JP2000163754A - Optical disk medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce crosstalk between the adjacent tracks of header information formed in a header area by a prepit in the optical disk medium of a land and groove system. SOLUTION: A groove 11 is not formed in a header area 4 for recording header information, a prepit as header information is formed in each of a groove recording track 1 and a land recording track 2, and formed as identical header information 14 in the same forming position of a track extended direction and in each of a pair of adjacent tracks. When playing is performed by a beam spot along the center of any one of the land and groove recording tracks, in the header area, one of both tracks adjacent to the track to be reproduced always has head information identical to that of the track being reproduced, and thus practically no crosstalk is generated from the track of this side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk medium for recording and reproducing information using light, and more particularly, to a land and a land for recording information on each of a groove and a land by forming a groove on a surface of an optical disk substrate. The present invention relates to an optical disk medium of a groove recording system and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as an effective means for improving the recording density in an optical disk medium, there is a method of reducing the pitch of spiral or concentric recording tracks formed on an optical disk substrate.
However, if the beam spot diameter of the optical head used for recording / reproduction does not change, a decrease in track pitch leads to an increase in crosstalk between adjacent tracks. Pitch is limited. In a read-only optical disk in which an embossed recording pit array is formed on the optical disk in advance, the track pitch is determined by the amount of crosstalk, and a DVD-ROM has a pitch of about 0.74 μm.

[0003] On the other hand, in a recordable optical disk, it is general to form a groove on the surface of an optical disk substrate and record data along the groove. It is known that a track pitch can be reduced by adopting a method of recording on both lands (land / groove recording method) as compared with a ROM using embossed pits. This is because crosstalk can be reduced due to the presence of the groove wall as compared with the case where recording pits are formed adjacently on a plane. Therefore, DVD-RO
Even when a beam spot diameter similar to M is used, high-density recording with a track pitch of about 0.6 μm can be realized.

[0004] Even in a recordable optical disk, it is necessary to provide information indicating a recording track position on the optical disk in advance. As one of the methods,
A recording track is divided into sectors each having a predetermined length, and a header area including position information and the like is formed at the head position by prepits. For example, JP-A-8-
In the technique described in Japanese Patent No. 273204, a header area is formed in each of the land and the groove. Further, in the technology described in this publication, the same header information is recorded in adjacent lands and grooves, thereby reducing crosstalk between lands and grooves,
Even when crosstalk occurs, it is possible to reduce reading errors since the header information is the same.

However, in this technique, since the recording surface position is different between the land and the groove, when recording the header information on each of the land and the groove, the focal position of the recording optical device is set between the land and the groove. It is necessary to adjust the change, and it is inevitable that the manufacturing process becomes complicated. On the other hand, in order to simplify the recording process of the header information on the land and the groove, the groove is not formed in the header area, and the header area of the groove and the land are respectively placed on the same height surface of the optical disc. To form. However, in the header region formed in this manner, the effect of reducing the crosstalk due to the above-described groove wall cannot be obtained, so that there is a problem that the crosstalk is large and sufficient reproduction information cannot be obtained.

Therefore, as a solution, as shown in FIG. 6, in a header area 4 provided between data areas 3, header information of header information is placed on a boundary between a pair of adjacent groove recording tracks 1 and land recording tracks 2. Pre-pit 13
A technique for forming the slab is considered. By doing so, even in the header area 4 where the groove 11 is not formed,
Since the radial interval between adjacent prepits 13 can be widened to twice the track pitch, crosstalk can be reduced.

[0007]

However, in this technique,
Prepits are formed at positions deviated from a beam spot for reproducing data along the center of a land recording track or the center of a groove recording track. Therefore, compared with the case of reproducing the pre-pit formed at the center of the track, there is a problem that a change in the reproduction characteristic becomes large with respect to the displacement of the beam spot in the lateral direction of the track and the deformation of the beam spot due to the disc tilt.

An object of the present invention is to provide an optical disk medium having a header area which solves the above-mentioned problem, and a method of manufacturing the same.

[0009]

According to the present invention, in a land / groove type optical disk medium, no groove is formed in a header area for recording header information including position information of the optical disk, and the header information is The same header is formed on each of the groove recording track and the land recording track and is formed at the same position in the track extending direction, and is identical to the adjacent pair of the land recording track and the groove recording track, respectively. The information is formed. In this case, a plurality of pieces of header information are formed in the header area in a direction along a track of each track, and one header area is adjacent to one groove or land recording track and one side thereof. The same header information is formed by the land or groove recording track, and the other one header area is formed by the same header information by the one groove or land recording track and the land or groove recording track adjacent to the other. May be adopted.

In the method of manufacturing the optical disk medium according to the present invention, a pre-pit as header information of each of the groove recording track and the land recording track may be provided on a master disk for molding the optical disk medium. The same pre-pits are formed simultaneously by simultaneously irradiating the adjacent groove recording track and land recording track with the light beam modulated in step (1). For example, the light beam is split into two light beams by a light beam splitting unit, and each of the split light beams is simultaneously irradiated on each of the tracks. In this case, the two split light beams are focused on the same plane.

