JP2002279628A - Optical disk, optical disk recorder, optical disk recording method, optical disk reproducing device and optical disk reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk suppressing offsets by inter-layer crosstalk by turning the amount of leakage to the almost same level even in the case that an adjacent layer is a groove part where data are recorded or in the case that it is a header part. SOLUTION: The groove part for recording user data and a pre-pit header part where address information or the like is recorded are provided on an information recording layer and design is performed so as to almost equalize the average level of the data reproducing signals of the groove part and the average level of the data reproducing signals of the header part. Thus, the crosstalk levels of the groove part and the pre-pit header part are matched.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk capable of recording and reproducing information, and more particularly to an optical disk having a plurality of information recording layers. The present invention also relates to an optical disk recording device and an optical disk recording method for recording information on such an optical disk. Further, the present invention relates to an optical disk reproducing apparatus and an optical disk reproducing method for reproducing information from such an optical disk.

[0002]

2. Description of the Related Art Rewritable DVs currently on the market
As D, there is DVD-RAM. A DVD-RAM can sufficiently withstand use as a secondary storage device of a computer like a magnetic disk.
This is different from the read-only type.

In the case of a DVD-RAM, a sector comprises a 128-byte header area, a 2-byte mirror area, and a 2567-byte recording area. In the case of a DVD-RAM, rewriting can be physically performed in sector units, and the boundary between sectors is a discontinuous point, so that there is an area that serves as a joint.

[0004] Since the contents of the user data area match the read-only type, it is possible to obtain address information from the head of the user data with respect to the portion where the data is written. In the unrecorded part,
Since there is no guarantee that the address information exists, the ID information is written at the beginning of each sector with uneven pre-pits that cannot be rewritten so that the address information can be obtained even in such an area. . Since the frequency and phase of the ID section and the rewritable data section do not always match depending on the state at the time of writing, there is a synchronization pattern at the beginning of each area to pull in the PLL at high speed.

[0005] As described above, the DVD-RAM requires a gap area, an ID area, and a synchronization pattern for connection, and thus has lower format efficiency than a read-only type. DVD-RAM
The physical arrangement of the pre-pits has a format as shown in FIG.

The DVD-RAM adopts a land / groove recording method as a high-density technology. Conventionally, information is continuously recorded on only one of the groove, which is a concave portion formed on the recording surface of the optical disk, and the land, which is a convex portion adjacent to the concave portion. This is a technique for improving the recording density by recording information in the medium.
Since the DVD / RAM adopts the land / groove recording method, pre-pits in which ID information is written are also required for each land and groove. Therefore, DVD-
The prepits of the RAM are arranged on the boundary between the land track and the groove track, and are shared by the land track and the groove track. In addition, the ID information is written in quadruple in order to increase the certainty of the information acquisition, is divided into two, and is shifted from the center line of the groove track by 1/2 track in the outer circumferential direction and the inner circumferential direction, respectively. I have. The pre-pit address arranged in this way is
It is called PA (Complimentary Allocated Pit Address).

FIG. 3 shows an example of such a DVD-RAM disk sectional structure. A recording layer for recording information in the form of recording marks is sandwiched between protective layers, and a reflective layer for reflecting light is provided above the upper protective layer. The record of information is
The phase change film of the recording layer is formed by reversibly transitioning between a crystalline state and an amorphous state by irradiating a laser beam to record and erase information bits (recording marks).

On the other hand, two information recording layers are provided in one disc.
DVD-RAMs having layers have also been proposed. FIG. 4 shows an example of the cross-sectional structure. Two upper and lower recording layers of a phase change film sandwiched between protective films are provided. A translucent reflective film is formed on the upper part of the lower recording layer, has a constant transmittance as a whole of the lower information recording layer, and allows the laser beam to reach the upper recording layer. . In addition, an intermediate layer made of, for example, an ultraviolet curable resin is provided between the two information recording layers to separate the two information layers.

[0009]

[Problems to be Solved by the Invention] DVD having two recording layers
-In a RAM, it is desirable that information from another layer be completely shut off while recording / reproducing one layer. To this end, it is desirable that the distance between two adjacent layers be as large as possible from the viewpoint of suppressing leakage of information from the other layer during recording and reproduction. However, in that case, a load is imposed on the optical system for recording and reproducing. In other words, if the focal length of the objective lens that focuses the laser beam is designed at the midpoint between the two information recording layers, half of the distance between the two layers will be out of focus from the design value, causing aberrations in the optical system. It is. Of course, if the focal length is set so as to be appropriate for one of the layers, a larger aberration will result for the other layer.

