JPH08180410A - Recording and reproducing method for optical information recording medium - Google Patents

Abstract

PURPOSE: To suppress deterioration in the repeated recording operations at start and end parts of a data part by selectively determine the irradiation energy of a laser beam for forming a mark to be recorded on a VFO region. CONSTITUTION: The recording is performed in such a manner that the energy of the laser beam for irradiation for forming the mark recorded in the front part at least among the marks to be recorded on the VFO region is made smaller than the energy of the laser beam for irradiation for forming the shortest mark among the recorded marks of the data. By this procedure, the VFO is surely reproduced even in the case where the recording is repeatedly made in many times. Also, the VFO and the data succeeding to the VFO are recorded/reproduced by the mark length modulation. Regarding a mark column recorded in the front part at least among the marks to be recorded on the VFO region, the recording is performed so that a ratio of the interval of recording marks to the length of recording mark is larger than 1. Thus, the VFO is surely reproduced when the recording is repeatedly made in many times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recording / reproducing information on / from an optical disk using laser light.

[0002]

2. Description of the Related Art As an optical disk capable of recording / reproducing signals and erasing signals, a phase change type optical disk using a chalcogenide as a recording thin film material is known. In general, a signal is recorded by setting the recording thin film material in a crystalline state as an unrecorded state, irradiating a laser beam, and melting and quenching the recording thin film material to an amorphous state. on the other hand,
In the case of erasing a signal, the recording thin film is heated to a crystalline state by irradiating a laser beam having a power lower than that in recording. In the crystalline state and the amorphous state, the complex refractive index, which is composed of the refractive index n and the extinction coefficient k, is different, and a signal is reproduced by using the resulting difference in reflectance or transmittance.

Recording thin film materials include, for example, Te, In,
It is common to use a material containing Sb, Se or the like as a main component and undergoing a phase change between an amorphous phase and a crystal, or a substance that causes a reversible phase change between two different crystal structures.

One of the merits of phase change recording is that an information signal can be overwritten by using only a single laser beam as a recording means. That is, when the laser output is modulated between the recording level and the erasing level according to the information signal and applied to the recorded information track, a new signal can be recorded while erasing the existing information signal. (JP-A-56-145530). Taking advantage of this feature, the phase change optical disc is used as a document file, an image file, and a data file.

In an optical disk system generally used for information processing, information is exchanged with the outside in fixed lengths called sectors. Although various sector format structures have been proposed, they are basically composed of an address portion, a data portion and a buffer portion as shown in FIG. The address part represents the physical address of the sector and is pre-formatted at the time of manufacturing the disc. The data section is an area where the user records information, and VFO is recorded at the beginning of the data section. This is a continuous and repetitive data pattern provided so that the information can be accurately reproduced even if the disk rotation changes. When the disk changes in rotation, the VFO code pattern also changes at the same time. Therefore, if the PLL is locked to this pattern to generate a clock for reading data, the data can be reliably reproduced.

Further, the recording system can be roughly classified into an inter-mark modulation system and a mark length modulation system. In the inter-mark modulation, the position of the mark is detected and the signal is detected during reproduction, whereas in the mark length modulation, both ends of the mark are detected and the signal is detected.
The mark length modulation can increase the recording density as compared with the inter-mark modulation.

[0007]

In a phase change optical disc, when information is repeatedly recorded in a specific sector a number of times, a recording thin film is formed at the start end (recording start part) and end (recording end part) of a series of recording areas. The phenomenon that the reproduced signal is disturbed due to the change of the shape of is observed. Particularly, when a track is divided into sectors and a relatively short series of data is recorded, the influence of the deterioration of the start end / end end becomes large. Deterioration at the beginning and end of repeated recording is caused by laser irradiation.
It is considered that this is because the recording thin film constituent elements mainly slightly diffuse and move in the disk circumferential direction, and the diffusion movement amount of the recording thin film constituent elements is integrated by repeated laser irradiation. It is considered that the movement of the elements constituting the recording thin film is caused by several factors (for example, Proceedings of the 2nd Phase Change Recording Research Group Symposium page 8-20, Proceedings of the 3rd Phase Change Recording Research Group Symposium 7-32). Page), but the exact point is not yet clear. Since the VFO is arranged at the start end as described above, when the number of repetitions increases, VFO
FO cannot be played. In this case, since the clock cannot be generated, the following data cannot be reproduced. In particular, when the mark length modulation recording is adopted, the start-end / termination deterioration appears more conspicuously than when the mark-interval modulation recording is adopted.

