JPH09128754A - How to record and play back information - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To record, reproduce and erase information with a simple optical system by using a reversible phase change type recording film capable of high speed phase change and to erase existing information. Meanwhile, there is provided a method of recording / reproducing information that can be overwritten to record new information. Kind Code: A1 An information recording / reproducing method for forming a recording mark on an information recording medium by irradiating light to record information, and reproducing the recorded information. First of all, the optical power is the first for reproducing information.
And a second optical power level higher than the second optical power level, and then raised to a third optical power level higher than the second optical power level to form a recording mark. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording, reproducing and rewriting method in an information recording device such as an optical disk, and particularly, a simple recording head using a reversible phase change type recording film capable of high speed phase change, The present invention relates to a so-called overwritable information recording / reproducing method in which information can be recorded, reproduced, and rewritten by one energy beam spot, and new information is recorded while erasing existing information.

[0002]

2. Description of the Related Art A light beam such as a laser beam is focused on a minute light spot, and a signal is recorded / reproduced at a high density on a reversible phase-change type optical disk medium which is an optical recording medium, and a signal once recorded is erased. The method is described in JP-A-59-71.
As disclosed in Japanese Patent Publication No. 140, the record of information is:
The light beam spot is sufficiently converged to irradiate the recording film for a short time, and the recording film is completely transformed into an amorphous state by rapid heating and quenching. On the other hand, the recording is erased from the track (guide groove). The recording is performed by gradually heating and slowly cooling using an elliptical light spot that is long in the direction to completely return the recording portion in an amorphous state to the original crystalline state. As described above, two different light beam spots are used for recording and reproduction and for erasing, or a single light beam spot is used as disclosed in JP-A-56-148740. A method has been proposed in which recording is erased by rotating the disk medium many times, and information is recorded in the next one rotation. In order to rewrite the recording by the latter method, the light spot had to pass the same place on the recording film of the disk medium many times.

[0003]

In the former of the prior arts described above, two different light beam spots are used, and it is attempted to track the two light beam spots on the same track (guide groove). In addition, there are some practical problems such as a complicated control system required, two light sources required to form two light beam spots, and a complicated optical system. In addition, in the latter case of the above-mentioned prior art, even when a single light beam spot is used, it is necessary to rotate the disk medium many times when rewriting the recording, and it takes time to rewrite the recording. There was a problem.

An object of the present invention is to solve the above-mentioned problems in the prior art, and to use a reversible phase-change type recording film capable of high-speed phase change to record, reproduce and erase information with a simple optical system. It is an object of the present invention to provide a method of recording and reproducing information that can be performed and that can be overwritten to record new information while erasing existing information.

[0005]

In order to achieve the above-mentioned object of the present invention, the present invention has a constitution as set forth in the claims. That is, the present invention provides a method for recording and reproducing information by forming a recording mark on an information recording medium by irradiating light to record information, and reproducing the recorded information. When recording the information, first, the optical power is set to the first value at the time of information reproduction.
To a second optical power level higher than the second optical power level, and then to a third optical power level higher than the second optical power level to form a recording mark. Things. According to a second aspect of the present invention, in the first aspect, when recording information, first, the optical power is changed to the second optical power higher than the first optical power level at the time of information reproduction. Level, then to a third optical power level higher than the second optical power level, and further modulating the light between the second and third optical power levels to provide a sequence of recording marks. This is a method for recording and reproducing information that forms According to a third aspect of the present invention, in the first aspect, when recording information, first, the optical power is set to a second optical power higher than the first optical power level at the time of information reproduction. Level, then to a third optical power level higher than the second optical power level, using the third optical power level to form a recording mark, and between the recording marks. A method for recording / reproducing information for irradiating the area with the second light power level or a light power level lower than the second light power level. The present invention also provides an information recording / reproducing method for recording information by forming a recording mark on an information recording medium by irradiating light, and reproducing the recorded information. Therefore, when recording the above information, (1) an operation of raising the optical power level to a second optical power level higher than the first optical power level at the time of reproducing information before entering the recording area is performed. After that, (2) an operation of raising the optical power level to a third optical power level higher than the second optical power or higher, and (3) an optical power level of the second optical power level. The following operation is a repeated information recording / reproducing method. Further, the present invention provides a method for recording information, in which a recording mark is formed on an information recording medium by irradiating light to record information, as described in claim 5. The information recording method satisfies the condition (3). (1) A portion at which the recording mark is formed is irradiated with light at a recording level. (2) Light is irradiated to a portion where the recording mark is not formed, at a level lower than the recording level. (3) In a portion where the recording mark is not formed, a portion immediately before the recording mark is irradiated with light of a higher level than a portion immediately after the recording mark. Further, according to the present invention, as described in claim 6,
An information recording / reproducing method of forming a recording mark on an information recording medium using the first, second and third optical power levels to record and reproduce information, which is described in (1) to (4) below. ) The method of recording information that satisfies the condition of). (1) The second optical power level is higher than the first optical power level, and the third optical power level is higher than the second optical power level. (2) The first optical power level is the optical power level used for reproducing information. (3) The second optical power level is an optical power level used at a portion between recording marks. (4) The third optical power level is the optical power level used at the place where the recording mark is formed.

