JP2707774B2 - Optical information recording method and recording apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recording a signal on an optical information recording member centered on an optical disk for recording and reproducing optical information at high speed and high density using a laser beam or the like, and It relates to a recording device.

2. Description of the Related Art Techniques for reproducing or recording high-density information using a laser beam are known, and are mainly used as optical disks. Optical discs are read-only, write-once,
They can be broadly classified into rewritable types.

The read-only type includes a compact disc (hereinafter referred to as CD) on which music information is recorded, and a laser video disc (hereinafter referred to as LVD) on which image information is recorded. In these, signals are recorded in advance on an optical disk, and the user can reproduce music and video information, but cannot record signals.

In addition, a write-once type records a signal by providing a metal thin film, a Te alloy, an organic thin film, etc. as a recording film on a substrate, and irradiating a laser beam or the like to make a change in the recording film such as making a hole or providing irregularities. Things.

Further, the rewritable type uses a recording thin film that reversibly changes between two or more states by changing the irradiation conditions of a laser beam or the like, and the main types are a magneto-optical type and a phase change type. The magneto-optical type uses a ferromagnetic thin film as a recording thin film, and records a signal by changing the direction of the magnetic domain. The phase change type mainly uses a Te alloy or a Se alloy as a recording thin film, and records a signal by changing the state of the recording thin film between an amorphous and a crystal or between a crystal and a crystal having a further different structure.

Both the write-once type and rewritable type recording utilize the temperature rise of the recording medium by irradiation with a laser or the like, and are therefore called heat mode recording. One of the problems of the heat mode recording is that the recording mark shape is not symmetrical in the longitudinal direction but is distorted like a teardrop.

In the case of recording with a signal waveform as shown in FIG. 20 (a), the temperature reached by the recording film is lower at the leading end as shown in FIG. as a result,
A teardrop-shaped recording mark as shown in FIG.

This distortion of the recording mark leads to distortion of the reproduced waveform and causes an increase in jitter. For this reason, the inventors have filed Japanese Patent Application No. 1-17.
[0207] In No. 0207, a recording method and a recording apparatus for reducing the shape distortion of the recording mark with a very simple apparatus structure were proposed.

In recent years, the development of optical discs has been focused on rewritable discs. One of the advantages that the phase change discs have over magneto-optical discs is that old recording marks recorded by a single laser spot can be used. Recording a new signal while erasing the signal, that is, so-called one-beam overwriting, can be easily realized (Japanese Patent Laid-Open No. 56-145530).
No.).

This is to record a new signal while erasing an old signal by modulating the laser power between two powers, a recording level and an erasing level, when recording a new signal, as shown in FIG. is there. However, even in this method, teardrop-like distortion of the recording mark occurs.

As means for solving this, JP-A-63-266632,
JP-A-63-279431, JP-A-1-150230, and JP-A-1-253828 have been proposed.

JP-A-63-266632 and JP-A-63-279431 disclose that a recording waveform for forming one recording mark is constituted by a pulse train composed of short pulses of the same shape.
Japanese Patent Laid-Open No. 1-150230 further discloses that a recording waveform for forming one recording mark is constituted by a pulse train composed of a plurality of pulses, and the pulse width and pulse interval are variously changed. Japanese Patent No. 253828 proposes that not only the recording waveform but also erasure is modulated into a pulse train, and the duty of the irradiation light pulse is gradually reduced to reduce the shape distortion of the recording mark.

Problems to be Solved by the Invention The above-described methods of reducing the shape distortion of the recording mark in one boom overwrite have respective problems.

JP-A-63-266632 and JP-A-63-279431 can be realized by a device having a simple structure, but the effect of improving shape distortion is small. Also, JP-A-1-150230,
Japanese Unexamined Patent Publication No. 1-253828 has a disadvantage that, although a large distortion reduction effect can be expected in some cases, the device configuration becomes very complicated. That is, there has not been a recording method and a recording apparatus based on one-beam overwriting that form a recording mark with small shape distortion by a very simple apparatus configuration.

An object of the present invention is to provide a recording method and a recording device that solve the above-mentioned problems.

Means for Solving the Problems In order to solve the above problems, the present inventors have disclosed in Japanese Patent Application No. Hei.
The optical information recording method and apparatus proposed in Japanese Patent No. 170207 were further improved, and a recording method and a recording apparatus by one-beam overwriting that form a recording mark with small shape distortion by a very simple apparatus configuration were newly developed.

