JPH0773475A - Optical disk - Google Patents

Abstract

PURPOSE:To obtain a tracking error signal of high precision with respect to the optical disk which has information tracks provided in guide grooves and between guide grooves to have a high recording density. CONSTITUTION:On this optical disk, information is recorded not only in circularly formed and recessed guide groove parts T1, T3, and T5 but also in parts T2 and T4 between guide grooves, and a preformat signal is formed in the guide groove part by information pits PG projecting from a bottom face BF of the guide groove part, and the preformat signal is formed in the part between guide grooves by information pits PL recessed from an upper face UF of the part between guide grooves. Thus, the tracking control of high precision is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk of write-once type, rewritable type, etc., and more particularly to an optical disk in which information tracks are provided between circumferential guide grooves and between the guide grooves.

[0002]

2. Description of the Related Art In a write-once type or a rewritable type optical disc, in order to increase the recording density, information is recorded in a tracking guide groove (hereinafter also referred to as a groove or G) and the guide groove is used. An optical disc has been proposed in which information is also recorded between the guide groove and the guide groove (hereinafter, also referred to as land or L). This optical disc has a recording layer provided on a transparent substrate such as polycarbonate, but the guide groove is formed so as to be concave with respect to the upper surface of the transparent substrate. FIG. 7 is a diagram showing a first example of an optical disc in which information is recorded in the guide groove and between the guide grooves. In FIG. 7, the optical disk 4 is an optical disk whose rotation is controlled with a constant linear velocity (hereinafter, referred to as CLV method) or a constant angular velocity (hereinafter, referred to as CAV method), an MCAV (Modified CAV) method, or an MCLV (Modified method). CLV) type optical disc, the solid line indicates a spiral guide groove G, and information is recorded in the guide groove G to form an information track.

A dotted line indicates a space (land L) between the guide grooves between the guide grooves, and information is recorded in the space L between the guide grooves to form an information track. In this information track, as shown in the drawing, the information track in the guide groove portion of about one turn and the information track in the guide groove portion of about one turn are alternately arranged in the direction of the information track. FIG. 8 is a diagram showing a second example of an optical disc in which information is recorded between the guide grooves. In FIG. 8, the optical disk 5 is an optical disk whose rotation is controlled by the CLV method, the CAV method, the MCLV method, or the MCAV method, the solid line indicates the spiral guide groove (groove G), and the dotted line indicates the space between the guide grooves ( The information tracks provided in the groove G and the land L are the information tracks of the guide groove portion continuous from the inner circumference to the outer circumference (or from the outer circumference to the inner circumference) and from the inner circumference to the outer circumference. Or, from the outer circumference to the inner circumference), it is constituted by a continuous land information track.

7 and 8, the information track adjacent to the information track in the guide groove portion is always the information track in the land portion, and the information track adjacent to the information track in the land portion is always the information track in the guide groove portion. . Incidentally, there has been proposed an optical disc as shown in FIGS. 7 and 8 in which guide grooves are concentrically formed, but the description thereof will be omitted. FIG. 9 is a diagram showing a first example of a conventional optical disc. 9 (E) is a plan view showing the track format of the optical disc, and FIG. 9 (F) is a sectional view taken along the cutting line XY in the radial direction of the optical disc.

The arrangement of the guide grooves and lands of the optical disk 6 is the same as that shown in FIG. 7 or 8, or these guide grooves are formed concentrically.
The optical disk 6 is an example of an optical disk whose rotation is controlled by the CLV system, and T15, T17, and T19 are information tracks in the guide groove portion, and T16 and T18 are information tracks in the land portion. The information track is formed by dividing the information track of one round into a plurality of sectors. Each sector includes a pre-pit area in which management information such as sector information and a sync signal is recorded and a recording area in which a user records data and the like.

The information recorded in the pre-pit area is also called a pre-format signal, and is formed as concave and convex pits P1 and P2 when the guide groove is formed. In the information track of the guide groove portion, for example, T19, user data is recorded in the recording area G3, and the prepit P1 is recorded as management information in the prepit area. In this case, no guide groove is formed in the prepit area. On the land information track, for example, T16, user data is recorded in the recording area L3, and the prepit P2 is recorded as management information in the prepit area.

