JP3170264B1 - Optical recording medium - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a read signal read error due to wobbling of a pre-pit, complication of substrate mastering, and a reduction in replica production yield in an optical recording medium having lands / grooves. SOLUTION: A pit rear edge position before wobbling is aligned in a radial direction, and a wobble pit is arranged with a front edge aligned after an interval longer than a minimum pit length. [Effect] Enlarged reproduction margin, simplified base mastering, and improved replica production yield.

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 A conventional example of a medium for performing high-density (narrow track) recording is disclosed in, for example, JP-A-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 conventional example, the pre-pit portion from the groove portion, the pre-pit portion from the inter-groove portion,
As in the case of the pre-pit portions, no consideration is given to the interval from the time when the pre-pit row starts to be arranged on one virtual straight line on the virtual extension line of the groove portion and the space between the groove portions on the next virtual straight line. 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, a rapid pattern must be injected at the time of replica production, which leads to a reduction in yield. In addition, the tolerance for distortion of a reproduction spot, tracking offset, and the like during signal reproduction is reduced, and a reading error is likely to occur.

An object of the present invention is to provide a high-density optical recording medium which solves the above-mentioned problems, and which can be demodulated even when a simple mastering, easy replica preparation and reading error occur.

[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 deflector) 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,
In the meantime, the AOM (acousto-optic modulator) is turned off, and the laser is not irradiated and no pit is drawn. This makes it possible to produce the substrate with a simple cutting machine. In addition, the yield at the time of replica creation is increased by eliminating many irregularities in a narrow area on the base.

(2) The pre-pits are arranged on a virtual extension line at the boundary between the groove and the groove, and the arrangement of the pit rows is from the right to the left of the virtual extension center line between the groove and the groove, or vice versa. , 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, if only pits with the original information are present, the rear edge position will not be aligned, but by adding a new pit, it is possible to align while keeping the rules at the time of recording it can.

(4) By aligning the leading edges of the pits in the radial direction immediately after the change of the pit row in (2), (2)
For the same reason as described above, problems relating to cutting and replica production can be solved. Also, from the point of signal reproduction, a synchronization signal is assigned to the pit information immediately after the above-mentioned pit sequence changes, and only the determination of the channel bit at the specific position is emphasized, so that the tolerance of the front edge position is increased. The reading error of the important data such as the address immediately before the address changes is reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is an enlarged partial plan view of an optical recording medium according to the present invention. 0.7μm width, 7 depth
The groove portions (grooves 84) of 0 nm and the inter-groove portions (lands 85) of 0.7 μm width are alternately arranged, and both regions are information tracks on which recording marks can be formed. 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 above pre-pit is about 18
It is radially aligned and divided into zones over 00 information tracks, ie, 900 grooves. The zones are arranged in a donut shape over the entire disc, and the entire disc has a total of 24 zones with a radius of 30 mm to 60 mm. In other words, in each zone, the number of pre-pit portions per revolution, that is, the number of sectors is constant, and the number of sectors is larger in a zone outside the disk. Each sector 4
In the structure of No. 1, for example, as shown in FIG. 4, a pre-pit portion 83 is provided at the head of the data recording area. As shown in FIG. 1, the pre-pit portion includes a first pre-pit portion 83.
1 and a second pre-pit section 832. In the first pre-pit section 831, the pits 82 are arranged above the center line of the land 85 in the figure, and in the second pre-pit section 832, the pits 82 are located below the center line of the land 85 in the figure. Have been placed. That is, the pits 82 of the first and second pre-pit portions are each arranged at a two-track pitch in the radial direction, and the pit of the first pre-pit portion and the pit of the second pre-pit portion correspond to one track in the radial direction. It is placed out of alignment. 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,
Address information allocated to the pre-pits can be favorably reproduced without crosstalk. In this example, the pre-pit address information is recorded by a 1-7 modulation code (channel bit length: 0.2 μm). That is, the linear recording density is 0.3 μm / bit.