Therefore, from the viewpoint of reducing the aberration of the optical system, it is better that the distance between the two layers is small. As a result, the distance between the layers has a trade-off relationship between the aberration of the optical system and the leakage between the layers. Therefore, in practice, it is unavoidable that the influence of the other layer, that is, the effect of the light reflected by the other layer, occurs when recording / reproducing one layer.

Particularly, in the case of the above-mentioned DVD-RAM, a groove portion for recording user data and a CAPA portion on which information such as addresses are recorded in the form of pre-pits coexist on the same recording surface. The difference in leakage into the layers is problematic. For example, FIG. 5 shows an example of a change due to interlayer crosstalk of a reproduction signal envelope during reproduction of one layer in a two-layer RAM disk. The vertical axis is the reflectance (Refrectivi
ty), and the horizontal axis shows the position (Position). The DC level of the signal changes depending on the state of the other layer (groove (a) or CAPA pre-pit (b)) shown below the waveform. That is, a signal level (mark level) in a state where a recording mark is recorded in a groove portion being reproduced and a signal level (non-mark level) in a state where a recording mark is not recorded.
However, it is raised at the same time when the other layer approaches the CAPA part. Such an offset due to interlayer crosstalk increases the possibility of causing an error in information reproduction, and thus poses a quality problem.

For example, Japanese Patent Application Laid-Open No. 9-237435 discloses a technique for suppressing crosstalk between tracks in a single-layer recording medium using both tracks of lands and grooves. However, this technique cannot suppress crosstalk between layers.

An object of the present invention is to solve the above-described problems, and an object of the present invention is to provide an optical disk, an optical disk recording device, an optical disk recording method, an optical disk reproducing device, and an optical disk reproducing method described below. I do.

(1) An optical disk capable of reducing the influence of a change in the state of an adjacent layer on a reproduction signal of a target layer.

(2) An optical disk recording apparatus and an optical disk recording method capable of recording information on an optical disk so that the influence of a change in the state of an adjacent layer on a reproduction signal of a target layer can be reduced.

(3) An optical disk reproducing apparatus and an optical disk reproducing method capable of reproducing information from an optical disk so that the influence of a change in the state of an adjacent layer on a reproduction signal of a target layer can be reduced.

[0017]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve the object, an optical disk recording apparatus, an optical disk recording method, an optical disk reproducing apparatus, and an optical disk reproducing method of the present invention are configured as follows.

(1) An optical disk according to the present invention is an optical disk having a plurality of information recording layers, having a groove section for recording user data and a header section on which address information and the like are recorded on the information recording layer. The average level of the data reproduction signal in the header section is substantially equal to the average level of the data reproduction signal in the header section.

As described above, by adjusting the average level of the data reproduction signal in the groove portion and the average level of the data reproduction signal in the header portion, the reflection level of the light beam irradiated to the adjacent layer in a defocused state is the same. Can be done. That is, whether the adjacent layer is a groove portion where data is recorded or a pre-pit header portion, the amount of leakage can be substantially the same level, and the offset due to interlayer crosstalk as described above can be reduced. Will be suppressed. In this case, the condition is that a recording mark has already been written in the groove portion of the adjacent layer.

(2) The optical disk recording apparatus of the present invention
An optical disc having a plurality of information recording layers, wherein the information recording layer has a groove portion for recording user data and a header portion on which address information is recorded, and the data reproduction signal average level of the groove portion is set to Cmark. When the average data reproduction signal level of the header portion is Cheader, and the signal level when the mirror area of the information recording layer is reproduced is I0, the relationship of -0.1 <(Cmark-Cheader) / I0 <0.1 is satisfied. Recording means for recording information on the optical disk so as to satisfy the following.

(3) The optical disk recording method of the present invention
An optical disc having a plurality of information recording layers, wherein the information recording layer has a groove portion for recording user data and a header portion on which address information is recorded, and the data reproduction signal average level of the groove portion is set to Cmark. When the average data reproduction signal level of the header portion is Cheader, and the signal level when the mirror area of the information recording layer is reproduced is I0, the relationship of -0.1 <(Cmark-Cheader) / I0 <0.1 is satisfied. Information is recorded on the optical disk so as to satisfy the following.