That is, a method of recording optical information in which a recording mark is overwritten on the information layer by irradiating a laser beam driven by a pulse width modulated signal onto an optical information recording medium having a phase change type information layer. The recording mark is erased by irradiating a laser at an erasing level at which the information layer forms a crystalline state, and the recording mark is formed by irradiating a pulse train including a start end, an intermediate portion, and an end. The intermediate portion irradiates a laser beam that is alternately switched at a constant period between a recording level at which the information layer forms an amorphous state and a level lower than the recording level, and the start end portion is included in the intermediate portion. Irradiate a laser beam of the recording level having a pulse width equal to or greater than the pulse width of the recording level, and the terminal portion is changed from the recording level to a level smaller than the erase level Gaité irradiated for a predetermined period held laser radiation. In the present invention, the erase power level may be further pulse-modulated.

The recording method is realized by irradiating a laser beam driven by a pulse width modulated digital signal on an optical information recording medium having a phase change type information layer, thereby overwriting a recording mark on the information layer. A method for recording optical information, wherein the erasing of a mark includes a means for flowing a current of a constant erasing level at which the information layer forms a crystalline state to a laser, and the formation of a recording mark includes the step of erasing one recording mark. As a means for performing irradiation by a laser pulse train composed of a plurality of pulses, a pattern setter that previously sets a pattern of a recording pulse train corresponding to the longest pulse width of an input signal, and a pattern setter having a length equal to or less than the longest pulse width of the input signal A modulator that cuts out a required length from the beginning of a setting recording pattern of the pattern setting device in order to form a pulse train corresponding to a pulse width. , Carried out by a recording apparatus having means for modulating the drive current of the laser by the pulse Stringified signal from the transducer.

The method of recording optical information by overwriting according to the present invention is capable of sufficiently erasing a recording mark and, at the same time, forming a recording mark, because the pulse width near the starting end is wide, so that the temperature reached by the recording film even at the starting end. It is sufficiently high, and it is possible to reduce teardrop-shaped distortion caused by a thinned recording mark at the start end.

In the optical information recording apparatus according to the present invention, all necessary patterns can be generated from one or two signal patterns set in advance, so that the recording method can be realized with a very simple configuration.

Embodiments The present invention will be described below in detail with reference to the drawings.

The most important feature of the optical information recording method according to the present invention is that when forming a recording mark corresponding to a new signal while erasing the recording mark, for example, as shown in FIG. In the case of recording a digital signal that changes discretely from to 11T, the laser signal is shaped as shown in FIG.
The purpose is to record a signal on an optical disk by performing modulation as shown in FIG.

First, the reason for modulating the laser light as shown in FIG. 1 (b) will be described.

In FIG. 4B, Pb is an erasing power level, and by keeping the laser power constant at this level, the amorphous portion is crystallized, that is, the recorded marks that have been recorded are erased.

When a new signal is recorded, that is, when a new recording mark is formed, the laser power is increased to the recording power level Pp and pulse modulation is performed.

For example, in the case of recording a signal as shown in FIG. 21 (a) in the heat mode recording, if a laser beam is directly modulated by a signal waveform and overwritten, a recording mark distortion as shown in FIG. 21 (c) occurs. Various recording methods as described above have been proposed.

These methods propose a means of controlling the heat of the laser beam irradiation part and keeping the overall temperature of the recording mark constant, and the phenomenon that the recording mark becomes thicker at the end and becomes teardrop-shaped Trying to prevent.

However, according to these conventionally proposed methods, there are actually problems such as (1) the effect of preventing the recording mark from becoming tear-drop-shaped and (2) the recording device becoming complicated.

Therefore, the present inventors have studied in detail an overwriting method that reduces distortion of a recording mark and does not complicate the device configuration.

As a result, in order to prevent teardrop-like distortion of a recording mark, (1) a signal pulse for forming one recording mark is modulated into a pulse train composed of a plurality of short pulses, and (2) at least a pulse train of the pulse train is formed. The pulse width at the start end is wider than the pulse at the intermediate portion following the pulse at the start end to optimize.

Was found to be effective.

Next, in order to realize the above method with a simple apparatus configuration, (3) the peak power at the time of recording is kept constant, and the achieved temperature is controlled by changing the pulse width. (4) The signal pulse is pulse trained. In such a case, the pulse width of the signal pulse and the number of pulses included in the pulse train are maintained in a constant relationship (for example, if the pulse width of the signal pulse is increased by one, the number of short pulses included in the pulse train is reduced by one. (5) The pulse width of the short pulse to be added is always constant.

As a recording method by one-beam overwriting that satisfies the above recording conditions (1) to (5), for example, a modulation method as shown in FIG. 2B is proposed. In other words, during the signal recording period, the erasing bias power Pb is constantly applied to the recording track, and when forming a recording mark, only the pulse at the beginning is wider than the intermediate pulse following the pulse at the beginning. And the intermediate pulses are all equal in pulse width. One pulse is added as the pulse width of the input signal becomes longer by T, and the laser is biased by a modulation signal having a repetition period T of the intermediate pulse. Irradiation is performed by modulating between Pb and peak power Pp.

