JP2004030917A - Optical disk and recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk which makes stably tracking-control in the previous recording information recording area of the land groove recordable optical disk, and also to provide its recording/reproducing device. <P>SOLUTION: This optical disk has a first width changing part GC1 in which the width of a first recording track of one of a groove G1/G2 or a land L1/L2 is changed to a first width and a second width, and a second width changing part GC2 in which the width of a first recording track adjacent to the first recording track formed in the first width changing part GC1 in a disk radial direction is changed to a first width and a second width. The second width changing part GC2 is arranged by being shifted from the first width changing part GC1 in a track direction. When the width of the groove G1/G2 is WL, the first width is W1, and the second width is W2, WG≈WL, and W1∠WG∠W2 are set. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical disk such as a magneto-optical disk capable of suppressing crosstalk of prerecorded information such as a pit row and a change in track width and realizing stable tracking control, and a recording / reproducing apparatus therefor.
[0002]
[Prior art]
Conventionally, a magneto-optical disk using a magneto-optical recording medium has been put to practical use as a rewritable optical recording medium. In such a magneto-optical disk, recording and erasing are performed by condensing and irradiating a light beam emitted from a semiconductor laser onto the optical recording medium to increase the local temperature of the magneto-optical recording medium. The recorded information is reproduced by irradiating the magneto-optical recording medium with a light beam having an intensity that does not occur and determining the polarization state of the reflected light. In these magneto-optical recording media, a pit row is formed continuously on a spirally or concentrically formed recording track on a disk substrate, and address information is reproduced by reproducing a change in reflected light amount due to the pit row. The method of obtaining is generally adopted.
[0003]
On the other hand, magnetic super-resolution reproduction using multilayer magnetic films has been actively developed, and the reproduction resolution of super-resolution magneto-optical recording media has been greatly improved. Research on a land-groove recording method for performing recording and reproduction in both the area and the area has been actively conducted. In this land / groove recording method, since each of the land and the groove is a recording track, address pits corresponding to each area are required.
[0004]
FIG. 20 is a diagram showing a configuration of an address pit described in Patent Document 1. Grooves (G1, G2) and lands (L1, L2) are formed in a spiral shape with substantially equal widths, and a first pit row P1 of concavities and convexities in which information of a first address is recorded continuously to the groove G1. The second pit row P2 is formed in the second address area, which is formed in the address area and is shifted in the track longitudinal direction from the first address area in which the first pit row P1 is formed, continuing from the groove G2.
[0005]
A method of reproducing the address information will be described. When the light beam BG1 relatively scans on the groove G1 with the rotation of the optical disk, the light beam BG1 scans the first pit row P1 in the first address area to reflect the address information of the groove G1 in a reflected light amount. After the reproduction is detected as a change, it passes through the second address area.
When the light beam BG2 relatively scans on the groove G2, the light beam BG2 passes through the first address area, and then scans the second pit row P2 in the second address area, thereby causing the light beam BG2 to scan the groove G2. The address information is reproduced and detected as a change in the amount of reflected light. On the other hand, when the light beam BL1 relatively scans over the land L1, the light beam BL1 scans the vicinity of the first pit row P1 in the first address area, thereby causing a leak signal from the first pit row P1 to be generated. As a result, the address information of the land L1 is reproduced and detected as a change in the amount of reflected light. When the light beam BL2 relatively scans over the land L2, the light beam BL2 scans the vicinity of the second pit row P2 in the second address area, thereby detecting a leak signal from the second pit row P2. As a result, the address information of the land L2 is reproduced and detected as a change in reflected light amount. In this way, it is possible to realize an optical disc capable of reproducing address information in each of the land and the groove.
[0006]
FIG. 21 is a diagram showing a configuration of an address described in Patent Document 2. Grooves (G1, G2) and lands (L1, L2) are formed with a width substantially equal to a spiral, and the first and second grooves G1 and G2 have irregularities wider than the groove width on which information of the first address is recorded. One pit row P1 is continuously formed in the first address area, and the first pit row P1 is continuously formed in the second address area shifted in the track longitudinal direction from the first address area in which the first pit row P1 is formed. Two pit rows P2 are continuously formed.
[0007]
In the method of reproducing the address information, as in the case of Patent Document 1, reproduction and detection are performed as changes in the amount of reflected light in the address area for each of the land and the groove. In this way, it is possible to realize an optical disc capable of reproducing address information in each of the land and the groove.
[0008]
FIG. 22 is a diagram showing a configuration of another address described in Patent Document 2 described above. Grooves (G1, G2) and lands (L1, L2) are formed in a spiral with substantially equal widths. A wobble groove in which address information is recorded continuously to the groove G1 is formed in the first address area. A wobbled groove in which address information is recorded is formed in a second address area shifted in the track longitudinal direction from the first address area, following G2.
[0009]
As in the above-mentioned Patent Document 1, the reproduction method of the address information is to reproduce and detect each land and groove as a change in the amount of light reflected by a wobble groove existing in the address area, or to push by a wobble groove existing in the address area. Reproduction is detected as a change in the pull signal.
[0010]
[Patent Document 1]
JP-A-7-153081 (released on June 16, 1995)
[0011]
[Patent Document 2]
JP-A-9-17033 (released on January 17, 1997)
[0012]
[Problems to be solved by the invention]
However, according to the contents described in Patent Document 1, there is a problem that tracking becomes unstable. FIG. 23 is an enlarged view of the first address area in FIG. 20, and the light beam spot BG1 for scanning the groove G1 is symmetrical because the first pit row P1 exists at the center position of the light beam spot BG1. A push-pull signal is obtained, and tracking is performed so that the first pit row P1 is always at the center of the light beam spot BG1. However, in the light beam spot BL1 that scans the land L1, the pit row P1 exists on the left side of the light beam spot BL1 in the first address area, so that the push-pull signal is asymmetric at the portion where the pit row P1 is interrupted. Thus, tracking is performed while the light beam spot BL1 moves to the left side of the drawing as shown in the figure, and the tracking stability is impaired. In the worst case, an abnormality such as a track jump occurs in the address area. For this reason, in the recording / reproducing apparatus for recording / reproducing the optical disk as described above, a process of interrupting the tracking control in the address area may be performed.
[0013]
Further, the first content described in Patent Document 2 also has a problem that tracking becomes unstable. FIG. 24 is an enlarged view of the first address area in FIG. 21. The light scanning the land L1 by forming a first pit row P1 having irregularities wider than the groove width in the first address area. Since the push-pull signal is asymmetric in the beam spot BL1, tracking is performed while moving to the right side of the drawing as shown in the figure, and tracking stability is impaired. In the worst case, an abnormality such as a track jump occurs in the address area. For this reason, in the recording / reproducing apparatus for recording / reproducing the optical disk as described above, a process of interrupting the tracking control in the address area may be performed.