In order to solve the above-mentioned problems of the prior art, the present invention is a signal recording for suppressing repetitive recording deterioration at the beginning and end of the data portion when mark length modulation recording is adopted in a rewritable phase change optical disk. The purpose is to provide a method.

[0009]

In order to achieve the above object, the first structure of the recording / reproducing method of the optical information recording medium according to the present invention records at least the front of the marks recorded in the VFO area. It is characterized in that the irradiation energy of the laser light for forming the mark is set smaller than the irradiation energy of the laser light for forming the shortest mark of the data recording mark.

The second structure of the recording / reproducing method for an optical information recording medium according to the present invention is to record / reproduce VFO and data following VFO by mark length modulation, and to perform VFO.
Among the marks to be recorded in the area (1), at least the mark row to be recorded in the front is recorded so that the ratio of the recording mark interval to the recording mark length is larger than 1.

[0011]

According to the first structure of the optical information recording / reproducing method of the present invention, the irradiation energy of the laser light for forming at least the mark to be recorded ahead of the marks to be recorded in the VFO area is set as the data irradiation amount. When the recording is performed with the irradiation energy of the laser beam for forming the shortest mark of the recording marks being smaller than that of the recording marks, the VFO can be surely reproduced even when the recording is repeated many times.

According to the second structure of the optical information recording / reproducing method of the present invention, the VFO and the data following the VFO are recorded / reproduced by the mark length modulation, and the mark to be recorded in the VFO area is recorded. By recording so that the ratio of the recording mark interval to the recording mark length is greater than 1 in at least the mark row to be recorded forward, it is possible to reliably reproduce the VFO even when recording is repeated many times. Become.

[0013]

EXAMPLES The present invention will be described in more detail below with reference to examples.

FIG. 1 is a schematic diagram showing the irradiation energy amount of a laser beam when writing a VFO and a mark row of data in the data section of the same sector for explaining the present invention.
In FIG. 1A, data following VFO is recorded / reproduced by mark length modulation, and irradiation energy of laser light for forming a mark to be recorded in a VFO area is used to form the shortest mark of data recording marks. The recording energy is shown to be smaller than the irradiation energy of the laser light for recording. When such recording is performed, if repeated recording is performed, VFO
Since the temperature rise history due to the recording in the area is smaller than the temperature rise history in the data part, the start edge deterioration in the repeated recording, in this case, the deterioration of the reproduction signal in the VFO is suppressed.

FIG. 1B shows a recording mark interval with respect to the VFO and the data following the VFO, which is recorded / reproduced by the mark length modulation, and at least the mark row to be recorded ahead of the marks recorded in the VFO area. A state in which recording is performed so that the ratio of recording mark lengths is larger than 1 is shown. Even in the case of such recording, when repeatedly recorded, the temperature increase history due to recording in the VFO area is smaller than the temperature increase history when the VFO mark is recorded with the mark interval narrowed, so repeated recording The start-end deterioration in the is suppressed.

In order to eliminate the influence of the deterioration of the terminal portion, dummy data is continuously recorded after the end of data recording,
The dummy data section may not be reproduced. The length of the dummy data differs depending on the expected disk usage. That is, when a large number of repetitions are expected, dummy data of a sufficient length is required accordingly, and when almost no repeated recording is performed, it is not necessary to provide dummy data. .

FIG. 3 is a schematic diagram showing a recording format in the data portion of the same sector for explaining the present invention. That is, in order to eliminate the influence of the deterioration of the reproduced waveform due to the repeated recording due to the thermal history nonuniformity of the temperature rise at the boundary between the VFO and the data area, the state of recording the damy data after the VFO, that is, at the beginning of the data Indicates.
The dummy data may be recorded with a mark by the same modulation method as the true data. Even if the dummy data cannot be reproduced by repeated recording, there is no problem if the true data can be reproduced. The head information of the data is recorded at the head of the true data. The length of the dummy data differs depending on the expected disk usage.