(4) The optical disk reproducing apparatus of the present invention
An optical disc having a plurality of information recording layers, wherein the information recording layer has a groove portion for recording user data and a header portion on which address information is recorded, and the data reproduction signal average level of the groove portion is set to Cmark. When the average data reproduction signal level of the header portion is Cheader, and the signal level when the mirror area of the information recording layer is reproduced is I0, the relationship of -0.1 <(Cmark-Cheader) / I0 <0.1 is satisfied. And reproducing means for reproducing information from the optical disc so as to satisfy the following.

(5) An optical disk reproducing method according to the present invention comprises:
An optical disc having a plurality of information recording layers, wherein the information recording layer has a groove portion for recording user data and a header portion on which address information is recorded, and the data reproduction signal average level of the groove portion is set to Cmark. When the average level of the data reproduction signal in the header portion is Cheader, and the signal level when the mirror area of the information recording layer is reproduced is I0, the relationship of -0.1 <(Cmark-Cheader) / I0 <0.1 is satisfied. The information is reproduced from the optical disk so as to satisfy the following.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

First, an apparatus for recording and reproducing the optical disk 1 according to the present invention will be described. FIG. 1 shows a block diagram of the optical disk device of the present invention.

The light beam emitted from the laser light source 11 is converted into parallel light by a collimating lens 12, enters a polarizing beam splitter (hereinafter referred to as PBS) 13, and passes therethrough. The beam transmitted through the PBS 13 transmits through the quarter-wave plate 14 and is focused on the information recording surface of the optical disc 1 by the objective lens 15.

The condensed beam is controlled by a focus servo / tracking servo system (not shown) so that the best minute spot is obtained on the recording surface.

When there are a plurality of information recording surfaces on the optical disk 1 in the stacking direction, the information recording surface to be recorded / reproduced is selected by the focus servo system, and the best minute spot on the target information recording surface. It is controlled so as to be maintained in the obtained state.

The beam irradiated on the optical disk 1 is reflected by a reflection film or a reflective recording film in the information recording surface. The reflected light passes through the objective lens 15 in the opposite direction and becomes parallel light again.

The reflected light passes through the quarter-wave plate 14, has polarization perpendicular to the incident light, and is reflected by the PBS 13. PBS
The beam reflected by 13 is converged by the condenser lens 16 and is incident on the photodetector 17. The light beam incident on the photodetector 17 is photoelectrically converted into an electric signal and sent to the preamplifier 18. The signal amplified by the preamplifier 18 is equalized and binarized by a signal processing circuit 19 and sent to a demodulation circuit 20. The demodulation circuit 20 performs a demodulation operation corresponding to a predetermined modulation method, and becomes reproduction data 21 of recording information.

On the other hand, recording data (data symbol) 22
Is modulated by the modulation circuit 23 into a predetermined channel bit sequence. The bit sequence 24 corresponding to the recording data 22 is converted into a laser driving waveform by the recording control circuit 25. The recording control circuit 25 drives the laser 11 in a pulsed manner, and records data corresponding to a desired bit sequence 24 on the optical disc 1.

FIG. 6 shows the arrangement of tracks and prepits on an optical disk according to an embodiment of the present invention. The present optical disc 1 is, for example, a rewritable optical disc having a phase-change type recording film. As shown in FIG. 6, a groove track 2 is formed as a concave portion on the optical disc 1, and a land track 3 is relatively formed between the grooves. As a recording track for recording user data, a land & groove recording method using both the groove track 2 and the land track 3 and a groove track
There is a groove recording method using only 2 (this is called for convenience, but also includes a recording method using only land track 3). Here, the groove recording method will be described as an example, but the present invention is effective even when the land & groove recording method is used.

The recording track has a data section 4 for recording user data and a header section 5 in which addresses and the like are recorded in advance. In the groove track 2 of the data section 4, for example, a mark due to a phase change is recorded. On the other hand, in the header section 5, pre-pits 6 on which address information and the like are recorded are formed along recording tracks. The prepit 6 is formed as a concave portion on the disk similarly to the groove, and the depth of the deepest portion is usually the same as the depth of the deepest portion of the groove 2.

