JPH07129959A - Disc recording method and disc recording apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] When data is PWM-recorded on a rewritable optical disk, thermal interference between marks and peak shift due to frequency characteristics at the time of reproduction are compensated at the time of recording to improve a reproduction error rate and high density recording. To achieve. A signal corresponding to a mark for PWM recording is generated by a start pulse generation circuit 2, a burst gate generation circuit 4, and a termination pulse generation circuit 6 at a start portion having a constant width, a burst-shaped intermediate portion, and a termination having a constant width. The signal is decomposed into parts and the binary laser output is switched at high speed to record the signal. The mark / space length detection circuit 89 detects the positions of the start and end of the mark so that the mark length is small. The peak shift caused by thermal interference and reproduction frequency characteristics is compensated at the time of recording by detecting this when the space length before and after the mark and the space length before and after the mark are small and recording while changing the position of the long mark and the space. Is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk recording method and a disk recording apparatus for recording data on a rewritable optical disk by a pit length recording method, and more particularly to shaping the recording data and edge position of a reproduction signal. It is related to record compensation to make

[0002]

2. Description of the Related Art A phase change type optical disk is one of disk-shaped recording media capable of high density recording of data. Data recording on a phase-change optical disk is performed by irradiating a rotating disk with a focused laser beam to heat and melt the recording film. The ultimate temperature of the recording film and the cooling process differ depending on the intensity of the recording laser light, and a phase change of the recording film occurs.

That is, when the laser light is strong, the recording film is rapidly cooled from a high temperature state so that the recording film becomes amorphous, and when the laser light is relatively weak, the recording film is crystallized because the medium temperature is gradually cooled. Turn into. The amorphized portion is usually called a mark, and the crystallized portion is called a space. Then, the binary information is stored in the mark and the space. In addition, the phase change type optical disk is capable of erasing old data and recording new data at the same time with one laser beam, that is, direct overwrite.

At the time of reproduction, weak laser light is emitted so that the recording film does not cause a phase change, and the reflected light is detected.
Amorphized mark portions have low reflectance, and crystallized space portions have high reflectance. Therefore, the difference in the reflected light amount between the mark portion and the space portion is detected to obtain the reproduction signal.

There are a pit position recording method (or pulse position recording method, abbreviated as PPM) and a pit length recording method (or pulse length recording method, abbreviated as PWM) as a method of recording data on a phase change optical disk. The PPM records relatively short marks having a constant pulse length with various spaces, and records information is assigned to the positions of the marks. On the other hand, PW
The M records marks of various lengths with various spaces, and allocates recording information to both the mark length and the space length. Therefore, the information recording density of PWM is higher than that of PPM.

When performing PWM recording, a long mark is recorded as compared with PPM recording. When a long mark is recorded on a phase change type optical disk by irradiating a constant laser power to the mark portion, the width in the radial direction becomes thicker toward the latter half of the mark due to the heat storage effect of the recording film. This seriously impairs the signal quality, such as the unerased portion occurring when direct overwriting is performed, or the signal crosstalk between tracks is generated during reproduction.

Further, as described above, in the phase change type optical disk, the mark portion has a lower light reflectance than the space portion. On the contrary, this means that the mark portion has a higher heat absorption rate. Further, the required heats of fusion differ depending on whether the phase of the recording film is amorphous or crystalline. Therefore, at the time of direct overwrite, even if the same laser power is applied to an existing mark and space for recording, the heat absorption amount and the reached temperature are different, and the edge position of the formed mark varies. Particularly, in the conventional recording method in which the irradiation light amount is weakened in the latter half of the mark, the edge position variation at the end of the mark becomes remarkable, and the deterioration of the overwrite characteristic is a problem.

Furthermore, in order to increase the recording density, it is conceivable to shorten the lengths of marks and spaces to be recorded. In this case, especially when the space length becomes small, the heat at the end of the recorded mark conducts through the space and affects the temperature rise at the start of the next mark, or conversely, the heat at the start of the next recorded mark is generated. Thermal interference occurs that affects the cooling process at the end of the previous mark. When thermal interference occurs in the conventional recording method, the edge position of the mark fluctuates, and there is a problem that the error rate during reproduction increases.