Such a modulation method can be easily realized by the optical information recording apparatus of the present invention, which will be described later, and the distortion of the recording mark in a teardrop shape can be greatly reduced.

In addition, the modulation waveform of FIG.
Alternatively, a modulation waveform as shown in FIG. That is, at the time of recording mark formation, the laser power is modulated between the peak power level Pp and the reproduction power level Pr or the power off level (0 level). In this case, since the film is rapidly cooled after being irradiated with a short pulse, an amorphous recording mark is easily formed. In (c), when shifting from the erasing power level Pb to the recording power level Pp or conversely, when shifting from the recording power level Pp to the erasing power level Pb, the reproduction power level Pr (power off may be used). Therefore, the temperature change at the beginning and end of the recording mark becomes sharp, and the boundary between the crystal and the amorphous, that is, the edge position of the recording mark becomes clear.

Further, as a recording method of a different mode according to the present invention, a laser power modulation method shown in FIG. 4B or FIG. 4C is proposed. In these methods, the erasing laser light is also pulse-modulated on the condition that it can be realized with a simple device configuration.

The advantage of pulse-modulating the erasing laser light will be described with reference to FIG. FIG. 5 (a) shows a recording method by one-beam overwriting when the erasing laser beam is not modulated, and FIG. 4 (c) shows a recording method by one-beam overwriting when the modulation is performed, and FIGS. The temperature reached by the recording film is shown. The recording film has a crystallization temperature Tx higher than room temperature T0.
By maintaining the above conditions, the amorphous portion is crystallized, and the temperature is raised to the melting point Tm or more.

In this case, it is important to (1) keep the temperature of the recording film constant at the time of forming and erasing the recording mark, and (2) at the time of moving from recording to erasing and from erasing to recording.
This is to end the temperature change in a short time.

According to (1), the formation distortion of the recording mark is reduced, and the rate at which the recording mark is erased is kept constant. (2) The starting and ending edge positions of the recording mark are clarified, and the jitter of the reproduced waveform is reduced. (In particular, it is important to quench at the end to clarify the edge).

By pulse-modulating the erasing laser light, the reproducing power level Pr (power off may be turned off) when the erasing power level Pb changes from the recording power level Pp to the recording power level Pp and vice versa. And it is possible to reduce the gradual rise in the reached temperature at the time of erasing. This recording method follows the end of the recording mark more than the method of FIG. 3 (c).
There is an advantage that the time to become Pr can be extended, that is, rapid cooling can be performed.

The recording methods described so far are based on the premise that they can be realized by a recording apparatus having a simple configuration, and a specific configuration of a recording apparatus according to the present invention will be described below.

FIG. 6 is a block diagram of an optical information recording apparatus according to the present invention for obtaining the waveform of FIG. 1 (b). During a signal recording period, that is, when the recording gate signal Wg is input, a bias current Ib for obtaining bias power (that is, erasing power) Pb flows through the semiconductor laser.

When a recording mark is formed, the switch 4 is operated by the s4 obtained by processing the recording signal s1 from the signal generator 1 by the modulator 2 to superimpose Ia on Ib, and the semiconductor laser incorporated in the optical head 5 Drive the peak power Pp
Is irradiated on the optical disk 7 being rotated by the spindle motor 6.

The greatest feature of this device lies in a modulation method for processing the signal s1 into s4.

The signal s1 to be recorded is transmitted from the signal generator 1 to the modulator 2 first.
Is input to This signal is a digital signal that has been subjected to pulse width modulation (PWM), and in the past, generally, this signal itself was used to drive and record a laser.

However, the modulator according to the present invention further converts each pulse in the input signal into a pulse train. The modulation method is based on the input signal s1
The modulation pattern corresponding to the longest pulse width included in
It is set in the pattern setting device 3 in advance. The modulator 2 detects the pulse width in s1, cuts out a required length from the beginning of the setting pattern of the pattern setting device 3 according to the length, generates a pulse train, outputs the pulse train, and outputs the switch 4 to the switch 4. Activate.

Therefore, by setting only one pattern for pulses having different pulse widths included in the input signal, all patterns can be converted into a pulse train. Further, the shape of the pattern to be set can be easily optimized so that the reproduced waveform distortion is minimized. Note that the input signal generator, modulator, and pattern setter are connected to the same clock C1 (an integer multiple of the input signal clock) so that the edge position of the input signal from the signal generator does not fluctuate due to the modulation of the pulse train. It is preferable to suppress the jitter of the recording signal by synchronizing with the above.

The modulator 2 and the pattern setting device 3 in FIG. 6 are hereinafter referred to as a multi-pulse circuit (referred to as an MP circuit) for simplicity.

The reference voltage setting circuit 9 in FIG. 6 generates a voltage necessary for obtaining Ib and Ia when the recording gate signal Wg is input. When Wg is off, the semiconductor laser emits light at the reproduction power Pr, and at this time, the current Ir flows.