The information recording / reproducing method of the present invention uses a reversible phase-change type information recording film of, for example, an In-Se type or Ge-Te type, which can be erased at a high speed. The power of energy beams, such as electron, ion, and ion beams, changes the state of the recording film (phase change)
By varying between a plurality of power levels that can cause Note that, for example, an In—Se-based recording film is a recording film containing at least In and Se, and further containing one or more other elements as necessary. According to the method of the present invention, information can be rewritten (erased and re-recorded) with one energy beam spot while the spot passes through the recording film once. Note that the reproduction level of the rewriting light spot is used only for tracking and automatic focusing, or the power of the reproduction level is set to almost 0 (zero), and signal reproduction, or reproduction, tracking, and automatic focusing are performed by different energy beam spots. May be performed. In the information recording film used in the method of the present invention, a phase change reversibly occurs in the recording film only by changing the power of the energy beam in the same irradiation time, whereby the refractive index, the reflectance, the transmittance, etc. Any film may be used as long as it has a change in optical constants and other physical constants, and has a component composition capable of recording and erasing information. The reversible change of the physical property constant in the recording film used in the method of the present invention is performed by utilizing the state transition of the recording material constituting the recording thin film, the transition between the amorphous state and the crystalline state of the thin film, or The transition between one amorphous state and another amorphous state, or the transition between one crystalline state and another crystalline state can be performed repeatedly. Dislocation is performed stably and reversibly, and a change in a physical property constant can be reversibly and stably generated at a high speed. For example, an InSe-based thin film, a Ge—Te-based thin film, and the like can be given. . In general, the recording material has a large number of states continuously or discretely between two states, for example, between a completely amorphous state and a completely crystalline (polycrystalline) state. Therefore, if the power of the energy beam is varied between the two levels, 2
A value or digital recording can be performed, and an analog recording or a multi-value recording can be performed if the recording is changed among three or more levels. The method for recording and reproducing information according to the present invention enables so-called overwriting, in which existing information is erased and new information is recorded at that location, so-called overwriting is possible, while the energy beam spot passes through the recording film once. Can be rewritten (erased and re-recorded). For example, first, a disk having an amorphous state on the recording tracks (between the grooves for tracking) and a crystalline state between the tracks is rotated, and information is reproduced by using one laser or electron beam spot. When there is a place to rewrite information, a plurality of power levels different from the reproduction level power (continuous oscillation) (normally higher than the reproduction power level, the recording level and the erasing level are 2
(For example, between two power levels), the information is rewritten by changing the power. The recording level and the erasing level were defined as laser powers optimal for recording and erasing, respectively, when the power was continuously maintained. (The reproduction power level is called the first power level because it has the lowest power among these power levels.
The lower of the recording level and the erasing level is the second
The higher power level is referred to as a third power level. In order to realize such a change in laser power, a conventional write-once optical disc is recorded on a waveform in which the power rises in a pulse manner from a reproduction level (first power level) to a recording level (third power level). This can also be realized by superimposing waveforms rising from the reproduction level to the erasure level (second power level) in the area where rewriting is performed (the higher power of both is used as the output power).
By adjusting the power of this overlapping waveform,
A rewritable optical disk and a write-once optical disk can be recorded and reproduced by the same device. When rewriting information by changing the power between two power levels of recording and erasing (the higher one is the third power level and the lower one is the second power level), immediately after the higher power level is set, Once the power is lower than the lower power level, a decrease in the cooling speed due to the residual heat of the recording film can be prevented, which is effective. On the other hand, when a crystalline state is changed to a recording state and an amorphous state is changed to an erased state using, for example, a reversible phase change type recording material, the power (third power level) is lower than the erase level (third power level). When recording is performed at the (second power level), for example, the recording may be performed by lowering the power in a pulsed manner from the erase level. In this case, it is preferable that the above-mentioned