JPS6394437A - Record eliminating method for optical disk - Google Patents

Abstract

PURPOSE:To contrive to recover the amplitude and noise level of a recording signal by projecting high power laser light and making the width of the molten part of a recording material wider than the time of recording when the recording signal is deteriorated. CONSTITUTION:When a light spot 1 of a high power narrowed up to about 1mum of the wavelength limit of a laser light along a track 3 on a rotating optical disk 1 is irradiated, a temperature quickly rises, a molten point Tm of a material is instantaneously passed through, the heat is spread, quickly cooled and an amorphous condition is obtained. The condition is a reflection factor lower than a crystal condition. When an eliminating light spot 2, which is elliptical and a power density lower than a circular light spot, passes through in the moving direction of a laser beam, a temperature up and a temperature down and smoothly executed, a crystal condition is obtained and a high reflection factor is obtained. When a recording signal is deteriorated, the recording light spot 1, which is a power higher than the time of usual signal recording and is not modulated, and the eliminating light spot 2 are alternately irradiated and recovered. In the condition molten by the laser light irradiation of a non- modulating high power, material composition is equalized, the amplitude and the noise level of the recording signal are recovered and the repetitive life of a material is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for recording, reproducing and erasing signals on an optical disc by focusing a laser beam onto the optical disc and making it possible to record, reproduce and erase signals.

BACKGROUND OF THE INVENTION Chalcogen-based optical recording materials are well known as recording media for optical discs on which signals can be recorded, reproduced, and erased. The final state is a crystalline state, and a signal is recorded by heating and rapidly cooling it by laser spot irradiation to turn it into an amorphous state.

Furthermore, by heating and slowly cooling, the crystalline state is restored, and the recorded signal is erased.

As a laser spot configuration on the disk that makes the above possible, the one shown in FIG. 3 (Japanese Patent Application Laid-Open No. 153540/1982) or FIG. There is. Spot 1 in FIG. 3 has a circular shape narrowed down to the waveform limit and is used for recording and reproduction. Spot 2 has an oval shape and is used for erasing. FIG. 3(B) shows the temperature change in the irradiation section when these two spots pass through. When the spot 1 passes, the temperature of the irradiated part increases rapidly and becomes a molten state, and then it is rapidly cooled, and an amorphous state is formed during this period.

When the spot 2 passes, the temperature of the irradiated part is gradually raised and then slowly cooled, and a crystalline state is formed during this time.

Also, spot 1 in Figure 4 is for recording and playback, spot 4,
6 is for erasing. In Figure 3, especially spot 4 is rounded.
The purpose is to achieve highly efficient erasing by applying high power to melt the irradiated area and then slowly cooling it using the spot 6.

Further, with the configurations shown in FIGS. 3 and 4, a new signal is recorded at spot 1 immediately after erasing. That is, simultaneous erasure is possible.

Recording and erasing of a recording material is performed using an erasing spot configuration that exceeds the problem that the invention aims to solve. Furthermore, a rewritable optical disc must be able to be repeatedly recorded and erased many times. In the process of repeatedly heating and cooling a recording material using a laser spot, variations occur such as variations in the power of the irradiated laser light and positional deviation of the spot. These elements accumulate in the recording material little by little and eventually degrade the recorded signal.

The present invention aims to extend the life of the recording material with respect to the number of repetitions by changing the light irradiation conditions to the recording material between normal times and when deterioration begins.

Means for resolving the problem During the process of repeatedly recording and erasing an optical disk, if deterioration of the recorded signal is observed, irradiate the eraser with a higher-power erasing laser light than usual, or High-power, non-modulated recording laser light and erasing laser light are irradiated.

Factors that degrade recorded signals on optical disks include power fluctuations and non-uniformity in the state of the material caused by spot deviation. These are significantly distributed in the direction perpendicular to the traveling direction of the laser beam. According to the present invention, by irradiating a high-power laser beam when a recording signal deteriorates, the width of the melted portion of the recording material is made wider than when recording the signal. In the molten state, molecules move actively and the material composition can be made uniform. As a result, the amplitude of the recording signal and the noise level can be restored, and the repetition life of the recording material can be improved.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. As described above, the recording material is one that takes two states depending on the cooling conditions after heating, that is, an amorphous state is obtained by heating and rapid cooling, and a crystalline state is obtained by heating and slow cooling. For example, chalcogenide thin films, Te0x(o(x(2
, o) is formed on a substrate such as glass or resin by vapor deposition or sputtering.