On the other hand, the arrangement of the pre-pits in the plane of the optical disk of the present invention is as shown in FIG.
The positions of the headers 5 may be aligned in the radial direction, that is, a so-called in-line arrangement may be adopted. Alternatively, as shown in FIG.
May not be aligned, and a so-called non-in-line arrangement, which is provided scattered, may be adopted. However, the present invention is more effective in an in-line arrangement in which a portion where pre-pits are concentrated is formed over the entire surface of the disk. In the above-described diagram of the arrangement of the prepits of the header portion 5 in the disk surface, an example is shown in which the prepits arranged inline have only one line in the disk surface, but four rows, eight rows, etc. The effect of the present invention does not depend on the number of in-plane rows of the prepit arrangement.

As shown in the sectional view of FIG. 4, the optical disc 1 of the present invention has a plurality of information recording layers having the data section 4 and the header section 5 in the same plane as shown in FIG. ing. Here, a case will be described in which there are two information recording layers, but the same discussion holds for an optical disc having more information recording layers. FIG. 9 shows how the light beam focused on each information recording layer is irradiated on another information recording layer. Fig. 9 (a) shows the layer close to the objective lens 15.
FIG. 9 (b) shows a case where the light beam is focused on (first layer # 1) for recording and reproducing, and a layer far from the objective lens 15 (second layer # 1) is shown.
FIG. 4 is a diagram showing a case where a light beam is focused and recording / reproducing is performed with a target of 2).

In the example of FIG. 9A, the light beam is focused on the first layer, and at the same time, a part of the light beam is transmitted through the first layer to form a defocused beam spot on the second layer. This is because the first layer has a certain transmittance from the beginning for recording and reproduction of the second layer as described above. The beam spot focused on the first layer is reflected according to the reflectance of the first layer,
Return to the objective lens 15. Similarly, the defocused beam irradiated on the second layer is also reflected according to the reflectivity of the second layer, and returns to the objective lens 15 except for a part outside the beam.

Similarly, in the example of FIG. 9B, the light beam transmitted through the first layer is focused on the second layer, and a part of the light beam is irradiated on the first layer in a defocused state. The light beam focused on the second layer is reflected according to the reflectance of the second layer, and returns to the objective lens 15. In addition, the light beam irradiated in the defocused state on the first layer is also reflected according to the reflectance of the first layer,
Most of the beam returns to the objective lens 15.

The reflected light from the second layer in FIG.
The reflected light from the recording layer other than the target recording layer, such as the reflected light from the first recording layer, causes crosstalk leaking into the information from the target recording layer, and becomes noise in information reproduction. If the crosstalk noise remains unchanged at a constant value with respect to the information reproduction signal, it can be removed by later signal processing, and does not cause a significant problem. But,
If the crosstalk noise fluctuates independently of the information reproduction signal, it is difficult to remove the crosstalk noise, which adversely affects the quality of the information reproduction signal. From the above description, the reflected light from the recording layers other than the target recording layer is
Since it occurs on the principle of a two-layer recording medium, it cannot be completely eliminated. However, it is possible to suppress the effect by making the crosstalk due to the reflected light as constant as possible.

Therefore, in the optical disk of the present invention, the crosstalk component is kept constant irrespective of the state of the adjacent layer by making the reflectivity in the groove portion and the header portion in a certain recording layer surface substantially constant. It is to suppress the influence from the layer.

The principle of this crosstalk suppression will be described with reference to FIG. 9A as an example. In this case, the reflected light from the defocused beam spot formed on the second layer returns to the opening of the objective lens 15, so that crosstalk is added to the reflected light from the first layer. This crosstalk level changes depending on the state of the recording surface of the second layer. FIG. 10 schematically shows a state of a beam spot formed on the second layer recording surface. The case where the recording surface of the second layer is an unrecorded groove (FIG. 10 (a)) and the case where the recording surface is a pre-pit header portion in an in-line arrangement (FIG.
With (b)), usually, the case where there are few concave portions as a whole in the beam spot (FIG. 10 (b)) has a higher reflectance,
The crosstalk level between the two is different. Therefore,
When the beam spot formed on the second layer transitions between the unrecorded groove portion and the pre-pit header portion, the target layer (1
The crosstalk component leaking into the reproduced signal from the (layer) fluctuates, which adversely affects the signal quality as described above. In both the unrecorded groove portion and the prepit header portion, the recording film is usually in a crystalline state, and the difference in the reflection level depends only on the structure. FIG. 11 is a diagram showing the groove (pit) depth dependency of the crosstalk component from the adjacent layer (wavelength of light source = 405 nm, refractive index of substrate = 1.62).
2). In this graph, the horizontal axis represents the groove and pit depths (Groove depth), and represents the reflection level (Reflectivity) due to crosstalk when the reflectance in the crystal part of both information recording layers is 4.2%. . Unrecorded groove (G
Comparing the crosstalk level due to roove (No mark)) and the crosstalk level due to the in-line arranged prepit header (Prepit header), the reflectivity of the prepit header portion is also higher. In addition, the difference between the two decreases as the groove (pit) depth decreases, and in principle, completely matches when the depth is zero. Therefore, in order to match the reflection levels of the two, a structure with extremely low feasibility, such as adopting a structure with an extremely shallow groove / pit depth, is adopted.

