KR100266950B1 - Optical disc - Google Patents

Abstract

The present invention relates to a high-density optical recording medium having a track width smaller than the optical spot diameter. When the optical spot causes grooves or lands to be tracked, tracking errors (tracking offsets) increase, making it difficult to perform high density recording that narrows the track pitch. In order to solve the problem of causing a problem, a groove and land are provided on the substrate, and there is an interruption area sandwiched between portions of the groove to provide an information recording area and a prepit area formed on both sides thereof. The prepit is disposed on the virtual extension line of the boundary between the groove and the land, is located on both sides of the virtual extension line of the center line of the groove, and is located on both sides of the virtual extension line of the center line of the land, and any specific position of the center line of the groove. An optical recording medium is provided on both sides of any specific position of the center line of the land, which does not exist on both sides.

By using such an optical recording medium, the substrate can be manufactured by a simple mastering device and the radiation can be easily prepared, thereby providing an inexpensive and high density optical recording medium.

Description

Optical disc

The present invention relates to an optical recording medium, and more particularly to an optical recording medium of high density having a track width smaller than the optical spot diameter.

As an example of the medium which performs a high density (narrow track) recording, there exist some described in JA-A-6-176404, for example. According to this example, in an optical information recording medium having grooves and groove portions (lands) formed on a substrate and an information recording area formed in association with both of the grooves and lands, the optical information recording medium has a free extension on the virtual extension line between the groove and land boundaries. A pit is arranged. In particular, the prepit is located only on one side of any particular position of the centerline of each groove.

In this structure, the recording information is formed on both the groove and the land, and the prepit has charges of address data representing the recording area, and one prepit is common in a pair of adjacent grooves and lands to provide the address data. Used as When the above technique is applied to a phase change recording medium or a magneto-optical recording medium, it is possible to prevent interference (crosstalk) between information between adjacent grooves or lands due to the optical interference effect in the optical spot, thereby making the track narrower. Can be achieved.

On the other hand, in the prepit area, free from the optical interference effect, the address data becomes common in the paired grooves and lands, and the track pitch can be effectively increased to reduce crosstalk.

However, in the example of JA-A-6-176404, the tracking error (tracking offset) increases when the arrangement of the prepit areas is offset from one side of the center line of the groove or land so that the light spot tracks the groove or land. This makes it difficult to perform high density recording to narrow the track pitch.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object of the present invention is to execute an effective arrangement of address data even when recording is performed on both a home and a land, and to a sufficiently low value or level in actual use. An optical recording medium capable of suppressing tracking offset is provided.

It is a second object of the present invention to provide a high density optical recording medium which ensures simple mastering and easy replica preparation and can perform decoding even in the case of a read error.

1 is an enlarged fragmentary plan view of a first embodiment of an optical recording medium according to the present invention;

2 is a waveform diagram reproduced from the medium of FIG.

3 is a block diagram of a recording / playback apparatus of an optical recording medium used in the present invention.

4 is an enlarged plan view of a second embodiment of an optical recording medium according to the present invention;

5 is an enlarged partial plan view of a third embodiment of an optical recording medium according to the present invention;

6 is an enlarged partial plan view of a fourth embodiment of an optical recording medium according to the present invention;

7 is a waveform diagram of a signal reproduced from the optical recording medium of FIG.

8 is an enlarged fragmentary plan view of a fifth embodiment of an optical recording medium according to the present invention;

Fig. 9 shows the information structure in the fifth embodiment of the optical recording medium according to the present invention.

10 is an enlarged partial perspective view between the prepit and the groove in the fifth embodiment.

11 is an enlarged partial plan view showing detailed positional displacement in an embodiment of an optical recording medium according to the present invention.

12 is an enlarged plan view of a sixth embodiment of an optical recording medium according to the present invention;

13 shows an example of a modulated code in the sixth embodiment of an optical recording medium according to the present invention.

The following means are used to achieve the first object described above.

(1) Grooves and lands are formed on the substrate of the recording medium, an information recording area is formed in association with both of the grooves and lands, and prepits are disposed on a virtual extension line between the grooves and the lands.