pulse-like power reduction is performed such that the power is particularly greatly reduced at the beginning. Thereby, the temperature can be quickly lowered to a temperature suitable for erasing. Also, during erasing, a method that uses a combination of a wavelength change accompanying a mode change due to a change in laser power, a decrease in the amount of high-frequency superposition, a change in the amount of return light, and chromatic aberration of the lens, or a beam deflector or the like is used. Increasing the beam spot on the disk medium by, for example, changing the optical path length and changing the focal position to achieve defocusing has the effect of increasing erasing time and preventing information from being left unerased. In the two or more state transitions of the recording film, it is possible to arbitrarily select which state is to be the recording state or the erasing state. A state with a low rate may be set as a recording state, and conversely, it may be set as an erasing state. However, it is preferable to shorten the time for irradiating the laser beam of high power (third power level) as much as possible in order to avoid adverse effects such as deformation of the recording film. The recording state is preferable. In the present invention, when recording is performed using a reversible phase change between the crystal and the amorphous of the recording film, if the recording tracks are made to be in a crystalline state in advance, the recording tracks become uneven during rewriting. Crystallization and generation of noise can be prevented. When the rotation speed of the disk is high, for example, even if an energy beam of a crystallization level is irradiated, the irradiation time of one point on the disk may be so short that complete crystallization may not occur. In this case, the crystallization proceeds when light of the crystallization level is applied again at the time of recording / rewriting, so that the reflectance of the crystallized portion is not constant but varies depending on the location. In such a case, of the crystallized portion, the reflectance of the portion closest to the reflectance of the portion in another state (amorphous state), or the reflectance of this portion and the reflectance of the amorphous portion ( If there is a width, it is preferable that the comparator level is set to a voltage corresponding to an arbitrary reflectance between (reflectivity closest to the crystal state) and the signal voltage in the crystal state is adjusted to a constant value. In this case, a voltage corresponding to the reflectance of the crystalline state closest to the amorphous state and the voltage corresponding to the reflectance of the amorphous state closest to the crystalline state, or an amorphous state closest to the crystalline state. When the comparator level is set to a voltage close to the voltage corresponding to the reflectance of the quality state, reliable reproduction can be performed. However, when the comparator level is set between the above intermediate voltage and the voltage of the crystal state closest to the intermediate voltage, the original waveform is obtained. Can be faithfully reproduced. The shaping may be performed using another waveform shaping device.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in more detail with reference to the drawings. <Embodiment 1> FIG. 1 is an example of a method for recording, reproducing and erasing information according to the present invention, and is a graph showing a temporal transition of a laser power (mW). First, a recording track of an optical disk medium having a diameter of 130 mm having an In-Se-based recording film on which information can be rewritten by a crystal-amorphous phase change is set to an amorphous state, and a space between the recording tracks is set to a crystalline state. . The recording track may be in a crystalline state. In this case, it is preferable that the recording track has a crystalline state in which the reflectivity is substantially equal to that of the part in the crystalline state of the track on which recording was actually performed. By maintaining a perfect crystalline state between the recording tracks, during recording and rewriting, heat diffuses between the tracks, causing the crystal to gradually crystallize non-uniformly, and the previously recorded information is mixed into the reproduced signal of new information. It is possible to prevent (a kind of remaining disappearance) and noise increase. After the optical disc medium is rotated, automatic focusing and tracking are performed while irradiating a laser beam (continuous light) of a reproduction level (first level) with one light beam spot along a groove-like track. Do. Then, at the same time as the recording rewrite location (A) is reached, the power is increased at once to the power of the crystallization level (the erasing level (second level)). Then, when a new recording location (B) is reached, the power is pulsedly increased to the laser power of the amorphization level (the recording level (third level)). After that, the laser power is reduced to the crystallization level [second level] (C). However, if the cooling rate is likely to be reduced due to the residual heat, the laser power is changed from the amorphization level (third level) to the crystallization level (second level) or lower ([C) to (dashed lines). D)