According to the present invention, when the beam spot is reproduced along the center of one of the land recording track and the groove recording track, in the header area, of the tracks on both sides adjacent to the track to be reproduced. On one side, the same head information is always formed as the track being reproduced, and it can be considered that there is substantially no crosstalk from the track on that side. Therefore, it is sufficient to consider only the crosstalk from the adjacent track on the opposite side having different header information. In this case, the amount of crosstalk is reduced by half compared to the case where different header information is formed on both sides, and The characteristics can be improved.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. 1 is an overall configuration diagram of an optical disk medium of the present invention, FIG. 2 is a schematic enlarged perspective view of a portion A in FIG. 1, and FIG. 3 is a plan view thereof. A groove 11 is formed concentrically or spirally on a disc-shaped optical disk 10, and the groove 11 forms the groove recording track 1. A land recording track 2 is formed on a land 12 between the grooves 11. Further, the optical disc 10 divides the data area 3 into a plurality of zones in the circumferential direction, and a header area 4 is formed in each of the divided areas, and the header area 4 is made of emboss. The header information 3 is recorded by the pre-pit 13. Here, the groove 11 such as the data area 3 is not formed in the header area 4. Therefore, each header area of the groove recording track 1 and the land recording track 2 is formed on the same plane on the surface of the optical disc 10. Will be. The header information (pre-pit) 13 provided in the header area 4 is formed on each of the groove recording track 1 and the land recording track 2.

That is, as can be seen from FIG. 3, the groove recording tracks 1 and the land recording tracks 2 are arranged at a required pitch along the radial direction of the optical disk 10, but the grooves 11 are formed in the header area 4. The header area 4 is not shown in FIG.
As shown by a dashed line, a pair of adjacent groove recording track 1 and land recording track 2 is paired, and the same header information 14 is formed as embossed prepits 13. The pre-pits 13 can be formed at the same time as the grooves 11 by cutting the molding master when forming the optical disc. In particular,
In this configuration, since the groove 11 does not exist in the header area 4, the pre-bit 13 can be formed by embossing the groove recording track 1 and the land recording track 2 on the same surface. Can be easily performed. If there is a groove also in the header area, it is necessary to form an emboss deeper than the groove depth in the groove, and it is necessary to form two types of depth by one cutting, which is difficult to manufacture. It will be. Also, in the photographic technology process when manufacturing the molding master, when each header information of the groove recording track and the land recording track is transferred to the molding master, both header information can be set to the same focal plane.

The optical disk 10 configured as described above
In the case where the beam spot is reproduced along the center of one of the groove recording track 1 and the land recording track 2 in the header area 4, one of the tracks on both sides adjacent to the track to be reproduced is always reproduced. The same prepit 13 as the track, that is, the broken line 14 in FIG.
In this state, the same header information is formed in the area surrounded by. Therefore, it can be considered that there is substantially no crosstalk from the track on that side. Therefore, it is sufficient to consider only the crosstalk from the adjacent track on the opposite side having different header information. In this case, the amount of crosstalk is reduced by half compared to the case where different header information is formed on both sides, and The characteristics can be improved.

Here, the adjacent groove recording track 1
And the land recording track 2, the same header information is reproduced. In the case of tracking the land and the case of tracking the groove, the track error signal for performing the track servo changes from the positive side to the negative side, or Since the polarity at the time of change from the negative side to the positive side is different, it is easy to distinguish the two tracks, and there is no problem in recording and reproducing data.

In the above embodiment, all of the header information is used as position information. However, in an actual application, a fixed pattern indicating a header area or a VFO for clock synchronization is used.
Since the pattern and the like are common to all headers, the same prepit is formed between adjacent tracks only in a portion where a part of the position information in the header area is recorded. Further, a wobbling for a clock may be formed in the groove portion.

FIG. 4 is a plan view of a header area 4 according to another embodiment of the present invention. Usually, the position information of the header area often includes two to three or more independent position information in order to reduce a reproduction error rate. In the case of such a header including two or more pieces of position information, adjacent tracks forming the same information for each piece of position information can be on different sides. In this embodiment, the header area 4
A and a pair of header information 14A, 1 surrounded by a broken line in the header including two pieces of position information of the header area 4B and the header information 4A.
As shown in FIG. 4B, the same prepit 13 is formed between different adjacent pairs of the groove recording track 1 and the land recording track 2. That is, in this example, for one land recording track 2, in the header area 4A, header information 14A consisting of the same prepit 13 as the outer circumferential groove recording track 1 is formed, and in the header area 4B, the inner circumferential groove recording track is formed. 1 forms header information 14B composed of the same pre-pits 13.

With this arrangement, even if the cross-talk is increased due to the deviation of the track position of the beam spot to be reproduced in one of the header areas to approach an adjacent track having different header information, the other header area has
Since the track approaches the track on which the same header information is recorded, crosstalk is reduced, and there is an advantage that either header information can always be accurately reproduced.

