JP3063314B2 - Digital signal recording / reproducing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for recording and reproducing a digital signal on a recording medium such as an optical disk, and more particularly to controlling a recording signal based on recording characteristics determined by a combination of a recording medium and a recording apparatus. Accordingly, the present invention relates to a recording / reproducing method suitable for realizing higher density of recorded information, higher transfer speed, and improved reliability.

[0002]

2. Description of the Related Art An optical disk device is one of means for recording a digital signal on a recording medium. In an optical disk, a laser beam is focused on a recording surface by a lens, the intensity of which is changed according to the information to be recorded, and the reflectivity of the recording film in an area irradiated with the laser beam, or in the case of magneto-optical recording. Is to record information by changing the magnetization direction by external magnetization or the like. When reproducing recorded information, a laser beam of weaker intensity than that at the time of recording is irradiated, and the change in the amount of light from the reflected light from the recording film or the polarization plane rotation due to the difference in the magnetization direction is detected. Do. The recording density is mainly determined by the size of the spot of the laser beam focused on the recording surface, and the size is about 1 μm at present.
m, so that high-density recording about 10 times that of a magnetic disk can be realized.

The mark length recording method in which information is recorded at positions before and after a recording mark recorded by modulating the irradiation light power is used because two or more data are recorded on one recording mark. This is an effective means for realizing high-density recording.

In the mark length recording method for recording and reproducing information on an optical disk at a high density, various signal processings are performed at the time of recording and reproducing data in order to realize high reliability of information. I have.

[0005] For example, in general, when the irradiation light power at the time of recording is small, the shape of a recording mark formed tends to be unstable.
Further, if the recording linear velocity is different, the amount of heat applied per unit area and the heat distribution are changed, so that the recording mark shape is different. Therefore, in order to actually perform recording and reproduction by forming a stable recording mark shape, "application of pit edge recording to a PbTbSe film" (Proceedings of the 70th Anniversary of the IEICE, p4-176) In, the recording irradiation light pulse is set to be relatively large, and the laser pulse length is shortened during recording so that the mark length does not become excessive according to the linear velocity, or the pulse length of the binarized signal during reproduction is reduced. Adjustments such as sharpening.

In general, the shape of a recorded mark mainly depends on the recording sensitivity and thermal conductivity of the recording medium, the intensity distribution of the condensed laser light used for recording, the wavefront aberration, and the like. When the combination of the recording media changes, the characteristics change. Furthermore, the level of the irradiation light power at the time of recording on the apparatus side changes with time. This phenomenon is inevitable in a certain range of fluctuation even when an automatic laser power control mechanism (APC) is provided, and the recording / reproducing characteristics also fluctuate due to this factor. This change leads to a change in the recording mark length during recording and a change in the pulse interval of the reproduced signal during reproduction.

For this reason, when the recording correction amount and the recording light power are set to fixed values in advance at the time of shipment of the apparatus, these setting specifications are obtained by measuring the recording / reproducing characteristics with a number of combinations of recording media and recording apparatuses. decide. then,
In consideration of the variation range of the recording / reproducing characteristics due to the difference of the combination, in order to guarantee the reliability at the time of detection in all cases, a large margin is provided for the recording density, and the recording density is sacrificed.

Therefore, in order to absorb the variation in characteristics due to the combination of the recording medium and the recording apparatus and to increase the recording density, a method of preliminarily recording a test pattern and obtaining information for adjusting recording conditions from a reproduced signal thereof. Has been proposed. For example, in the apparatus described in JP-A-61-239441, the irradiation light power level, which is a constant value at the time of recording, is adjusted to the level described in JP-A-61-74178.
In the apparatus described in Japanese Patent Application Laid-Open No. 63-304427, a certain adjustment amount regarding the recording pulse width is used.
And the automatic equalization coefficient at the time of reproduction is adjusted at the same time.

Further, since the optical disk is basically a recording method using thermal diffusion, a phenomenon in which the shape of a recording mark changes due to the diffusion of heat distribution due to a plurality of recording pulses before and after the recording mark (hereinafter, referred to as a recording mark). Thermal interference). This phenomenon also leads to variations in the pulse interval of the reproduced signal during reproduction. Therefore, it is necessary to consider the influence of the thermal interference in order to perform the optimum correction at the time of recording. As a countermeasure, in the recording method described in JP-A-63-48617, the width of each recording pulse is changed according to the interval to the immediately preceding recording pulse.

[0010]

Among the above-mentioned prior arts, the following recording pulse width adjusting method according to the interval up to the immediately preceding recording pulse has the following problems.

That is, when high-density recording is aimed at such an extent that the recording mark shape and the interval between the recording marks are equal to or smaller than the size of the laser spot focused on the recording film surface, the thermal interference of the optical disk is reduced. Is greater than the shortest recording mark length. That is, the length of a plurality of recording pulse intervals of the recording irradiation light pulse has an influence on the determination of the edge position of a certain recording mark due to the diffusion of heat. As a result, recording pulses of the same length are irradiated. However, the edge position changes due to the combination of the recording patterns located earlier in time. In particular, in the case of a recording medium having a high recording sensitivity with respect to the intensity of laser light and capable of recording with a low laser power, the thermal conductivity is generally large, and the range affected by the thermal interference is large.