Therefore, in order to solve the above-mentioned problems, the width of a long mark in the radial direction is recorded to be almost constant, the fluctuation of the mark edge position at the time of direct overwriting is reduced, and the mark is small even in a short space. We have already proposed a disk recording method in which thermal interference does not occur and edge position fluctuation does not occur (Japanese Patent Application No. 5-80491).

[0010]

[Patent Document 1] Japanese Patent Application No. 5-80491
In the disk recording method described in No. 6, it was necessary to use a means called adiabatic pulse in order to prevent thermal interference in a short space, and to use three-valued power or more for driving the laser. This has a problem in that, although high performance is obtained, the scale of implementation of the device is increased and the cost is increased.

Further, when the recording marks and spaces are made shorter by further high-density recording and reproducing, even if the marks and spaces having the correct lengths are formed on the disc, the high frequency of the reproducing optical system. Due to the frequency characteristic of the attenuation, there arises a problem that the edge positions of the short marks and spaces detected during reproduction are reproduced differently from the ideal values. The difference between the detected edge and the ideal value is generally called peak shift.

This will be described with reference to FIG. a represents the state of marks and spaces recorded at high density on the disc, and b represents ideal reproduction data in which the edge position of a is geometrically reproduced. c is a reproduced signal waveform when a is reproduced by the disc reproducing apparatus without correction of frequency characteristics, and d is reproduced data obtained by binarizing the reproduced signal c at a slice level. Similarly, e is a reproduction signal waveform when a is reproduced by correcting the frequency characteristic by the disc reproducing device, and f is reproduction data obtained by binarizing e at the slice level. Here, the reproduction data of the short mark g and the short space h portion in FIG.
It becomes a problem that the value is different from.

That is, in the case of c and d in which the frequency characteristic is not corrected at the time of reproduction, the reproduction characteristic of the disk has a high frequency attenuation characteristic, so that the signal of a short mark / space has a high frequency and therefore the amplitude is greatly attenuated. At the slice level position, the width becomes smaller than the ideal value, and peak shift occurs.

On the contrary, in the case of e and f in which the frequency characteristic is excessively corrected at the time of reproduction, the signal of the short mark / space has a large amplitude, and the width becomes larger than the ideal value at the slice level position. A peak shift in the opposite direction occurs.

Therefore, it is possible to set the correction amount of the frequency characteristic to a value at which the peak shift does not occur, but this makes the SNR (signal-to-noise ratio) of the reproduced signal the best and the reproduced data with less noise can be obtained. Does not always match the conditions.

That is, in the high density recording, there is a problem that the peak shift occurs due to the frequency characteristic of the reproducing system in addition to the peak shift due to the thermal interference between the marks during recording.

The present invention solves all of the above-mentioned problems. When data is PWM-recorded on a rewritable optical disk, the width of a long mark is made substantially constant by binary laser power, and further direct overwriting is performed. Provided are a disc recording method and a disc recording device capable of preventing an increase in jitter at the end of a mark during writing and compensating for thermal interference between marks during high-density recording and occurrence of peak shift due to frequency characteristics during reproduction. The purpose is to

[0018]

In order to achieve the above object, the digital recording method of the present invention comprises a first laser beam method.
When the power is higher than the second power, the start and end portions of the mark irradiate the first power with a constant width, and the middle portion of the mark receives the laser light of the first power and the laser light of the second power of the data clock. The data is recorded by alternately irradiating it with a cycle of one cycle or less, and the positions of the start end portion and the end portion of the mark are changed depending on the mark length to be recorded and the space lengths before and after the mark, and the data is recorded.