FIG. 7 shows a specific configuration of the modulator 2. The rising detector detects the rising edge position of the pulse of the input signal s1 and sends a start signal to the pattern generator 12.
After the pattern generator sets the pattern setter 3 by the start signal and calls the pulse train pattern,
Transmission is started as a modulation signal one step at a time from the beginning.

Thereafter, the rising edge detector 10 detects the edge position of the falling edge of the pulse of the input signal s 1, and sends a stop signal to the pattern generator 3. In response to the stop signal, the pattern generator stops sending the set pattern, that is, the modulated signal, and waits for the next input signal pulse. Therefore, a pulse-like modulation signal s4 having a length corresponding to the input pulse width is always transmitted from the pattern generator.

In this case, rise detector 10 and fall detector 1
1. Since all the pattern generators 12 operate in synchronization with the clock C1, the jitter of the modulated signal to be recorded can be suppressed.

 Next, specific examples of the present invention will be described.

Embodiment 1 FIG. 8 shows a block diagram of an MP circuit used in this embodiment. As the input signal s5, an EFM (8-14 modulation) signal used for a music reproduction CD was used. EFM from 3T to 11
This is a PWM signal composed of nine types of pulses having different pulse widths up to T. Here, T is a clock cycle, and T = 230 nsec. Modulated pulse example signal s12
In the same manner as in FIG. 6, the switch 14 is operated to drive the laser, and a signal is written on the optical disk.

As the optical disk, a rewritable layer-change type optical disk having the structure shown in FIG. 9 was used. As the optical disk substrate 21, a 5 ″ polycarbonate substrate on which signal recording tracks were formed in advance was used. The recording film 23 was made of a TeGeSb-based material and had a thickness of 400 °.
A protective film 22 made of ZnS is provided above and below the recording film, and a reflective film 24 made of Au is provided on the side opposite to the incident side of the laser beam.
Then, a back cover 26 for protecting these thin films was provided.

The recorded state and the erased state of the signal correspond to the amorphous state and the crystalline state of the recording film, respectively. In a signal recording experiment, a signal was recorded in advance on a recording track, and a new signal was recorded thereon by one-beam overwriting while erasing a previously recorded recording mark. The relative speed between the optical disk and the recording spot of the converged laser beam was 1.25 m / sec.

Evaluation of the recorded signal was performed by measuring the jitter of the reproduced signal. The jitter is defined as the standard deviation by repeatedly measuring the time from one zero cross to the next zero cross for each of nine types of pulses having different pulse widths, using the zero cross of the reproduced waveform as a judgment level.

Here, the operation principle of the MP circuit of FIG. 8 will be described with reference to the timing chart of FIG.

This circuit corresponds to the longest pulse width 11T, a pulse train consisting of 44 regions is set in the pattern setting unit 18 in advance, and is set according to the pulse width of the input 3T to 11T pulse. A pulse train of a required length is created from the beginning of the pattern and sent to the laser drive circuit. In other words, the clock cycle T of the EFM signal s5 is divided into four, T
/ 4 is the clock C2 of this circuit system. Note that the timing chart of FIG. 10 shows a case where a 4T pulse is converted into a pulse train.

First, when the EFM signal s5 is input, a start signal s9 is generated by the data flip-flops DFF13 and DFF14 and the NAND15, and the parallel-in / serial-out shift register: P
S / SR17 starts. The PS / SR 17 calls the setting pattern from the pattern setting unit 18 and sends out the setting pattern one step at a time in synchronization with the clock C2. A pattern setting method is performed by providing switches SW1 to SW44 for each of 44 steps corresponding to the longest pulse width 11T. Therefore, an arbitrary pattern can be set by turning on / off each switch.

Next, a stop signal s10 is generated by DFF13, DFF14, and NAND16. In the case of a 4T pulse, the stop signal s10 synchronized with the 16th clock is output. This stop signal causes PS / SR
The output of the 17-step transition from 17 stops, and a pulse train like s12 is eventually obtained. The DFF 20 resynchronizes the pulse train and the clock to reduce jitter, and then sends the pulse train to the laser drive circuit. In this way, all the pulses of 3T to 11T can be formed into a pulse train in the shape of the set pattern.

With this device, the setting pattern shown in FIG.
Using the modulation waveform in the case of 11T, the EFM signal was pulse trained in accordance with this pattern, the laser was modulated and driven, the signal was overwritten, then reproduced and the jitter of the reproduced signal was measured.The overwrite bias power Pb was 4 mW.

Fig. 11 shows the recording power Pp (value on the optical disc surface)
2 shows the relationship between the jitter and the jitter. Fig. 11 shows the measurement results of jitter when the signal is overwritten by directly modulating the laser with the EFM signal, which is a conventional general recording method.
Shown for comparison.