Further, in this recording pulse width adjustment method, since the information on the adjustment amount uses a preset value regardless of the recording conditions at that time, it is possible to change the adjustment amount related to the fluctuation of the recording characteristics. However, as the recording characteristics deviate from those at the time of setting, errors appear in the adjustment, and the adjustment is not accurate.

On the other hand, in the method of obtaining the information for adjusting the recording condition, the power of the recording irradiation light or the single amount of the recording pulse width is adjusted. Not be.

Conventionally, a linear equalizer such as a transversal filter is generally used in the field of communication and magnetic recording as a measure against intersymbol interference components on the reproducing side. This is to reduce linear intersymbol interference generated by superimposition on a nearby waveform due to a narrow base of a reproduction signal pulse due to a narrow frequency band of the signal reproduction system.

However, the above-mentioned influence of thermal diffusion mainly appears as a waveform shift in the time direction during reproduction.
This is a non-linear intersymbol interference component that cannot be expressed simply as a linear superposition of basic waveforms according to recording information. Therefore, the edge position fluctuation component cannot be dealt with by the linear equalizer, and it is actually very difficult for the reproduction side to deal with this interference component in real time.

For the above reasons, even if the conventional method can cope with the fluctuation of the recording characteristics, the fluctuation of the recording mark length due to the influence of the thermal interference cannot be reduced at all, or the recording mark due to the influence of the thermal interference can not be reduced. There is an adjustment error in the variation of the length, and it cannot cope with the variation of the recording characteristics at all. Particularly, in mark length recording in magneto-optical recording using a recording medium having high thermal conductivity, these fluctuation components are large, and a margin is provided for them, so that the recording density has to be greatly sacrificed.

[0017]

According to the present invention, a change in the edge position of a recording mark due to thermal interference is determined for each edge in accordance with a combination of a plurality of recording pulses positioned before the recording pulse. The laser is recorded with the adjusted recording pulse signal, and a predetermined recording signal is recorded and reproduced at predetermined time intervals, and recording is performed based on the result. The fluctuation of the recording mark length under any recording conditions can be obtained by detecting the fluctuation of the light beam intensity at the time and the environmental temperature and changing the light beam intensity at the time of recording and the adjustment amount of each edge position according to the result. No, highly accurate information recording is performed,
More accurate edge position control of a recording mark for high-density recording by mark length recording can be realized.

[0018]

According to the present invention, the position of the edge of a recording mark caused by thermal interference is adjusted to be temporally shifted forward or backward for each edge in accordance with a combination of a plurality of immediately preceding recording pulses. By recording the laser with the recording pulse signal, it is possible to absorb the variation in the recording mark length when the recording pattern sequence is different due to the influence of thermal interference.

In response to the fact that the recording linear velocity varies depending on the recording radius, a plurality of types of adjustment amount tables are prepared according to the recording linear velocity, and the adjustment amount table suitable for the linear velocity at the time of recording is used. Thus, the recording pulse can be accurately adjusted at any position on the recording medium.

When the use of the apparatus is started, when the recording medium is replaced, and at predetermined time intervals,
Recording and reproduction are performed using a predetermined recording signal, the duty of the pulse length corresponding to the recording mark portion of the reproduction signal and the duty of the gap length corresponding to the portion other than the recording mark are detected, and the light beam intensity during recording is determined from the information. The deviation of the temperature of the recording medium from the set value is extracted, and according to the result, if the light beam intensity at the time of recording deviates from the set value, the light beam intensity at the time of recording is changed, and the recording medium is changed. If the temperature deviates from the set value, change the light beam intensity during recording, if it can be adjusted by changing the light beam intensity during recording, or the contents of the adjustment table. The recording pulse can be accurately adjusted even when the value fluctuates.

As described above, it is possible to more accurately control the edge position of a recording mark in high-density recording by mark length recording.

[0022]

Next, an embodiment of the present invention will be described with reference to the drawings.

First, the process of shifting the edge position and the principle of suppression will be described.

FIG. 2 schematically shows how the edge position shifts due to thermal interference.

In FIG. 2, the horizontal direction indicates the passage of time or spatial coordinates on the recording medium where the light spot moves. The recording signal 201 modulates the recording information and shows the temporal change of the intensity of the light spot irradiated on the recording medium, and the recording mark 202 shows the shape of the recording mark formed on the recording medium by the recording signal 201. . Also, the reproduction signal 2
Numeral 03 is obtained by scanning the recording mark 202 with a light spot having a light intensity of a readout level, receiving reflected light from the recording medium at that time by a photodetector, and performing photoelectric conversion.
The binarized reproduction signal 204 is obtained as a result of binarizing the reproduction signal 203 reflecting the recording mark shape depending on whether the signal level is above or below a predetermined signal level.

Note that the first rising edge of the recording signal 201, the leftmost front edge position of the recording mark 202, and the first rising edge position of the binarized reproduction signal 204 are shown together. L [i] and B [i] represent the length of each pulse interval (from the rising edge to the falling edge) of the recording signal 201 and the length of the gap interval (from the falling edge to the rising edge). , A serial number (0 at the beginning) from the recording pulse (binary reproduction pulse).