For recording and erasing, spots as shown in FIG. 3 (m) are used. A guide track 3 for laser light is formed on the substrate, and each spot moves along this guide track 3. FIG. 3(B) shows the temperature of the recording material when each spot passes through it. When a rotating optical disk is irradiated with a circular recording/re-spot 1 focused to the wavelength limit of approximately 1 μm, the power of the laser beam is increased, the temperature of the irradiated area rises rapidly, and the material melts instantly. passing through the heating temperature Tm.

After passing the spot 1, the heat is diffused into the substrate, and the irradiated area is rapidly cooled and becomes an amorphous state.

This state has a lower optical constant and exhibits lower reflectance than the crystalline state. In addition, when the erasing spot 2, which is long in the direction of movement of the laser beam and has a lower power density than a circular spot, passes, the temperature of the irradiated area gradually increases and then decreases, and the recording material changes to a crystalline state. Become. In this state, the optical constant is large, so it exhibits high reflectance.

Signals are recorded using the difference in reflectance between these two states. Since signals can be recorded with a higher density using a circular spot, recording is performed by modulating the power of this spot, and the recorded signal is reproduced by lowering the power and irradiating the spot. Erasing is also performed by irradiating an oval spot 2.

The signal can be rewritten by alternately irradiating the two spots. FIG. 2 shows the changes in the signal when recording and erasing the signal are repeated.

The quality of the recorded signal is expressed in 07N ratio.

Here, C corresponds to the signal amplitude of the recording section, that is, the difference in reflectance between the amorphous state and the crystalline state, and N is the noise level included in the recording signal component, and the variation in the shape of the recorded bits (amorphous state). This corresponds to the reflectance distribution in each state. The other is the erasure rate, which corresponds to the difference between the value of the signal amplitude C during recording and the signal component remaining after erasing, and the larger this value is, the better the erasing characteristics are.

As shown in FIG. 2, the C/N ratio and erasure rate change with the number of repetitions. Until the number of repetitions is about 105,
Although they show approximately the same C/N ratio and erasure rate, there is a tendency for the C/N ratio to suddenly decrease and the erasure rate to decrease after 105 subscripts. However, the conditions used here are that the linear velocity of the disc is 5 m/s, and the recording spot diameter is 0.9
μm, recording power 7mW, erase spot length 8μm
, width 1 μm.

The power was 121!1W. The C/N ratio and erasure rate change by changing the conditions described above.

In general, the higher the recording power and erasing power, the higher the initial C.
/N ratio and erasure rate are improved, but the starting point of deterioration when repeated is a small number of times. On the other hand, if the power is lowered, the initial C/N ratio and erasure rate will deteriorate, but the starting point of deterioration when repeated repetitions will move toward the large number of repetitions. From these points,
The conditions used in FIG. 2 are such that the optimum recording/erasing power is selected according to the required signal quality.

The deterioration caused by repeated recording and erasing is thought to be due to the gradual accumulation of non-uniformity in the recording material in the light irradiated area. The causes include the intensity distribution and power fluctuation of the irradiated laser beam, the temperature distribution in the temperature rising state of the recording material caused by the deviation of the spot in the track direction, and the like. In particular, the laser beam focused by the lens diameter has an intensity distribution as shown by a glass distribution curve, and the power density is high at the center of the spot and decreases as it moves away from the center. When such a spot is repeatedly irradiated onto the disk, material non-uniformity occurs in the irradiated portion in the direction perpendicular to the track.

In the present invention, when it is detected that the recording signal has deteriorated, the recording spot 1 and the erasing spot 2 are alternately irradiated with higher power than in normal signal recording and without modulation. to recover the recorded signal state. When the high-power recording spot 1 passes without modulation, the irradiated area becomes hotter than during normal recording, and the area where the recording material melts increases.

In the molten state, atoms move more actively and randomness increases. As a result, the history of the melted portion is completely erased, and the material state and recorded signal are considered to be restored to their initial state. FIG. 1 shows the results when the treatment of the present invention was applied to such a recording section which had deteriorated due to repeated use. When recording and erasing a 2M1IZ signal under the same conditions as in Fig. 2, with a recording power of amp and an erasing power of 12 mW, the C/N ratio changes to the initial value of 55 in 105 times.
dB is 52.5 dB, which is a 2.5 dB decrease, and the erasure rate is also 42 dB, which is 3.5 dB worse than the initial 45.5 dB.

Here, after increasing the power of the recording sponge to 10 mW, irradiating it without modulation, and then irradiating the erase spot, we returned to the original recording conditions and recorded the signal. As a result, the C/N ratio was 64. .8 +iB, erasure rate is 45.0
(iB was able to recover to almost the initial recording and erasing state. With further repeated operations, 2X1
At about 05 times, the signal state becomes like that at 105 times,
The signal condition was restored by performing the same process as the 105th time. As a result of performing this operation every 105 times up to 106 times, the C/N ratio was E52 at the 106th point. OdB,
The erasure rate was 41 dB, and the result of processing according to the present invention was C.
The /N ratio was 53.5 dB and the erasure rate was 43.0 dB. From these results, if deterioration of the recording signal is observed, by performing the process of the present invention each time, it is possible to extend the repeated life of the optical disc by more than 10 times.