Then, the laser power is raised (D) to the crystallization level (second level), and the existing information is erased. In this case, the average laser power between (C) and (D) is preferably from level 0 to just below the crystallization level (second level), and a more preferable range is the crystallization level (second level). 1/4 or more and 3/4 of power
It is as follows. Information can be overwritten by repeating the above laser power cycle. For example, assuming that the rotational speed of the disk is 2400 rpm, 1.8
When a carrier wave of MHz is recorded, the bandwidth is 30 kHz.
The measured carrier-to-noise ratio (C / N) was about 50 dB. Next, when rewriting is performed in the same place with a carrier wave of 0.9 MHz, a reproduced signal of 0.9 MHz is obtained.
Its C / N was also about 50 dB. At this time, the laser power at the amorphous level (third level) is about 15 mW, the laser power at the crystallization level (second level) is about 7 mW,
The reproduction level was about 1 mW. In the above-described laser power cycle, recording can be performed even when the level is immediately returned from the amorphization level (third level) to the crystallization level (second level). Is considered to be slightly lower, the C / N of the reproduced signal is slightly increased.
And S / N (signal / noise) may be deteriorated.
Immediately after raising the laser power from the crystallization level (second level) to the amorphization level (third level), recording is performed by adding a peak power for slightly increasing the power as shown by a broken line. Amorphization of the film can be promoted. Even if the magnitude of the peak power is higher than the amorphization level (third level) to the power difference between the amorphization level (third level) and the crystallization level (second level). Good, but not less than 1/4 and 3/4 of the above power difference
The following ranges are more preferred. The light beam spot was defocused during erasing to prevent unerased information. This was performed by using a focusing lens having chromatic aberration and utilizing the fact that the wavelength changes due to a mode change accompanying a change in laser power. If the focus is set during recording, defocus occurs at an erasing power (second power level) lower than the recording power (third power level). Next, FIG. 3 shows an example of the structure of the optical recording / reproducing / erasing apparatus used in the first embodiment. This optical system has almost the same structure as that of an optical system for write-once optical disks which is currently commercially available. However, at the time of recording and erasing, the reflected light from the recording film 2 may increase to cause a malfunction. Filter 11
So that the amount of incident light was reduced. Further, the output voltage of the detector may be attenuated only during this period without using a filter. When the rotation speed of the disk is high, the irradiation time at one point on the disk is short, and the disk is not completely crystallized. In this case, when light of the crystallization level is again applied during recording / rewriting, crystallization proceeds, so that the reflectivity of the crystallized portion is not constant and varies depending on the location as shown in FIG. Therefore, the comparator level was set between the reproduction output voltage when the light of the reproduction level was applied to the amorphous portion and the reproduction output voltage of the crystallized portion where crystallization had not progressed most, and the waveform was shaped. If the comparator level is set between the two or closer to the output voltage of the amorphous part, the certainty of detection will increase, but if the comparator level is set closer to the output voltage of the crystal part than the middle, the reproduced waveform more faithful to the original waveform Is obtained. In addition, when the amorphous point comes at the beginning of the recording area,
First, it is possible that the laser power is increased from the reproduction level (first level) to the amorphous level (third level) without passing through the crystallization level (second level). When the reproduction is performed by another method or another beam spot, the level is first changed from 0 (zero) level to the crystallization level or the amorphization level. Note that any of the crystallization state and the amorphous state may be considered as recording and any of them may be considered as erasing. But,
Since the laser power is higher in the amorphization, it is preferable that the time during which the power is at the amorphization level (third level) is shorter. In an optical disk device currently on the market, a recording pulse is emitted for a shorter time, so that it is preferable to consider amorphization as recording. In this case, the portion for rewriting the laser drive pulse of a commercially available optical disk device is shown in FIG.
As shown in (1), a rewritable optical disk can be used only by improving the current corresponding to the difference between the reproduction level (first level) and the crystallization level (second level). In the case of FIG. 5, since the amorphization level (third level) of the composite waveform becomes too high, the top of the waveform is limited. By lowering the level of the current to be superimposed and, in some cases, setting it to 0 (zero), it is possible to record / reproduce the write-once optical disc with a rewritable optical disc apparatus. In this embodiment mode, if the amorphous state is changed to another crystalline state or the crystalline state is changed to another amorphous state,
The same applies to the amorphous phase change.