As an information recording mechanism, in an optical information recording method in which a recording mark is formed basically by heat given by a light spot, heat given by the light spot diffuses in a recording medium in a cooling process. As a result, the temperature around the light spot increases. Therefore, when the size of the recording mark and the interval between the recording marks are reduced in order to perform high-density recording, the individual pulse shapes of the recording signal not only determine the corresponding recording mark shapes but also the surrounding recording marks. It also affects the shape. Conversely, the shape of each recording mark is not determined only by the corresponding recording pulse shape, but is affected by the temporally adjacent recording pulse shapes.

As described above, the recording mark is affected by the recording pulses which are temporally adjacent to each other. As a result, a shift occurs between the pulse interval of the recording signal 201 and the edge position of the recording mark 202. As a result, relative shifts e [i] and f [i] between each edge position of the recording signal and each edge position of the binarized reproduction signal 204 occur. Here, e [i] is the recording signal 2
01 represents the deviation between the falling edge of the binarized reproduction signal 204 and the falling edge of the binarized reproduction signal 204, and f [i] represents the deviation between the rising edge of the recording signal 201 and the rising edge of the binarization reproduction signal 204. Also, i is a serial number (0 at the beginning) from the rising edge and the falling edge of the first recording pulse (binary reproduction pulse), and f [0] is zero.

At this time, the edge shift amounts e [i] and f [i] vary depending on the heat conduction characteristics and the recording density of the recording medium. For example, TbFeCo, which is the most common magneto-optical recording medium, is used.
For a recording medium having a structure composed of a magnetic film, a dielectric film, a protective film, and a reflective film, when the recording linear velocity is about 10 to 20 m / s and the shortest recording mark length is about half the light spot diameter as the recording density, recording is performed. It can be expressed by the following equation using the pulse length L [i] of the signal and the gap length B [i].

[0030]

(Equation 1)

[0031]

(Equation 2)

Here, Se () and Sf () represent functions. That is, e [i] is the immediately preceding pulse interval L [i],
It is determined by the preceding gap interval B [i-1], and f [i] is the immediately preceding gap interval B [i-1] and the preceding pulse interval L [i-1].
Determined by [i-1].

Note that, with respect to e [i], the pulse interval L [i-1]
Regarding the effect before the gap interval B [i] and the effect after f [i], the effect before the gap interval B [i-2] and the effect after the pulse interval L [i] are small and need not be considered.

Next, a description will be given of how the influence of the edge shift is suppressed by adjusting each edge position of the recording signal using the information of the edge shift amount described above, with reference to FIG. In FIG.
The horizontal direction represents the passage of time or spatial coordinates on the recording medium on which the light spot moves. The recording signal 301 is an electric signal obtained by modulating the recording information, and the adjusted signal 302 is each rising edge of the recording signal 301. Represents the temporal transition of the electric signal level in which the falling edge position is shifted according to the recording pattern, and this signal modulates the intensity of the light spot irradiated on the recording medium.

Further, the recording mark 303 is the signal 30 after the adjustment.
Reference numeral 2 denotes the shape of the recording mark formed on the recording medium. The reproduction signal 304 is obtained by operating the recording mark 303 with a light spot having a light intensity of a readout level, receiving the reflected light from the recording medium at that time with a photodetector, and performing photoelectric conversion. The binarized reproduction signal 305 represents an electric signal obtained as a result of binarizing the electric signal reflecting the recording mark shape depending on whether the signal level is above or below a predetermined signal level.

Note that the first rising edge of the recording signal 301, the leftmost front edge position of the recording mark 303, and the first rising edge position of the binarized reproduction signal 305 are shown together. L [i] and B [i] represent the length of each pulse interval (from the rising edge to the falling edge) of the recording signal 301 and the length of the gap interval (from the falling edge to the rising edge), and E [i] ], F
[i] indicates a shift amount of each falling edge and rising edge of the adjusted signal 302 from each edge position of the recording signal 301. Further, i is a serial number (0 at first) from the first recording pulse (binary reproduction pulse).
Is represented.

The principle of adjusting the recording pulse edge position is as follows. The edge position of the recording mark 303 always deviates from the edge position of the recording signal 301. However, conversely, by shifting each edge position of the original recording signal 301 in advance to obtain the adjusted recording signal 302, each edge position of the binarized reproduction signal 305 becomes the recording signal 3
02, the original recording signal 3
The edge position of 01 coincides with the edge position. Recording signal 3
The deviation amount of the edge position of the recording mark 303 with respect to the edge position of 01 is determined using the above-mentioned relational expression by referring to the recording pattern. Therefore,
The amount by which the edge position is shifted using the inverse function of this relational expression,
The shift amount of the binarized reproduction signal with respect to the recording signal can be determined so that the sign is opposite and the magnitude is the same. That is,

[0038]

(Equation 3)

For

[0040]

(Equation 4)

[0041]

[0042]

(Equation 5)

For

[0044]

(Equation 6)

As shown, the inverse functions Cf () and Ce
()

[0046]

(Equation 7)

[0047]

(Equation 8)

E [i] and F [i] can be obtained as follows. In Equations 7 and 8, the functions Ce () and Cf () include the edge position shift amount. However, the shift amounts are E [0], F [1], E [1], F [2], E [2],. . .
If, for example, F [i] is obtained, E [i-1] and F [i-1] are calculated at the previous time in Equation 7, and E [i] is calculated as At the time of calculation, F [i] and E [i-1] are calculated at the time before that in Equation 8, so that Equation 7
F [i] and e [i] can be calculated from Equation 8, respectively.