A disk recording apparatus for embodying the disk recording method includes a start pulse generating circuit for generating a start pulse having a constant width at a start position of a Hi period of data, and a High pulse period of data when the Hi period of data is long. A burst gate generating circuit that generates a burst gate signal at the middle position of the mark and does not generate a burst gate signal when the Hi period of data is short, and a terminating pulse generating a terminating pulse of a certain width at the terminating position of the Hi period of data. Circuit and data H
When the i period is n clocks, an nT mark signal including the start pulse and the end pulse is generated, and the Lo period of data is m.
A mark / space length detection circuit for generating an mT space signal including the end pulse and the start pulse at both ends of the space at the time of the clock (where n and m are natural numbers existing in the data string), the nT mark signal and the mT space An encoder for generating a select signal for controlling a start selector and an end selector, which will be described later, a start selector for selecting and outputting one of a plurality of start set values by the select signal, and the start selector The start end set value output of the selector is updated only when the start end pulse comes, and when it does not come, the start end sample / hold circuit holds the previous value and the start end set value of the output of the start end sample / hold circuit. A programmable delay line for a start point, which outputs a delayed start pulse obtained by delaying the start pulse by changing the delay amount, The termination selector that selects and outputs one of a plurality of termination setting values by the select signal and the termination setting value output of the termination selector is updated only when the termination pulse comes, and when it does not come, the previous A termination sample / hold circuit for holding a value, and a termination sample / hold circuit
A programmable delay line for termination, which outputs a delayed termination pulse obtained by delaying the termination pulse by changing the delay amount according to the termination setting value of the output of the hold circuit, and the burst gate signal and the clock are ANDed to generate the burst signal. An AND gate for outputting, an OR gate for outputting a recording signal by ORing the delayed start pulse, the burst signal and the delayed end pulse, an erase current source for supplying an erase current of a laser diode, and the erase current A recording current source for supplying a recording current of a laser diode in parallel with the source, and turning on / off the current of the recording current source with the recording signal.
It has a configuration including a switch for FF, and a laser diode which is driven in parallel by the erase current source and the recording current source to record a signal on a disk.

[0020]

Therefore, according to the present invention, the signal corresponding to the mark of the PWM recording is decomposed into the fixed width start end portion, the burst-shaped middle portion, and the fixed width end portion, and the binary laser is obtained. The output is switched at high speed and recorded. Then, the intermediate portion of the long mark is irradiated with the minimum power necessary for forming the mark by driving the laser current in a burst shape, so that the mark width does not widen and becomes almost constant. Since the laser light of a constant width is sufficiently irradiated to the start and end portions of the mark, the jitter of the edge portion of the formed mark does not increase even during direct overwriting. In addition, the positions of the beginning and end of the mark
Detects when the mark length is small and when the space length before and after the mark is small, and records by changing the position of the long mark and the space and recording the peak shift caused by thermal interference and reproduction frequency characteristics. Sometimes it will be possible to compensate.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a block diagram of an embodiment of a disk recording apparatus for realizing the disk recording method of the present invention, and FIG. 2 shows a signal waveform diagram of each part of this embodiment.

First, the drawings will be described. In FIG.
1 is data, 2 is a start pulse generation circuit, 3 is a start pulse, 4 is a burst gate generation circuit, 5 is a burst gate signal, 6 is a termination pulse generation circuit, 7 is a termination pulse, 8 is a mark / space length detection circuit, 9 is a 2T mark signal, 1
0 is a 2T space signal, 11 is an encoder, 12 is a select signal, 13 is a plurality of start end set values, 14 is a start end selector, 15 is a selected start end set value, 16 is a start end sample /
A hold circuit, 34 is a hold start end set value, 17 is a start end programmable delay line, 18 is a delayed start end pulse, 19 is a plurality of end set values, 20 is an end selector,
Reference numeral 21 is a selected termination setting value, 22 is a termination sample / hold circuit, 35 is a hold termination setting value, 23 is a termination programmable delay line, 24 is a delayed termination pulse, and 2
5 is a clock, 26 is an AND gate, 27 is a burst signal, 28 is an OR gate, 29 is a recording signal, 30 is an erasing current source, 31 is a recording current source, 32 is a switch, and 33 is a laser diode.

