JP2571776B2 - How to record and erase information - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to recording of information suitable for shortening access time by utilizing a change in an optical constant due to a change in atomic arrangement such as a phase change type. It relates to an erasing method.

[Conventional technology]

When recording information on an optical disc or erasing recorded information, it is necessary to check whether the information to be recorded or erased is actually recorded or erased. Conventionally, as a method of the above-described confirmation, after recording or erasing, the disc is waited for one rotation, and then confirmed by a reading light. Japanese Patent No. 1264450 discloses a method of confirming the presence or absence of recording by detecting reflected light of recording light in a perforated type write once optical disk. However, in a single-write or rewritable optical disk utilizing a change in the atomic arrangement such as a phase change type, the reflected light waveform of the recording light is different from that of the above-mentioned perforated type optical disc, so that the reflected light of the recording light and the erasing light is reflected. There was no example in which the presence and absence of the recording and erasure were detected.

[Problems to be solved by the invention]

In the above prior art, in an optical disk using an atomic arrangement change such as a phase change type, a time for one rotation of the disk (for example, 3
3ms), and the access time is long.

An object of the present invention is to provide a recording and erasing method with a short access time.

[Means for solving the problem]

The object is to irradiate a recording medium with a single laser beam whose irradiation power level is changed at least between an erasing level and a recording level to record and erase information. A reproduction signal waveform of the reflected light from the laser beam is formed, the reproduction signal waveform is divided based on the clock timing, and the reproduction at the time of irradiating the recording level and the erasing level of the laser light from the divided reproduction signal waveform is performed. This is achieved by extracting each signal waveform, separately evaluating the extracted reproduced signal waveforms, and confirming recording and erasing, respectively.

[Action]

According to the method for recording and erasing information according to the present invention, during recording or erasing, the reflection level of recording light or erasing light changes during recording or erasing by laser irradiation between a plurality of states having different atomic arrangement regularities. Utilizing that the optical constant changes according to the reflectance of the recording film to be detected, the change is detected as an electric signal in real time, and the normal recording or erasing was performed by the change in the waveform and intensity of the electric signal. Check if. Detection is performed by using two states among the plurality of states having different regularities of the atomic arrangement. The two states may be a state having a high regularity and a state having a low regularity, for example, a crystalline state and an amorphous state. And two crystal states with different crystal forms, or two with different forms of disorder.
It may be in one crystal state.

It is optional to determine in which direction the change in the atomic arrangement between the two states of the recording film is considered as recording or erasing, and may be determined in advance.

When recording or erasing is performed by irradiating one laser beam, at least one reflected light of recording light (high-power laser light) or erasing light (low-power laser light) is extracted by a clock, and recording or erasing is performed reliably. Check if it is. At this time, it is preferable that the reflected light of the recording light and the reflected light of the erasing light be extracted by a clock to confirm the recording and the erasing, respectively.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. First
FIG. 2 is a cross-sectional view showing an information recording medium used for the method of recording and erasing information according to the present invention, FIG. 2 is a view showing a waveform of a single laser beam applied to the recording medium, and FIGS.
(E) shows a reflected light signal of the high-power laser light extracted by the clock, (f) to (j) show error signals of the above signals, and FIGS. 4 (a) to (e) show stable errors, respectively. FIG. 5A to FIG. 5D show a method for obtaining a signal.
(D) is a diagram showing a reflected light signal of a high-power laser beam taken out by a clock, FIGS. 6 (a) to (e) are diagrams showing a method of obtaining a stable error signal, and FIG. 7 (a). (C) is a diagram showing a reflected light signal of a low-power laser beam extracted by a clock, and (d) to (f) are diagrams showing an error signal of the signal.

Example 1 In FIG. 1, reference numeral 1 denotes a substrate in which a replica of a tracking groove is formed on the surface of a disk-shaped chemically strengthened glass having a diameter of 130 mm and a thickness of 1.1 mm by an ultraviolet curable resin, and 2 denotes magnetron sputtering on the substrate 1 Is a protective layer made of SiO ₂ formed by the method, and the thickness of the protective layer 2 is 110 n
m. Reference numeral 3 denotes a thin recording film formed on the protective layer 2. The recording film 3 is formed by evaporating Ge, Te and Se independently from each other. Reference numeral 4 denotes SiO ₂ formed on the recording film 3 by a magnetron sputtering method.
The thickness of the protective layer 4 is 110 nm. When the above-mentioned information recording medium is irradiated with continuous light of the semiconductor laser light, the elements in the recording film 3 can be sufficiently reacted, and initialization can be performed.

Next, when the information recording medium was irradiated with a rectangular pulse of a single laser beam as shown in FIG. 2, it was confirmed whether or not a change according to the high-power laser beam and the low-power laser beam occurred. When irradiated with high power laser light,
Irrespective of whether the state before irradiation is a crystalline state (erased state) or a non-crystalline state (recorded state), the state becomes a non-crystalline state (low reflectivity), and when a low power laser beam is irradiated. Should be in a crystalline state (high reflectivity). Therefore, when the intensity signal of the reflected laser light is separately extracted for each unit of a newly recorded signal using a clock, the results are as shown in FIGS. 3 and 6, respectively. When the recording film 3 is once melted and becomes amorphous after irradiation with the high-power laser beam, FIG. 3 (a) or (b)
When the melting state continues, the waveform shown in FIG. 3E is obtained, and when no change occurs (when an error occurs), the waveforms shown in FIGS. 3C and 3D are obtained. . (A) and (c) in the figure are initially in a crystalline state,
(B) and (d) are in an amorphous state. Next, in FIG.
When the comparator level is set as shown in (2) and an error signal is generated at a position where one unit of the input signal ends and the signal is larger than the comparator level, only at the time of (c) and (d), An error signal is generated as shown in (h) and (i). In the above method, the recording film 3
Since the error rate is high with respect to the non-uniformity of the formation of the pattern and the change in the reflectance caused by the rewriting, nothing changes.
As a method for generating an error signal in the case of (d), the following method is more preferable. That is, a signal delayed by 1/2 of the pulse width of the reflected light signal with respect to the reflected light signal (FIG. 4 (a)) is shown in FIG. 4 (b).
Make like. Next, when the two signals are passed through a comparator so that the comparator output becomes a high level when the delayed signal is larger than the original signal, the output signal of the comparator shown in FIG. 4C is obtained. . If an error signal is generated only when the laser drive pulse falls within 20 ns from the rise of the comparator output, as shown in FIG.
As shown in FIG. 3E, an error signal appears in the cases of FIGS. 3C and 3D. However, in the above method, the third
Since an error signal is also generated in the case shown in FIG.
It is necessary to use it in combination with the above error detection method.