As is clear from FIG. 11, according to the recording method and the recording apparatus of the present invention, since the waveform distortion of the recording mark is reduced, the jitter of the reproduced waveform is also reduced, and thus the error rate of the reproduced signal can be reduced, The recording density can be improved.

Although the pattern setting in FIG. 8 is performed by turning on and off the switches SW1 to SW4, for example, a ROM (reproduction only memory) in which a setting pattern is recorded in advance as a pattern setting device may be used. If a ROM is used, since this circuit does not include a delay element or the like, it can be integrated, and the device can be downsized.

(Example 2) Next, using the apparatus shown in Example 1, the relationship between the set pattern and the jitter was obtained by variously changing the waveform set in the pattern setting unit. The measuring method of the input signal, the optical disk, the relative speed between the optical disk and the recording spot, the bias power, and the jitter are the same as those in the first embodiment. FIG. 12 shows the measured pattern shapes, and Table 1 shows the jitter values measured for the signals reproduced after recording with the respective waveforms. The jitter is the minimum value when the recording peak power is changed, and the recording peak power at that time is also shown in Table 1.

As can be seen from Table 1, patterns (h), (k),
Except for (l), the jitter is as small as 100 nsec or less. Patterns (h), (k) and (l) are comparative examples for the present invention. The pattern (l) is equivalent to a method of driving the laser with the EFM signal itself, and shows a large jitter. The pattern (k) is a pattern in which short pulses having the same pulse width are arranged at equal intervals and recorded as a pulse train. Although the jitter is improved as compared with the pattern (1), the pattern (k) has a large jitter. This is probably because the temperature does not rise sharply at the start end, and the start end of the recording mark is thin. Also, the jitter is increased in the pattern (h).

In any case, the recorded mark is erased by irradiating the laser with the laser power kept constant at the erasing power level, and the recording mark is formed by recording a recording waveform for forming one recording mark by a plurality of pulses. After the pulse train is formed, the laser power is modulated, and the pulse width of at least the start pulse of the recording pulse train is made larger than the pulse width of the intermediate pulse following the start pulse. Is constant, each pulse width in the middle part pulse train is equal to the pulse period, and the number of pulses in the middle part when forming the n-th recording mark is na + b (a and It is understood that jitter can be suppressed to a small value if the condition that b is a constant and a is a positive integer and b is an integer is satisfied.

In particular, the patterns are (a), (f), (g),
When (j), (m), (n), and (o), the jitter is 50
nsec or less. These features include: increasing the width of the next pulse at the beginning or at the beginning, adding one pulse if the subsequent intermediate pulse has the same pulse width and the same pulse interval, and the recording mark length increases by one In this case, the period of the intermediate pulse is T. In addition,
(A), (f), (g), (j), (m), (n),
Each pattern of (o) is represented by (a), (j): a = 1, b = 0,
(F), (g), (m), (n), (o): a = 1, b = −
It is when it is set to 1.

When the pulse width of the intermediate pulse is short as seen in the patterns (n) and (o), the cooling rate after irradiation increases with each pulse, and the jitter decreases.

The MP circuit used in this experiment divided the 11T signal pulse into 44, but if it is further divided into 88, the pulse width of the intermediate pulse following the start pulse can be set to T / 8. However, if a further fine division is attempted, the clock frequency of the MP circuit becomes too high, and circuit design becomes difficult.

That is, in consideration of the results shown in Table 1 and the ease of circuit design, it is considered that the pulse width of the intermediate pulse is preferably set to T / 8 or more and T / 2 or less.

(Example 3) Further, using the same apparatus as in Examples 1 and 2, the patterns (d) and (g) of Example 2 are set in the pattern setting unit,
The blood of jitter was determined while changing the relative speed between the optical disk and the recording spot. The measuring method of the input signal, the optical disk, and the jitter is the same as in the first embodiment.

FIG. 13 shows the relationship between the measured jitter value and the relative speed in the reproduced signal.

For the jitter, the minimum value was obtained by changing the recording peak power and the bias power, and the value was recorded. In both patterns (g) and (d), the jitter increased when the relative speed was high. The increase in jitter occurs at a lower relative speed in (g) than in pattern (d), and the point is the repetition period of the intermediate pulse (T = 230 ns in pattern (g)).
In c and (d), T / 2 = 115 nsec coincides with the vicinity where λ / L (λ is the wavelength of the laser and 0.83 μm in this embodiment, L is the relative speed).

This is because the distortion generated in the recording mark due to the intermittent irradiation of laser light has a magnitude on the order of the wavelength of the laser light and is reproduced optically, resulting in distortion of the reproduced waveform and increased jitter. It is thought to be.