The arrangement of the prepits simultaneously satisfies the following conditions (a) to (c).

(a) The prepit is located on both sides of the virtual extension line of the center line of the groove.

(b) Prepits are located on both sides of the virtual extension line of the centerline of the land.

(c) The prepit is not located on either side of any specified position of the centerline of the groove.

(d) Prepits are not located on either side of any particular position of the land.

In this structure, the arrangement of the prepits is not offset at either side of the virtual extension line of the center line of the groove or land to ensure that the tracking offset hardly occurs, and the prepit information between adjacent tracks taken in the reproduced spot. Since there are no prepits on both sides of any particular position of the center line of the groove or land to prevent interference of the tracks, high-density narrowband track recording can be achieved.

(2) When the prepits are arranged in the circumferential direction, one side of the groove is not distinguished from the other or one side of the land is distinguished from the other, and at least two consecutive arrangements of the prepits associated with the groove or land are Periodically, the two arrangements are made differently to provide the same arrangement of prepits.

(3) grooves associated with at least one pair of pits disposed on both sides of the centerline of the grooves in the prepit area and adjacent grooves not associated with the pits disposed on both sides of the centerline of the grooves in the prepit area alternately in the radial direction. Are arranged.

As a result, the pit is hardly reproduced, so that the prepits associated with the home can be distinguished from those associated with the land, thereby improving the reliability of information recording and reproduction.

(4) One of the synchronization information and the address data is represented by a prepit disposed on either side of the groove.

(5) Only one of the synchronization information and the address data is represented by the prepits arranged on either side of the groove, and both the synchronization information and the address data are represented by the prepits arranged on the other side of the groove.

This allows the address data to be reproduced with correct synchronization. In addition, since the phase margin between both prepits can be extended, the manufacture of the recording medium can be facilitated.

(6) The prepits and grooves have the same depth of 70 nm or less. More preferably, the depth is 40 nm or more and 60 nm or less.

This structure not only provides the advantage of crosstalk cancellation between the grooves and lands, but also provides an excellent tracking servo signal. Formation and manufacture of a recording medium can be facilitated. If the depth of the groove is 70 nm or more, the formation of the groove becomes difficult. When the groove depth is about 50 nm, the tracking servo is minimized. When the groove depth is about 50 ± 10 nm, substantially the same effect can be obtained.

(7) The grooves and lands have substantially the same width between 0.3 µm and 0.7 µm.

This structure makes it possible to achieve both excellent tracking and high density recording. If the width of the grooves and lands is smaller than 0.3 mu m, both of the grooves and lands are limited in one light spot, and an excellent tracking signal cannot be obtained. On the other hand, if the width of the grooves and lands exceeds 0.7 m, efficient high density recording cannot be performed.

(8) The minimum size of the prepits has a diameter smaller than the respective widths of the grooves and lands. More preferably, the diameter is in the range of 0.25 µm to 0.55 µm.

As a result, an excellent prepit signal without crosstalk can be obtained. If the diameter is smaller than 0.25 mu m, the prepit signal is extremely reduced, and if the diameter exceeds 0.55 mu m, crosstalk occurs.

In the present invention, the prepits are arranged on both sides of the virtual extension line of the center line of the groove or land in the light spot scanning direction. Therefore, the offset is reduced so that the tracking offset hardly occurs, and since there are no prepits on both sides of any particular position of the center line of the groove or land, the interference of the prepit information between adjacent tracks in the reproduced spot is prevented. In this way, high-density narrowband track recording can be realized.

Further, even when there is a tracking offset, the amount of tracking offset can be accurately detected by comparing the amplitudes of the signals appearing at both prepits. Therefore, the tracking offset can be suppressed by feedback control of the information indicating the comparison result with the scanning apparatus.

When the prepit column on the virtual extension line of the boundary between the groove and the land moves to the prepit column on the adjacent virtual extension line, a gap is formed between the groove and the prepit region, between the land and the prepit region, and between the prepit region. However, the above-described JP-A-6-176404 does not consider this gap. Thus, if there is no gap or the gap is very short, the mastering of the substrate is not processed by one beam cutting and requires two beam cutting. In addition, during the preparation of the replica, the injection must be applied to a steep pattern, thereby reducing manufacturing efficiency. In addition, when the signal is reproduced, the tolerance for the disturbance of the tracking offset and the reproduced spot is reduced and lead errors occur.