[0014]
Further, in the second content described in Patent Document 2 shown in FIG. 22, since the address is formed by the wobble groove, the push-pull signal is asymmetric, but since the groove is meandering right and left, The light beam spot is located substantially on the center of the wobble of the wobble groove, and stable tracking can be realized. However, since the wobble groove is formed so as to continuously meander to the left and right, the signal detected and reproduced also has a gentle change corresponding to the continuous meandering, and the reproduction signal quality of the address information is not good. Have a problem.
[0015]
An object of the present invention is to solve the above-mentioned problem, and it is possible to suppress crosstalk of prerecorded information such as a pit row and a change in track width, and to realize an optical disk such as a magneto-optical disk capable of realizing stable tracking control and its recording and reproduction. It is intended to provide a device.
[0016]
[Means for Solving the Problems]
The optical recording medium of the present invention that achieves the above object is as follows.
[0017]
An optical disc according to the present invention is an optical disc having both a groove and a land as recording tracks, wherein the width of the first recording track, which is either the groove or the land, changes to the first width and the second width. The width of the first recording track adjacent to the first recording track on which the first width changing portion is formed and the first recording track on which the first width changing portion is formed changes to the first width and the second width. A second width change portion, wherein the second width change portion is arranged to be shifted in the track direction with respect to the first width change portion, the width of the groove being WG, the width of the land being WL, When the first width is W1 and the second width is W2, WG ≒ WL and W1 <WG <W2.
[0018]
Further, the optical disc of the present invention is characterized in that, in the optical disc of the above-mentioned invention, the width of the pits constituting each of the first pit row and the second pit row in the disc radial direction is wider than the width of the groove and the land. I do.
[0019]
Further, the optical disc of the present invention is the optical disc of the above invention, wherein the groove width WG, the first width W1, and the second groove W2 satisfy (WG-W1) Ｗ (W2-WG). Features.
[0020]
Further, the recording / reproducing apparatus of the present invention is a recording / reproducing apparatus for recording or reproducing information on or from the optical disk of the present invention, further comprising tracking control means for controlling a light beam to scan a desired recording track. The tracking control means also performs tracking control when scanning the first width change section and the second width change section.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in Embodiments 1 to 6.
[0022]
[Embodiment 1]
Embodiment 1 of the present invention will be described below with reference to FIGS.
[0023]
FIG. 1 is a sectional view of a magneto-optical disk to which the present invention is applied. An uneven land 2 and a groove 3 are formed on the surface of the optical disk substrate 1. The interference layer 4 made of a transparent dielectric such as AlN and the magnetization information of the recording magnetic layer are transferred onto the optical disk substrate 1 for reproduction. A reproducing magnetic layer 5 made of an amorphous rare earth transition metal alloy such as GdFeCo, an intermediate layer 6 for controlling the transfer from the recording magnetic layer to the reproducing magnetic layer, and a TbFeCo or the like in which information is recorded by the magnetization direction. A super-resolution magneto-optical recording medium is formed in which at least a recording magnetic layer 7 made of an amorphous rare earth transition metal alloy and a protective layer 8 for protecting each magnetic layer from deterioration such as oxidation are laminated.
[0024]
FIG. 2 is a plan view of an address area of the optical disc substrate 1 of the optical disc according to the first embodiment. The optical disc according to the first embodiment has grooves (G1, G2) and lands (L1, L2) formed with substantially equal widths, and both of them are recording tracks. An address area for giving position information of the optical disc is composed of a first address area and a second address area shifted in the track longitudinal direction.
The first address area and the second address area are provided at the same angular position in each track. Further, similarly to Patent Document 1 described in FIG. 20, a first pit row P1 forming a first address area continuously from a groove (G1, G2: first recording track) and a second address area are formed. A second pit row P2 is formed.
[0025]
In the optical disc of the present invention, each pit constituting each of the first pit row P1 and the second pit row P2 is formed to have a discontinuous portion having a fixed length. Address information is recorded at intervals. The length DP of the discontinuous portion is set to be equal to or less than half the radial width WP of the pits forming each pit row.
[0026]
The address information of the groove G1 is obtained by detecting a change in the amount of reflected light at a discontinuous portion when the light beam spot BG1 passes over the first pit row P1 in the first address area. The address information of the land L1 is obtained by detecting a leak signal from the first pit row P1 when the light beam spot BL1 passes through the first address area. Since the first pit row exists in the light beam spot BL1, the leakage signal causes a change in the amount of reflected light at the discontinuous portion even when the light beam spot BL1 passes through a portion continuous to the land L1. Is a signal obtained by The address information of the groove G2 is obtained by detecting a change in the amount of reflected light at the discontinuous portion when the light beam spot BG2 passes over the second pit row P2 in the second address area. The address information of the land L2 is obtained by detecting a leak signal from the second pit row P2 when the light beam spot BL2 passes through the second address area.
[0027]
Here, in Patent Document 1 shown in FIGS. 20 and 23, pits are discretely arranged in order to record an address according to the interval between the pits and the length of the pits. Since there is a large area, when passing through the address area continuous to the land, a push-pull signal that is asymmetrical with respect to the light beam spot is generated with respect to the light beam spot, and stable tracking cannot be performed. Had.
[0028]
On the other hand, in the optical disc shown in FIGS. 1 and 2 of the present embodiment, the length of the discontinuous portion of the pit row is set to be less than half the radial width of the pits constituting the pit row. In addition, the disturbance of the tracking signal at the discontinuous portion is small (very short time), and it is possible to realize more stable tracking as compared with the optical disc in which pits are discretely arranged as described above. Become. Further, since the pit rows adjacent to each other in the radial direction of the disk (that is, the first pit row P1 and the second pit row P2) are formed so as to be shifted in the track direction, the first pit row and the second pit row when scanning the land. Signals from the pit row are not superimposed, and they can be read accurately.
[0029]
FIG. 3 is an enlarged view of the first address area of the optical disc of the present invention shown in FIG.
Since the address information of the groove G1 is obtained by the light beam spot BG1 passing over the first pit row P1 in the first address area, asymmetry of the push-pull signal does not occur, and stable tracking is realized. On the other hand, in the light beam BL1 that scans the land L1, the push-pull signal is asymmetric in the discontinuous portion of the pit row P1 because the pit row exists on the left side of the light beam spot BL1 in the first address area. However, since the length of the discontinuous portion is set to be equal to or less than half the radial width of the pits constituting the pit row, the leakage signal from the first pit row P1 can be obtained without impairing the tracking stability. Can be detected.
[0030]
Next, FIG. 4 shows a modification of the optical disc shown in FIG. 3, in which the width WP of the first pit row is made larger than the widths (WL, WG) of the lands and grooves formed to have substantially the same width. The form is shown.