On the other hand, there is a case where the recording surface of the second layer is a recorded (marked) groove portion (FIG. 10C). in this case,
Considering the relationship between the pre-pit header portion (FIG. 10 (b)) and the in-line arrangement, the parameter called the mark reflection level increases from the relationship between the two (FIG. 10 (a) and FIG. 10 (b)). Therefore, as compared with the case where the adjustment is performed only by the groove (pit) depth, the reflection levels of the two can be substantially matched at the realistic groove (pit) depth. For example, consider the case of a so-called low-to-high recording film in which the reflectivity of a crystal part (unrecorded part) is 4.2% and the reflectivity of a mark is 10.8%. At this time, the crosstalk components when the state of the adjacent layer is the pre-pit header section and when the state of the adjacent layer is the recorded groove section are as shown in FIG. There is a point in the crosstalk level between the recorded groove portion and the pre-pit header portion in the in-line arrangement that matches when the depth is not zero. In this case, the groove
(Pit) When the depth is about 1/8 of the wavelength in the medium,
The two reflection levels are almost the same. Therefore, by designing the medium in this way, even if the beam spot formed on the second layer transitions between the recorded groove portion and the pre-pit header portion, the reproduced signal from the target layer (first layer) The leaked crosstalk component does not fluctuate, and does not adversely affect the signal quality.

FIG. 13 shows an example of a change in the reproduction signal envelope of the target layer due to interlayer crosstalk in this case. FIG.
When an adjacent layer transitions between an unrecorded groove portion and a pre-pit header portion as shown in FIG. 13A, an offset occurs in the reproduced signal envelope, but a mark is recorded in the groove as shown in FIG. Thus, no offset occurs at the time of transition between the groove portion and the pre-pit header portion. Therefore, the influence of the crosstalk of the adjacent layer is suppressed.

In order to suppress the fluctuation of the crosstalk component based on such a principle, it is necessary to remove an unrecorded groove portion in advance. This may be performed, for example, by performing a certification step of recording marks (dummy recording marks) on the entire surface (groove portion on the entire recording layer) at the time of shipping the disk. This certification process is performed by the recording process of the optical disk device shown in FIG. The recording mark recorded in this certification step is formed of, for example, a signal sequence including a sparsest mark row. The sparsest mark row is a mark row formed by alternately arranging the longest mark and the longest space.

Designing an optical disk medium under the above conditions results in the following signals being obtained from the optical disk.

The reflected light level when the recorded groove portion is irradiated with the defocused beam spot is proportional to the center level of the reproduction signal of the sparsest mark array by the focused beam spot. Similarly, the reflected light level when the defocused beam spot is applied to the pre-pit header portion is proportional to the center level of the reproduction signal of the narrowest pre-pit row by the condensed beam spot. The sparse pre-pit row is a pre-pit row formed by alternately arranging the longest pre-pit and the longest space. When the track density of the mark row and the track density of the pre-pit row are the same, it can be considered that the proportional coefficients of the two are almost the same. Therefore, in order to make the reflected light levels coincide with each other when the defocused beam spot is applied to the recorded groove portion and the prepit header portion, it is necessary to use the most sparse mark row and the most sparse prepit row by the focused beam spot. It suffices to match the center level of the reproduced signal. A sparse mark sequence and a sparse pre-pit sequence are collectively referred to as a sparse data sequence.