Second Embodiment FIG. 2 shows another example of a method for recording, reproducing and erasing information according to the present invention, and is a graph showing a temporal transition of laser power (mW). is there. This is an example where the recording level is lower than the erasing level. The recording film and the automatic focusing and tracking method used in the present embodiment are the same as those in the first embodiment. First, at the same time as the place (a) to be rewritten comes, the power is raised at once to the power of the erasing level (third level) and is maintained at the same power. During this time, the information has been erased. Then, when a new recording location (b) comes, recording is performed by reducing the power to a laser power of the recording level (second level) in a pulsed manner. At this time, it is possible to sufficiently record even if the power is lowered to the recording level as described above. However, when the power is lowered, the laser power is reduced as shown by a broken line [between (b) and (c)] in FIG. Is greatly reduced once below the recording level, and then slightly raised to return to the recording level, the recording can be performed more reliably by increasing the time at the recordable temperature. The power at the time of lowering the recording level is preferably just below the power of the recording level, and a more preferable range is 1/4 or more and 3/4 or less. Thereafter, the laser power is raised to the erasing level. As shown by the broken line in FIG. 2, the power is once raised above the erasing level (c), and then lowered again to the erasing level (d).
Thus, erasure can be performed reliably. At this time (c) ~
The average power during (d) is larger than the erasing level, and the power of the erasing level may be added to the power difference between the erasing level and the recording level.
1/4 or more of the power difference between the erase level and the recording level, 3
A power of / 4 or less is more preferable. Further, the method for preventing the remaining unerased information is performed in the same manner as in the first embodiment, and the recording, reproduction, and erasure of the information in the present embodiment use the optical system shown in FIG. 3 in the first embodiment. I went. In this embodiment, FIG. 6A shows a change in laser power when performing multi-level recording, and FIG. 6B shows a reproduced waveform. This is an example in which the recording state is ternary, but multi-level recording can be performed by increasing the number of levels, and analog recording can be performed by continuously changing the level. However, since the relationship between the change in the power level and the change in the reproduction voltage is usually not linear, conversion of at least one of the recording waveform and the reproduction waveform is necessary to obtain a desired reproduction waveform.