[0031]
In FIG. 3, when address information for the groove G1 is reproduced, the light beam spot BG1 scans over the first pit row P1, so that the discontinuous portion of the pit row P1 passes through the center of the light beam spot BG1. However, when the address information for the land L1 is reproduced, the light beam spot BL1 scans over the center of the first pit row P1 and the adjacent groove G2. Only the left end portion passes over the discontinuous portion of the pit row P1, and the change in the amount of reflected light becomes small.
[0032]
Therefore, in the configuration of FIG. 4, the light beam spot BL1 is formed between the first pit row P1 and the adjacent groove G2 by making the width WP of the first pit row P1 wider than the width of the land and groove (WL, WG). When scanning over the center, the discontinuous portion of the first pit row P1 passes through a wider area in the light beam spot BL1, and even when reproducing the address information of the land L1, a large change in the reflected light amount occurs. Can be obtained. In this case, when scanning over the land, the width of the pit row is large, so there is a risk that the light beam spot may scan a position slightly deviated from the center of the land. Because of the presence, the shift amount of the light beam spot position is smaller than that of the conventional one shown in FIGS.
Desirably, the pit width of the pit row in FIG. 4 is set so that the average width of the entire pit row including the discontinuous portion is substantially equal to the groove width.
[0033]
Next, a recording / reproducing apparatus for recording / reproducing the above-described magneto-optical disk will be described with reference to FIG.
[0034]
At the time of recording / reproduction, the spindle 105 controlled by the rotation control means drives the magneto-optical disk 101 to rotate. Then, a light beam is emitted from the optical pickup 103 to the recording / reproducing position on the magneto-optical disk 101, and a magnetic field is applied from the magnetic field application device 104 in accordance with an instruction from the magnetic field control means 106 during recording. Thereby, recording and reproduction are performed. The optical pickup 103 is configured to irradiate a desired recording / reproducing position with a light beam by performing focusing and tracking control by an optical pickup control unit (including a tracking control unit) 107. When using the magneto-optical disk 101 of the present embodiment, the optical pickup control means 107 can perform control so as to execute tracking control even in the portion where the first pit row and the second pit row are formed. Thereby, a favorable recording / reproducing operation can be performed even in the portion where the first pit row and the second pit row are formed.
[0035]
Next, a manufacturing process of the optical disk substrate used in the present embodiment as described above will be described with reference to FIG.
[0036]
First, a photoresist film 10 is applied on a quartz glass substrate 9 (see FIG. 5A).
[0037]
Next, after exposing the photoresist film 10 using the laser cutting apparatus shown in FIG. 6, development is performed to form an uneven pattern of the photoresist film 10 (see FIG. 5B). Here, in laser cutting, a quartz glass substrate 9 coated with a photoresist film 10 is placed on a rotatable turntable 12, and a laser beam 13 such as a HeCd laser capable of exposing the photoresist film 10 is subjected to light modulation. After passing through the vessel 14 and the mirror 15, the light is focused and irradiated onto the photoresist film 10 by the objective lens 16. When forming lands and grooves forming a recording track, continuous exposure is performed by continuously irradiating a laser beam 13. When forming an address pit row, exposure is performed by pulsing the laser beam 13 using the optical modulator 14.
[0038]
Next, using the photoresist film 10 as a mask, the quartz glass substrate 9 is dry-etched to form an uneven etching pattern on the quartz glass substrate 9, and then the photoresist film 10 is removed to form the master master 9. (See FIG. 5 (c)).
[0039]
Next, a metal such as Ni is electroformed on the master master 9 to form a stamper 11 (see FIG. 5D).
[0040]
Finally, the master master 9 and the stamper 11 are separated (see FIG. 5E).
[0041]
The stamper 11 formed as described above is mounted on an injection molding machine, and a resin such as polycarbonate is injection-molded to complete an optical disk substrate.
[0042]
Here, the desired groove depth of the unevenness formed on the optical disk substrate differs depending on whether address information is obtained from a push-pull signal or address information is obtained from a reflected light amount signal.
[0043]
Assuming that the refractive index of the substrate is n and the wavelength of the semiconductor laser used for recording / reproducing is λ, the push-pull signal is maximum when the groove depth is λ / (8n), and when the groove depth is λ / (4n). It becomes zero. In order to perform stable tracking, it is necessary to obtain a push-pull signal that can be tracked, and for that purpose, the groove depth is in the range of λ / (16n) to (3λ) / (16n). It is desirable. When address information is obtained from a push-pull signal, it is necessary to obtain a large push-pull signal, and the groove depth is desirably in the range of λ / (16n) to (3λ) / (16n). On the other hand, when address information is obtained from a reflected light amount signal, it is possible to obtain address information in a groove depth range of λ / (16n) to (3λ) / (16n). At λ / (4n), the change in the amount of reflected light is maximal, so that a push-pull signal that can be tracked is obtained. ) / (16n).
[0044]
According to the above description, the optical disc of the first embodiment shown in FIG. 2 was produced. The width (WG, WL, WP) of the groove, land and address pit was set to 0.3 μm, the length LP of the address pit was set to 0.6 μm, and the depth of the concave / convex groove was set to 40 nm.
In this configuration, tracking was performed for 60 seconds using a semiconductor laser having a wavelength of 410 nm and an optical pickup having an objective lens having a numerical aperture of 0.6 while changing the length DP of the discontinuous portion of the address pit. When the length DP of the continuous portion was 0.15 μm or less, no tracking error occurred in the tracking of the land portion. On the other hand, when the length DP of the discontinuous portion was longer than 0.15 μm, It was confirmed that a tracking error occurred during tracking. For example, when the length DP of the discontinuous portion is 0.19 μm, a tracking error occurs 25 seconds after the start of tracking. That is, in the present embodiment, it is necessary that the length DP of the discontinuous portion is set to be equal to or less than half the radial width WP of the pits forming the pit row.
[0045]
Next, in the above configuration, an optical disk shown in FIG. 4 was prepared in which the length DP of the discontinuous portion was 0.11 μm and the width WP of the address pit was 0.4 μm. In an optical disc in which the length DP of the discontinuous portion is 0.11 μm and the width WP of the address pit is 0.3 μm, the address pit is compared with the change in the amount of reflected light when the light beam spot BL1 passes through the address pit row. By increasing the width WP to 0.4 μm, the change in the amount of reflected light can be increased by 30%.
[0046]
In the above embodiment, the case where the present invention is applied to a magneto-optical disk has been described. However, it is needless to say that the present invention can be applied to other optical disks such as a phase change type. In the case of a phase change type optical disk, the magnetic field applying device 104 and the magnetic field control means 106 shown in FIG. 25 are not required.
[0047]
[Embodiment 2]
Embodiment 2 of the present invention will be described below with reference to FIGS.