In order to achieve the above-mentioned second object, the following means are used.

(1) Grooves and lands are formed on the substrate, and prepits are disposed on the virtual extension line between the grooves and the lands. In particular, since the prepits are arranged on both sides of the extension of the center line of the grooves or lands, the optical axis of the laser beam must be moved during cutting. AOD (acoustic-optical deflector) is used to change the optical axis. However, after transmitting a signal for changing the optical axis, it takes time to move the AOD to the desired optical axis position, and when the modulated laser beam is irradiated along the original optical axis, the pits are obliquely formed on the substrate. Thus, the pattern is not formatted between the land or groove and subsequent prepits to provide a gap, and the acoustic-optical modulator (AOM) is stopped in response to the gap to prevent laser irradiation and pit drawing. Thus, the substrate can be manufactured by simple cutting. In addition, since a large number of non-uniformities are not formed in a narrow area on the substrate, it is possible to increase the efficiency in preparing the replica.

(2) In the arrangement in which the prepits are arranged on the virtual extension line of the boundary between the groove and the land, the arrangement of one prepit row of the virtual extension line of the boundary between the groove and the land is different from the arrangement of the other prepit rows. When changed, the falling edges of each one of the prepit rows are aligned with each other in the radial direction of the substrate. Subsequent pit rows are separated from these falling edge positions in the circumferential direction or the recording / reproducing direction, and the falling edges of the subsequent pit rows are likewise aligned with each other. If the gap formed conforms to the recording rule, all of the substrate can be conveniently formatted, and a portion without pit is collected in a specific area on the substrate, thereby solving the problems involved in cutting and replica preparation as described above. have.

(3) Radially adjacent pits, each having only the original information pits, are not aligned with each other at the falling edges in the radial direction. Thus, a new pit can be added to ensure alignment of the falling edge in the radial direction while complying with the rule during recording.

(4) As described in (2) above, in the movement of the arrangement of the pit rows from one side to the other, the rising edges of the pit in the other arrangement may be aligned in the radial direction, as described in (2) above. The problems involved in cutting and replica preparation can be solved. In particular, from the point of view of signal reproduction, a synchronization signal is assigned to the pit information immediately after the movement of the pit sequence, so that the determination of the channel bits at a specific position is important, thereby increasing the tolerance of the rising edge position. Important data at the location, for example, can reduce the read error of the address.

Example 1 Optical Recording Medium

1, which is a partially enlarged plan view of an optical recording medium of the present invention.

Each groove 84 having a width of 0.6 mu m and a depth of 50 nm and each land 85 having a width of 0.6 mu m are alternately arranged in the radial direction of the medium, and the recording marks 81 are formed on two kinds of areas. do. That is, each groove 84 and land 85 function as a recording area. Although no groove is formed in the prepit 83, the pit 82 is disposed on the extension of the boundary between the land and the groove. Each pit has a width of 0.35 μm and a depth of 50 nm. The prepit area is divided into a first prepit area 831 and a second prepit area 832. In the first prepit area 831, the pit 82 is disposed above the centerline of the land 85, as shown in the figure, and in the second prepit area 832, the pit 82. ) Is disposed below the centerline of the land 85 as shown in the figure. Thus, for example, when the light spot 21 scans the land 85, only one pit is always reproduced so that there is no fear of crosstalk between adjacent tracks. Thus, address data recorded in the prepit format is sufficiently recorded without crosstalk.

Since the pits 82 are not adjacent to each other in the radial direction, they can be easily formed. Further, since the pit 82 is uniformly arranged on both sides of the track (groove or land), the influence of the tracking servo signal generated by the pit 82 can be eliminated. Therefore, the tracking offset can be sufficiently reduced.