Next, the principle of a method for detecting a change in the light beam intensity during recording and a change in the temperature of the recording medium and coping with the change will be described.

Even when the light beam intensity at the time of recording changes or the temperature of the recording medium changes, a deviation occurs between each edge position of the recording signal and the edge position of the recording mark. For example, if the light beam intensity during recording has decreased,
The recording mark is generally smaller, and the position of the front edge of the recording mark is shifted to the rear side, and the position of the rear edge of the recording mark is shifted to the front side.

The amount by which each edge position of the recording mark is shifted differs for each recording mark to be formed. Therefore, in order to reduce the deviation of the edge position of the recording mark that occurs when the light beam intensity at the time of recording is changed by changing the edge adjustment amount for each recording pattern as described above,
It is necessary to change the edge adjustment function for each light beam intensity at the time of recording, and the circuit system becomes large-scale. Therefore, if it is detected that the light beam intensity at the time of recording has changed in order to prevent edge displacement with a simpler system,
An adjustment is made so that the light beam intensity at the time of recording returns to the original value.

On the other hand, even when the temperature of the recording medium decreases, the recording mark becomes smaller as a whole. Also in this case, the position of the front edge of the recording mark is on the rear side, and the position of the rear edge of the recording mark is on the front side. Shift. The temperature cannot be directly controlled to a constant value unless a temperature control mechanism is provided in the apparatus. Here, the edge position fluctuation characteristics of the recording mark due to the temperature fluctuation show a tendency that is considerably close to the case where the light beam intensity at the time of recording changes in a range where the fluctuation amount from the assumed temperature is small. Therefore, this range is dealt with by changing the light beam intensity at the time of recording, and when the value greatly fluctuates with respect to the set value, the function for adjusting the edge position at the time of recording is changed.

In order to detect the above change, a predetermined recording signal is recorded in a dedicated area on the recording medium at predetermined time intervals. Immediately after that, the signal is reproduced to detect the shift amount of each edge position, and the change in the light beam intensity at the time of recording and the temperature change of the recording medium are separately detected from the result. FIG. 4 shows an example of a recording signal pattern used at that time. In this recording signal 401, a plurality of edge intervals in a range of recording mark lengths that can be taken at the time of normal information recording are arranged so that a pulse interval becomes equal to a gap interval immediately after the edge interval, and this is repeated a plurality of times. To use. The reason for using the repetition is to reduce the influence of noise components included in the detection result and improve the accuracy of the measurement result by the averaging process. Here, 2-7 RLLC (Run Length Limited Coated)
de), the recording signal is configured as code-modulated, and Pw [1], Pw [2],. . . Indicates the edge interval of the recording signal pulse as Gw [1], Gw
[2],. . . Represents the edge interval of the recording signal gap. Note that T in the other edge interval notation of the recording signal 401 is a time length per information bit.

A reproduction signal 402 represents a binarized reproduction signal waveform when a recording mark written by the recording signal is read. Also, Pr [1], Pr [2],. . . Represents the edge interval of the reproduced signal pulse as Gr [1], Gr
[2],. . . This represents the edge interval of the reproduction signal gap.

FIG. 5 shows the recording signal 401 and the reproduction signal 40.
2 shows means for separately detecting a change in the light beam intensity during recording and a change in the temperature of the recording medium from the relationship of 2. The horizontal axis represents the pulse interval Pw [i] of the recording signal 401, and the vertical axis represents the gap interval Gr immediately after the pulse interval Pr [i] of the reproduction signal 402.
[i] is subtracted, and the measurement points in each recording situation are plotted. If the entire measurement point is above the 0 level in this measurement result, the light beam intensity at the time of recording has changed in a direction larger than the set value or the temperature of the recording medium has changed in a direction higher than the assumed value. is there. Conversely, if the entire measurement point is below the 0 level, the light beam intensity during recording has changed in a direction smaller than the set value, or the temperature of the recording medium has changed in a direction lower than the assumed value. Is represented.

When the light beam intensity at the time of recording changes, a measurement point comes on one curve in a fixed curve group. Therefore, when the light beam intensity at the time of recording changes, the curve group drawn by the measurement point is checked in advance, and the information is stored in the apparatus, so that all of the curves are plotted on one of the curves. Whether or not a change in the light beam intensity at the time of recording can be determined can be determined based on whether or not the measurement point is set. If all the measurement points are not on one curve, it is detected whether the curve is shifted to the lower right or lower to the left, and the temperature of the recording medium rises from the result. Is determined, and the edge position adjustment table for recording is changed accordingly.

Next, an embodiment including the above-described principle of adjusting the edge position and determining the recording condition will be described.

FIG. 1 is a block diagram showing the configuration of the embodiment.