[0048]
FIG. 7 is a plan view of an address area of the optical disc substrate according to the second embodiment. The optical disk according to the second embodiment has grooves (G1, G2: first recording tracks) and lands (L1, L2) formed with substantially equal widths, and both of them are recording tracks. The address area for giving the position information of the optical disk is composed of a first address area and a second address area which are shifted in the track longitudinal direction. The first address area and the second address area are provided at the same angular position in each track.
[0049]
The first address area has a first width change portion GC1 composed of a first groove width W1 and a second groove width W2 continuous with the groove G1, and in the second address area, It has a second width change portion GC2 composed of a first groove width W1 and a second groove width W2 continuous with the groove G2. The second width change portion GC2 is provided in a groove adjacent to the groove in which the first width change portion GC1 is formed in the disk radial direction. Here, the portion having the first groove width W1 and the portion having the second groove width W2 are arranged according to a signal obtained by modulating address information by frequency modulation, phase modulation, or the like. In this case, the portion having the first groove width W1 and the portion having the second groove width are set to have substantially the same length as the entire disk.
[0050]
When the groove width is WG, the land width is WL, the first groove width is W1, and the second groove width is W2, WG ≒ WL and W1 <WG <W2. are doing.
[0051]
The address information of the groove G1 is obtained by detecting a change in the amount of reflected light caused by a difference in groove width when the light beam spot BG1 passes through the first address area. Next, the address information of the land L1 is obtained by detecting a change in the amount of reflected light caused by a land width change when the light beam spot BL1 passes through the first address area. Next, the address information of the groove G2 is obtained by detecting a change in the amount of reflected light caused by a difference in groove width when the light beam spot BG2 passes through the second address area. Next, the address information of the land L2 is obtained by detecting a change in the amount of reflected light caused by a land width change when the light beam spot BL2 passes through the second address area.
[0052]
Here, in Patent Document 2 described in FIGS. 21 and 24, only a portion wider than the groove width is formed in the address area, so that the push-pull signal becomes asymmetric in the land portion, and stable tracking is performed. There was a problem that it could not be performed. On the other hand, in the optical disk of the second embodiment, the first grooves smaller than the groove width and the second grooves larger than the groove width are alternately formed in the address area. Asymmetry of the pull signal is reduced, and more stable tracking can be realized.
[0053]
FIG. 8 is an enlarged view of the first address area of the optical disc of the present invention shown in FIG.
Since the address information of the groove G1 is obtained by the light beam spot BG1 passing through the first address area, asymmetry of the push-pull signal does not occur, and stable tracking is realized. On the other hand, for the light beam BL1 that scans the land L1, in the first address area, asymmetry of the push-pull signal occurs, but the first groove that is narrower than the groove width and the first groove that is wider than the groove width are used. Since the two grooves are alternately formed, the edge between the land L1 and the groove G1 in the address area changes symmetrically with respect to the extension of the edge between the land L1 and the groove G1 in the data area. Become. Therefore, the light beam spot BL1 scans the center position on the extension of the land L1 in the data area in the address area, and realizes stable tracking.
[0054]
As described above, in the second embodiment, the edge between the land L1 and the groove G1 in the address area is changed symmetrically with respect to the extension of the edge between the land L1 and the groove G1 in the data area. That is, since the groove width WG, the first groove width W1, and the second groove width W2 are formed such that (WG-W1) ≒ (W2-WG), stable tracking is realized. be able to.
[0055]
The recording / reproducing apparatus for recording / reproducing the optical disc according to the second embodiment can have the same configuration as that shown in FIG. 25 described in the first embodiment, and is stable even when scanning the first changing portion and the second width changing portion. Tracking control can be performed. If the present optical disc does not require application of a magnetic field, such as a phase change optical disc, the magnetic field applying device 104 and the magnetic field control means 106 are not required.
[0056]
The optical disc substrate of the second embodiment can be formed in the same manner as in the first embodiment. The optical disk substrate of the second embodiment is formed by modulating the intensity of laser light to be exposed by an optical modulator when exposing an address area by laser cutting.
[0057]
According to the above description, the optical disc of the second embodiment shown in FIG. 7 was created. The width (WG, WL) of the groove and the land is 0.3 μm, the length LG1 of the portion having the first groove width and the length LG2 of the portion having the second groove width are 0.6 μm (length LG2 Varies according to address information in an actual optical disc, but here, LG2 = 0.6 μm was adopted as a test condition), and the depth of the concave and convex grooves was set to 40 nm.
In this configuration, the first groove width W1 is set to 0.2 μm, the second groove width W2 is set to 0.4 μm, and an optical pickup having a semiconductor laser having a wavelength of 410 nm and an objective lens having a numerical aperture of 0.6 is used. As a result of tracking for seconds, no tracking error occurred when tracking the land portion. On the other hand, the optical disk shown in FIG. 21 in which the first groove width W1 is 0.3 μm, which is the same as the groove and land widths (WG, WL), and the second groove width W2 is 0.4 μm, is shown in Comparative Example 2. As a result of a similar experiment, it was confirmed that a tracking error occurs 30 seconds after the start of tracking in tracking the land portion.
[0058]
[Embodiment 3]
Embodiment 3 of the present invention will be described below with reference to FIGS.
[0059]
FIG. 9 is a plan view of an address area of the optical disc substrate according to the third embodiment. The optical disc according to the third embodiment has grooves (G1, G2: first recording tracks) and lands (L1, L2) formed with substantially equal widths, and both of them are recording tracks. An address area for giving position information of the optical disc is composed of a first address area and a second address area shifted in the track longitudinal direction. The first address area and the second address area are respectively provided at the same disk center angle and the same disk radial position in each track.
[0060]
The first address area and the second address area are respectively composed of a first pit row P1 and a second pit row P2 formed continuously in a groove. The first pit row P1 of the first address area in each groove has the same arrangement as the first pit row P1 in the groove adjacent to one of the inner circumference side and the outer circumference side of the disk. The second pit row P2 in the address area has the same arrangement as the second pit row P2 in the groove adjacent to the other side.
[0061]
Specifically, in FIG. 9, a first pit row P1 having a similar arrangement is formed in a first address area continuous with the groove G1 and the groove G2 on the right side thereof, and the groove G1 and the groove on the left side thereof are formed. A second pit row P2 having a similar arrangement is formed in a second address area following G2.
[0062]
The address information of the groove G1 is obtained by detecting a change in the amount of reflected light when the light beam spot BG1 passes on the first pit row P1 in the first address area and on the second pit row P2 in the second address area. . Next, the address information of the land L1 is obtained by detecting a leak signal from the first pit row P1 formed in the same arrangement in the grooves on both sides when the light beam spot BL1 passes through the first address area. can get. This leak signal is a signal obtained by a change in the amount of reflected light even when the light beam spot BL1 passes through a portion continuous to the land L1 because the first pit row P1 exists in the light beam spot BL1. is there. Next, the address information of the groove G2 is obtained by detecting a change in the amount of reflected light when the light beam spot BG2 passes on the first pit row P1 in the first address area and on the second pit row P2 in the second address area. can get. Next, the address information of the land L2 is obtained by detecting a leak signal from the second pit row P2 formed in the same arrangement in the grooves on both sides when the light beam spot BL2 passes through the second address area. can get.