In FIG. 9, the heights of the surfaces other than the guide groove and the prepits are substantially the same as the upper surface UF of the transparent substrate 10C of the optical disk, and the height of the bottom surface of the guide groove is indicated by BF. As shown in FIG. 9F, the pre-pit P
1 and P2 are formed to be concave with respect to the upper surface UF of the transparent substrate 10C, like the guide groove. FIG. 10 is a diagram showing a second example of a conventional optical disc. In FIG. 10, (G) is an optical disk 7 whose rotation is controlled by the CAV method.
FIG. 3H is a plan view of FIG. 3B, which is a cross-sectional view taken along a cutting line ST in the radial direction of the disk. Optical disc 7
Is the same as the optical disc 6 shown in FIG. 6 except that the rotation is controlled by the CAV method. T22 and T24 are information tracks provided in the guide grooves, and T16 and T18 are information tracks between the guide grooves.

In FIG. 10, in the information track of the guide groove portion, for example, T24, user data is recorded in the recording area G4, and the prepit signal such as management information is recorded in the prepit area by the prepit P3 when the guide groove is formed. It In the information track of the land portion, for example, T21, user data is recorded in the recording area L4, and the prepit signal is recorded in the prepit area by the prepit P4 when the guide groove is formed. The height of the surface other than the guide groove and the prepits is the same as the upper surface UF of the transparent substrate 10D of the optical disk, and the height of the bottom surface of the guide groove is indicated by BF. The pre-pits P3 and P4 are formed on the transparent substrate 10 in the same manner as the guide grooves.
The upper surface UF of D is formed to be concave.

FIG. 6 is a diagram showing the relationship between the guide groove and the tracking error signal. The reflected light from the optical disk is received by a photodetector such as a four-division photodiode and a tracking error signal is detected by a known detection method such as a push-pull method. This tracking error signal is output according to the deviation of the laser light spot from the center line of the information track as shown in FIG. In FIG. 6, G indicates the guide groove of the optical disk, and L indicates the space between the guide grooves. Further, the tracking error signal TE is controlled by the polarity shown by the solid line when the laser light spot scans the guide groove portion, and the tracking control is performed by switching the polarity as shown by the dotted line when scanning the land portion. . In this case, a problem arises in tracking control in the prepit area.

This problem will be described below. For example, in the optical disk 7 shown in FIG. 10, when the light spot scans the information tracks T21 and T23 in the guide groove portion, there is a problem that the polarities of the tracking error signals are inverted between the prepit area and the recording area. is there. Further, for example, in the optical disc 6 shown in FIG. 9, the preformatted signals are not aligned at the same disc rotation angle position but at random positions. Therefore, for example, focusing on the prepit indicated by Q in the figure, since one adjacent information track T17 is in the guide groove portion and the other adjacent information track T15 is in the guide groove portion, from both sides of the prepit Q. There is a problem that a difference occurs in the reflected light and an unnecessary offset is superimposed on the tracking error signal, and the accuracy of tracking control decreases. Further, when the information track T16 is scanned, there is a problem that the polarities of the tracking error signal detected in the prepit area where the prepit P2 is recorded and the tracking error signal detected in the recording area L3 are reversed.

[0011]

The optical disc of the present invention is made in view of the above problems, and an object thereof is an optical disc having an information track provided between guide grooves. An object of the present invention is to provide an optical disc that can obtain a highly accurate tracking error signal.

[0012]

The optical disc of the present invention comprises:
An optical disc for optically recording / reproducing information tracks provided between a concave guide groove formed in a spiral shape or a concentric circle and between the guide grooves. At the time of fabrication, a pre-format signal such as a control signal is formed in advance as concave and convex pits together with a concave guide groove. The pre-format signal is formed in the guide groove by pits that are convex with respect to the bottom surface of the guide groove, and is formed between the guide grooves by pits that are concave with respect to the upper surface between the guide grooves.

[0013]