In FIG. 2, a to n are data 1 in FIG. 1, start pulse 3, burst gate signal 5, clock 25, end pulse 7, 2T mark signal 9, 2T space signal 10, select signal 12, hold start setting. Value 3
4, signal waveforms of the delayed start pulse 18, the hold end set value 35, the delayed end pulse 24, the burst signal 27, and the recording signal 29 are shown. o indicates the state of marks and spaces recorded on the disc, p indicates a reproduction signal obtained by reproducing the marks and spaces recorded by the disc reproducing device, and q indicates reproduction data obtained by binarizing the reproduced signals at the slice level. Is.

Next, the operation will be described. In this embodiment, the data 1 has a length of a clock unit, and is PWM data (FIG. 2a) having a Hi period and a Lo period of two clock cycles or more, and the Hi period of the data is marked on the disk and the Lo period is Record according to the space. Also,
The width of the start pulse 3 and the end pulse 7 is one cycle of the clock, and the width of one burst signal 27 is one half of the clock.
Let it be a cycle. Further, the mark / space length detection circuit 8 is
Space length where thermal interference between marks occurs in high density recording,
Also, the mark / space length at which peak shift occurs due to the frequency characteristic of the reproducing system is detected. In this embodiment, the shortest 2T mark and 2T space existing in the data string to be recorded are detected.

First, the start pulse generator 2 generates a start pulse 3 having a width of one cycle of the clock at the start of the Hi period of the data 1 (FIG. 2b). In the burst gate generation circuit 4, a burst gate signal 5 is generated at a mark intermediate position with a length of (mark length-3 clocks). However, when the mark length is 3 clocks or less, the burst gate signal is not generated (FIG. 2c). In the termination pulse generation circuit 6, a termination pulse 7 having a cycle width of the clock is generated at the termination portion of the Hi period of the data 1 (FIG. 2e).

In the mark / space length detection circuit 8,
2 clock width data, that is, 2T mark and 2T space are detected, and when the 2T mark comes, a 2 clock width 2T mark signal 9 is generated so as to include the start pulse and the end pulse of the 2T mark (FIG. 2f). When the 2T space arrives, the 2T space signal 10 having a 4-clock width is generated so as to include the end pulse and the start pulse at both ends of the 2T space (FIG. 2g).

In the encoder 11, the attributes of the start pulse 3 and the end pulse 7 are determined by the 2T mark signal 9 and the 2T space signal 10, and the select signal 1 is selected.
Output as 2. That is, 3T or more mark is 3T or more space normal, 3T or more mark is 2T space 2Ts, 2T mark is 3T or more space 2
If the 2T space is classified into 4 types of attributes named 2Ts-2Tm with Tm and 2T marks, for example, in FIG. 2, the start pulse 100 is 2Ts, the end pulse 101 is normal, the start pulse 102 is 2Tm, and the end pulse 103 is 2Ts-2Tm (Fig. 2h).

Next, in the start end selector 14, a plurality of start end set values 13, that is, the start end set value at the time of normal, the start end set value at 2Ts, the start end set value at 2Tm, and 2Ts-2Tm are set. One of the starting end set values of 1 is selected by the select signal 12 and the selected starting end set value 15 is output. In the starting end sample / hold circuit 16,
It is updated only when the start pulse 3 comes, and when the start pulse 3 does not come, it holds the previous value and outputs it as the hold start set value 34 (FIG. 2i). Then, in the start-end programmable delay line 17, the start-end pulse 3 is output as a delayed start-end pulse 18 after a delay time of a value based on the hold start-end set value 34 (FIG. 2j).

Similarly, the termination selector 20 selects one of the plurality of termination setting values 19 by the select signal 12 and outputs the selected termination setting value 21, and the termination sample / hold circuit 22 outputs the termination pulse 7 When the end pulse 7 does not come, the previous value is held and output as the hold end set value 35 (FIG. 2k).
Then, in the terminating programmable delay line 23, the terminating pulse 7 is output as a delayed terminating pulse 24 after a delay time of a value based on the hold terminating set value 35 (FIG. 21).

Further, the AND gate 26 logically ANDs the burst gate signal 5 and the clock 25 to generate a burst signal 27 (FIG. 2m). In the OR gate 28, the delayed start pulse 18 and the burst signal 2
7 and the delayed end pulse 24 are logically summed to obtain the recording signal 2
9 (FIG. 2n).