[0063]
Here, in Patent Document 1 shown in FIG. 20, when passing through an address area continuous with a land, pits are discretely arranged on one side of a light beam spot, and therefore, the pits are asymmetrical with respect to the light beam spot. There has been a problem that a push-pull signal is generated and stable tracking cannot be performed.
[0064]
On the other hand, in the optical disc of the third embodiment, when passing through the address area continuous to the land, the arrangement of the left and right pit rows in either the first address area or the second address area is formed to be the same. As a result, more stable tracking can be realized as compared with an optical disc in which pits are discretely arranged.
[0065]
Further, for example, there is a portion where the left and right pit rows are asymmetric when scanning the land, such as a first address area which is continuous with the land L2. For example, the difference between the left and right pit rows is only one bit. (That is, by recording address information using a gray code), the scanning position of the light beam spot can be set substantially at the center of the left and right pit rows, and a stable tracking operation can be realized.
[0066]
Further, in the present embodiment, when reproducing the address of the groove, it is only necessary to reproduce a pit string continuous with the groove, and since the pit passes through the center position of the light beam spot, there is a large change in the amount of reflected light, and it is stable. It is possible to reproduce the address of the groove. Also, when reproducing the address of the land, since the address is reproduced from the pit rows of the same arrangement formed on both sides of the land, a larger change in the amount of reflected light can be obtained than in the configuration shown in FIGS. . However, even in this case, it is necessary to reproduce the leak signal from the pits existing at both ends of the light beam spot, so that there is a problem that the change in the amount of reflected light is smaller than that in the groove address reproduction.
[0067]
Therefore, as in the modification shown in FIG. 10, the radial width WP of the pits constituting the pit row is made larger than the groove width WG and the land width WL formed substantially equally, thereby reproducing the address of the land. In this case, the leakage signal from the pits existing at both ends of the light beam spot becomes large, and the address of the land can be reproduced stably.
[0068]
The recording / reproducing apparatus for recording / reproducing the optical disc according to the third embodiment described above can be realized with the same configuration as that of the first embodiment shown in FIG. 25, and can realize stable tracking control even when scanning a pit row. . If the present optical disc does not require application of a magnetic field, such as a phase change optical disc, the magnetic field applying device 104 and the magnetic field control means 106 are not required.
[0069]
Further, the optical disc substrate of the third embodiment can be formed in the same manner as in the first embodiment. In order to form the optical disk substrate of the third embodiment, when exposing the address area by laser cutting, the intensity of the laser beam to be exposed by the optical modulator is pulsed, and the pit is exposed in synchronization with the adjacent groove. Is realized by:
[0070]
According to the above description, the optical disc of the third embodiment shown in FIG. 9 was created. The width (WG, WL, WP) of the groove, the land and the address pit is set to 0.3 μm, the length LP of the address pit is set to 0.6 μm, and the length DP of the discontinuous portion of the address pit is set to 0.6 μm (length Although LP and DP change in accordance with the address information in an actual optical disk, the above-mentioned conditions were adopted as test conditions here), and the depth of the concave and convex grooves was set to 40 nm. This optical disc was tracked for 60 seconds using an optical pickup having a semiconductor laser having a wavelength of 410 nm and an objective lens having a numerical aperture of 0.6. As a result, no tracking error occurred in tracking of the land. In the case of an optical disk in which address pits having the same shape are formed by the conventional configuration shown in FIG. 20, a tracking error occurs 12 seconds after the start of tracking.
[0071]
Next, the optical disk shown in FIG. 10 having the above configuration and having the address pit width WP of 0.4 μm was prepared. In an optical disk having an address pit width WP of 0.3 μm, by increasing the address pit width WP to 0.4 μm as compared with the change in the amount of reflected light when the light beam spot BL1 passes through the address pit row, The change in the amount of reflected light can be increased by 35%.
[0072]
[Embodiment 4]
Embodiment 4 of the present invention will be described below with reference to FIGS.
[0073]
FIG. 11 is a plan view of an address area of the optical disc substrate according to the fourth embodiment. The optical disk according to the fourth embodiment has grooves (G1, G2: first recording tracks) and lands (L1, L2) formed with substantially equal widths, and both of them are recording tracks. An address area for giving position information of the optical disc is composed of a first address area and a second address area shifted in the track longitudinal direction. The first address area and the second address area are provided at the same angular position in each track.
[0074]
The first address area and the second address area are respectively composed of a first pit row P1 and a second pit row P2 formed continuously in a groove. The first pit row P1 of the first address area in each groove has the same arrangement as the first pit row P1 in the groove adjacent to one of the inner circumference side and the outer circumference side of the disk. The second pit row P2 in the address area has the same arrangement as the second pit row P2 in the groove adjacent to the other side.
[0075]
In the optical disc of the fourth embodiment, discontinuous portions are formed at regular intervals between the pits forming the first pit row P1 and the second pit row P2, and the length of the discontinuous section is pit length. The width is set to be equal to or less than half the radial width of the pits constituting the row.
[0076]
The address information of the groove G1 is to detect a change in the amount of reflected light when the light beam spot BG1 passes through a discontinuous portion on the first pit row P1 of the first address area and the second pit row P2 of the second address area. Is obtained by Next, the address information of the land L1 is obtained from the first pit row P1 when the light beam spot BL1 passes through the first address area in which the first pit row P1 is formed in the same arrangement on both sides of the land L1. It is obtained by detecting a leak signal from a discontinuous portion. This leak signal is that the reflected light amount changes even when the light beam spot BL1 passes through the portion continuous to the land L1 because the discontinuous portion of the first pit row P1 exists in the light beam spot BL1. Is a signal obtained by Next, when the light beam spot BG2 passes through the discontinuous portions on the first pit row P1 in the first address area and the second pit row P2 in the second address area, the address information of the groove G2 is It can be obtained by detecting a change in the amount of reflected light at. Next, the address information of the land L2 is obtained from the second pit row P2 when the light beam spot BL2 passes through the second address area in which the second pit row P2 is formed in the same arrangement on both sides of the land L2. It is obtained by detecting a leak signal from a discontinuous portion.
[0077]
In the fourth embodiment, since address pits are composed of a pit row, more stable tracking can be realized as compared with an optical disc in which pits are discretely arranged, as in the third embodiment. It becomes possible. Further, since the length of the discontinuous portion of the pit row is set to be equal to or less than half of the radial width of the pits constituting the pit row, for the same reason as in the first embodiment, It is possible to realize more stable tracking as compared with the third embodiment.