In the optical disk of the present invention, a circular guide groove for tracking control is formed, and information is recorded in the guide groove portion, and information is also recorded between the guide grooves. It Management information such as a control signal (preformat signal) is formed in the guide groove portion and the inter-guide groove portion by a pit having an uneven shape when the guide groove of the disk master is formed. In the pre-format signal, pits are formed in the guide groove portion of the optical disk so as to be convex with respect to the bottom surface of the guide groove, and in the inter-guide groove portion of the optical disk, the transparent substrate in the optical disk is formed. The pits are formed in a concave shape with respect to the upper surface of the guide groove portion. Therefore, the polarity of the detected tracking error signal is reversed between the guide groove portion and the guide groove portion, but the polarity is the same in the prepit area where the preformat signal is formed and the recording area where the user data is recorded. Is. Further, since the information tracks on both sides of the prepit are both the guide groove portion or the guide groove portion, the signal offset due to the prepit is small. Therefore, by inverting the polarity of the tracking error signal depending on whether the area to be recorded or reproduced is the guide groove portion or the guide groove portion, good tracking control can be performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical disk of the present invention is an optical disk in which an information track is provided in a concentric or spiral guide groove and an information track is provided between the guide grooves to improve the recording density. At the time of manufacturing the master, management information such as sector information and synchronization signals are discretely formed as a preformatted signal in the guide groove portion and the land portion in the uneven shape. Then, the tracking error signal is not disturbed by the pre-pits as the pre-format signal so that highly accurate tracking control can be performed. The information tracks of the optical disk of the present invention are provided in the guide groove (groove G) and the space between the guide grooves (land L), and the arrangement of the guide grooves is substantially the same as that shown in FIG. 7 or 8. However, the guide grooves may be arranged concentrically.

FIG. 1 is a diagram showing a first embodiment of an optical disk according to the present invention. The optical disc 1 shown in FIG. 1 is a CLV.
The rotation is controlled by a method, and the arrangement of the grooves and lands will be described below by taking the arrangement shown in FIG. 7 as an example. In FIG. 1, (A) is a plan view showing the track format of the optical disc 1, and (B) is a sectional view taken along the cutting line XY in the radial direction of the optical disc. In the figure, T
1, T3 and T5 are information tracks provided in the guide grooves, and T2 and T4 are information tracks provided between the guide grooves.

In the figure, an information track, for example T5, provided in the guide groove is divided into a plurality of sectors in one round, and each sector has a prepit area in which a prepit signal is preformed and a user. And a recording area G1 for recording data, and the prepit PG formed in the prepit area is provided so as to be convex with respect to the bottom surface BF of the guide groove in the transparent substrate 10A of the optical disc 1. The upper surface of the PG is the upper surface UF of the transparent substrate 10A.
It is almost the same height as. An information track provided between the guide grooves, for example, T4, is divided into a plurality of sectors about one round. In each sector, a prepit area in which prepits PL and the like are previously formed and a user record data. And a region L1.

Pits P formed in the pre-pit area
L is the upper surface UF of the transparent substrate 10A of the optical disc 1.
On the other hand, the bottom surface of the pit PL, which is provided in a concave shape, has substantially the same height as the bottom surface BF of the guide groove in the transparent substrate 10A. Here, a specific example of dimensions of the optical disc 1 will be described. For example, the track pitch is approximately 800 nm, the prepit width is approximately 270 nm, and the guide groove depth is approximately 60 nm. In the device for recording / reproducing information on / from the optical disc 1, for example, the wavelength of the laser light is 680 nm and the numerical aperture NA of the objective lens is about 0.6.

In FIG. 1, the information track adjacent to the information track provided in the guide groove is the information track of the land portion, and the information track adjacent to the information track of the land portion is the information track of the guide groove. . Therefore, both in the information track of the guide groove and in the information track between the guide grooves (lands), both sides of the pit in the prepit area are substantially symmetrical, and the presence of this prepit gives the offset amount of the tracking error signal. Little impact. Also,
Although the amplitude of the tracking error signal decreases to some extent in the pre-pit area, its polarity is not reversed.

For example, when the light spot scans the information track T4 between the guide grooves shown in FIG. 1, the adjacent information track T5 does not have a prepit and the information track T3 has a prepit in the portion where the prepit PL exists. But,
The light radiated to the information tracks T5 and T3 has a weak intensity at the bottom of the light spot, and has little influence on the tracking error signal. FIG. 2 is a diagram showing a second embodiment of the optical disc according to the present invention. The optical disk 2 shown in FIG. 2 is controlled in rotation by the CAV method, and the arrangement of guide grooves and information tracks will be described below by taking the one shown in FIG. 7 as an example.

The optical disc 2 has a guide groove portion of about one turn and a guide groove portion of about one turn.
Peripheral guide groove portions are alternately arranged. The MCAV system and the MCLV system are the same as the optical disc 2 shown in FIG. 2 except for the zone switching section. In FIG.
(C) is a plan view showing the track format of the optical disc 2, and (D) is a cutting line S in the radial direction of the optical disc.
It is sectional drawing at the time of cutting by T. In the figure, T7 and T9
Is an information track provided in the guide groove, T6, T8
Is an information track provided between the guide grooves.