Therefore, it is better to set the repetition period of the intermediate pulse so that τ ≦ λ / L τ: the repetition period of the intermediate pulse λ: the wavelength of the laser L: the relative speed between the optical disk and the recording spot.

In the above-described first to third embodiments, the pulse train is modulated between the bias power level Pb and the peak power level Pp as shown in FIG. 1 (b). Next, as shown in FIGS. 3 (b) and 3 (c). Next, a recording apparatus that modulates between a peak power level and a reproduction power level Pr will be described.

FIG. 14 shows the configuration. EFM signal s from signal generator 1
5 is input to the MP circuit 21 similar to that shown in FIG. 5, is modulated into a pulse train, is output as a signal s12, and operates the switch 24. At the same time, the signal s13 from the Q of DFF14 in FIG.
After the phase is adjusted by the DFF 22, the signal s14 is generated via the inverter 23, and the switch 25 is operated. Thus, when the input signal s5 has a waveform as shown in FIG. 15 (a), s12 and s14 are as shown in (b) and (c), respectively.

That is, since the bias current Ib does not flow when forming the recording mark, the semiconductor laser has the peak power Pp
And reproduction power Pr. In the erasure area, since the bias power is maintained at Pb, the already recorded recording mark is crystallized. Note that the recording gate signal
If the reference voltage setting circuit 26 is set so that Ir does not flow when Wg is input, the peak pulse
Modulated between Pp and power off.

 Next, a detailed example using this recording apparatus will be described.

(Example 4) As setting recording patterns, (a), (f),
(M) was used. The measuring method of the input signal, the optical disk, the relative speed between the optical disk and the recording spot, the bias power, and the jitter are the same as those in the second embodiment. Table 2 shows the jitter values measured for the signals recorded and reproduced after each waveform. The jitter is the minimum value when the recording peak power is changed, and the recording peak power at that time is also shown in Table 2.

This result is smaller than the jitter corresponding to each waveform in Table 1. This is when the recording mark is formed
This is presumably because the cooling rate after the short pulse irradiation was high, so that the film was easily made amorphous and a large recording mark was obtained. In particular, in the case of the waveform (m), the effect of reducing jitter is great. This is the peak power from the bias power Pb
Contrary to the case of shifting to Pp, bias power is changed from peak power Pp
This is presumably because the transition to Pb temporarily passes the reproduction power level Pr, so that the temperature change of the recording film becomes sharp before and after the recording mark, and the edge position of the recording mark becomes clear.

In the first to fourth embodiments, the recording method and apparatus in which erasing is performed by irradiating with a constant bias power have been described. Next, a case where the erasing power is pulse-modulated as shown in FIGS. 4 (b) and 4 (c) will be described. explain.

FIG. 16 shows a configuration of a recording apparatus for obtaining a waveform as shown in FIG. 4 (b). The EFM signal s5 from the signal generator 1 is
The signal is input to the MP circuit A27 similar to that shown in FIG. 8, is modulated into a pulse train, and is output as a signal s12. At the same time, the signal s5 is supplied to the MP circuit B28 via the inverter 29.
Is also entered.

The MP circuit B is exactly the same as the MP circuit A, and is for pulse-modulating the erasing laser light. For example, when the waveform shown in FIG. 17A is set in the pattern setting device of the MP circuit B and a signal as shown in FIG. 17B is input, the MP circuit A forms a recording mark. (C) is output, and at the same time, the MP circuit B outputs the pulse train (d) of FIG.

Therefore, as shown in FIG. 4B, the output of the semiconductor laser is modulated between Pr and Pp when a recording mark is formed, and is modulated between Pr and Pb when erasing. . When the recording gate signal Wg is input, Ir
If the reference voltage setting circuit 32 is set so as not to flow, the recording pulse train is modulated between Pp and power off, and the erase pulse train is modulated between Pb and power off.

 Next, a detailed example using this recording apparatus will be described.

(Embodiment 5) As setting recording patterns, FIG.
(M) was used. The measuring method of the input signal, the optical disk, the relative speed between the optical disk and the recording spot, and the jitter are the same as those in the second embodiment. The power Pb of the erase pulse train is 4.
5 mW. Table 3 shows the jitter values measured for the signals recorded and reproduced after each waveform. The jitter is the minimum value when the recording peak power is changed, and the recording peak power at that time is also shown in Table 3.

This result is smaller than the jitter corresponding to each waveform in Table 2. This is because the erase laser beam is pulse-modulated, (1) the temperature reached at the erased portion is constant, and the already-recorded recording mark is uniformly crystallized, and (2) the recording pulse train is changed to the erase pulse train. This is considered to be because the recording film temporarily cools at the end of the recording mark because the power temporarily passes through the reproduction power level Pr when shifting, and the end edge position of the recording mark becomes clear.