[0078]
Further, in the present embodiment, when reproducing the address of the groove, it is only necessary to reproduce the discontinuous portion of the pit row continuous with the groove, and since the discontinuous portion of the pit passes through the center position of the light beam spot, a large reflection occurs. Since there is a change in the amount of light, the address of the groove can be reproduced stably, and when reproducing the address of the land, the address is reproduced from the pit row of the same arrangement formed on both sides of the land. A larger change in the amount of reflected light can be obtained than in the configurations shown in FIGS. However, even in this case, it is necessary to reproduce the leak signal from the pits existing at both ends of the light beam spot, so that there is a problem that the change in the amount of reflected light is smaller than that in the groove address reproduction.
[0079]
Therefore, as shown in FIG. 12, by making the radial width WP of the pits constituting the pit row wider than the groove width WG and the land width WL formed almost equally, the light of the land address is reproduced in the reproduction of the land address. Leakage signals from discontinuous portions of the pits at both ends of the beam spot become large, and it becomes possible to stably reproduce the address of the land.
[0080]
The recording / reproducing apparatus for recording / reproducing the optical disc according to the fourth embodiment described above can be realized with the same configuration as that of the first embodiment shown in FIG. 25, and can realize tracking control even when scanning a pit row. If the present optical disc does not require application of a magnetic field, such as a phase change optical disc, the magnetic field applying device 104 and the magnetic field control means 106 are not required.
[0081]
The optical disc substrate of the fourth embodiment can be formed in the same manner as in the third embodiment. In order to form the optical disk substrate of the fourth embodiment, when exposing the address area by laser cutting, the intensity of the laser beam to be exposed by the optical modulator is pulsed, and the pit is exposed in synchronization with the adjacent groove. Is realized by:
[0082]
According to the above description, the optical disc of Embodiment 4 shown in FIG. 11 was created. The width (WG, WL, WP) of the groove, the land, and the address pit is set to 0.3 μm, and the length LP of the address pit is set to 0.6 μm (the length LP changes according to the address information in an actual optical disc. The above conditions were adopted as test conditions), and the depth of the concave and convex grooves was set to 40 nm. In this configuration, the optical disc has a tangential tilt of 5 mrad using a semiconductor laser having a wavelength of 410 nm and an optical pickup having an objective lens having a numerical aperture of 0.6 by changing the length DP of the discontinuous portion of the address pit. When the length DP of the discontinuous portion is 0.15 μm or less as a result of performing the tracking for 60 seconds, the tracking error of the land portion does not occur. When the length was longer than 0.15 μm, it was confirmed that a tracking error occurred in tracking of the land portion. For example, if the length DP of the discontinuous portion is 0.22 μm, a tracking error occurs 45 seconds after the start of tracking. This means that, compared to the optical disc of the third embodiment shown in FIG. 9, the optical disc of the fourth embodiment shown in FIG. 11 can realize more stable tracking when the optical disc has a tilt. It indicates that there is.
[0083]
Next, an optical disc shown in FIG. 12 was prepared in which the length DP of the discontinuous portion was set to 0.11 μm and the width WP of the address pit was set to 0.4 μm. In an optical disc in which the length DP of the discontinuous portion is 0.11 μm and the width WP of the address pit is 0.3 μm, the address pit is compared with the change in the amount of reflected light when the light beam spot BL1 passes through the address pit row. By increasing the width WP to 0.4 μm, the change in the amount of reflected light can be increased by 30%.
[0084]
[Embodiment 5]
The fifth embodiment of the present invention will be described below with reference to FIGS.
[0085]
FIG. 13 is a plan view of an address area of the optical disk substrate according to the fifth embodiment. The optical disk according to the fifth embodiment has grooves (G1, G2: first recording tracks) and lands (L1, L2) formed with substantially equal widths, and both of them are recording tracks. The address area for providing the position information of the optical disc is composed of a first address area (first width change section GC1) and a second address area (second width change section GC2) shifted in the track longitudinal direction. The first address area and the second address area are provided at the same angular position in each track.
[0086]
The first address area and the second address area record the address information by changing the width of the groove between the first groove width and the second groove width. The groove width in the first address area of each groove is changed in the same manner as that for recording the same information as the first address area in the groove adjacent to one of the inner circumference side and the outer circumference side of the disk, and The groove width in the second address area is similarly changed to record the same information as in the second address area in the adjacent groove on one side.
[0087]
Here, when the groove width is WG, the land width is WL, the first groove width is W1, and the second groove width is W2 (see FIG. 14), WG ≒ WL, and W1 <WG. <W2. Note that the groove width is changed by meandering both side walls of the groove substantially uniformly.
[0088]
The address information of the groove G1 is obtained by detecting a change in the amount of reflected light caused by a difference in groove width when the light beam spot BG1 passes through the first address area and the second address area. Next, the address information of the land L1 is to detect a change in the amount of reflected light caused by a land width change caused by a similar change in the left and right grooves when the light beam spot BL1 passes through the first address area. Is obtained by Next, the address information of the groove G2 is obtained by detecting a change in the amount of reflected light caused by a difference in groove width when the light beam spot BG2 passes through the first address area and the second address area. Next, the address information of the land L2 detects a change in the amount of reflected light caused by a land width change caused by a similar change in the left and right grooves when the light beam spot BL2 passes through the second address area. It can be obtained by:
[0089]
Here, in the second embodiment, when reproducing the address of the land, since the land width of only one side of the light beam spot fluctuates, the change in the amount of reflected light is smaller than when reproducing the address of the groove. However, in this embodiment, when reproducing the address of the land, the width of the left and right grooves fluctuates similarly, and as in the case of reproducing the address of the groove, the amount of reflected light changes greatly. Can be obtained.
[0090]
FIG. 14 is an enlarged view of the first address area of the optical disc of the present invention shown in FIG. The address information of the groove G1 is obtained when the light beam spot BG1 passes through the first address area, and the groove width of the first address area changes symmetrically with respect to the center of the light beam spot BG1, so that the push-pull is performed. Signal asymmetry does not occur, and stable tracking is realized. In addition, the light beam spot scans the symmetrical land portion with respect to the light beam spot BL1 that scans the land L1, so that asymmetry of the push-pull signal does not occur and stable tracking is realized.
[0091]
Further, by changing the edges of the land portion and the groove portion of the address region symmetrically with respect to the extension of the edge between the land L1 and the groove G1 of the data region, the grooves on both sides of the land change asymmetrically. In the address area on the side (for example, when the light beam spot BL2 scanning the land L2 passes through the first address area), the asymmetry of the push-pull signal can be further reduced, and more stable tracking is realized.
[0092]
As described above, in the present embodiment, the edge between the land portion and the groove portion of the address region is changed symmetrically with respect to the extension line of the edge between the land L1 and the groove G1 of the data region. Stable tracking can be realized. That is, it is desirable that the groove width WG, the first groove width W1, and the second groove width W2 are formed so that (WG-W1) ≒ (W2-WG).