[0009]

As described in detail above, the information recording / reproducing method according to the method of the present invention can be applied to a reversible phase-change optical disk medium capable of high-speed erasing, or a state change only by a change in irradiation power level. By using a recording medium that can be recorded and erased, new information can be quickly and reliably rewritten with one beam spot using a simple system while erasing existing information.
Further, the irradiation beam used is not limited to a light beam, and an energy beam such as an electron beam or an ion beam can be used. In addition, the recording medium is not limited to a disk, but may be in another form such as a tape or a card. It is applicable to recording media, and its industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a graph showing a temporal transition of laser power exemplified in Embodiment 1 of the present invention.

FIG. 2 is a graph showing a temporal transition of laser power exemplified in Embodiment 2 of the present invention.

FIG. 3 shows an optical recording exemplified in the first embodiment of the present invention,
The schematic diagram which shows the structure of a reproducing and erasing apparatus.

FIG. 4 is a diagram showing an example of a reproduced signal waveform exemplified in the first embodiment of the present invention and a waveform shaping method.

FIG. 5 is a diagram showing a rewrite waveform synthesizing method exemplified in the first embodiment of the present invention;

FIG. 6 is a diagram showing the principle of multi-level recording exemplified in the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk substrate 2 ... Phase change type recording film 3 ... Protective film 4 ... Focusing lens 5 ... Galvano mirror 6 ... 1/4 wavelength plate 7 ... Polarizing prism 8 ... Prism 9 ... Coupling lens 10 ... Semiconductor laser 11 ... Filter 12 ... Convex lens 13 ... Half mirror 14 ... Cylindrical lens 15 ... Knife edge 16 ... Detector for automatic focusing 17 ... Detector for tracking and signal reproduction

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Noriyoshi Horigo 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. Central Research Laboratory

Claims (6)

[Claims] 1. An information recording / reproducing method for forming a recording mark on an information recording medium by irradiating light to record information, and reproducing the recorded information. In this case, first, the optical power is set to the first value when reproducing information.
Of a second optical power level higher than the second optical power level, and then raised to a third optical power level higher than the second optical power level to form a recording mark. Recording and playback method. 2. When recording information, the optical power is first raised to a second optical power level higher than the first optical power level at the time of reproducing information, and then the second optical power is set.
Information that is characterized in that a recording mark row is formed by raising a third optical power level higher than the optical power level of the above and further modulating light between the second and third optical power levels. Recording and playback method. 3. When recording information, the optical power is first raised to a second optical power level higher than the first optical power level at the time of reproducing information, and then the second optical power is set.
To a third optical power level higher than the optical power level of, and a recording mark is formed by using the third optical power level, and the second optical power level is set in a region between the recording marks. An information recording / reproducing method characterized by irradiating an optical power level at or below a power level. 4. An information recording / reproducing method for forming a recording mark on an information recording medium by irradiating light to record information, and reproducing the recorded information. In this case, (1) after performing the operation of raising the optical power level to the second optical power level higher than the first optical power level at the time of reproducing information before entering the recording area,
(2) Next, the operation of raising the optical power level to a level equal to or higher than the third optical power level higher than the second optical power, and (3) the state of lowering the optical power level to the second optical power level or lower. A method for recording and reproducing information, characterized in that the operation is repeated. 5. An information recording method for forming a recording mark on an information recording medium by irradiating light to record information, which satisfies the following conditions (1) to (3): How to record characteristic information. (1) A portion at which the recording mark is formed is irradiated with light at a recording level. (2) Light is irradiated to a portion where the recording mark is not formed, at a level lower than the recording level. (3) In a portion where the recording mark is not formed, a portion immediately before the recording mark is irradiated with light of a higher level than a portion immediately after the recording mark. 6. An information recording / reproducing method for recording and reproducing information by forming a recording mark on an information recording medium by using first, second and third optical power levels, which is described below. A method for recording information, characterized in that the conditions 1) to 4) are satisfied. (1) The second optical power level is higher than the first optical power level, and the third optical power level is higher than the second optical power level. (2) The first optical power level is the optical power level used for reproducing information. (3) The second optical power level is an optical power level used at a portion between recording marks. (4) The third optical power level is the optical power level used at the place where the recording mark is formed.