FIG. 2 is an enlarged perspective view, partially in section, showing the relationship between the pre-pit portion and the groove portion of this embodiment.

In this embodiment, the pre-pit sections 831 and 83
Gap portions 87 are provided before and after 2. The interval between the gap portions is about 1.0 μm apart in this example.
In this example, since the data is recorded by the 1-7 recording method, the intervals are separated by about 5 channel bits. Since the length of 5 channel bits is just intermediate between the longest mark length (8 channel bit lengths) and the shortest mark length (2 channel bit lengths) allowed in the 1-7 recording system, the gap between the prepits The length when reproducing is from the shortest mark length to the longest, even if the pit shape and position change at the time of pit formation, and the light spot shape and scanning position change (servo offset) at the time of reproduction occur. It is very reliable because it is reproduced up to the mark length. In this example, since the total of the fluctuations of these mark positions is designed to be suppressed to 0.6 μm (3 channel bit length) or less at worst, the effective (at the time of reproduction) length is the shortest. Since the length is 2 channel bits and the maximum length is 8 channel bits, the rule of the 1-7 modulation code is satisfied, and no problem occurs during reproduction. Here, if the detection 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. Further, when the length is shorter than two channel bits, the mark becomes a minute mark having a resolution equal to or less than the resolution of the reproduction light spot, and thus cannot be detected. Therefore, it is desirable to suppress the gap length to an intermediate value 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 nominal gap length is 3
The length may be up 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 effect of the pits 82 on the tracking servo signal is offset. Therefore, the track offset can be kept 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 pre-pit portion 831 and the second pre-pit 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 when the addresses of the first and second pre-pits are different, there is a correlation between the two addresses, and this fact can be used to increase the efficiency of the error correction code.

At this time, the first pre-pit portion, the second
It is preferable that both information for synchronization (VFO) and address information are arranged in each of the pre-pit portions.

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 the positional deviation 963 between the prepit portions of the adjacent tracks of the medium and the positional deviation 962 between the prepits of the adjacent tracks in detail. In an actual medium, pits may be displaced 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 apparently deviates 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 having a wavelength of 680 nm and a collimating lens 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 a light intensity control means 71 having an automatic light intensity control function. The light 22 emitted from the light generating means 31 is focused on the magneto-optical recording medium 8 by the focusing means 32. The condensing means 32 includes at least one lens. In this example, the beam splitter 32
Four. Condensing means 3 for condensing light on optical recording medium 8
The aperture ratio of the objective lens No. 2 was 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 any position on the optical recording medium 8 by the scanning means 6. In this example,
The scanning means 6 includes at least a motor 62 for rotating the disk-shaped magneto-optical recording medium 8 and an automatic position control means 61 having functions of automatic focus control and automatic tracking. The automatic position control means 61 performs feedback control by detecting the light spot position with the light detection means 33 using the reflected light 23 from the magneto-optical recording medium 8. 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 obtains a servo signal and a reproduction signal by calculating outputs of the plurality of light detectors.

In the present invention, the optical recording medium according to the first embodiment is used.
Was used. The address information is demodulated by inputting the pre-pit signal to the address detecting means. At the same time, the timing of the signals of the first pre-pit portion and the second pre-pit portion is detected, and the first pre-pit portion is detected based on the timing information. (Average maximum amplitude) and the amplitude (average maximum amplitude) of the second pre-pit portion are stored.
The stored amplitudes are compared by the amplitude comparing unit and fed back to the position moving unit (scanning unit) as track offset information. When the light spot is slightly offset, the amount of the track offset corresponds to the amplitude difference between the prepit signals from the first prepit 831 and the second prepit 832.