The laser diode 33 is the erase current source 30.
Is biased to emit the erasing power of the phase change type optical disk. A recording current source 31 is provided in parallel with the erasing current source 30 and a switch 32 is used to provide the recording current source 3
When the current of 1 is turned on / off, the laser diode 3
The drive current of 3 can be switched between the recording current and the erasing current. That is, by controlling the switch 32 with the recording signal 29, the laser diode 33 can be made to emit light while switching between recording power and erasing power, and an optical head (not shown) incorporating the laser diode 33 is used. , Marks and spaces are formed on the phase-change optical disk (FIG. 2o).

With the above series of operations, the disk recording apparatus of the present embodiment changes the positions of the start and end portions of the mark depending on the mark length for recording and the space length before and after the mark, respectively, to generate PWM data. Corresponding marks and spaces can be recorded.

FIG. 4 shows an embodiment of a disc reproducing apparatus for obtaining a reproduction signal from a disc on which data is recorded. In FIG. 4, 200 is a disc on which data is recorded, 201 is a spindle motor for rotating the disc 200, 202 is an optical head for obtaining a reproduction signal from the disc 200, 203 is a preamplifier for amplifying the reproduction signal, and 204 is a reproduction. An equalizer 205 corrects the frequency characteristic of the signal, a comparator 205 which binarizes the reproduction signal 208 of which the frequency characteristic is corrected by a slice level voltage 206, 2
Reference numeral 07 is the obtained reproduction data.

Reproduction signal 208 and reproduction data 207 of FIG.
Has a waveform like p and q in FIG. According to this embodiment, the obtained reproduction data 207 (FIG. 2q) has the same waveform as the data 1 (FIG. 2a) before recording.
The frequency characteristic of the equalizer 204 may be flat, but the high frequency attenuation characteristic of the reproduction system of the disc is corrected to prevent peak shift, and the frequency distribution of the noise included in the reproduction signal 208 is changed to change the SNR of the reproduction signal. It is desirable to set the characteristics such that the (signal to noise ratio) is improved and the reproduction error rate is improved. However, it is often difficult to implement an equalizer having characteristics that maximize both the peak shift and the SNR.

However, in the disk recording apparatus of the embodiment of the present invention, the optimum values in accordance with the reproduction frequency characteristics of the disk reproducing apparatus to be used are respectively used as the plurality of start end setting values 13 and the plurality of end setting values 19. You can Therefore, the equalizer 204 realizes the reproduction frequency characteristic in which the SNR of the reproduction signal is the best, and the peak shift generated at that time is compensated by the disk recording apparatus of the present embodiment, so that the start and end edges of the reproduced marks and spaces are reduced to noise. It has less jitter and can be detected at an accurate position.

In this embodiment, the rewritable optical disk has been described by taking the phase change type optical disk as an example, but the same operation can be performed with a magneto-optical disk. However, when performing optical modulation recording on a magneto-optical disk, a binary output of laser light is used as a binary output of recording power and zero or reproduction power.
Use the type. Further, the widths of the start pulse and the end pulse are not limited to one cycle of the clock and may be other values. However, if one clock cycle is used as in the present embodiment, a pulse having one clock cycle width can be easily generated by the synchronous circuit, so that there is a great advantage that the implementation circuit scale can be reduced. For the same reason, the width of the burst signal may be ½ cycle of the clock that can be directly generated from the clock.

[0037]

As described above, according to the disk recording method and the disk recording apparatus of the present invention, in the application of recording data on the rewritable optical disk by the pit length recording method, the fluctuation of the edge position of the recording signal is suppressed to the minimum. It is also possible to improve the overwrite characteristics. Furthermore, it is possible to compensate in advance for the edge position variation of the reproduction data caused by the frequency characteristic of the reproduction system during recording.
Therefore, the error rate of the disc reproducing apparatus can be improved, and as a result, the data recording density can be significantly improved. Therefore, when it is used in an image file device having a huge amount of data information, its performance improving effect is remarkable.

