Application Laid-Open No. 7-244877 proposed by the applicant of the present application, and are omitted here.

The recording data recorded on such a magneto-optical disk is code-modulated by the encoder 11, and the pulse signals W1, W2, W3 are generated by the recording pulse generating circuit 12. FIG. 2 is a timing chart of pulse signals W1, W2 and W3 used in the magneto-optical recording method according to the present invention.
2A shows the recording data, and FIG. 2B shows the clock signal. 2 (c), 2 (d) and 2 (e) show pulse signals W1, W2 and W3, respectively. As shown in the figure, the pulse signal W1 forming the first pulse is a pulse forming the front edge of the recording mark, and has a pulse width of (3/2) T. The pulse signal W2 forming the second pulse has a pulse width of (1/2) T, and the number of pulse trains corresponding to the length of the recording mark is generated. The pulse signal W3 that forms the third pulse is a pulse signal for shutting off heat in the space and preheating light emission, and has a pulse width T. These pulse signals W1, W2, W3
Switch is on when each is'H ',
It turns off when it is'L '.

The modulated signal is also input to the control unit 13. FIG. 3 is a flowchart showing the processing procedure of the control unit 13, and the operation of the control unit 13 will be described based on the flowchart. The modulation signal is input to the control unit 13 (step S11), and the parameter value of the recording data is calculated using the modulation signal (step S12). D as a parameter value
When the SV value or the integrated value is used, it can be said that the degree of heat accumulation of the recording pattern being formed increases as the value increases. That is, it indicates that the recording pattern has a high frequency of appearance of recording marks, a large number of long recording marks, or a low frequency of appearance of spaces. Next, it is determined whether or not the third switch 15c is off (step S
13) At the time of turning off, that is, when forming a space, the predetermined value set in advance is compared with the calculation result (step S14). If the calculation result does not exceed the predetermined value, it is determined that the heat accumulation is small, and a normal signal for normal recording is output to each DAC (step S15). here,
The predetermined value is a value that has been experimentally and empirically obtained in advance.

The period for which the parameter value is to be calculated is set in advance, and it is determined whether or not the predetermined period for which the parameter value is to be calculated has ended (step S16). If not, the parameter value is subsequently calculated (step S16). In step S12), the same processing as described above is continued. The predetermined period is set by a predetermined number of clock signals. Note that any other setting may be used as long as the setting is based on the time count.

In this way, each DA to which the normal signal is input
C14a, 14b, 14c, 14d are current sources 15a to 1 for which the current value for emitting the laser light of the normal power value
Set to 5d. As a result, the set values of the current sources 15a to 15d are set to the LD driver 16 according to the opening / closing operation of each switch.
The laser diode LD irradiates the magneto-optical disk with laser light. A recording magnetic field is applied to the magneto-optical disk by a magnet (not shown), and the magnetization direction of the recording layer is reversed by irradiation with laser light to form a recording mark.

On the other hand, when the calculation result exceeds the predetermined value in step S14, it is estimated that the front edge of the recording mark to be formed next is greatly affected by heat.
In this case, a change signal for changing the power value of the laser light is output (step S17). As a result, the power value can be changed from the front edge of the recording mark. After outputting the change signal, the process proceeds to step S16 to determine whether or not the predetermined period for calculating the parameter value has ended.

As described above, each DA to which the change signal is input
C14a, 14b, 14c and 14d set current values in the current sources 15a to 15d such that the power value of the laser light becomes lower than the normal power value. As a result, the laser diode LD irradiates the magneto-optical disk with laser light having a power value lower than usual, and a recording magnetic field is applied to form a recording mark. Here, the changed power value is a value that is experimentally and empirically obtained in advance. If the parameter value becomes smaller than a predetermined value after the power value is changed, the power value at the time of normal recording is restored to form a recording mark.

When changing the power value of the laser light, all values of the current sources 15a, 15b, 15c, 15d may be changed, or only some of the current sources may be changed. It may be.

First Embodiment Using the magneto-optical recording / reproducing apparatus and the magneto-optical disk having the above-mentioned structure, a recording pattern was formed by the above-mentioned procedure. FIG. 4 is a diagram showing the recording data, the recording power and the reproduction waveform of the first embodiment. The reproduction waveform of the conventional example in which the power value of the laser light is not changed is also shown. The recorded data is (1,7) RL as shown in FIG.
The recording pattern is L-modulated. The value indicated by the broken line in FIG. 4B is the predetermined value of the DSV to be compared with the calculated value. The DSV value is a value obtained by cumulatively adding for each clock signal with the recording mark (+1) and the space (-1) for the modulation code of the recording data.