In the figure, in the information track provided in the guide groove, for example, T9, the prepit P is formed in the prepit area.
Management information is recorded in advance by G, and user data is recorded in the recording area G2. In the information track in the guide groove portion, for example, T8, management information is recorded in advance in the prepit area by the prepits PL, and user data is recorded in the recording area L2. In this optical disc 2, the prepit areas of each information track are arranged at positions of substantially the same angle on the disc, but the depths and directions of the prepits PG, PL are the same as those of the optical disc 1 shown in FIG. FIG. 3 is a view showing a main part of a recording device of the master of the optical disc shown in FIG. 1, and shows a recording device for forming guide grooves and prepits on the master of the optical disc 1 shown in FIG.

The outline of the optical disc master making process will be described below. Photoresist is applied to the polished glass master, and laser light is irradiated by a recording device as shown in FIG. After that, development, electroconductivity, and plating are performed to form a stamper. A material such as polycarbonate is pressed by this stamper to obtain a transparent substrate for an optical disc. In this case, generally, the portion irradiated with the laser beam becomes a concave portion with respect to the upper surface of the transparent substrate and becomes a guide groove or a prepit between the guide grooves. However, depending on the method of manufacturing the stamper, the portion not irradiated with the laser light may be a recess with respect to the upper surface of the transparent substrate. In the recording apparatus shown in FIG. 3, 11 is a laser light source, 12 and 22 are polarization beam splitters, 13 and 23 are beam splitters, 14,
Reference numerals 24 and 26 are mirrors. Further, 15 is an optical modulator which is modulated by a preformat signal, 16, 17, 18
Is an optical modulator for adjusting the amount of light, 19, 20 and 21 are optical deflectors for changing the optical axis, and 25 is an optical system.
Reference numeral 7 denotes a recording lens for focusing the laser light on the master disk 28 of the optical disk.

FIG. 4 is a diagram showing the positions of the light beam when recording the guide groove and the preformat signal, and the positions of the three light spots on the master 28 when recording is performed by the master recording apparatus shown in FIG. Show the relationship. In the master recording apparatus shown in FIG. 3, an example of forming the guide groove and the prepit on the master 28 of the optical disk is given. As the laser light source 11, an argon ion laser having a wavelength of 458 nm or a krypton ion laser having a wavelength of 413 nm is used. , Or wavelength 4
A 42 nm helium-cadmium laser is used, and the laser light is split into three beams by a beam splitter.

Of the three beams, two beams pass through the light quantity adjusting optical modulators 16 and 17, respectively, and the beam position adjusting optical deflectors 19 and 20. The remaining one beam is a beam for recording a preformat signal, and after passing through the optical modulator 15 for modulating the preformat signal, it passes through the light amount adjusting optical modulator 18 and then the optical deflector 21. The three beams are combined on a substantially same optical axis by a beam splitter or the like, pass through an optical system 25 for enlarging the beam diameters, and the respective beam diameters are enlarged, and are collected on a master 28 of an optical disc by a recording lens 27. Be illuminated.

The positional relationship between the three focused beams is as shown in FIG. 4, for example. In FIG. 4, the central beam BC is a beam for recording a preformat signal. In addition, each of the three beams is expanded through a beam diameter expansion optical system to expand the beam diameter, and then the three beams are combined,
It may be condensed on the recording master through the recording lens. When recording on the information track of the guide groove, the optical disk is irradiated with a light beam with the three beams being ON (irradiation), and only the beam BC is turned ON-OFF (according to the preformat signal at the time of prepit recording). Irradiation-non-irradiation). When the information track between the guide grooves is recorded, the beam BC is turned on according to the preformat signal only when the prepit is recorded while the three beams are off. In this way, the guide groove portion and the guide groove portion are alternately recorded for each rotation.

The switching information between the guide groove portion and the guide groove portion is recorded as uneven prepits in the same manner as the recording of the preformat signal. This switching information is
It can also be done by modulating the width of the guide groove. Further, in order to correct the offset or the like during tracking control, the edges on both sides of the guide groove are displaced in the guide groove width direction at different frequencies together with the preformat signal shown in FIG. It is also possible to make corrections and record address information. In the above description, the light-irradiated portion is a recess with respect to the upper surface of the transparent substrate, but this may be reversed depending on the stamper manufacturing method.