[Brief description of drawings]

FIG. 1 is a block diagram of a disk recording apparatus according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram of each part of the disk recording apparatus in the embodiment of the present invention.

FIG. 3 is a signal waveform diagram for explaining a problem to be solved by the present invention.

FIG. 4 is a block diagram of a disc reproducing apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 2 start edge pulse generation circuit 4 burst gate generation circuit 6 end pulse generation circuit 8 mark / space length detection circuit 11 encoder 14 start edge selector 16 start edge sample / hold circuit 17 start edge programmable delay line 20 end edge selector 22 end edge sample / Hold circuit 23 Programmable delay line for termination 26 AND gate 28 OR gate 30 Erase current source 31 Recording current source 32 Switch 33 Laser diode

Claims (5)

[Claims] 1. A disk recording method for irradiating a disk-shaped storage medium with laser light of a plurality of powers switched and recording data as length information of marks and spaces, wherein the first power of the laser light is a second power. When the power is larger than the power, the start and end portions of the mark are irradiated with the first power having a constant width, and the middle portion of the mark is irradiated with the laser light of the first power and the laser light of the second power within one cycle of the data clock. A disk characterized in that data is recorded by irradiating by switching alternately in a cycle, and the positions of the start end portion and the end portion of the mark are changed at any time depending on the mark length to be recorded and the space length before and after the mark, and then recorded. Recording method. 2. The width of the start and end portions of the mark is about one cycle of the data clock, and the switching period of the middle portion of the mark is about one half cycle of the data clock. Disc recording method described. 3. The positions of the start and end portions of the mark are set so that the reproduction data obtained by binarizing the frequency characteristic of the reproduction signal of the disc without correction has the original mark length and space length. The disc recording method according to claim 1, wherein the recording is performed under control. 4. The positions of the start and end portions of the mark are set so that the reproduction data obtained by correcting the frequency characteristic of the reproduction signal of the disc and binarizing it have the original mark length and space length. The disc recording method according to claim 1, wherein the recording is performed under control. 5. A data Hi period is marked on the disc.
A disk recording device for recording a Lo period in correspondence with a space, and a start pulse generating circuit for generating a start pulse of a constant width at a start position of a Hi period of data, and an intermediate mark between marks when the Hi period of data is long. A burst gate signal that generates a burst gate signal at a position and does not generate a burst gate signal when the Hi period of data is short; and a termination pulse generation circuit that generates a termination pulse of a certain width at the termination position of the Hi period of data, When the data Hi period is n clocks, an nT mark signal including the start pulse and the end pulse is generated, and when the data Lo period is m clocks, the mT space signal including the end pulse and the start pulse at both ends of the space is generated. With the generated mark / space length detection circuit (however,
n and m are natural numbers existing in the data string), an encoder for generating a select signal for controlling a start end selector and a end selector described later from the nT mark signal and the mT space signal, and a plurality of start ends by the select signal. A selector for the start end that selects and outputs one from the set values,
A start end sample / hold circuit that updates the start end set value output of the start end selector only when the start end pulse comes, and holds the previous value when it does not come, and a start end of the output of the start end sample / hold circuit. A programmable delay line for a start end that outputs a delayed start pulse by delaying the start pulse by changing the delay amount according to a set value, and a end for selecting and outputting one of a plurality of end set values by the select signal. A selector and a termination sample / hold circuit for updating the termination set value output of the termination selector only when the termination pulse comes and holding the previous value when the termination pulse does not come; and a termination sample / hold circuit. A programmable delay line for termination that outputs a delayed termination pulse obtained by delaying the termination pulse by changing the delay amount by the termination setting value of the output, An AND gate for outputting a burst signal ANDs serial burst gate signal and the clock,
An OR gate that outputs a recording signal by ORing the delayed start pulse, the burst signal, and the delayed end pulse, an erase current source that supplies an erase current of the laser diode, and a laser diode in parallel with the erase current source. A recording current source for supplying the recording current, a switch for turning on / off the current of the recording current source with the recording signal, and a laser diode which is driven in parallel by the erasing current source and the recording current source to record a signal on a disk. A disk recording device comprising: