JPH09147365A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high density recording medium capable of demodulation even when a read error is generated by providing each space in some degree between a grooves and adjacent prepits in the recording and reproducing direction, a land and a prepits and mutual prepits themselves respectively. SOLUTION: The groove 84 and the land 85 are alternately disposed, and both areas are information tracks capable of forming recording marks. A prepit part 83 is not formed with the grooves, and pits 82 are disposed on an extended line of a boundary between the land part 85 and the groove part 84 respectively. Each prepit has its prepit part 82 ahead of a data recording area, and the pripit part is split into prepit parts 831 and 832. Then, when the land 85 is scanned by a light spot 21, one part of either of adjacent pit parts is to be always reproduced, so that no cross talk is generated from the adjacent track.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a conventional example of a medium for performing high density (narrow track) recording, for example, Japanese Patent Laid-Open No. 6-17
6404. In this example, in an optical recording medium having a groove portion and an inter-groove portion on a substrate as a recording medium and having an information recording area in both the groove portion and the inter-groove portion, a virtual extension of a boundary portion between the groove portions and the inter-groove portion is provided. Pre-pits are placed on the line. Thereby, the recording information is recorded in both the groove portion and the groove portion, and the address information indicating the recording area is assigned to the pre-pit, and the address information for the pair of groove portion and the groove portion is recorded by one pre-pit. We share. When this method is applied to, for example, a phase-change type recording medium or a magneto-optical recording medium, in the groove portion and the inter-groove portion, the information of the adjacent inter-groove portion or the groove portion is not mixed due to the interference effect in the light spot ( Since crosstalk is eliminated), the track can be narrowed, and high-density recording can be performed.

[0003]

However, in the above-mentioned conventional example, the groove portion to the pre-pit portion, the inter-groove portion to the pre-pit portion,
As in the pre-pit portion, the interval from when one pre-pit row starts to be arranged on one virtual extension line between the groove portion and the groove portion to the next virtual straight line is not considered. Therefore, when there is no or very short interval, mastering of the substrate cannot be performed by one-beam cutting, and two-beam cutting is required. In addition, since the injection has to be performed on a steep pattern also at the time of replica production, the yield is reduced. Furthermore, the tolerance for distortion of the reproduction spot, tracking offset, etc. during signal reproduction becomes small, and reading errors are likely to occur.

An object of the present invention is to solve the above problems and provide a high-density optical recording medium which can be easily mastered, easily made a replica, and can be demodulated even if a read error occurs.

[0005]

To achieve the above object, the following means are used.

(1) A groove and an inter-groove portion are formed on a substrate, and prepits are arranged on a virtual extension line at a boundary between the groove and the inter-groove portion. Since the prepits are arranged to be shifted rightward or leftward from an extension from the center line of the groove or the space between the grooves, it is necessary to move the optical axis of the laser beam during cutting.
An AOD (acousto-optic polarizer) is used to change the optical axis. However, since the AOD requires a long time from sending a signal for changing the optical axis to reaching a desired optical axis position, if the modulated laser is irradiated as it is, pits are formed diagonally on the substrate. Therefore, there is nothing as a format between the groove or the space between the groove and the next pre-pit,
During that time, the AOM (acousto-optic modulator) is turned off, laser is not irradiated, and no pit is drawn. This allows the substrate to be made with a simple cutting machine. In addition, since many irregularities are eliminated in the narrow area on the substrate, the yield at the time of replica production is increased.

(2) The pre-pits are arranged on a virtual extension line at the boundary between the groove and the groove, and the pit row is arranged from the right to the left of the virtual extension center line of the groove and the groove, or from there. On the other hand, when changing, the pit row adjacent in the direction perpendicular to the information track aligns the trailing edge of the pit before the change in the radial direction of the base. After leaving an interval in the recording / reproducing direction from the rear edge position, the next pit is similarly drawn in the radial direction. As long as the recording rule is satisfied, the format of the entire board is not inconvenient if it complies with the recording rules, and a part without pits can be secured in a specific area on the board. Solvable.