For example, in the case of reproducing the land 85, the reproduction of the address data in the second prepit area 832 is continuously performed in the reproduction of the address data in the first prepit area 831. Therefore, when two areas are combined in one area in which information is arranged to provide address data for one track, the land address (track number) and the address of the groove are set independently of each other. That is, by sequentially reproducing the address data portions in the first and second prepit areas 831 and 832, it is possible to ensure the distinction between the land and the groove.

In particular, the address data indicated by the prepits arranged in the first prepit area for reproduction of the groove is made the same as the address data indicated by the prepits arranged in the second prepit area, The address data indicated by the prepits arranged in the first prepit area for reproduction is made different from the address data indicated by the prepits in the second area. If the addresses indicated by the prepits in the first and second prepit areas are different from each other, the two addresses may be set as a correlation, and the use of this correlation may increase the efficiency of the error correction code. have.

Preferably, the synchronization information (VFO) 86 and the address data 87 may be arranged in each of the first and second prepit areas.

In this embodiment, the prepit area is divided into first and second prepit areas, but may be divided into a plurality of areas. For example, when the number of divisions is four, the pits in the first and third prepit areas may be arranged on one side of the grooves, and the pits in the second and fourth prepit areas may be arranged on the other side of the grooves. By increasing the number of divisions of the prepit area, for example, reliability of defects can be improved.

Here, a phase change recording material (GeSbTe) was used as the recording film. Thus, the recording mark is formed in the form of the amorphous domain.

An example of the configuration in which the optical recording medium of the present invention is applied to an optical recording / reproducing apparatus will be described with reference to FIG. In the apparatus, a semiconductor laser and a collimating lens having a wavelength of 680 nm are used as the light source 31. If necessary, a beam profile former such as a prism may be provided. The power of the semiconductor laser is controlled by the optical power controller 71 having an automatic optical power control function. The light beam 22 emitted from the light source 31 is focused on the magneto-optical recording medium 8 by means of the focusing optical system 32. The focusing optical system 32 includes at least one lens, and in this embodiment also includes a beam splitter. The objective lens for focusing the light beam on the optical recording medium 8 is designed to have an aperture of 0.6. Therefore, the light spot 21 on the optical recording medium 8 has a diameter of 1.0 mu m. The light spot can be moved to a desired position on the optical recording medium 8 by means of the scanning device 6. The scanning device 6 includes a motor 62 for rotating an optical recording medium such as a disk and an automatic position controller having a function of automatic focus control and automatic tracking. The automatic position controller 61 uses the reflected beam 23 in the optical recording medium 8 so that the photodetector 33 detects the light spot position used for the feedback control. The light spot position can be detected by detecting the power of the diffracted light beam from the groove. The photodetector 33 is composed of a lens, a beam splitter, and a plurality of photodetectors, and the output signals of the plurality of photodetectors are calculated to generate a reproduction signal and a servo signal.

By using the optical recording medium as shown in FIG. 1, the signal shown by 14 in FIG. 2 as a prepit signal is generated. The signal is inputted to the address detecting device to decode the address data and the signal timing of the first and second prepit areas is detected, and the amplitudes of the first and second prepit areas according to the timing information. (Mean peak to peak amplitude) is stored. The amplitudes thus stored are compared with each other by means of an amplitude comparator to produce tracking offset information fed back to the position shifting device (scanning device). In Fig. 2, when the light spot scans the grooves, the magneto-optical reproduction signal 11 and the prepit signal 14 (upper part in the drawing) are reproduced, and when the light spot scans the land, The prepit signal 14 (lower in the figure) corresponding to the reproduction signal 12 is reproduced. In this embodiment, since the light spot is slightly offset as shown in Fig. 1, the prepit signal in the first prepit area 831 and the prepit signal in the second prepit area 832 Amplitude difference 13 occurs. This amplitude difference corresponds to the tracking offset amount.

By using the apparatus of FIG. 3, even when various kinds of external disturbances such as deviation of light spots are considered, the tracking offset can be reduced to ± 0.03 mu m or less. There was no optical deviation under normal conditions, and the tracking offset was below ± 0.015 μm.