Next, there will be described a method of manufacturing an optical disk master for forming the same header information between adjacent tracks. It is possible to separately form land recording tracks and groove recording tracks.However, if there is a rotational misalignment during the production of the master, the position will shift even between adjacent tracks, so good crosstalk may not be obtained. There is. Thus, as schematically shown in FIG. 5, one beam emitted from the light source 21 and modulated by the header information is transmitted to the optical system 22.
And then split into two beams by a diffraction grating or a beam splitter 23. One of these split beams is reflected as it is by a mirror 24, and both beams are directed in parallel. By performing the above-described transfer by simultaneously irradiating the tracks 1 and 2 of the adjacent groove and land of the optical disk master 10A, prepits can be formed on each track at the same time. In addition, it is possible to manufacture a molding master for an optical disk with reduced manufacturing time.

When the same pre-pit is formed at a different position in the header area 4A and the header area 4B as in the embodiment shown in FIG. 4, the divided beams are wobbled integrally by a track pitch in the radial direction of the optical disk. If it is moved, it can be formed similarly. In this case, as described above, in the optical disk medium of the present invention, since the header area is formed as a plane on which no groove is formed, the beam is moved in the radial direction of the optical disk between the header area 4A and the header area 4B. Even in this case, the prepits of the land recording track and the groove recording track can be formed on the same plane, and there is no need to adjust the focal point of the beam between the groove and the land, making it very easy to manufacture.

[0021]

As described above, according to the present invention, in a land / groove type optical disk medium, no groove is formed in a header area for recording header information including position information of the optical disk, and the header is not formed. The information is formed on each of the groove recording track and the land recording track, and is formed at the same position in the extending direction of the track, and is adjacent to each other in a pair with the land recording track and the groove recording track. When the beam spot is reproduced along the center of either one of the land recording track and the groove recording track, the same area is formed in the header area on both sides of the track adjacent to the track to be reproduced. One of them always has the same head information as the track being played. Will be have been made, the crosstalk from the track there side can be regarded as the same as no substantial. Therefore, it is sufficient to consider only the crosstalk from the adjacent track on the opposite side having different header information. In this case, the amount of crosstalk is reduced by half compared to the case where different header information is formed on both sides, and The characteristics can be improved.

In the method of manufacturing an optical disk medium according to the present invention, the groove is not present in the header area and is flat, so that the groove recording tracks and the land recording are formed on the master disk for molding the optical disk medium. An optical disk medium can be manufactured by simultaneously irradiating a pre-pit as header information of each track on the adjacent groove recording track and land recording track with a light beam modulated by the header information and simultaneously forming the same pre-pit. In addition, the manufacturing process can be simplified, and the device can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a plan view showing a schematic configuration of an optical disk medium of the present invention.

FIG. 2 is an enlarged perspective view of a portion A in FIG.

FIG. 3 is a plan view of a header area of FIG. 2;

FIG. 4 is a plan view of a header area according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of an optical system for explaining a manufacturing method of the present invention.

FIG. 6 is a plan view of a header area of a conventional optical disk medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Groove recording track 2 Land recording track 3 Data area 4, 4A, 4B header area 10 Optical disk 10A Optical disk master 11 Groove 12 Land 13 Prepit (empos) 14, 14A, 14B Header information 21 Light source 23 Beam splitter

Claims (6)

[Claims] 1. An optical disc medium comprising: a groove recording track formed along a spiral or concentric groove formed on an optical disc; and a land recording track formed along a land between the grooves. The groove is not formed in a header area for recording header information including position information and the like,
The header information is formed on each of the groove recording track and the land recording track, and is formed at the same position in the extending direction of the track, and is adjacent to each one pair of the land recording track and the groove. An optical disk medium characterized in that the same header information is formed on a recording track. 2. A plurality of header information is formed in the header area in a direction along a track of each track, and one header area is adjacent to one groove or land recording track on one side thereof. The same header information is formed on the land or groove recording track, and the other
2. The optical disk medium according to claim 1, wherein in one header area, the same header information is formed by the one groove or land recording track and the land or groove recording track adjacent to the other groove or land recording track. 3. The optical disc medium according to claim 1, wherein the header information is an emboss pit formed on the optical disc. 4. An optical disc comprising: a groove recording track formed along a spiral or concentric groove formed on an optical disc; and a land recording track formed along a land between the grooves. The groove is not formed in the header area for recording the header information including: the header information is formed on each of the groove recording track and the land recording track, and the formation position is in the radial direction of the optical disc. A method for manufacturing an optical disk medium, wherein the same header information is formed on one land recording track and one groove recording track that are adjacent to each other at the same position and are adjacent to each other. On the master, each header information of the groove recording track and the land recording track A light beam modulated with header information on the adjacent groove recording track and land recording track at the same time to form the same prepit at the same time. 5. The apparatus according to claim 4, wherein the light beam is split into two light beams by a light beam splitting unit, and each of the split light beams is simultaneously irradiated on each of the tracks. A method for manufacturing an optical disk medium. 6. The method for manufacturing an optical disk medium according to claim 4, wherein the two split light beams are set to have a focal point on the same plane.