(3) In the above adjacent pit row,
In order to align the rear edge in the radial direction of the base, the rear edge position will not be aligned if only the pits that have the original information, but by adding new pits, it is possible to align them while observing the rules at the time of recording. it can.

(4) By aligning the leading edges of the pits immediately after the change of the pit row in (2) in the radial direction, (2)
For the same reason as above, the problem concerning cutting and replica production can be solved. From the point of signal reproduction, a synchronization signal is assigned to the pit information immediately after the pit row is changed, and only the judgment of the channel bit at that specific position is emphasized to improve the tolerance of the front edge position and to improve the pit row. The reading error of important data such as address just before is changed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 FIG. 1 shows a partially enlarged plan view of an optical recording medium of the present invention. A groove portion (groove 84) having a width of 0.7 μm and a depth of 70 nm and an inter-groove portion (land 85) having a width of 0.7 μm are alternately arranged, and both areas are information tracks capable of forming recording marks. ing. That is, both the land 84 and the groove 85 are recording areas. No groove is formed in the pre-pit portion 83, and the pit 82 is arranged on an extension of the boundary between the land portion and the groove portion. The pre-pit portion is divided into zones aligned in the radial direction over about 1800 information tracks, that is, 900 grooves. The zones are arranged in a donut shape over the entire disc and have a radius of 30
There are a total of 24 zones for mm-60 mm. That is, in each zone, the number of pre-pit parts per round, that is, the number of sectors, is constant, and the zone outside the disk has a larger number of sectors. The structure of each sector 41 is, for example, as shown in FIG. 4, having a pre-pit portion 82 at the head of the data recording area. The prepit portion is divided into a first prepit portion 831 and a second prepit portion 832, as shown in FIG. First pre-pit section 83
In No. 1, the pit 82 is arranged above the center line of the land 85 in the figure, and in the second pre-pit portion 832, the pit 82 is arranged below the center line of the land 85 in the figure. Therefore, for example, when the light spot 21 scans over the land 85, only one of the pits is always reproduced, and there is no fear that crosstalk from an adjacent track will occur. Therefore, the address information arranged in the pre-pit can be reproduced well without crosstalk. In this example, the pre-pit address information is 1-
It is recorded by 7 modulation codes (channel bit length 0.2 μm). That is, the linear recording density is 0.3 μm / bit.

FIG. 2 is a partially sectional enlarged perspective view showing the relationship between the prepit portion and the groove portion of this embodiment.

In this embodiment, the pre-pit sections 831 and 83
A gap portion 87 is provided before and after 2. The distance between the gaps is about 1.0 μm in this example. In this example, since the data is recorded by the 1-7 recording method, the intervals are separated by more than about 5 channel bits. Since the length of 5 channel bits is just an intermediate length between the longest mark length (8 channel bit length) and the shortest mark length (2 channel bit length) allowed in the 1-7 recording method, the gap portion between the prepits is formed. The length when playing back the pit shape, position variation when forming the pit,
Even if there is a change in the light spot shape or scanning position (servo offset) during reproduction, the reproduction is performed from the shortest mark length to the longest mark length, so that the reliability is very high. In this example, the total variation of these mark positions is designed to be kept to 0.6 μm (3 channel bit length) or less at the worst, so that it is effective (during reproduction).
Since the length is 2 channel bits in the shortest case and 8 channel bits in the longest case, the rule of 1-7 modulation code is satisfied and no problem occurs during reproduction. Here, if
If the detected length is longer than the 8 channel bit length, it is not preferable because it is confused with a special synchronization pattern such as a recording address mark. Also, 2
When the length is shorter than the channel bit, the mark becomes smaller than the resolution of the reproduction light spot and cannot be detected. Therefore, it is desirable to keep the gap length between the longest mark length and the shortest mark length as in this embodiment. Depending on the specifications of the pit forming apparatus, it is possible to suppress the fluctuation of the mark position to one channel bit length or less. In this case, the length of the nominal gap may be 3 to 7 channel bits, but in that case, the pit forming apparatus becomes expensive. Further, since the possibility of receiving a signal error also increases with respect to a track offset or the like at the time of reproduction, it is preferable that the length be set to an intermediate length between the longest mark length and the shortest mark length allowed for the recording method as described above. A medium having a gap is desirable.