The setting pattern of the erase pulse train is shown in FIG.
Further, a short pulse P as shown by a broken line is added to the head, and jitter is measured by adding a pulse to the head of the erase pulse train shown in FIG.
In the case where the short pulse P shown in Table 3 is not added, 25
Since the jitter value of nsec deteriorated to 30 nsec, it was found that rapid cooling at the end of the recording mark was more effective in reducing the jitter than a configuration in which an erasing pulse was added to the end of the recording mark and slow cooling was performed.

Further, if the erase pulse cycle is set to be the same as the pulse cycle of the intermediate pulse in the recording pulse train, the MP
The circuit A and the MP circuit B can have the same configuration, which is convenient.

Next, FIG. 18 shows a configuration of a recording apparatus for obtaining a waveform as shown in FIG. 4 (c). EFM signal s from signal generator 1
5 is input to the MP circuit A27 similar to that shown in FIG. 8, is modulated into a pulse train, is output as a signal s12, and operates the switch 30. At the same time, the signal s5 is sent to the MP circuit via the inverter 29.
After being input to B28, the signal s16 passes through the inverter 33 again.
Then, the switch 31 is operated.

The MP circuit B is exactly the same as the MP circuit A, and is for pulse-modulating the erasing laser light. When, for example, the waveform shown in FIG. 19 (a) is set in the pattern setting device of the MP circuit B and a signal as shown in FIG. 19 (b) is input, the MP circuit A outputs a signal for forming a recording mark. The pulse train shown in FIG. 19C is output, and at the same time, the pulse train shown in FIG. 19C for modulating the erasing power is output from the MP circuit B.

Therefore, as shown in FIG. 4C, the output of the semiconductor laser is modulated between Pb and Pp when a recording mark is formed, and is modulated between Pr and Pb when erasing. . When the recording gate signal Wg is input, Ir
If the reference voltage setting circuit 34 is set so as not to flow, the erase pulse train is modulated between Pb and power-off.

 Next, a detailed example using this recording apparatus will be described.

(Embodiment 6) As setting recording patterns, (a), (f),
(M) was used. The measuring method of the input signal, the optical disk, the relative speed between the optical disk and the recording spot, and the jitter are the same as those in the second embodiment. The power Pb of the erase pulse train is 4.
5 mW. Table 4 shows the values of jitter measured for signals reproduced after recording with each waveform. The jitter is the minimum value when the recording peak power is changed, and the recording peak power at that time is also shown in Table 4.

As a result, the jitter is slightly larger than that in Table 3, but the recording peak power can be suppressed to a small value. This is because the bias power Pb exists in the recording pulse train.

According to the optical information recording method and recording apparatus of the present invention,
With a very simple device configuration, new recording can be performed while suppressing jitter while erasing the signal of the recording mark already recorded after the overwriting. This leads to a reduction in the aerial rate of the optical disk, and thus the recording capacity of the optical disk can be increased.

[Brief description of the drawings]

1, 2, 3 and 4 are recording waveform diagrams for explaining the present invention, FIG. 5 is a diagram showing the relationship between the recording waveform and the ultimate temperature of the recording film, and FIGS. FIG. 8, FIG. 14, FIG. 16, FIG.
FIG. 18 is a block diagram of an optical information recording apparatus according to the present invention, FIG. 9 is a sectional view of an optical disk on which a signal is recorded, FIG. 10 is a timing chart for explaining the signal flow in the circuit of FIG. FIG. 11 is a diagram showing the relationship between the jitter and the recording peak power, FIG. 12 is a diagram showing the recording pattern set in the pattern setting device, FIG. 13 is a diagram showing the relationship between the jitter and the relative speed, FIG.
17 and 19 are explanatory diagrams of the functions of the circuits in FIGS. 14, 16 and 18, respectively. FIGS. 20 and 21 are explanatory diagrams of a recording method according to a conventional example. DESCRIPTION OF SYMBOLS 1 ... Signal generator, 2 ... Modulator, 3 ... Pattern setting device, 5 ... Optical head, 6 ... Spindle motor, 7
…… optical disks, 13,14,20,22 …… data flip-flops, 19,23,29,33 …… inverters, 15,16 …… NAND circuits, 17 …… parallel-in-serial outshift registers, 18 …… patterns Setting device, 21, 27, 28: Multi-pulse circuit.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Noboru Yamada 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Inside

Claims (13)