As described above, in the present invention, the prepit is disposed on both sides of the virtual extension line of the center line of the groove or land as shown in FIG. Thus, the offset is reduced so that tracking offset hardly occurs. Since there are no prepits on both sides of any particular position of the center line of the groove or land, interference of prepit information between adjacent tracks does not occur within the reproduced spot, thereby ensuring high density narrowband track reproduction. have.

In addition, when the tracking offset occurs as shown in Fig. 2, the tracking offset amount can be accurately detected by comparing the signal amplitudes of the prepits located on both sides. Therefore, the tracking offset can be suppressed by feedback control of the information indicating the comparison result with the scanning apparatus.

In addition, the identification between the groove and the land can be easily performed.

By using the optical recording medium of the present invention, not only can the tracking offset be substantially reduced to a sufficiently small level (0.03 mu m or less), but also address data can be easily obtained even at high density narrow band track recording. By using the optical recording / reproducing apparatus of the present invention, the tracking offset can be immediately reduced by feedback control.

Example 2

A fourth embodiment of the present invention will be described with reference to FIG. In the medium of this embodiment, the synchronization information feet 861 to 864 are disposed above the center lines of the grooves 841, 842, 843, 844, and 845 (as seen in the drawing), In the first embodiment, only the synchronization information feet 861-864 and the address data feet 871-874 are disposed on both sides of the center line of the respective grooves 84 (as seen from the drawing). The difference is that. Preferably, the address data pits 871-874 are continuously arranged in the synchronization information pits 861-864. In the case of the land 85, the relationship between the upper side and the lower side is reversed.

Different from the first embodiment, since the present embodiment has address data arranged only above or below the center line of the groove or land, the same address data is assigned to the land and the groove. In this embodiment, four divided prepit areas 831 to 834 are provided to improve the reliability of the prepit areas, but the prepit areas are not always divided. In this embodiment, the sync pit 861 in the first prepit area 831 is the area of the second to fourth prepits by compensating the effect of aliasing of the signal passing through the low pass filter. It is designed to have a length longer than the synchronous feet within. Preferably the pits disposed above and below are spaced at least 0.5 mu m from each other in the manufacture of the medium. In particular, they are spaced by a distance of about 1 mu m, which is the diameter of the reproduced optical disc spot.

Example 3

A third embodiment in which the identification mark 88 is used to distinguish the land in the groove is described according to FIG. In this embodiment, an identification mark 88 for distinguishing between the groove and the land is provided separately from the prepit area in the first and second embodiments.

In this embodiment, the pair of pits (identification marks) 88 are arranged above and below (as seen in the drawing) the centerline of the grooves 841, 843 or 845, but not the grooves 842. Or 844. When the medium provided with the identification mark is reproduced, if the light spot moves relatively from left to right in the drawing and the identification mark appears due to the light spot, the status is " Yes " Assume a case, "Y, Y" is maintained for groove 841, "N, Y" is maintained for land 851, "N, Y" is maintained for groove 842, "Yes" is maintained for land (852). In addition, "Y" is maintained for the groove 843, "Y," is maintained for the land 853, "Y, nothing" is maintained for the groove 844, "Y, Nothing is retained for land 854. That is, one of "Y, Y" and "N, N" is maintained for the home, and "N, Y" and "Y, N" are reserved for the land. Therefore, it is used to perform identification of the home and land in accordance with the reproduction signal. In order to ensure reliability, several pairs of identification marks may be provided, and it is more preferable that the paired pits are spaced several micrometers or more from each other in the information track direction or the circumferential direction of the medium perpendicular to the radial direction. For example, it is preferable that the prepit area and the identification mark area of the above-described embodiment are alternately arranged in the circumferential direction.

Example 4

An optical recording medium according to a fourth embodiment of the present invention will be described with reference to FIG. Grooves 84 each having a width of 0.5 mu m and a depth of 40 nm and a land 85 having a width of 0.5 mu m are alternately arranged, and recording marks 81 are formed on two kinds of regions. That is, each land 85 and groove 84 function as a recording area. In the prepit area 83, no groove is formed, but a substantially circular pit 82 (0.3 m in diameter and 40 nm in depth) is disposed on the extension of the land and groove boundary. The prepit area is divided into a VFO (variable frequency oscillation) area 833 and an address area 834.