In this embodiment, since the pits 82 are evenly arranged on both sides of the track (land portion or groove portion), the influence of the pits 82 on the tracking servo signal is canceled. Therefore, the track offset can be suppressed sufficiently small. Further, for example, when the land portion 85 is reproduced, the address information of the first pre-pit portion 831 and the address information of the second pre-pit portion 832 are reproduced continuously. Therefore, by arranging information so that address information is obtained by combining the two, an address (track number) can be set independently of the land portion and the groove portion. That is, by continuously reproducing the address information of the first prepit portion 831 and the second prepit portion 832, the land portion and the groove portion can be identified. Specifically, when reproducing a groove portion, information is arranged so that the addresses of the first and second pre-pits are the same, and when reproducing a land portion, the first and second pre-pits are arranged. Is arranged so that the addresses of the information are different. Even if the addresses of the first and second prepits are different, there is a correlation between the two addresses, and this can be used to improve the efficiency of the error correction code.

At this time, the first prepit portion and the second prepit portion
Information (VFO) 8 for synchronization with each of the pre-pit portions
6 and the address information 87 are preferably arranged.

In this example, the first and second two sets of pre-pit portions are shown. However, any number of pre-pit portions may be used. For example, in the case of four sets as shown in FIG. Third
May be arranged on the left side of the groove, and the second and fourth pre-pits may be arranged on the right side of the groove. By increasing the number of pre-pit portions, reliability against defects and the like is improved.

Here, a phase change type recording film (GeSbTe) was used as the recording film. Therefore, the recording mark is formed in the form of an amorphous region.

FIG. 6 shows in detail the positional deviation 963 between the pre-pit portions of the adjacent tracks of this medium and the positional deviation 962 between the pre-pits of the adjacent tracks. In an actual medium, pits may be misaligned between adjacent tracks due to various causes during pit formation. The gap portions 86 are effectively shortened or elongated due to the displacement amounts 961, 962, and 963.

The position of the reproduced signal is apparently deviated due to various fluctuations (aberration, servo deviation, etc.) during reproduction in addition to the positional deviation. For this reason, the displacement may be a serious problem, but in the present invention, the nominal length of the gap portion is set to an intermediate length between the shortest mark and the longest mark of the 1-7 modulation code. The above displacement is ±
Acceptable up to 0.6 μm.

<Embodiment 2> FIG. 3 shows an example of a configuration in which the optical recording medium of the present invention is applied to an optical recording / reproducing apparatus. In this embodiment, a semiconductor laser 311 having a wavelength of 680 nm and a collimating lens 312 are used as the light generating means 31. If necessary, a beam shaping means such as a prism may be provided. The intensity of the semiconductor laser is controlled by the light intensity control means 71 having an automatic light intensity control function. Light generation means 3
The light 22 emitted from 1 is focused on the magneto-optical recording medium 8 by the focusing means 32. The light collecting means 32 includes at least one lens 321. In this example, a beam splitter 324 is additionally provided. The aperture ratio of the objective lens 321 focusing on the optical recording medium 8 was set to 0.6. For this reason, the diameter of the light spot 21 on the optical recording medium 8 is 1.
0 μm. The light spot can be moved to an arbitrary position on the optical recording medium 8 by the scanning means 6. In this embodiment, the scanning means 6 comprises a disk-shaped magneto-optical recording medium 8.
, And at least an automatic position control means 61 having functions of automatic focus control and automatic tracking. The automatic position control means 61 uses the reflected light 23 from the magneto-optical recording medium 8 to detect the light spot position by the light detection means 33 and performs feedback control. The light spot position is detected by detecting the intensity of the diffracted light from the groove. The light detecting means 33 includes a lens, a beam splitter, a plurality of light detectors, and the like, and outputs are calculated by the plurality of light detectors.
A servo signal and a reproduction signal are obtained.