That is, as shown in FIG. 14, the center level of the signal amplitude of the sparsest mark row due to the focused beam spot is Cmark, the center level of the signal amplitude of the sparsest prepit string is Cheader, and the mirror level is I0. When you do, (Che
ader-Cmark) should be approximately 0. In addition, always completely 0
Is impossible in consideration of the manufacturing margin of the disk, etc., and by satisfying the following expression as a practical range, suppression of interlayer crosstalk can be achieved.

-0.1 <(Cheader-Cmark) / I0 <0.1 (formula)
That is, when the optical disk device shown in FIG. 1 records information on the optical disk 1, a reproduction signal obtained from the optical disk 1 satisfies the above expression. When the optical disk device shown in FIG. 1 reproduces information from the optical disk 1, a reproduced signal obtained from the optical disk 1 also satisfies the above expression.

It should be noted that the present invention is not limited to the above-described embodiment, and can be variously modified in an implementation stage without departing from the gist of the invention. In addition, the embodiments may be implemented in appropriate combinations as much as possible, in which case the combined effects are obtained. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriate combinations of a plurality of disclosed constituent elements. For example, even if some components are deleted from all the components shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effects described in the column of the effect of the invention can be solved. If you get
A configuration from which this configuration requirement is deleted can be extracted as an invention.

[0049]

According to the present invention, the following optical disk, optical disk recording apparatus, optical disk recording method, optical disk reproducing apparatus, and optical disk reproducing method can be provided.

(1) Whether the adjacent layer is a groove portion where data is recorded or a header portion, the amount of leakage can be made substantially the same level, and the offset due to interlayer crosstalk is suppressed. Optical disc.

(2) Whether the adjacent layer is a groove portion where data is recorded or a header portion, the amount of leakage can be made almost the same level, and the offset due to interlayer crosstalk is suppressed. OPTICAL DISC RECORDING DEVICE AND OPTICAL DISK RECORDING METHOD FOR RECORDING INFORMATION ON OPTICAL DISC

(3) Whether the adjacent layer is a groove portion where data is recorded or a header portion, the amount of leakage can be made almost the same level, and the offset due to interlayer crosstalk is suppressed. Optical disk reproducing apparatus and optical disk reproducing method capable of reproducing information from an optical disk.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of an optical disk recording device and an optical disk reproducing device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an arrangement of CAPA pre-pits.

FIG. 3 is a diagram showing an example of a cross-sectional structure of a DVD-RAM disk.

FIG. 4 is a diagram illustrating an example of a cross-sectional structure of a two-layer DVD-RAM.

FIG. 5 is a diagram illustrating an example of the influence of crosstalk between two layers.

FIG. 6 is a diagram showing a track structure of an optical disc according to an embodiment of the present invention.

FIG. 7 is a diagram showing a pre-pit arrangement in an optical disk surface according to the present invention.

FIG. 8 is a diagram showing another pre-pit arrangement in the optical disk surface of the present invention.

FIG. 9 is a diagram showing a state of beam irradiation on an adjacent layer of a two-layer disc.

FIG. 10 is a schematic diagram showing a recording state and a beam spot on an adjacent layer of a two-layer disc.

FIG. 11 is a diagram showing groove (pit) depth dependence of a crosstalk component from an adjacent layer (in the case of a pre-pit header portion and in the case of an unrecorded groove portion).

FIG. 12 is a diagram showing the dependence of crosstalk components from adjacent layers (in the case of a pre-pit header portion and in the case of a recorded groove portion) on the groove (pit) depth.

FIG. 13 is a diagram showing crosstalk between layers in the optical disc according to the present invention.

FIG. 14 is a diagram showing each level of a reproduction signal of the optical disc according to the present invention.

[Explanation of symbols]

 1 optical disc 2 groove track 3 land track 4 data section 5 header section 6 pre-pit 11 laser light source 12 collimating lens 13 PBS 1/4 wavelength plate 15 objective lens 16 condenser lens 17 photodetector 18 preamplifier 19 signal processing circuit 20 demodulation circuit 23 modulation circuit 25 recording control circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D029 JB13 WA31 WB17 WC04 WC05 WD16 5D090 AA01 BB05 CC01 CC04 DD01 EE02 EE13 FF08 FF11 FF41 GG16 KK03

Claims (18)