FIG. 1C is a diagram showing another recording method for eliminating the influence of the deterioration of the reproduced waveform due to the repeated recording caused by the nonuniform thermal history at the boundary between the VFO and the data area. That is, VFO records / reproduces by mark-to-mark modulation, data following VFO records / reproduces by mark-length modulation, and VF
FIG. 8 is a diagram showing a state in which the irradiation energy of laser light for forming a mark to be recorded in the front of the O region is smaller than the irradiation energy of laser light for forming a mark to be recorded in the rear of the VFO region. is there. By recording in this way, abrupt heat history nearness does not occur at the boundary between the VFO and the data area, and deterioration of the reproduced waveform due to repeated recording is greatly suppressed. Therefore, dummy data is recorded between the VFO and the data. Alternatively, the area of the dummy data can be made very short. In this case, V
Even if the length of the mark forming the FO changes, it is necessary to devise a recording / reproducing method so that a clock having a constant frequency can be generated when the VFO is reproduced. The first record
The reproducing method is a method of recording so that the centers of the VFO marks are arranged in a constant cycle and only the mark centers are detected during reproduction. The second method is a method of recording so that the front ends of the VFO marks are arranged at regular intervals, and only the front ends of the marks are detected during reproduction. A third method is a method of recording so that the rear ends of the VFO marks are arranged in a constant cycle, and only the rear ends of the marks are detected during reproduction.

Further, in order to prevent the deterioration of the reproduced waveform due to the repeated recording, as described in JP-A-2-94113, the relative positional relationship between the recording start point of VFO and data and the optical information recording medium is defined as follows. Better recording characteristics can be obtained by using a method of recording by changing the recording for each repeated recording.

FIG. 4 is a block diagram showing an example of an optical disk recording apparatus using this method. This apparatus includes a rotating optical disc A, an optical system B for converging laser light on the optical disc A, an information recording section C for modulating the laser light,
It is composed of a reproduction controller D for reproducing information from the optical disc A and controlling the light spot.

The optical disk A is composed of a substrate 1 and a recording thin film 2 on the substrate 1. The substrate 1 is a PMM.
A, resin such as polycarbonate or glass or the like having a smooth surface is used. In the case of an optical disc, the normal substrate plane 3
Are covered with spiral or concentric tracks to guide the laser light. A recording thin film material that records a signal by causing a phase change upon irradiation with laser light is mainly composed of a substance that reversibly changes its structure between a crystalline state and an amorphous state, such as Te or In, Se, or the like. It consists of a phase change material. Te-S is the main component of well-known phase change materials.
b-Ge, Te-Ge, Te-Ge-Sn, Te-Ge-Sn-Au, Sb-
Te, Sb-Se-Te, In-Te, In-Se, In-Se-Tl,
In-Sb, In-Sb-Se, In-Se-Te and the like can be mentioned.

In the data section following the address section, first, V
The VFO pattern train stored in the FO generation unit 4 is read in synchronization with the gate signal output from the recording gate generation unit 5, and the drive circuit 6 generates a pulse having a waveform corresponding to the VFO pattern train. . Subsequently, the data signal temporarily stored in the buffer memory 7 is read in synchronization with the gate signal output from the recording gate generator 5, modulated by the modulator circuit 8 for example 2-7, and then the data signal is read by the drive circuit 6 as described above. -7 Generates a pulse having a waveform corresponding to the modulated data. If dummy data is placed between the VFO pattern row and the data or after the data, the dummy data
This can be dealt with by storing each dummy data in the data generator 9. One VFO pattern
Even when changing within the area of FO, the information is changed to VFO.
It may be stored in the generation unit 4.

In the optical system B, the light of the semiconductor laser 10 is collimated by the collimator lens 11, passes through the polarization beam splitter 12 and the quarter-wave plate 13, and is reflected by the objective lens 14 onto the recording thin film 2 of the optical disc A. Collected. The condensed light is reflected by the recording thin film 2,
After passing through the objective lens 14 and the quarter-wave plate 13 again, the light is reflected by the polarization beam splitter 12, and the photodetector 15
Is received by. The signal photoelectrically converted by the photodetector 15 is amplified by the preamplifier 16 of the reproduction controller D.