In FIG. 1, an optical disk 1 is rotated at a constant angular velocity by a spindle motor 2, and a laser beam for recording and reproduction is condensed by an optical pickup 3 on a recording film surface on the disk 1 by a focusing lens. Optical pickup 3
Can be moved in the radial direction of the disc in accordance with the information recording position.

The signal detected by the detector in the optical pickup 3 is amplified by the amplifier 4 to a desired level, and then the waveform is equalized by the equalizing circuit 5 to ensure the resolution of the reproduced signal. Ruru. Thereafter, this signal is converted by a binarization circuit 6 into a reproduced binary signal 7 which is a digital signal, separated by a PLL (phase lock loop) circuit 8 into a data signal and a clock signal, and is demodulated by a demodulation circuit 9.
Is used as playback data.

The above is the data reproduction signal processing system of the optical disk system employing the normal mark length recording method. The reproduction signal processing system of the present invention further includes a circuit for detecting changes in the light beam intensity during recording and the temperature on the recording medium, and updating the calculation of the pulse interval adjustment amount and recording power during recording. Has a system.

This circuit system comprises an edge interval measuring circuit 10 and a recording condition judging circuit 11. First, the reproduced binarized signal 7 passes through the edge interval measuring circuit 10, and its pulse interval and gap interval are measured. The measurement result is input to the recording condition determination circuit 11, where the amount of change in light beam intensity during recording and the amount of change in temperature on the recording medium are separately detected, and the result is transmitted to the controller 12.

This recording condition determination circuit operates in a recording condition determination mode instructed by the controller at predetermined time intervals other than during normal information recording / reproduction. FIG. 6 shows the flow of the recording condition determination mode.

During operation of the present system, a predetermined time interval is monitored by the controller 12 in the present system, and this mode is started at each time interval. First, at the beginning of this mode, the present system is set in a busy state so that normal recording / reproducing operations are not accepted. If there is any work (recording / reproduction) currently being processed by the present system, the processing is terminated. Wait for.

Next, the light spot is moved to a dedicated area for recording and reproducing a predetermined recording signal for checking recording conditions. This area is set at a plurality of locations having different rotation radii per recording medium.

When the movement is completed, recording is performed on a recording medium using a predetermined recording signal for checking recording conditions. Then, the recorded mark is reproduced. At this time, the edge interval measurement circuit 10 and the recording condition determination circuit 11 operate in response to a command from the controller. The determination result is transmitted to the controller, and the controller changes the light beam intensity at the time of recording and changes the pulse interval adjustment amount at the time of recording according to the determination result.

For example, if the result of the determination indicates that the light beam intensity at the time of recording has changed to a value greater than the set value and that the amount of change has exceeded the allowable amount, the light beam intensity at the time of recording is determined by the step size. Decrease ΔP. Similarly, if it is determined in the determination result that the light beam intensity at the time of recording changes to a value smaller than the set value, and it is determined that the amount of change has exceeded the allowable amount, the light beam intensity at the time of recording is increased by the increment ΔP. .

If the result of the determination indicates that the temperature on the recording medium has changed to a value higher than the assumed value, and that the amount of change has exceeded the allowable range, if the change in the light beam intensity during recording has occurred. If the light beam intensity at the time of recording exceeds the range that can be handled by changing the light beam intensity at the time of recording, the light beam intensity at the time of recording is reduced. Along with the operation of decreasing the step amount ΔP of the beam intensity, the pulse interval adjustment amount at the time of recording is changed. Similarly, if the determination result indicates that the temperature on the recording medium has changed to a value lower than the expected value, and that the amount of change has exceeded the allowable range, if the change in the light beam intensity at the time of recording is taken, the response will be taken. Is within a possible range, the light beam intensity at the time of recording is increased by an increment ΔP,
If the change in the light beam intensity during recording exceeds the range that can be dealt with, the step size ΔP of the light beam intensity during recording
The pulse interval adjustment amount at the time of recording is changed together with the operation of increasing the minute.

If it is determined from the result of the determination that each variation does not exceed the allowable range, no change regarding the recording condition is made.

Then, in response to the above determination result, a corresponding operation is performed, a signal in the dedicated recording area is deleted, the busy state of the present system is released, and the system returns to the normal information recording / reproducing mode. .

The time interval for generating the recording condition determination mode is determined by a change in the light beam intensity during recording and by how long the temperature change on the recording medium changes. For example, regarding the light beam intensity during recording,
It must be set within a time interval that does not change more than the change step width ΔP at the maximum.

Returning to FIG. 1, the signal recording system in this embodiment will be described. When information is recorded, the recording information is code-modulated by the modulation circuit 13 so as to match the characteristics of the optical information recording system. For this code-modulated recording signal,
In the edge position adjusting circuit 14 and the edge position adjusting tables 15 and 16, each edge position is adjusted according to the edge interval information immediately before. Then, the recording signal after the adjustment is input to the laser driver circuit 17, the laser intensity in the optical pickup 3 is modulated according to the signal, and information is recorded on the disk 1. The edge position adjustment tables 15 and 16 are changed by the edge position adjustment table switching circuit 18 when it is determined that the edge adjustment amount needs to be changed as a result of the recording condition determination mode and when the recording linear velocity changes. Its contents are changed.