According to basic experiments, the output of high-power laser light
In the case of a particularly large power of 15 mW or more, the reflected light signal divided and extracted by the clock is as shown in FIG. When amorphization occurs, the waveforms shown in FIGS. 5A and 5B are obtained, and when no change occurs (when an error occurs), the waveforms shown in FIGS. 5C and 5D are obtained. become. The following method was used as a method for generating an error signal only in cases (c) and (d). That is, a signal is produced which is delayed from the reflected light signal shown in FIG. 6 (a) by の of the pulse width (unit length of information) (FIG. 6 (b)). Next,
When the two signals are passed through a comparator so that the output of the comparator becomes high when the original signal is larger than the delayed signal, and the output of the comparator is delayed by 1/2 of the pulse width, FIG. The signal shown in (c) is obtained. If an error signal is generated within 20 ns from the rise of the comparator output only when the laser drive pulse falls as shown in FIG. 6 (d), as shown in FIG. 6 (e), FIG. (C),
An error signal appears only in case (d).

On the other hand, when crystallization occurs when a low-power laser beam is irradiated, the waveform shown in FIGS. 7A and 7B is obtained, and when no change occurs, the waveform shown in FIG. 7C is obtained. become. Next, the comparator is set to the level shown in FIG. 7B, and at the position where the unit length of information ends, an error signal is generated when the signal is lower than the comparator level. The error signal appears only at

The error rate was 1 × 10 ⁻⁶ when both the above confirmation at the time of high-power laser light irradiation (at the time of amorphization) and the confirmation at the time of low-power laser light irradiation (at the time of crystallization) were performed simultaneously. On the other hand, when performing only one of them, the error rate was 5 × 10 ⁻⁵ when the confirmation was performed only at the time of ^{amorphization} ,
When it was confirmed only at the time of crystallization, it was 7 × 10 ^-5 . This is because amorphization is more reliably performed than crystallization.

In the description of the above embodiment, a method of confirming recording or erasing using reflected light during recording or erasing is described, but even if transmitted light is used, except that the apparatus becomes complicated, It is possible to confirm recording or erasing by the same method.

〔The invention's effect〕

As described above, in the information recording and erasing method according to the present invention, the recording medium is irradiated with a single laser beam whose irradiation power level is changed at least between the erasing level and the recording level, and the information is recorded and erased. In the information recording and erasing method, a reproduction signal waveform of the reflected light from the recording medium is formed, the reproduction signal waveform is divided based on a clock timing, and the recording of the laser light is performed based on the divided reproduction signal waveform. By extracting the reproduced signal waveforms at the time of each irradiation of the level and the erase level, evaluating the extracted reproduced signal waveforms separately, and confirming the recording and erasing, respectively, without having to wait for the rotation of the disk as in the conventional case. Since recording or erasing can be confirmed in real time, access time can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an information recording medium used in the information recording and erasing method according to the present invention, FIG. 2 is a diagram showing a waveform of a single laser beam applied to the recording medium, and FIGS.
(E) shows a reflected light signal of the high-power laser light extracted by the clock, (f) to (j) show error signals of the above signals, and FIGS. 4 (a) to (e) show stable errors, respectively. FIG. 5A to FIG. 5D show a method for obtaining a signal.
(D) is a diagram showing a reflected light signal of a high-power laser beam taken out by a clock, FIGS. 6 (a) to (e) are diagrams showing a method of obtaining a stable error signal, and FIG. 7 (a). (C) is a diagram showing a reflected light signal of a low-power laser beam extracted by a clock, and (d) to (f) are diagrams showing an error signal of the signal. 3… Recording medium 5,6… Laser spot

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Norio Ota 1-280 Higashi-Koigabo, Kokubunji City, Hitachi, Ltd. Central Research Laboratory Co., Ltd. 72) Inventor Toshimitsu Kaku 1-280 Higashi Koigabo, Kokubunji City, Hitachi, Ltd. Central Research Laboratory Co., Ltd. (72) Inventor Keikichi Ando 1-280 Higashi Koigabo, Kokubunji City, Hitachi Central Research Laboratory Co., Ltd. 53-6516 (JP, A) JP-A-59-558633 (JP, A)

Claims (1)

(57) [Claims] An information recording and erasing method for irradiating a recording medium with a single laser beam whose irradiation power level is changed at least between an erasing level and a recording level to record and erase information. A reproduction signal waveform of the reflected light from the medium is formed, the reproduction signal waveform is divided based on the clock timing, and the divided reproduction signal waveforms are used to irradiate the recording level and the erasing level of the laser light, respectively. A method of recording and erasing information, comprising extracting a reproduced signal waveform, separately evaluating the extracted reproduced signal waveform, and confirming recording and erasing, respectively.