In particular, in the VFO region, the pits 82 are alternately arranged on the upper side and the lower side of the centerline of the land 85. Pits 82 are alternately arranged in the same period as in the VFO in the address area. Thus, no pit exists on both sides of the location of the center line of the land or groove.

In addition, in the address area, data for a specific track is encoded so that it differs by one foot from data for adjacent tracks. That is, the data takes the form of gray codes. With this arrangement, when the light spot 21 scans the land 85, for example, only one of the pits is always reproduced so that there is no fear of crosstalk between adjacent tracks. Therefore, the address data distributed in the pits can be reproduced sufficiently without crosstalk. Since the pits 82 for the adjacent tracks are not adjacent to each other, this can be easily formed. In addition, since the pit 82 is uniformly arranged on both sides of the track (land or groove), the influence of the tracking servo signal by the pit 82 can be eliminated. Therefore, the tracking offset can be minimized.

When the medium of the embodiment of Fig. 6 is reproduced by the apparatus of Fig. 3, since the reproduction signal as shown in Fig. 7 indicating that different data portions can be obtained for each track, the address data is generated. It is efficiently recorded at high density. As a result of using the gray code, the address is reproduced even in the case of track-to-track access, which is suitable for high-speed access. In addition, since errors rarely occur even when crosstalk exists due to the use of gray codes, they are also suitable for narrowing the tracks.

Example 5

An optical recording medium according to a fifth embodiment of the present invention will be described with reference to FIG. Grooves 84 each having a width of 0.7 µm and a depth of 70 nm and lands 85 having a width of 0.7 µm are alternately arranged in the radial direction, and the two kinds of regions function as information tracks on which recording marks are formed. .

That is, each land 85 and groove 84 function as a recording area. In the prepit area 83, no groove is formed, but the pit 82 is disposed on the extension of the boundary between the land and the groove. The prepit area is divided into about 1800 information tracks, that is, bands arranged in a radial direction over 900 grooves.

This band is arranged concentrically on all of the disks so that in a disk having a radius of 30-60 mm, there are 24 bands in total. In particular, the number of prepits to be detected in one revolution in each band, that is, the number of sectors is constant, and the number of sectors is larger in the outer band than the inner band.

An example of the structure of each sector 41 is shown in FIG. The sector 41 has a prepit area 83 at the head of the data recording area.

As shown in FIG. 8, the prepit area is divided into a first prepit area 831 and a second prepit area 832. In the first prepit area 831, the pit 82 is arranged above the center line of the land 85 (as seen in the drawing), and in the second prepit area 832, the pit 82 is formed. ) Is arranged below the centerline of the land 85. Thus, for example, when the light spot 21 scans the land 85, only one of the pits is always reproduced so that there is no fear of leakage occurring between adjacent tracks. Thus, the address data allocated to the prepits can be reproduced without crosstalk. The address data represented by the prepits is recorded in the form of 1-7 modulation codes (channel bit length is 0.2 mu m). That is, the linear recording density is 0.3 mu m / bit.

In the present invention, the relationship between the groove and the prepit area will be described with reference to FIG. 10, which is a partially enlarged cross-sectional perspective view.

In this embodiment, the gap region 87 is provided at a distance of about 1.0 μm between the first and second prepit regions 831 and 832. In this embodiment, since the data is recorded according to the 1-7 recording, the gap length corresponds to the length of about 5 channel bits. The five channel bit length is the exact intermediate length between the longest mark length (eight channel bit length) and the shortest mark length (two channel bit length). Therefore, even if the shape and position of the pit are changed while the form of the pit and the light spot is affected by the shape change and the die change (servo offset), the gap area between the first and second prepit areas is the shortest mark. The length lying between the length and the longest mark length is recorded, thus ensuring very high reliability. In this embodiment, the mark is designed to have a total change at the position where the mark is suppressed to 0.6 µm (3 channel bit length) even in the worst case, so that the effective length (at the time of reproduction) is matched with the rule of 1-7 modulation code. Since the shortest length is 2 channel bits and the longest length is 8 channels, it does not cause problems during playback. If the detection bit is longer than the eight-channel bit length, it interferes with a specific synchronization pattern such as an address mark written in reverse.