In FIG. 1, an optical disk 1, a spindle motor 2, an optical pickup 3, an amplifier 4, an equalizing circuit 5,
Binarization circuit 6, PLL circuit 8, demodulation circuit 9, modulation circuit 1
3. The laser driver circuit 16 may have the same configuration and function as those used in the conventional optical disk device, and a detailed description thereof will be omitted.

Hereinafter, other components will be described.

FIG. 7 shows an edge interval measuring circuit 1 in FIG.
FIG. 3 is a diagram illustrating an example of the configuration of a 0.

The reproduced binarized signal 7 output from the binarizing circuit 6 is also input to the impulse signal generating circuit 701.
The impulse signal generation circuit 701 outputs an impulse-like signal waveform at each timing when the polarity of the input signal changes, and this output signal is sent to the recording condition determination circuit 11 and the A / D converter 702 as a signal representing the polarity inversion timing. Is entered.

On the other hand, the reproduced binary signal 7 is also input to an integrating circuit 703 composed of an amplifier. The "H" level in the reproduced binary signal 7 is set to V
When the H and "L" levels are VL, an integration reference signal 704 representing a level of-(VH + VL) / 2 is also input. The integration circuit 703 outputs a signal representing the difference between the reproduction binary signal 7 and the integration reference signal, and the A / D converter 702
Is input to

A signal from the controller is input to the flip-flop 709. This flip-flop 7
A signal indicating the polarity inversion timing is also input to 09 as a clock signal. The output of the flip-flop 709 detects the first rising edge of the reproduced binary signal 7 from the start of the edge interval measurement.
10 is switched, and the integrating circuit 703 is operated.

The A / D converter 702 converts the output signal of the integrating circuit 703 into a digital signal by using a signal representing the timing of the polarity inversion as a timing clock for performing a digital conversion operation. The conversion result is output as the polarity inversion interval signal 14 and input to the recording condition determination circuit 11. The conversion accuracy of the A / D converter 702 has sufficient accuracy as an output value of the pulse interval adjustment amount, and quantization accuracy and the number of bits that do not cause overflow.

Next, the operation of the edge interval measuring circuit 10 of FIG. 7 will be described with reference to FIG. The reproduction binarization signal 7 is an output signal of the binarization circuit 6, and takes an "H" or "L" level depending on the presence or absence of a recording mark at the irradiation light spot position on the recording film surface. The reproduced binary signal 7 passes through an impulse signal generation circuit 701 and becomes a signal indicating the timing of polarity reversal that generates an impulse waveform at the timing when the polarity changes, and is used as a trigger signal in the A / D converter 702. You.

The integration circuit 703 calculates the pulse interval of the reproduced binary signal 7 and outputs it. This integration circuit 703
In general, when the input signal is X (t), the output signal Y (t) is

[0082]

(Equation 9)

Is obtained. That is, the output signal Y (t)
Is the initial value (the output signal level at the time when the edge interval measuring circuit starts operating) Y (0) is the analog switch 7
Since it becomes 0 by the operation of 10, the reproduction signal 402 of FIG.
Pulse intervals Pr [1], Pr [2],. . . , And gap intervals Gr [1], Gr [2],. . . , The integration circuit 703
Is output signal level Vo, the polarity of the reproduced binary signal 7 is "
At the time of inversion from “L” to “H”,

[0084]

(Equation 10)

The polarity of the reproduced binary signal 7 is "H".
At the time of inversion from

[0086]

[Equation 11]

## EQU10 ## Here, A in the above equation is the integration circuit 7
It is a constant determined by the amplification factor of 03. That is, the output signal level at this time represents the result of integrating the pulse interval when the "H" level is represented by a negative value and the "L" level is represented by a positive value for the pulse interval of the reproduced binary signal 7. ing.

The A / D converter 702 converts the integrated signal level at that time into a digital value, and inputs the conversion result to the recording condition determination circuit 11. That is, the output is given by Equations 10 and 11,

[0089]

(Equation 12)

Alternatively,

[0091]

(Equation 13)

(B is a constant).

FIG. 9 shows the recording condition determination circuit 11 in FIG.
1 is a configuration example.

In this circuit, each Pr [i] -Gr in FIG.
The calculation of [i] and the calculation of summing the repetition signal are performed, and the calculation results are transmitted to the controller 12.

Latch circuits 901 and 902 and subtraction circuit 90
In the case of 3, the number 1 sent from the edge interval measuring circuit 10
This is the part where the value of each B (Pr [i] -Gr [i]) is obtained from the edge interval data represented by Expression 2 and Expression 13. The reproduction binary signal 7 is input to the latch circuit 901 as a signal for trigger timing, and the edge interval data is sampled and held at the rising edge thereof.
That is, at the time of the rising edge of the reproduced binary signal 7, the data represented by Expression 12 is held and output. In the latch circuit 902, the data is delayed by one trigger.

The subtraction circuit 903 subtracts the output of the latch circuit 901 from the output of the latch circuit 903 of the edge interval data, and outputs the result. Since the output of the latch circuit 902 and the output of the latch circuit are the result represented by Expression 12 shifted by one trigger timing, B (Pr [i] -Gr [i]) is obtained from the output of the subtraction circuit 903. ing.