(57) [Claims] An optical information recording medium having a phase change type information layer is irradiated with a laser beam driven by a pulse width modulated digital signal to thereby overwrite a recording mark on the information layer. A recording method, wherein erasing a recording mark is performed by irradiating a laser at an erasing level at which the information layer forms a crystalline state, and forming a recording mark is performed by irradiating a pulse train including a start end, an intermediate part, and an end part. The intermediate portion is irradiated with a laser beam that is switched at a constant cycle between a recording level at which the information layer forms an amorphous state and a level lower than the recording level, and the start portion is the intermediate portion. Irradiating a laser beam of the recording level with a pulse width equal to or greater than the pulse width of the recording level included in the, the end portion from the erasing level from the recording level Recording method of an optical information, which comprises irradiating a small level of the laser beam from the erase level holding predetermined period lowered to again level. 2. An optical information recording medium having a phase-change type information layer, which is irradiated with a laser beam driven by a pulse width modulated digital signal to thereby overwrite a recording mark on the information layer. A recording method, wherein erasing a recording mark is performed by irradiating a laser beam of an erasing pulse train in which an erasing level at which the information layer forms a crystalline state and a bell lower than the erasing level are alternately switched to form a recording mark. The irradiation is performed by irradiating a pulse train including a start end, an intermediate portion, and an end portion.The intermediate portion irradiates a laser beam that alternately switches a recording level and a level lower than the recording level at a constant period, The section irradiates a laser beam of the recording level having a pulse width equal to or greater than the pulse width of the recording level included in the intermediate section, Recording method of an optical information, which comprises irradiating a small level of the laser beam than the erase level. 3. The method for recording optical information according to claim 1, wherein the modulation of the recording pulse train is performed between any one of a reproduction level, an erasing level, and a power-off level and the recording level. . 4. When shifting from an erasing level to a recording level,
3. The method for recording optical information according to claim 1, wherein the optical information temporarily passes through a level lower than the erasing level. 5. The pulse according to claim 1, wherein the pulse width of the pulse in the pulse train in the intermediate portion is not less than 1/8 and not more than 1/2 of the repetition period of the pulse in the intermediate portion. How to record optical information. 6. The method according to claim 1, wherein the repetition period τ in the pulse train at the intermediate portion satisfies τ ≦ λ / L, where λ: wavelength of the recording light source, L: relative speed between the optical disk and the recording spot. A method for recording optical information according to 7. The optical information recording method according to claim 2, wherein the pulse period in the erase pulse train is the same as the pulse period in the intermediate pulse train. 8. An optical information recording medium having a phase change type information layer, which is irradiated with a laser beam driven by a pulse width modulated digital signal to thereby overwrite a recording mark on the information layer. A recording apparatus, wherein for erasing a mark, the information layer has a means for flowing a current of a constant erasure level for forming a crystalline state to a laser, and forming the recording mark is performed by applying a plurality of pulses to one recording mark. As a means for irradiating a laser pulse train consisting of, a pattern setter that previously sets a pattern of a recording pulse train corresponding to the longest pulse width of the input signal, and a pulse width less than the longest pulse width of the input signal A modulator that cuts out a required length from the beginning of a setting recording pattern of the pattern setting device to form a pulse train to be formed, An optical information recording apparatus, comprising: means for modulating a driving current of a laser by a signal converted into a pulse train. 9. An optical information recording medium having a phase change type information layer, which is irradiated with a laser beam driven by a pulse width modulated digital signal to thereby overwrite a recording mark on the information layer. A recording apparatus, comprising: means for modulating a laser with an erase pulse train that alternately switches between an erase level at which the information layer forms a crystalline state and a level lower than the erase level, for erasing a mark, and As a means for forming a recording mark by irradiating a single recording mark with a laser pulse train composed of a plurality of pulses, a pattern setter that previously sets a pattern of a recording pulse train corresponding to the longest pulse width of an input signal, In order to form a pulse train corresponding to a pulse width equal to or less than the longest pulse width of the input signal, the setting recording pattern of the pattern setting device is used. An optical information recording apparatus, comprising: a modulator that cuts out a required length from the beginning of a turn; and a unit that modulates a drive current of a laser by a signal that is converted into a pulse train from the modulator. 10. A recording pulse train is generated by detecting a rising edge of a pulse of an input signal to start generation of a set recording pattern, and detecting a falling edge to end generation of the set recording pattern. Claim 8
Or a recording device for optical information according to any one of [9] to [9]. 11. A means for generating an erase pulse train, comprising: a pattern setting device for presetting an erase pulse train pattern corresponding to the longest pulse interval of an input signal; and a pattern setter for setting a pulse interval shorter than the longest pulse width of the input signal. 10. The optical information recording apparatus according to claim 9, further comprising a modulator that cuts out a required length from the beginning of the set erase pattern of the pattern setter to form a corresponding erase pulse train. 12. An erase pulse train by detecting the falling edge of a pulse of an input signal to start generation of a set erase pattern, and detecting the rising edge of the next input signal pulse to terminate the generation of the set erase pattern. 12. The optical information recording device according to claim 11, wherein: 13. The optical information recording apparatus according to claim 8, wherein the operation of the modulator and the pattern generator is controlled by the same clock signal as that of the signal generator.