[0093]
The recording / reproducing apparatus for recording / reproducing the optical disk according to the fifth embodiment described above can be realized with the same configuration as that in FIG. 25 shown in the first embodiment, and is stable in the first width changing portion and the second width changing portion. Tracking control can be executed. However, if the present optical disc does not require application of a magnetic field, such as a phase change optical disc, the magnetic field applying device 104 and the magnetic field control means 106 are not required.
[0094]
The optical disk substrate of the fifth embodiment can be formed in the same manner as in the first embodiment. In order to form the optical disk substrate of the fifth embodiment, when exposing the address area by laser cutting, the optical modulator modulates the laser beam intensity in synchronization with the adjacent groove and performs exposure.
[0095]
According to the above description, the optical disk of the fifth embodiment shown in FIG. 13 was created. The width (WG, WL) of the groove and the land is 0.3 μm, and the length LG1 of the portion having the first groove width and the length LG2 of the portion having the second groove width are 0.6 μm (length LG1, LG2 changes according to the address information in an actual optical disc, but here, the above conditions were adopted as test conditions), and the depth of the concave and convex grooves was set to 40 nm. In this configuration, the first groove width W1 is set to 0.2 μm, the second groove width W2 is set to 0.4 μm, and an optical pickup having a semiconductor laser having a wavelength of 410 nm and an objective lens having a numerical aperture of 0.6 is used. As a result of tracking for seconds, no tracking error occurred in tracking the land portion. Further, in the optical disc of the second embodiment shown in FIG. 7, when reproducing the address information of L1 and L2, only the groove width on one side fluctuates, so that it can be obtained by reproducing the address information of G1 and G2. Although there was a problem that only a smaller change in the amount of reflected light was obtained as compared with a change in the amount of reflected light, in the optical disk of the fifth embodiment shown in FIG. 13, when reproducing the address information of L1 and L2, Since the groove width fluctuates similarly, a change in the amount of reflected light substantially equal to the change in the amount of reflected light obtained by reproducing the address information of G1 and G2 could be obtained.
[0096]
[Embodiment 6]
Embodiment 6 of the present invention will be described below with reference to FIGS.
[0097]
FIG. 15 is a plan view of an address area of the optical disk substrate according to the sixth embodiment. The optical disk according to the sixth embodiment has grooves (G1, G2: first recording tracks) and lands (L1, L2) formed with substantially equal widths, and both of them are recording tracks.
[0098]
An address area for giving position information of the optical disc is composed of a first address area and a second address area shifted in the track longitudinal direction. The first address area and the second address area are formed at the same angular position in each track. In the first address area, an uneven first wobble pit row P1 on which information of the first address is recorded is formed continuously with the groove G1, and in the second address area, the second wobble pit row P2 is formed continuously with the groove G2. An uneven second wobble pit row P2 in which address information is recorded is formed.
[0099]
In the optical disk described in Patent Literature 2 shown in FIG. 22, address information is formed in a wobble groove in which the groove meanders right and left in the address area, following the groove (G1, G2), and the wobble state of the groove is changed. Although it is detected as a change in the reflected light amount or a change in the push-pull signal, the change in the reflected light amount and the change in the push-pull signal become continuous because the groove continuously meanders to the left and right. And the number of address detection errors increases.
[0100]
On the other hand, in the optical disk according to the sixth embodiment, in the address area, address information is formed in a wobble pit row meandering left and right, and the wobble state of the groove is reproduced and detected. By being formed, the change in the wobble state at the pit edge becomes steep, and in the reproduction of the address information, the reproduction jitter can be further reduced and the address detection error can be reduced.
[0101]
FIG. 16 is an enlarged view of the first address area of the optical disc of the present invention shown in FIG. The address information of the groove G1 is reproduced by detecting a change in the push-pull signal when the light beam spot BG1 passes through the wobble pit row P1 in the first address area. There is asymmetry of the push-pull signal depending on whether the address pit is on the right or on the left. However, since the address pits are formed alternately on the left and right, the light beam spot BG1 scans on the extension of the groove G1 and is stable. Tracking can be realized.
[0102]
On the other hand, the address information of the land L1 is reproduced by detecting a change in the push-pull signal when the light beam spot BL1 passes on the right side of the wobble pit row P1 in the first address area.
[0103]
Here, the pit interval of the wobble pit row will be described. FIG. 17 is an explanatory diagram thereof. When the interval DP1 between the pits forming the wobble pit row is increased, the area where no pits are present is widened, so that the asymmetry of the push-pull signal is increased and the amount of reflected light in the areas where no pits are present is remarkably increased. This makes it difficult to reproduce stable wobble information. Therefore, it is desirable that the pit interval DP1 be equal to or less than the groove width WG for stable reproduction of wobble information.
[0104]
On the other hand, wobble pits can be formed so that the pits overlap as shown in FIG. 18, but in order to reduce the reproduction jitter and reduce the address detection error in address information reproduction. It is necessary that wobble pits are formed so that at least adjacent pits do not contact each other.
[0105]
Therefore, as shown in FIG. 16, the position of the trailing edge PE1 of one pit P1 constituting the address pit row and the position of the leading edge PE2 of the continuously formed pits P1 are made to substantially match. It is more desirable.
[0106]
The recording / reproducing apparatus for recording / reproducing the optical disk according to the sixth embodiment described above can be realized with the same configuration as that shown in FIG. 25 shown in the first embodiment, and performs stable tracking control even when scanning a wobble pit row. it can. If the present optical disc does not require application of a magnetic field, such as a phase change optical disc, the magnetic field applying device 104 and the magnetic field control means 106 are not required.
[0107]
The optical disc substrate of the sixth embodiment can be formed by a process similar to that of the first embodiment using a cutting device (exposure device) shown in FIG. In order to form the optical disc substrate of the sixth embodiment, when exposing the address area by laser cutting, the laser beam to be exposed is wobbled by the optical deflector 17 and synchronized with the wobble by the optical modulator 14. This is realized by pulsing the laser light.
[0108]
According to the above description, the optical disk of the sixth embodiment shown in FIG. 16 was created. The width (WG, WL, WP) of the groove, land and wobble pit was set to 0.3 μm, the length LP of the wobble pit was set to 0.6 μm, and the depth of the concave / convex groove was set to 40 nm. The position of the trailing edge PE1 of the pits constituting the address pit row on this optical disc coincides with the position of the leading edge PE2 of the pits formed continuously. Further, as Comparative Example 6, an optical disk shown in FIG. 22 was prepared in which the width (WG, WL) of the groove and the land was 0.3 μm, the wobble grooves were formed at a period of 0.6 μm, and the depth of the concave and convex grooves was 40 nm. did.