The reproduction control unit D is converted by the focus / tracking control unit 17 into a control signal by using the low frequency component of the signal from the preamplifier 16, and the objective lens 14 is operated.
The voice coil 18 for supporting the optical disk is driven to focus and track the light spot on the optical disk. On the other hand, the demodulation circuit 19 demodulates the signal from the mark row formed on the optical disc A using the high frequency component of the signal from the preamplifier 16. The reproduction data thus demodulated is temporarily stored in the buffer memory 20.
By reading the data stored in the buffer memory 20, the data recorded on the optical disk is reproduced.

The effects of the present invention will be described below with reference to specific examples. An optical disc A was prepared and rotated at a speed such that the linear velocity in the recording section was 10 m / s to record a signal. The optical disc A is provided with a polycarbonate resin having an address area and a guide groove for tracking on the surface of the substrate, a Ge ₂ Te ₂ Sb ₅ recording thin film, and a protective layer made of ZnS and an aluminum reflecting layer on both sides of the recording thin film. It has a different configuration. The data used for recording is 2-7RLL
The code mark length modulation recording and EFM were used to set the shortest mark length and the shortest mark interval to 0.8 μm. The Reed-Solomon code was used as the signal error correction method. Also, VF
The region of O had a length of 50 μm. Recording on an optical disk is performed by modulating the power of a semiconductor laser having a wavelength of 780 nm between a recording power and an erasing power according to a data signal. Here, the data recording power is 13 mW, the erasing power is 6 mW, and the reproducing power is 1 mW.
And The recording power and the erasing power are the powers at which the reproduced signal error does not occur in the center of the data portion by the repeated recording of 50,000 times. The recording power of VFO was changed as needed. The laser light irradiation conditions for VFO mark formation can be freely set by rewriting the data stored in VFO generation.

Under the same laser beam irradiation conditions for the recording section,
If the mark period is the same in the VFO part, VF
As the irradiation energy of the laser beam for forming the O mark was lowered, the repeated deterioration at the head of the VFO was reduced. As a method of lowering the energy, the recording power was lowered, the irradiation time of the recording power was shortened, or a combination of the two was tested. Table 1 shows, as one of the experimental results, a VF of a mark row which is periodic with a mark having a mark period of 1.6 μm and a duty of 50% (corresponding to the shortest mark length in the data).
The recording power for forming a VFO mark when O is recorded and the length of the reproduction waveform deterioration area after recording 50,000 times at the beginning of the VFO are shown. The modulation method is mark length modulation recording of 2-7 RLL code. The length of the waveform deterioration area was defined as the length of the area where the signal was reproduced by mistake. In this case, the recording power holding time for forming marks in VFO was set equal to the recording power holding time for forming the shortest marks in data. From Table 1, when the recording power for forming marks in the VFO is lowered, the length of the waveform deterioration area at the VFO head portion becomes shorter, and the V
It can be seen that the FO can be reproduced. However, if the recording power is lowered too much, the amplitude of the reproduced waveform becomes small and the reproduction cannot be performed correctly.

[0027]

[Table 1]

Here, when attention is paid to the boundary portion where the VFO area ends and the data mark row starts, a waveform distortion of about 10 μm was observed. It is considered that this is because the average light irradiation power in the VFO area is smaller than the average light irradiation power in the next data portion, and an uneven boundary occurs in the thermal history of temperature rise. Considering this point, VF
By gradually increasing the irradiation energy of the laser light for forming the mark in O within the region of VFO and approaching the average laser light irradiation energy in the data, it is possible to suppress the distortion of the reproduced waveform between the VFO and the data. It was confirmed.

Next, when the VFO and the data mark have the same modulation method, the same recording power, and the same recording power irradiation duty, the VFO mark interval / mark length ratio is within a range permitted by each modulation method. investigated. As a result, it was found that, when the ratio of mark interval / mark length was made larger than 1, when VFO was recorded with periodic data, the length of waveform deterioration due to repeated recording at the head of VFO was short. Further detailed examination revealed that the effect is remarkable when the ratio of mark interval / mark length is set to be larger than 1.5. That is, it was confirmed that the deterioration length of the VFO head was 60% or less compared to the case where the same ratio was 1. Further, in order to reduce the distortion of the reproduced waveform seen at the boundary where the VFO area ends and the data mark row starts, in the VFO area, the ratio of mark interval / mark length is set to the rear side. It has been confirmed that it is effective to bring the ratio closer to 1, that is, to reduce the same ratio in the rear.