Addition circuit 904 and shift register 9
At 05, the sum is calculated for each B (Pr [i] -Gr [i]) in the repeated data. Shift register 905
The number of stages is designed to be equal to the number of pulses in one cycle of the recording signal shown in FIG. 4, and an output line is output for each stage and sent to the controller. When the reproduction signal 402 is read to the end, the output result at each stage of the shift register is represented by B (Pr [i] -Gr) in repeated data for each i.
[i]), the result is used to check whether the light beam intensity during recording and the temperature of the recording medium have changed based on the criterion shown in FIG.

FIG. 10 is a structural example of the edge position adjusting circuit 14 and the edge position adjusting table 15 in FIG.

In this circuit, the function C in Equations 7 and 8 is used.
f () and Ce () are obtained by referring to the contents of the edge position adjustment tables 15 and 16 formed of storage elements such as a RAM. That is, when obtaining F [i], the pulse / gap of the recording signal 301, which is the element of the first and second parameters in the function Cf (), is determined by the address signal line input to the edge position adjustment table 15. Interval L [i-1],
By inputting B [i-1] and the amounts representing the edge position adjustment amounts F [i-1] and E [i-1] which are the conversion results immediately before obtaining F [i], the data signal line Output as the function value. Similarly, when E [i] is obtained, the recording signal 301 which is an element of the first and second parameters in the function Ce () is determined by the address signal line input to the edge position adjustment table 16.
Pulse / gap intervals B [i-1] and L [i], and edge position adjustment amounts E [i-1], which are conversion results immediately before obtaining E [i],
By inputting an amount representing F [i], it is output from the data signal line as its function value.

The counter circuits 1001 and 1002 detect how many pulse / gap intervals of the signal transmitted from the modulation circuit 13 correspond to the number of basic clock intervals of the modulation signal, and connect the address lines of the edge position adjustment table to the address lines. Has become. Also, the latch circuits 1003, 1004, 100
5, 1006 are edge position adjustment tables 15 and 1
The shift register circuits 1007 and 1008 are used to adjust the timing between the modulation signal and the edge position adjustment amount in order to adjust the timing of each address signal line input to 6. The selector circuit 1009 is a circuit that alternately switches the rising and falling edge position adjustment amounts.
Reference numeral 009 denotes a circuit for delaying the edge position by the edge position adjustment amount and adjusting the edge position. Therefore,
This output signal is input to the laser driver circuit 17 as the adjusted signal 302.

FIG. 11 shows an example of the configuration of the edge position adjustment table switching circuit 18 in FIG.

This circuit switches the contents of the edge position adjustment table in accordance with the change in the recording linear velocity and the temperature of the recording medium, and adjusts the edge position for each recording linear velocity in the range of use and the temperature of the recording medium. It is composed of a conversion table data buffer 1102 in which an amount of data is stored, and a circuit for controlling the switching operation.

As a result of the detection in the recording condition determination mode, when it is determined that the content of the edge position adjustment table needs to be changed, and when the light spot moves and the linear velocity changes, a table change command is issued from the controller 12. The signal is input to the counter circuit 1101 to start changing the contents of the edge position adjustment tables 15 and 16. In this content change operation, first, the conversion table data buffer 110
2, the moving speed of the light spot on the recording medium and the temperature of the recording medium detected in the recording condition determination mode are input and stored in the conversion table data buffer 1102.
Determine which edge position adjustment table is to be selected. Then, a conversion table data buffer 1102 is provided for each address number input from the counter circuit 1101.
, Each edge adjustment amount is transmitted and stored in each conversion table. In addition, among the output signals of the counter circuit, 1
The book is used as a table switching signal for selecting one of the edge adjustment amount tables 15 and 16,
The remaining signals are the conversion table data buffer 1102,
And the address signals of the edge position adjusting circuits 15 and 16 are used.

The preceding is an explanation of an embodiment of the present invention. By using this recording pulse edge adjustment amount calculation method, it is possible to eliminate a change in edge position in a reproduced waveform due to thermal interference, which occurs due to a different recording pattern in the same recording pulse.

As the dedicated area used for the recording condition measurement, a plurality of locations including the inner circumference side, the outer circumference side, and between them are used. The area may be specially provided or a general data recording area. In the latter case, if there is already recorded data in that area, use another free area or store the information written in that area to use that area in another memory, such as the memory in the temporary controller. The process of evacuating to the location is performed.

The present invention is a rewritable and is a recording method using heat, the principle of which is any information recording method, and a method of controlling recording conditions such as recording power and recording pulse interval applicable to a recording medium. A recording method and a recording medium which have a particularly high heat diffusion effect and are sensitive to recording conditions, that is, a recording characteristic that appears as a difference in recording characteristics due to slight changes in recording power, environmental temperature, configuration of recording medium, characteristics of recording apparatus, and the like. In the case of, it is an indispensable technology for ensuring the reliability of the recorded data. For example, this technique is important for ensuring practicality in a magneto-optical disk, a magneto-optical disk capable of overwriting using exchange coupling force, an optical disk utilizing phase change capable of overwriting, and the like.