[0109]
The optical discs of Embodiment 6 and Comparative Example 6 were reproduced with an optical pickup having a semiconductor laser having a wavelength of 410 nm and an objective lens having a numerical aperture of 0.6 using the push-pull signal to reproduce the L1 address. While the L1 address reproduction signal in Example 6 has 8% jitter, the L1 address reproduction signal in Embodiment 6 has only 5% jitter, thus reproducing more accurate address information. Has been confirmed to be possible.
[0110]
Next, as shown in FIG. 17, a similar investigation was performed on an optical disc in which wobble pit rows were formed at intervals of the width DP1. When DP1 is 0.30 μm or less, individual pits are formed separately, and address information can be reproduced with 5% jitter, similarly to the L1 address reproduction signal in the sixth embodiment. there were. However, it was confirmed that when DP1 was larger than 0.30 μm, the jitter of the address reproduction signal gradually increased, and when DP1 was 0.40 μm, the address reproduction signal had 9% jitter. That is, in the present embodiment, in order to realize stable reproduction of wobble information, the pit interval DP1 needs to be equal to or less than the groove width WG.
[0111]
Next, as shown in FIG. 18, the same investigation was performed by overlapping the wobble pit rows with the width DP2. When DP2 is set to 0.1 μm, individual pits are formed separately, so that address information can be reproduced with 5% jitter, similarly to the L1 address reproduction signal in the sixth embodiment. However, when DP2 is set to 0.13 μm, individual pits cannot be formed separately, adjacent pits are continuously formed, and the address reproduction signal of L1 is 8% as in Comparative Example 6. It was confirmed to have jitter. That is, in the present embodiment, in order to realize stable reproduction of wobble information, it is necessary that wobble pits are formed so that at least adjacent pits do not contact each other.
[0112]
As described above, the present invention has been described with reference to the first to sixth embodiments. However, the present invention is not limited to these, and various modifications can be made without changing the gist of the present invention.
For example, in the first to sixth embodiments, the first address area and the second address area are provided at the same angular position in each track. However, the present invention is not limited to this. In such a case, the first address area and the second address area may be provided at the same angular position in each zone.
[0113]
In the first, third, fourth, and sixth embodiments, the pit row (or wobble pit row) is provided continuously in the groove. However, it goes without saying that the pit row may be provided continuously in the land. In the present invention, “continuously in a groove” or “continuously in a land” includes on a groove and a land.
[0114]
Further, in the second and fifth embodiments, the width change portion is provided in the groove, but it is needless to say that the width change portion may be formed in the land. In the above embodiments, the pit row, the width change portion, the wobble pit, Although an example in which address information is recorded by a column has been described, the present invention can be applied to a case in which other prerecorded information (at least, for example, information different between adjacent grooves) is recorded in each track.
[0115]
【The invention's effect】
As described above, according to the optical disc of the present invention, the prerecorded information including any of the pit row, the groove (land) width changing section, and the wobble pit row can be reproduced without crosstalk, and the prerecorded information recording section can be reproduced. , The asymmetry of the push-pull signal is eliminated, and the tracking stability can be maintained even when the light beam scanning the land scans the pre-recorded information recording area.
[0116]
Further, if the pre-recorded information is formed by a wobble pit row, the reproduced and detected signal shows a steep change corresponding to discontinuous pits, and it is possible to obtain good reproduced signal quality.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an optical disc of the present invention.
FIG. 2 is a plan view illustrating the optical disc of the first embodiment.
FIG. 3 is an enlarged plan view illustrating a main part of the optical disc of FIG. 2;
FIG. 4 is an enlarged plan view illustrating a modification of the optical disc of FIG. 2;
FIG. 5 is a process chart illustrating a method of manufacturing an optical disc according to the present invention.
FIG. 6 is a diagram illustrating an optical disc exposure method according to the present invention.
FIG. 7 is a plan view illustrating an optical disc according to a second embodiment.
FIG. 8 is an enlarged plan view illustrating a main part of the optical disc of FIG. 7;
FIG. 9 is a plan view illustrating an optical disc according to a third embodiment.
FIG. 10 is an enlarged plan view illustrating a main part of the optical disc of FIG. 9;
FIG. 11 is a plan view illustrating an optical disc according to a fourth embodiment.
FIG. 12 is an enlarged plan view showing a modification of the optical disc of FIG. 11;
FIG. 13 is a plan view illustrating an optical disc according to a fifth embodiment.
FIG. 14 is an enlarged plan view illustrating a main part of the optical disc of FIG.
FIG. 15 is a plan view illustrating an optical disc according to a sixth embodiment.
16 is an enlarged plan view illustrating a main part of the optical disc of FIG.
FIG. 17 is an enlarged plan view illustrating a modified example of the optical disk of FIG.
18 is an enlarged plan view illustrating a comparative example of the optical disc of FIG.
FIG. 19 is a view illustrating an optical disc exposure method according to the present invention.
FIG. 20 is a plan view illustrating a conventional optical disc.
FIG. 21 is a plan view illustrating a conventional optical disc.
FIG. 22 is a plan view illustrating another conventional optical disk.
FIG. 23 is a plan view illustrating another conventional optical disk.
FIG. 24 is a plan view illustrating another conventional optical disk.
FIG. 25 is a block diagram illustrating a recording / reproducing apparatus for recording / reproducing an optical disc according to the present invention.
[Explanation of symbols]
1 Optical disk substrate
2 lands
3 grooves
4 Interference layer
5 Reproduction magnetic layer
6 middle class
7 Recording magnetic layer
8 Protective layer
9 Master substrate
10 Photoresist
11 Stamper
G1, G2 Groove
L1, L2 Land
P1 1st pit row
P2 2nd pit row
W1 First groove width
W2 Second groove width

Claims (4)

In an optical disc having both grooves and lands as recording tracks,
A first width change portion in which the width of a first recording track, which is one of a groove and a land, changes to a first width and a second width;
A second width changing portion in which the width of the first recording track adjacent to the first recording track in which the first width changing portion is formed in the radial direction of the disc changes to a first width and a second width; Has,
The second width change portion is arranged to be shifted in the track direction with respect to the first width change portion, the width of the groove is WG, the width of the land is WL, the first width is W1, and the second width is the second width change portion. An optical disk characterized in that when the width is W2, WG ≒ WL, and W1 <WG <W2. 2. The optical disk according to claim 1, wherein pits constituting each of the first pit row and the second pit row have a width in a radial direction of the disk larger than a width of the groove and the land. 2. The optical disc according to claim 1, wherein the groove width WG, the first width W1, and the second groove W2 satisfy (WG-W1) ≒ (W2-WG). A recording / reproducing apparatus for recording or reproducing information on / from the optical disc according to claim 1 or 3,
It has tracking control means for controlling the light beam to scan a desired recording track,
The recording / reproducing apparatus, wherein the tracking control means performs tracking control even when scanning the first width changing section and the second width changing section.

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