Note that the above-mentioned experimental results were obtained when the recording spot and the erasing spot were irradiated only once, but by alternately irradiating the recording spot and the erasing spot several more times, the effect of recovering the C/N ratio and the erasing rate increases. Furthermore, although the recovery of the erasing rate is smaller than the C/N ratio, this can be brought close to the same value by increasing the power of the erasing spot.

Processing such as that of the present invention must be executed while signals are actually being recorded and erased on the optical disc. but,
It is impossible to change the C/N and erasure rate each time. Therefore, by recording information that manages how many times recording has been repeated in a part of the directory for data management or the recording start part of each signal on the optical disk, recording and erasure can be performed a certain number of times. There is a method of performing the process of the present invention each time the process is performed.

Another method is to record signals on optical discs that include double or triple error correction codes in addition to the original signal, and when playing back signals that include correction values. Since the method is to perform circuit processing to generate the original signal, it is possible to use this method. That is, in the process of creating an original signal from this reproduced signal, a reference value for error correction is provided, and if correction on a fixed scale is necessary, the process of the present invention may be performed only for that area.

Next, other embodiments of the present invention will be described.

There is a method of using two spots for erasing recorded signals, the configuration of which is shown in FIG. 4(m). Record spot 1
is the same as above. Starting with circular erase spot 4,
Immediately after that, an oval erase spot 5 is placed. When such erase spots 4 and 6 pass over the recorded bits,
First, the temperature of the irradiated portion of the leading circular spot 4 rises rapidly and becomes molten. After passing the spot 4, it is rapidly cooled, but immediately after that, the oblong erasing spot 5 is irradiated, so the temperature in the cooling process gradually decreases as shown in FIG. 4(B), and the irradiated part Becomes a crystalline state. As a result, the signal is erased.

The erasing method using these two spots is characterized in that the leading circular spot 4 melts the irradiated area, so it exhibits a higher erasing rate than the erasing using only the elliptical spot described above.

Regarding the erasure method using two spots, repeated experiments similar to those in Example 1 were conducted, and the C/N ratio and erasure rate were measured. Recording spot 1 and circular erasing spot 4
The power of is equal to 7 mW, and the oval erasing spot 5
The power was 8 mW. Under these conditions, the initial C/N was 65.0 dB and the erasure rate was 52.0 d.
B, and the C/N ratio was 52.0 dB and the erasure rate was 49.0 + iB after 100 times. Here, the power of the first circular erasing spot 4 is increased to 1011IW, and after only erasing is performed several times, when signal recording is performed, the C/N ratio becomes s.
4. sdB and erasure rate of 51 dB, which was able to restore the recording/erasing level to almost the initial state. A similar phenomenon was observed in the elimination method using two spots, in which the same process as in Example 1 was repeated up to 106 times.

From the above, in the erasing method using two spots, if deterioration of the recorded signal is observed, the power of the first circular erasing spot 4 is increased each time and processing is performed to irradiate the two spots. This makes it possible to extend the repeatable life of the optical disc.

Effects of the Invention According to the present invention, in a rewritable optical disc,
The repeat performance of an optical disc can be improved by a simple method of adding processing that changes the laser beam irradiation conditions during repeated recording and erasing.

[Brief explanation of the drawing]

FIG. 1 is a graph showing repetition characteristics in an embodiment of the present invention, FIG. 2 is a graph showing repetition characteristics in a conventional example, and FIGS. 3 and 4 are diagrams showing examples of arrangement of recording and erasing spots. . Name of agent: Patent attorney Toshio Nakao and one other person Yugoji, C/~ (dBl Mowango Φ, C
/N (dB) Figure 3 (A) Time Figure 4 (A) - Relaxation speed

Claims (3)

[Claims] (1) In a method of recording and erasing using a change in optical properties based on a reversible phase change between an amorphous phase and a crystalline phase, the signal is inspected after recording, and if the signal is not recorded normally, , a method for erasing records on an optical disc, which is characterized in that the power of the light is increased higher than in normal times, the data is erased, and then the data is re-recorded. (2) As a means for erasing by increasing the power of light, a recording spot with higher power than normal and unmodulated;
2. The optical disc recording and erasing method according to claim 1, wherein an oblong erasing spot is used. (3) A method for recording and erasing information on an optical disc according to claim 1, wherein the function of inspecting a signal after recording is operated by a signal detected from error correction information of a reproduced signal.