Until the calculated DSV value exceeds a predetermined value, the light emission waveform has a power value P as shown in FIG. 2 (c).
First pulse with w1 and Pa as upper and lower edges, power value Pw
2, a second pulse having an upper edge of Pa, and a power value P
It is composed of a third pulse whose upper and lower edges are a and Pb.
Then, when the DSV value exceeds a predetermined value (time A), the power value of the laser light is changed from the next space formation time (time B) to change the upper and lower edges of the first pulse and the upper and lower edges of the second pulse, respectively. Lowered to form recording marks. When the DSV value was similarly calculated after the formation of the recording mark (time C), it was found that it exceeded the predetermined value, so the laser beam was irradiated at the changed power value to form the recording mark in the next stage.

The recording mark formed by the above procedure was reproduced. The reproduced waveform is shown in FIG. Figure 4
When compared with the reproduced waveform according to the conventional example shown in (e),
It can be seen that the shift of the front edge of the recording mark indicated by the arrow is prevented.

Second Embodiment FIG. 5 is a diagram showing the recording data, recording power and reproduction waveform of the second embodiment. As shown in FIG. 5A, recording marks of recording data different from those of the first embodiment were formed, and the edge shift thereof was examined. The recording method of the recording mark is the same as in the first embodiment. Figure 5 (d)
As is apparent from the reproduced waveform shown in FIG. 5, it is understood that the shift of the front edge of the recording mark indicated by the arrow is prevented as compared with the conventional example of FIG.

Third Embodiment FIG. 6 is a diagram showing the recording data, recording power and reproduction waveform of the third embodiment. In the third embodiment,
The integrated value by the modulation code was used as the evaluation parameter of the recording pattern. The integrated value is a value obtained by calculating the area for each time with the central value of the amplitude of the recorded data as a reference, with the upper part (+) and the lower part (-) above the standard. The power value of the laser beam was changed according to the calculated integrated value to form a recording mark, and the edge shift thereof was examined. The recording data is a (1,7) RLL-modulated recording pattern, as shown in FIG. Other recording procedures are the same as those in the first and second embodiments.

As is clear from the reproduced waveform shown in FIG. 6D, the shift of the front edge of the recording mark indicated by the arrow is prevented as compared with the conventional example shown in FIG. 6E. I understand.

[0033]

As described above, in the present invention, the power value of the beam light is changed according to the degree of heat accumulation of the recording pattern, so that the influence of heat accumulation on the front edge of the recording mark is affected. Does not reach. This makes it possible to prevent edge shifts of recording marks recorded at high density on the optical recording medium, and the present invention has excellent effects.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a magneto-optical recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a timing chart of pulse signals used in the magneto-optical recording method of the present invention.

FIG. 3 is a flowchart showing a processing procedure of a control unit of the magneto-optical recording apparatus of the present invention.

FIG. 4 is a diagram showing recording data, recording power, and a reproduction waveform according to the first embodiment.

FIG. 5 is a diagram showing recording data, recording power, and a reproduction waveform according to the second embodiment.

FIG. 6 is a diagram showing recording data, recording power, and a reproduction waveform according to the third embodiment.

FIG. 7 is a diagram showing recording marks and temperature distribution formed by conventional rectangular waveform light emission.

FIG. 8 is a diagram showing recording marks and temperature distribution formed by conventional multi-pulse light emission.

FIG. 9 is a diagram showing a reproduced waveform for a conventional data pattern.

[Explanation of symbols]

11 encoder 12 Recording pulse generation circuit 13 Control unit 15a, 15b, 15c, 15d Current source 16 LD driver 17 Optical head LD laser diode

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Claims (2)

(57) [Claims] 1. A method of forming a recording pattern at a recording mark and a space between recording marks corresponding to information to be recorded by irradiating the optical recording medium with a beam of light, and recording the information on the optical recording medium. , A step of forming a recording pattern by irradiating the light beam with a predetermined power value, a step of calculating an evaluation parameter of the formed recording pattern, and a value of the calculated evaluation parameter is obtained in advance.
Compared with a certain value, the evaluation parameter exceeds a certain value
If it is determined that the effect of heat accumulation is
If the power value of the light beam is larger than the predetermined power value,
An information recording method for an optical recording medium, comprising: a step of changing to a lower value and a step of irradiating a beam light with the changed power value to form a next recording pattern. 2. An apparatus for forming a recording pattern at a recording mark corresponding to information to be recorded and a space between the recording marks by irradiating the optical recording medium with beam light, and recording the information on the optical recording medium. A light source that emits the light beam, a calculation unit that receives information to be recorded, and calculates an evaluation parameter of the formed recording pattern,
Determination means for determining the magnitude of the calculated evaluation parameter value and the predetermined value, and the evaluation parameter value is greater than the predetermined value
If it is judged that the effect of heat accumulation is large because it is large,
And a means for changing the power value of the light beam to a lower value when the information recording apparatus for an optical recording medium.