[0030]

As described above, according to the present invention,
Recording is performed by setting the irradiation energy of laser light for forming at least a mark to be recorded ahead of the marks to be recorded in the VFO area smaller than the irradiation energy of laser light for forming the shortest mark of data recording marks. By doing so, it becomes possible to reliably reproduce the VFO even when recording is repeated many times.

Further, the VFO and the data following the VFO are recorded / reproduced by mark length modulation, and at least the mark row to be recorded ahead of the marks to be recorded in the VFO area, the recording mark interval and the recording mark length are set. By recording so that the ratio becomes larger than 1, it becomes possible to surely reproduce the VFO even when recording is repeatedly performed many times.

[Brief description of drawings]

FIG. 1A is a diagram showing an example of a recording method according to an embodiment of the present invention, FIG. 1B is a diagram showing another recording method, and FIG. 1C is a diagram showing another recording method.

FIG. 2 is a diagram showing the structure of a sector format on an optical disc.

FIG. 3 is a diagram showing a recording format in a data section of the same sector in an embodiment of the present invention.

FIG. 4 is a diagram showing an embodiment of an optical information recording / reproducing apparatus according to the present invention.

[Explanation of reference numerals] 1 substrate 2 recording thin film 3 substrate surface 10 semiconductor laser 11 collimator lens 12 polarization beam splitter 13 quarter wave plate 14 objective lens 15 photodetector 18 voice coil

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Akabira 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (9)

[Claims] 1. An optical information recording medium provided with a recording thin film on a substrate, which is capable of reversibly shifting to a state having different optical constants by causing a phase change by irradiation of laser light, and irradiating laser light of a predetermined wavelength. Is a method of continuously recording / reproducing information in the data part of a sector into which a track is divided, in which VFO is recorded at the beginning of the data part, data is subsequently recorded, and data following the VFO is The irradiation energy of the laser beam for recording / reproducing by mark length modulation and forming at least the mark to be recorded ahead of the marks to be recorded in the VFO area is used to form the shortest mark of data recording marks. A recording / reproducing method for an optical information recording medium, which is characterized in that recording is performed by making the irradiation energy of the laser beam smaller. 2. An optical information recording medium provided with a recording thin film on a substrate, which is capable of reversibly shifting to a state having different optical constants by causing a phase change by irradiation of laser light, and irradiating laser light of a predetermined wavelength. Is a method of continuously recording / reproducing information in the data part of a sector into which a track is divided, in which VFO is recorded at the beginning of the data part, data is subsequently recorded, and VFO and VFO are recorded. Subsequent data is recorded / reproduced by mark length modulation, and is recorded so that the ratio of the recording mark interval to the recording mark length is greater than 1 for at least the mark row to be recorded ahead of the marks to be recorded in the VFO area. A recording / reproducing method for an optical information recording medium, characterized in that 3. The VFO area is recorded so that a ratio of a recording mark interval and a recording mark length is greater than 1.5 with respect to at least a mark row to be recorded ahead of a mark to be recorded. 2. A recording / reproducing method for the optical information recording medium described in 2. 4. The recording is performed with irradiation energy of laser light for forming a mark to be recorded in front of the VFO area being smaller than irradiation energy of laser light for forming a mark to be recorded in the rear of the VFO area. The recording / reproducing method for an optical information recording medium according to claim 1, wherein 5. A recording / reproducing method for an optical information recording medium according to claim 1, wherein the dummy data is continuously recorded after the data recording is completed. 6. The recording / reproducing method for an optical information recording medium according to claim 1, wherein dummy data is recorded between the VFO and the data. 7. The VFO is recorded so that the front end intervals of the marks are equal, the VFO is reproduced by detecting the front end of the mark, and the data following the VFO is recorded / reproduced by mark length modulation. A recording / reproducing method for the optical information recording medium according to claim 2. 8. The VFO is recorded such that the trailing edges of the marks are evenly spaced, the VFO is reproduced by detecting the trailing edge of the mark, and the data following the VFO is recorded / reproduced by mark length modulation. The recording / reproducing method of the optical information recording medium according to claim 2. 9. The optical information recording according to claim 1, wherein the relative positional relationship between the recording start point of VFO and data and the relative position of the optical information recording medium is changed for each repeated recording. Recording / playback method of media.