FIG. 5 is a diagram showing a third embodiment of the optical disc according to the present invention. The difference between the optical disc 3 shown in FIG. 5 and the optical disc 2 shown in FIG.
The only difference is that is provided. Chidori Pit C
G and CL are for correcting an offset or the like during tracking control which is caused by movement of the objective lens or tilt of the disk during tracking control, and as is well known, tracking is performed by the difference in the output of the chirp pit. The offset is corrected.

In order to record the puddle pits CG and CL, the left and right light beams BL and BR shown in FIG. 4 are turned on and off by the recording device shown in FIG. Chidori Pit CG, C
The recording of the preformat signals other than L is performed by turning on and off the light beam BC according to the preformat signal, as in the case of the optical disc 1 shown in FIG. The optical disk 3 shown in FIG. 5 is an example of the CAV system, but MC
Even in the case of an AV type or MCLV type optical disc,
Except for the zone switching part, it is the same within a certain zone.

In FIG. 5, the shaded portion has substantially the same height as the bottom surface of the guide groove, and the portion other than the shaded portion has substantially the same height as the upper surface of the transparent substrate of the optical disk. The information track in the guide groove, for example, the puddle pit CG formed in T14 has the same height as the portion other than the pit in the adjacent track, and the information track in the guide groove, for example, the puddle pit CL formed in T13, is the adjacent track. It has the same height as the bottom of the guide groove of, and the width of the chidori pit is substantially wider, and the same effect as the information track pitch is increased, the detection sensitivity of the chidori pit is improved, and the tracking control stability is improved. Is improved. However, in the optical disk of the conventional example, the chirp pits contribute to the offset during tracking control, like other prepits.

In the MCAV type or MCLV type optical disc, the number of sectors on the outer side information track is 1 compared to the number of sectors on the inner side information track in the zone switching portion.
The information tracks are continuously formed, although the number is up to two. MC
In the case of the LV system, at the zone switching portion, for example, 10 to 10
Although the number of revolutions is gradually changed over 20 information tracks, the number of sectors can be changed at once between adjacent tracks.

For this reason, at the zone switching portion, the position (angle) at which the prepit area differs is different between adjacent information tracks, but in this case as well, the deterioration of the tracking control due to the prepits is small. In the case of the optical disc as shown in FIG. 8, the guide groove portion and the guide groove portion are continuously formed from the inner circumference to the outer circumference (or the outer circumference to the inner circumference). In this case, the guide groove portion and the guide groove portion are recorded as a pair on the master.

[0032]

According to the optical disk of the present invention, the offset during tracking control due to the prepits formed by the uneven shape in the prepit area is small, and the polarity of the tracking error signal is inverted between the prepit area and the recording area. There is no such thing. Further, the detection of the chirping pits formed on the center line of the information track on the optical disc is performed with high sensitivity, so that the offset during tracking control caused by the inclination of the disc can be greatly improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of an optical disc according to the present invention.

FIG. 2 is a diagram showing a second embodiment of the optical disc according to the present invention.

FIG. 3 is a diagram showing a main part of a recording device for a master of an optical disc.

FIG. 4 is a diagram showing positions of a light beam when recording a guide groove and a preformatted signal.

FIG. 5 is a diagram showing a third embodiment of the optical disc according to the present invention.

FIG. 6 is a diagram showing a relationship between a guide groove and a tracking error signal.

FIG. 7 is a diagram showing a first example of an optical disc in which information is recorded in the guide groove and between the guide grooves.

FIG. 8 is a diagram showing a second example of an optical disc in which information is recorded in the guide groove and between the guide grooves.

FIG. 9 is a diagram showing an example of a first example of a conventional optical disc.

FIG. 10 is a diagram showing an example of a second example of a conventional optical disc.

[Explanation of reference numerals] 1, 2, 3 Optical discs 10A, 10B of the present invention Transparent substrates of optical discs G1, G2 Recording areas of information tracks provided in guide grooves L1, L2 Recording areas of information tracks provided between guide grooves T1, T3, T5, T7, T9 Information groove in guide groove T2, T4, T6, T8 Information track between guide grooves PG Pre-pit formed in guide groove PL Pre-pit formed between guide grooves BF Transparent substrate upper surface Bottom of UF guide groove

Claims (1)

[Claims] 1. An optical disc in which information is recorded in a concave guide groove formed in a circular shape, and between the guide grooves between the guide grooves. The pre-format signal is formed in the guide groove by the information pit having a convex shape, and the pre-format signal is formed between the guide groove by the information pit having a concave shape with respect to the upper surface between the guide grooves. optical disk.