In the present invention, the optical recording medium according to the first embodiment is used.
The one shown in was used. Therefore, the signal 14 as shown in FIG. 2 is obtained as the pre-pit signal. The address information is demodulated by inputting this signal to the address detecting means, and at the same time, the first pre-pit portion and the second
And the amplitude of the first pre-pit portion (average maximum amplitude) and the amplitude of the second pre-pit portion (average maximum amplitude) are stored based on the timing information. The stored amplitudes are compared by the amplitude comparing means and fed back to the position moving means (scanning means) as track offset information. Here, FIG.
FIG. 3 shows a prepit signal 13 when a light spot is located on a groove (on a groove) and a land (between grooves), and magneto-optical reproduction signals 11 and 12 on a groove and a land. In this example, the light spots are slightly offset as shown in FIG.
An amplitude difference 13 occurs between the pre-pit signal from the second pre-pit section 832 and the pre-pit signal from the second pre-pit section 832. This amplitude difference 13 corresponds to the amount of track offset.

By using the apparatus of this embodiment, the track offset can be reduced to ± 0.03 μm or less even when various disturbances such as aberration of the light spot are taken into consideration. In a nominal state having no spot aberration or the like, the value was ± 0.015 μm or less.

<Embodiment 3> In the above embodiment, the 1-7 modulation method was used as the recording modulation method.
An FM (Eight to Fourteen Modulation) recording method was used. The channel bit length is 0.2 μm for baking. In this method, the shortest mark length is 3 channel bit length and the longest mark length is 11 channel bit length. Actually, there are marks with a length of 12 channel bits or more, but their use is limited to special applications such as synchronization patterns.
For this reason, it is necessary to avoid patterns in the data that can be confused with these special patterns. The arrangement of the pre-pit portion, the groove portion, and the inter-groove portion is the same as that of the first embodiment except for the points described later. That is, they are arranged as shown in FIG. However, the width of the groove and inter-groove is about 0.75μ
m, the depth of the groove portion and the prepit is about 0.075 μm.

In this embodiment, the arrangement of the pre-pits and the grooves is arranged as shown in FIG. That is, four sets of pit areas 831, 832, 833, 834 are arranged at the beginning of one sector. Further, a VFO section for synchronizing with a reproduction signal and an address section for recording address information such as a track and a sector are continuously arranged in each pre-pit pit section. Further, the start position and the end position of the pit are arranged so as to be substantially aligned in the radial direction, and a gap portion 86 is provided between the end portion of the groove portion and the start end of the pit portion. Similarly, gap portions 87, 88, 89 are provided between the pre-pit portions. FIG. 4 shows details of misalignment such as the start position of a pit and the start position of a subsequent pit. If there is a deviation as shown in FIG. 4, the gap portion 86 is effectively shortened or lengthened as in the first embodiment. To align the ends of the pits at the ends of the pre-pit portions 831, 832, 833 in the radial direction. An additional pit pattern 11 as shown in FIG. 7 was used. The additional pattern is selected from four types (a), (b), (c), and (d) according to the preceding data and used. Thus, regardless of the previous data,
The trailing edge position 99 of the pit at the end can always be aligned at the same position, and the length of the gap and the length of the pit allowed for the modulation code can be limited. As a result, the gap between the succeeding pre-pit 12 and the trailing edge position 99 of the pit at the end can be set to an intermediate length between the longest mark and the shortest mark of the modulation code. As in Example 1, during pre-pit molding and
The margin during playback is greatly expanded.

In the above embodiment, a phase change type recording medium is shown as a medium, but the present invention is not limited to the above embodiment. For example, a magneto-optical recording film may be used as the recording film. Further, the modulation code may be a form in which the above EFM is expanded in addition to 2-7 and 8/9.

[0025]

According to the present invention, in an optical recording medium having lands / grooves, a substrate can be produced by a simple mastering device and a replica can be easily produced, and a medium production margin and a read margin which are sufficiently large in practical use are secured. You can Therefore, an inexpensive and high-density optical recording medium can be provided.