If the detection bit is shorter than the two channel bit length, it becomes a small mark that is less than or equal to the resolution of the reproduction light spot and is not detected. Therefore, it is preferable to suppress the gap length to the middle between the longest mark length and the shortest mark length as in this embodiment.

According to the characteristics of the pit forming apparatus, the change in the mark position can be suppressed to less than one channel bit length. In this case, it is preferable to suppress the normal gap length to 3 to 7 channel bit lengths, but the pit forming apparatus for this purpose is expensive. Since the signal must have a high possibility of overcoming an error due to the tracking offset at the time of reproduction, it is preferable that the medium is halfway between the longest mark length and the shortest mark length that the gap length can accurately allow recording as described above.

In this embodiment, the pit 82 is uniformly arranged on both sides of the centerline of the track (groove or land), so that the influence on the tracking servo signal generated by the pit 82 can be eliminated. Therefore, the tracking offset can be suppressed to a sufficiently small level. Further, for example, when the land 85 is reproduced, the reproduction of the address data in the second prepit area 832 is performed in succession of the reproduction of the address data in the first prepit area 831. Therefore, when two areas are combined in one area in which information is arranged to provide address data for one track, the land address (track number) and the address of the groove are set independently of each other. In other words, by sequentially reproducing the address data portions in the first and second prepit areas 831 and 832, the identification between the land and the groove is ensured.

In particular, the address data represented by the prepits arranged in the first prepit area for reproducing the groove becomes the same as the data represented by the prepits arranged in the second prepit area, For this reason, the address data represented by the prepit in the first prepit area is different from the data represented by the prepit in the second prepit area. If the addresses indicated by the prepits in the first and second prepit areas are different from each other, the correlation may be set between two addresses, and the use of this correlation may increase the efficiency of the error correction code. .

Preferably, both the synchronization information VFO 86 and the address data 87 may be arranged in each of the first and second prepit areas.

In this embodiment, the prepit area is divided into two of the first and second prepit areas, but it is sufficient to divide it into several areas. For example, as shown in Fig. 5, when the number of divisions is four, the pits in the first and third prepit areas are arranged on one side of the groove, and the pits in the second and fourth prepit areas are grooved. It may be arranged on the other side of the. By increasing the number of divisions of the prepit area, for example, reliability of defects can be improved.

Here, a phase change recording material (GeSbTe) was used as the recording film. Thus, the recording mark is formed in the form of the amorphous domain.

Referring to Fig. 11, the positional displacement amount 963 between the prepit areas of adjacent tracks in the medium, the positional displacement amount 961 between the prepits of adjacent tracks, and the positional displacement amount 962 between the grooves of the adjacent tracks are shown. It demonstrates in detail. In real media, positional displacements sometimes occur between the pits of adjacent tracks depending on various conditions in forming the pits. The positional displacement amounts 961, 962, and 963 increase or decrease the length of the gap regions 86, 87.

In addition to the above-described positional displacement amount, various variations (deviation, servo error, etc.) during reproduction also generate positional displacement of the reproduction signal. Thus, positional displacement sometimes causes serious problems. However, in the present invention, since the conventional gap length is set to an intermediate length between the shortest mark length and the longest mark length based on the 1-7 modulation code, the amount of positional displacement of ± 0.6 mu m is acceptable.

The optical recording medium shown in FIG. 8 can be reproduced with the apparatus shown in FIG. 3 as described in connection with the first embodiment, and the tracking offset is ± 0.3 μm or less even in consideration of various external disturbances such as optical deviation. There is an advantage that can be reduced, and can be reduced to less than ± 0.015㎛ especially under a steady state without optical deviation.

Example 6

Although the embodiment of Fig. 8 uses 1-7 modulation coding as recording modulation coding, this embodiment uses 8-14 modulation (EFM) recording. The channel bit length is about 0.2 μm. In this recording, the shortest mark length is three channel bits long, and the longest mark length is 11 channel bits long. In fact, a mark having a length of 12 channel bits or more is also useful, but this type of mark is limited to a particular application such as a sync pattern. Therefore, data should avoid the inclusion of patterns that might interfere with certain patterns. The prepit areas, grooves and lands are arranged in the same manner as in the fifth embodiment of FIG. 8 except for the following. That is, arranged as shown in Fig. 10, in particular each groove and each land has a width of 0.75 mu m, and each groove and each prepit has a depth of 0.075 mu m.