[0107]

According to this signal recording / reproducing method, it is possible to eliminate the variation related to the edge position of the reproduced signal due to thermal interference. In addition, in order to cope with changes in the light beam intensity during recording and the temperature of the recording medium, optimal recording conditions are always realized, and higher-density recording using mark length recording is possible during production. It can be easily realized without strict adjustment,
Moreover, the reliability of the recorded data is greatly improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment.

FIG. 2 is a schematic diagram showing a state in which an edge position shifts due to thermal interference.

FIG. 3 is a diagram for explaining a state in which each edge position of a recording signal is adjusted using information on an edge shift amount to suppress the influence of the edge shift;

FIG. 4 is a diagram illustrating an example of a recording signal pattern for recording condition measurement.

FIG. 5 is a view for explaining means for separately detecting a change in the light beam intensity during recording and a change in the temperature of the recording medium from the measurement result.

FIG. 6 is a flowchart of a recording condition determination mode.

FIG. 7 is a diagram illustrating a configuration example of an edge interval measurement circuit;

FIG. 8 is a diagram for explaining the operation of the edge interval measuring circuit.

FIG. 9 is a diagram illustrating a configuration example of a recording condition determination circuit;

FIG. 10 is a diagram illustrating an example of a configuration of an edge position adjustment circuit and an edge position adjustment table.

FIG. 11 is a diagram illustrating a configuration example of an edge position adjustment table switching circuit;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Spindle motor 2, 3 ... Optical pickup, 4 ... Amplifier, 5 ... Equalization circuit, 6 ... Binarization circuit, 7 ... Reproduction binarization signal, 8 ... PLL circuit, 9 ... Demodulation circuit, 10: Edge interval measuring circuit, 11: Recording condition judgment circuit, 12: Controller, 13: Modulating circuit, 14: Edge position adjusting circuit, 15: Edge position adjusting table, 16
... Edge position adjustment table, 17 ... Laser driver circuit, 18 ... Edge position adjustment table switching circuit, 20
DESCRIPTION OF SYMBOLS 1 ... Recording signal, 202 ... Recording mark, 203 ... Reproduction signal, 204 ... Binarization reproduction signal, 301 ... Recording signal, 30
2: Adjusted signal, 303: Recording mark, 304: Reproduction signal, 305: Binary reproduction signal, 401: Recording signal, 40
2. Reproduction signal, 701: Impulse signal generation circuit, 70
2 A / D converter, 703 integration circuit, 704 integration reference signal, 709 flip-flop, 710 analog switch, 901, 902 latch circuit, 903 subtraction circuit, 904 addition circuit, 905 shift register , 1
001, 1002 ... counter circuit, 1003, 100
4, 1005, 1006 ... Latch circuit, 1007, 10
08: shift register circuit, 1009: selector circuit,
1010: Programmable delay line circuit, 110
1 ... Counter circuit, 1102 ... Conversion table data buffer.

Continuation of the front page (56) References JP-A-3-250466 (JP, A) JP-A-64-23425 (JP, A) JP-A-61-294649 (JP, A) JP-A-61-258367 (JP, A) JP-A-59-60742 (JP, A) JP-A-63-39138 (JP, A) JP-A-64-78437 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB G11B 7/00-7/013 G11B 7/125

Claims (5)

(57) [Claims] In a digital signal recording / reproducing method for performing recording and reproduction by irradiating a recording medium with a light beam, a recording mark having the same recording pulse length is always formed in a constant shape at the time of information recording regardless of recording conditions. As described above, for each of the leading and trailing edges of each recording pulse, the amount of adjustment of the edge position is obtained by using a combination of a plurality of recording pulse intervals at least temporally ahead of the edge, and the amount of edge position adjustment is calculated. A digital signal recording / reproducing method for adjusting each edge position of a recording pulse back and forth by using the method. 2. The edge position adjustment amount is stored in advance in the apparatus as information on recording characteristics as a table.
2. The digital signal recording / reproducing method according to claim 1, wherein the information is obtained based on the data of the table when recording information. 3. The edge position adjustment amount is obtained by recording a recording characteristic in advance on a recording medium and reading the recording characteristic into a dedicated storage area provided on the apparatus side when the recording medium is mounted on the apparatus. 2. A digital signal recording / reproducing method according to claim 1, wherein a table is formed and the information is obtained based on the data of the table when recording information. 4. An overwritable magneto-optical disk or a heavy duty
In a digital signal recording / reproducing method for recording and reproducing a mark length by irradiating a light beam onto a recording medium using a phase change capable of writing, the recording characteristics of the recording medium are stored in advance in the apparatus as a table. A digital signal recording / reproducing method for adjusting the edge position of a recording pulse forward or backward by using data of the table when recording information. 5. An overwritable magneto-optical disk or a heavy duty disk.
In a digital signal recording / reproducing apparatus for recording and reproducing a mark length by irradiating a light beam onto a recording medium utilizing a phase change capable of writing, a storage means which previously stores a table relating to recording characteristics of the recording medium, A digital signal recording / reproducing apparatus comprising: edge position adjusting means for adjusting an edge position of a recording pulse forward or backward using data in the table during recording.