[Brief description of the drawings]

FIG. 1 is an enlarged partial plan view of an embodiment of the optical recording medium of the present invention.

FIG. 2 is an enlarged partial perspective view of an embodiment of the optical recording medium of the present invention.

FIG. 3 is a block diagram of an apparatus for recording / reproducing an optical recording medium of the present invention.

FIG. 4 is a diagram showing an information arrangement of the optical recording medium of the present invention.

FIG. 5 is an enlarged partial plan view of an embodiment of the optical recording medium of the present invention.

FIG. 6 is an enlarged partial plan view of an embodiment of the optical recording medium of the present invention.

FIG. 7 is a diagram showing an example of a modulation code of an embodiment of the optical recording medium of the present invention.

[Explanation of symbols]

3 optical head, 6 scanning means, 8 magneto-optical recording medium, 2
1: light spot, 22: laser light, 23: reflected light, 31
... light generating means, 32 ... light collecting means, 33 ... light detecting means, 6
DESCRIPTION OF SYMBOLS 1 ... Automatic position control means, 62 ... Motor, 71 ... Light intensity control means, 82 ... Pre-pit, 83 ... Pre-pit part, 83
DESCRIPTION OF SYMBOLS 1 ... 1st pre-pit part, 832 ... 2nd pre-pit part, 86, 87, 88, 89 ... Gap part, 84 ... Groove part, 85 ... Inter-groove part, 93 ... Reproducing means, 41 ... Data sector, 42 ... Data Recording section, 11: additional pit, 12: subsequent pre-pit section.

Claims (9)

[Claims] The present invention has a groove on a substrate and a groove between the grooves, an information recording area on both the groove and the groove, and a groove between the grooves is partially cut off. Instead, a pre-pit, which is a minute depression, which gives a phase difference to specific light is arranged on a virtual extension line at the boundary between the groove and the groove, and the pre-pit is a virtual line of the center line of each of the groove and the groove. In the optical recording medium which is located right and left with respect to the extension line so that no pre-pits are present on both sides of the virtual extension line at the same time, the groove and the inter-groove portion and the information track on the virtual extension line are recorded. An optical recording medium characterized by having a certain interval between a groove and a prepit adjacent to each other in a reproducing direction, between a groove and a prepit, and between a prepit and a prepit. 2. The optical recording medium according to claim 1, wherein the pre-pit portion is recorded by a recording method in which information is provided at an edge of a mark. 3. The optical recording medium according to claim 2, wherein the interval in the recording / reproducing direction of the pre-pit portion adjacent to the information track direction located on the left and right with respect to the virtual extension line of the center line between the grooves is equal to the recording length. An optical recording medium having a length equal to or longer than a shortest mark length determined by a method. 4. The optical recording medium according to claim 3, wherein, in adjacent prepits, an edge behind a prepit to be recorded or reproduced earlier and an edge behind a prepit adjacent to an information track in a direction perpendicular to the information track are formed. An optical recording medium having a portion aligned in the direction. 5. The recording medium according to claim 4, wherein the rear edge of the prepit previously recorded or reproduced and the rear edge of the prepit vertically adjacent to the information track are aligned in this direction. An optical recording medium characterized by further adding a pit after the pre-pit. 6. A recording medium according to claim 5, wherein a prepit added for aligning a trailing edge in a direction perpendicular to the information track is separated from an original pit by a minimum mark length or more. Medium. 7. The optical recording medium according to claim 3, wherein a front edge of a prepit to be recorded or reproduced later and a front edge of a prepit adjacent to an information track in a direction perpendicular to the information track are aligned in the direction. An optical recording medium comprising: 8. An optical recording medium according to claim 3, wherein the interval between prepits adjacent in the recording / reproducing direction is a value between the maximum mark length and the minimum mark length. 9. The light according to claim 8, wherein the interval between prepits adjacent in the information track direction is at least one step smaller than the maximum mark length determined by the recording method and at least one step larger than the minimum mark length. recoding media.