In this embodiment, the prepit area and the groove are arranged as shown in FIG. Four prepit areas 831, 832, 833, and 834 are allocated to the head of one sector. In each pit area, a VFO area synchronized with the reproduction signal and an address area for recording address data of tracks and sectors are sequentially arranged. Not only the start position but also the end position of the pit are arranged to be aligned almost radially, and the gap region 86 is provided between the end of the groove and the start of the pit region. Similarly, gap regions 87, 88 or 89 are provided between adjacent prepit regions.

As described above, the positional displacement between the start position of the pit and the start position of the preceding pit is described in FIG. The displacement as shown in FIG. 11 increases or decreases the effective length of the gap region 86 as in the fifth embodiment of FIG. An additional pit pattern 110 as shown in FIG. 13 is used to align the ends of the final pits of the prepit areas 831, 832 and 833 in the radial direction. Depending on the previous data, additional patterns selected from four formats (a), (b), (c) and (d) are used. This allows the falling edge 99 of the last pit to always be aligned in the same position, regardless of previous data, and to limit the gap length and pit length to the length based on the modulation code. In this method, the gap length between the preceding prepit area 120 and the falling edge position 99 of the last pit can be set to an intermediate length between the shortest mark length and the longest mark length based on the modulation encoding. As in the embodiment of the prepit formation and regeneration can be greatly increased.

In the above-described embodiment, although described as a medium of the phase change recording material, it is of course possible to use other materials that can achieve the advantages of the present invention. For example, a magneto-optical recording film may be used as the recording film. Although the modulation codes have been described as 2-7 and 8/9 encoding, other forms in which the above-described EFM is extended may be used.

According to the present invention, in an optical recording medium having lands and grooves, a substrate can be manufactured by a simple mastering device, and a replica can be easily prepared, resulting in a substantially enough medium production margin and lead margin. It can be secured. Therefore, an inexpensive and high density optical recording medium can be provided.

Claims (8)

In an optical recording medium having a prepit portion radially aligned over a plurality of tracks, the prepit portion has first and second prepit portions divided in a track direction, and the first and second prepit portions All of the address information prepits are arranged on the boundary lines of the tracks of the several tracks, and the first and second prepit portions each have an address information prepit arranged at two track pitches in the radial direction. The address information prepits of the first prepit part and the address information prepits of the second prepit part are shifted by one track in the radial direction, and the prepit part is arranged in the first prepit part and the second prepit part. It further has a 1st gap part between a pit part, The track direction length of a said 1st gap part is more than the shortest mark length-less than the maximum mark length determined by a recording method. Optical recording medium. 2. The area according to claim 1, wherein the area in which the address information prepits in the radial direction of the first prepit part are not arranged is an area not recorded, and the address information in the radial direction of the second prepit part. An area in which no prepits are arranged is an area in which no prepits are recorded. The optical recording medium according to claim 1, wherein the track direction length of the first gap portion is at least one channel bit smaller than the maximum mark length and at least one channel bit larger than the shortest mark length. 3. The optical recording medium according to claim 2, wherein the track direction length of the first gap portion is at least one channel bit smaller than the maximum mark length and at least one channel bit larger than the shortest mark length. The optical recording medium according to claim 3, wherein the track direction length of the first gap portion is 1/2 of a sum of the maximum mark length and the shortest mark length. The optical recording medium according to claim 4, wherein the track direction length of the first gap portion is 1/2 of a sum of the maximum mark length and the shortest mark length. The optical recording medium according to any one of claims 1 to 6, wherein the recording method is a method in which information is provided at an edge of a mark. 8. The optical recording medium according to claim 7, wherein the plurality of tracks include a plurality of tracks having a groove information recording area and a plurality of tracks having a land information recording area disposed between the groove information recording areas. .

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