By using the apparatus of the present embodiment, the track offset could be reduced to ± 0.03 μm or less even in consideration of various disturbances such as aberration of the light spot. 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 system was used as the recording modulation system.
An FM (Eight to Fourteen Modulation) recording method was used. The channel bit length is about 0.2 μm. In this method, the shortest mark length is 3 channel bits long, and the longest mark length is 11 channel bits long. In practice, there are also marks having a length of 12 channel bits or more, but their use is limited to special uses such as synchronization patterns.
For this reason, it is necessary to avoid patterns that may confuse these special patterns in the data. 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 the space between the grooves is about 0.75μ
m, the depth of the groove and the prepit are 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, and 834 are arranged at the head of one sector. In each pre-pit portion, a VFO portion for synchronizing with a reproduction signal and an address portion for recording address information such as a track and a sector are continuously arranged. In addition, the start position and the end position of the pit are arranged substantially in the radial direction, and a gap portion 86 is provided between the end portion of the groove and the start end of the pit portion. Similarly, gap portions 87, 88, 89 are provided between the pre-pit portions. FIG. 6 shows details of the dislocation such as the pit start position and the subsequent pit start position. When there is a shift as shown in FIG.
Become shorter or longer. Pre-pit section 83
To align the ends of the pits at the ends of 1, 832, 833 in the radial direction. An additional pit pattern 11 as shown in FIG. 7 was used. The additional pattern is selected from the four types (a), (b), (c), and (d) according to the preceding data and used. This makes it possible to always align the trailing edge position 99 of the end pit at the same position irrespective of the previous data, and to limit the length of the gap and pit to the length allowed for the modulation code. can do.
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. In addition, the margins during pre-pit molding and reproduction are greatly increased.

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

[0025]

According to the present invention, in an optical recording medium having lands / grooves, a base can be manufactured by a simple mastering device, a replica can be easily manufactured, and a medium manufacturing margin and a reading margin sufficiently large for practical use can be secured. Can be. 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 configuration diagram of an apparatus for recording and reproducing an optical recording medium according to 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 one 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 ... Condensing 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

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-64-59632 (JP, A) JP-A-6-96447 (JP, A) JP-A-6-176404 (JP, A) International Publication 96/25736 (WO, A1) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B ^7/ 00-7/013 G11B 7/24

Claims (6)

(57) [Claims] 1. An optical recording medium having a pre-pit portion radially aligned over a plurality of tracks, wherein the pre-pit portion is divided in a track direction and arranged on a boundary between the tracks of the plurality of tracks. First and second pre-pit portions, and the first and second pre-pit portions each have a radius of 2 mm.
It has address information pre-pits and synchronization information pre-pits arranged at a track pitch, and the address information pre-pits and synchronization information pre-pits of the first pre-pits are separated from the address information pre-pits and synchronization information pre-pits of the second pre-pits. The pre-pit portion is shifted from the first pre-pit portion by one track in the radial direction.
An optical recording medium, further comprising a gap portion having a length in the track direction equal to or greater than the shortest mark length and equal to or less than the maximum mark length determined by a recording method, between the pre-pit portion and the pre-pit portion. 2. The optical recording medium according to claim 1, wherein
The area where the address information pre-pit and the synchronization information pre-pit are not arranged in the radial direction in the first pre-pit section is a non-recording area, and the address information pre-pit and the synchronization information pre-pit in the radial direction in the second pre-pit section are not recorded. An optical recording medium, wherein the non-arranged area is an unrecorded area. 3. The optical recording medium according to claim 1, wherein the length of the gap in the track direction is at least one channel bit smaller than the maximum mark length and at least one channel bit larger than the shortest mark length. An optical recording medium characterized by the above-mentioned. 4. The optical recording medium according to claim 3, wherein
The optical recording medium according to claim 1, wherein a length of the gap in the track direction is one half of a sum of the maximum mark length and the shortest mark length. 5. The optical recording medium according to claim 1, wherein the recording method is a method in which information is provided at an edge of a mark. 6. The optical recording medium according to claim 1, wherein the plurality of tracks includes a plurality of tracks having a groove information recording area and an inter-groove portion sandwiched between the groove information recording areas. An optical recording medium comprising a plurality of tracks having an information recording area.