[Claims] 1. An optical disc having a plurality of information recording layers, wherein the information recording layer has a groove section for recording user data and a header section on which address information is recorded, and reproduces data from the groove section. An optical disc, wherein an average level of a signal is substantially equal to an average level of a data reproduction signal of the header section. 2. The data reproduction signal average level of the groove section is Cmark, the data reproduction signal average level of the header section is Cheader, and the signal level when the mirror area of the information recording layer is reproduced is I0. 2. The optical disk according to claim 1, wherein the following relationship is satisfied: -0.1 <(Cmark-Cheader) / I0 <0.1. 3. The optical disk according to claim 2, wherein the data reproduction signal is a signal obtained by reproducing data including a sparse data sequence. 4. The optical disk according to claim 1, wherein said header portions are provided in the information recording layer surface of said optical disk so as to be aligned in a radial direction. 5. The depth of said groove portion and the depth of prepits recorded in advance in said header portion are approximately assuming that the wavelength of a light source for reproducing said optical disk is λ and the refractive index of a substrate of said optical disk is n. The optical disk according to claim 1, 2, 3, or 4, wherein λ / 8n. 6. The optical disk according to claim 1, wherein a dummy recording mark is recorded in advance in said groove portion on the entire surface of said recording layer. 7. A dummy recording mark is recorded in advance in the groove portion on the entire surface of the recording layer by a phase change, and pre-pits indicating address information are recorded in the header portion in advance by embossing. The optical disk according to claim 1, 2, 3, or 4. 8. The optical disk according to claim 6, wherein said dummy recording mark is constituted by a signal sequence including a row of sparsest marks. 9. An optical disc having a plurality of information recording layers, wherein said information recording layer has a groove section for recording user data and a header section on which address information is recorded, and reproduces data from said groove section. When the signal average level is Cmark, the data reproduction signal average level of the header portion is Cheader, and the signal level when the mirror area of the information recording layer is reproduced is I0, -0.1 <(Cmark-Cheader) / I0 <0.1 An optical disc recording apparatus, comprising: recording means for recording information on the optical disc so as to satisfy the following relationship. 10. The optical disk recording apparatus according to claim 9, wherein said recording means records a dummy recording mark in said groove on the entire surface of said recording layer. 11. A pre-pit indicating address information is recorded in advance in said header portion by embossing, and said recording means records a dummy recording mark in a phase change in said groove portion on the entire recording layer. 10. The optical disk recording device according to claim 9, wherein: 12. The optical disk recording apparatus according to claim 10, wherein said recording means records a signal sequence including a row of sparsest marks as said dummy recording marks. 13. An optical disc having a plurality of information recording layers, wherein said information recording layer has a groove section for recording user data and a header section on which address information is recorded, and reproduces data from said groove section. When the signal average level is Cmark, the data reproduction signal average level of the header portion is Cheader, and the signal level when the mirror area of the information recording layer is reproduced is I0, -0.1 <(Cmark-Cheader) / I0 <0.1 An optical disc recording method, wherein information is recorded on the optical disc so as to satisfy the following relationship. 14. The optical disk recording method according to claim 13, wherein a dummy recording mark is recorded on said groove portion on the entire recording layer. 15. A method according to claim 15, wherein pre-pits indicating address information are recorded in advance in said header portion by embossing, and dummy recording marks are recorded by phase change in said groove portions on the entire recording layer. An optical disk recording method according to claim 13. 16. The optical disk recording method according to claim 14, wherein a signal sequence including a row of sparsest marks is recorded as the dummy recording mark. 17. An optical disc having a plurality of information recording layers, wherein said information recording layer has a groove section for recording user data and a header section on which address information is recorded, and reproduces data from said groove section. When the signal average level is Cmark, the data reproduction signal average level of the header portion is Cheader, and the signal level when the mirror area of the information recording layer is reproduced is I0, -0.1 <(Cmark-Cheader) / I0 <0.1 An optical disc reproducing apparatus, comprising: reproducing means for reproducing information from the optical disc so as to satisfy the following relationship. 18. An optical disc having a plurality of information recording layers, wherein the information recording layer has a groove section for recording user data and a header section on which address information is recorded, and reproduces data from the groove section. When the signal average level is Cmark, the data reproduction signal average level of the header portion is Cheader, and the signal level when the mirror area of the information recording layer is reproduced is I0, -0.1 <(Cmark-Cheader) / I0 <0.1 An optical disc reproducing method characterized by reproducing information from the optical disc so as to satisfy the following relationship.