JPH1139657A - Optical disk and its reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk and a reproducing device capable of obtaining roughly identical reproducing signal characteristics from the substrates of respective layers. SOLUTION: In multi-layer structure optical disk constructed by stacking a plurality of substrates 11 and 12 each having recorded information, when lights are selectively converged in the information recording surfaces of the plurality of substrates 11 and 12 from one surface side, reflected lights from the light converged substrates 11 and 12 are obtained from one surface side. In this case, a reflected light from any one of the light converged substrates 11 and 12 is roughly equal to another while it is obtained from one surface side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk having a multilayer structure in which a plurality of substrates on each of which information is recorded are laminated, and an improvement of a reproducing apparatus therefor.

[0002]

2. Description of the Related Art As is well known, as shown in FIG. 16A, an optical disc having a multi-layer structure as shown in FIG. 16A has a zero-layer in which a pit forming surface is provided with a translucent film 11a of Au (gold). A two-layer structure in which a substrate 11 and a one-layer substrate 12 in which a pit formation surface is provided with a total reflection film 12a of Al (aluminum) are adhered with a transparent adhesive 13 so that a reproduction surface distance is about 55 μm. Optical disk 14 is in the mainstream.

An optical disk 14 having such a two-layer structure has
Information recorded on the zero-layer substrate 11 and the one-layer substrate 12 is selectively read by an optical pickup provided on the zero-layer substrate 11 side. That is, the optical pickup uses the 0-layer substrate 11
When reading the information recorded in the holographic recording medium, the objective lens 15 is controlled in the focus direction so that the laser light is focused on the pit formation surface of the 0-layer substrate 11, and the light reflected by the translucent film 11a is reproduced by photoelectric conversion. I try to get a signal.

[0004] The optical pickup has a single-layer substrate 1.
2 to read the information recorded in
The objective lens 15 is controlled in the focus direction so that the light passes through the layer substrate 11 and is condensed on the pit formation surface of the one-layer substrate 12. The conversion is performed to obtain a reproduced signal.

In this case, the translucent film 11a of the zero-layer substrate 11
The amount of the laser light reflected by the first layer substrate 12 and the amount of the laser light reflected by the total reflection film 12a of the first layer substrate 12 and passing through the zero layer substrate 11 are set to be substantially equal. In addition, the substrates 11, 1 on the side from which information is read
The setting is made so that the reflected light from the substrates 12 and 11 on the side from which information is not read does not adversely affect the reflected light from the second.

Here, in the optical disk 14 called DVD, which has become popular in the market in recent years, if the length corresponding to one bit of recorded information is T, the length of the shortest pit portion is 3T.
The length of the longest pit portion is set to 14T. In this case, the level of light reflected from the optical disk is as shown in FIG.
It changes as shown in FIG.

That is, in FIG. 16B, the vertical axis represents the level of reflected light, and the horizontal axis represents time. Then, the reflected light level of the longest land portion on the pit formation surface of the optical disk 14 becomes I14H, the reflected light level of the longest pit portion becomes I14L, the reflected light level of the shortest land portion becomes I3H, and the reflected light level of the shortest pit portion becomes I
3L.

For this reason, the reflected light level of the land having a length between the longest land and the shortest land is I14.
H and I3H, the reflected light level of a pit having a length between the longest pit and the shortest pit is I
It will be between 14L and I3L.

As parameters for expressing the amplitude characteristics of the reflected light level, three types of modulation degree M, asymmetry A and resolution D are defined. These parameters are M = (I14H-I14L) / I14H A = [(I14H + I14L)-(I3H + I3L)] / [2 (I14H-I14L)] D = (I3H-I3L) / (I14H -I14L).

FIG. 17 shows an optical disc reproducing apparatus for reproducing the optical disc 14 as described above, which measures jitter, which is an element comprehensively representing good characteristics of a reproduced signal output from an optical pickup. FIG. That is, the optical disc 14 having a two-layer structure
Is driven to rotate by a disk motor 16, and recorded information is read by an optical pickup 17.

The reproduced signal output from the optical pickup 17 is amplified by a preamplifier circuit 18 and subjected to a frequency characteristic compensation process by an equalizer circuit 19.
The data is supplied to the data slice circuit 20, binarized, and taken out from the output terminal 21. The binarized data output from the data slice circuit 20 is a PLL (Phas
e Locked Loop) is supplied to a circuit 22 to generate a clock synchronized with the binarized data, and the clock is taken out from an output terminal 23.

In the optical disk reproducing apparatus, jitter is measured by sampling the phase difference between the edge of the binary data output from the output terminal 21 and the edge of the clock output from the output terminal 23. ing. In this case, it can be said that the smaller the jitter is, the better the reproduced signal characteristic is.

FIG. 18 to FIG.
3 shows a manufacturing process of the optical disc 14 having a layer structure. First, FIGS. 18A to 18D show a manufacturing process of the zero-layer substrate 11. That is, FIG. 18A shows the exposure master 11b. The exposure master 11b is obtained by applying a resist 11d to the surface of a glass substrate 11c and irradiating light to leave only the resist 11d at a necessary portion. The depth of the eleven pits is determined.

From this exposure master 11b, as shown in FIG. 18B, a stamper 11 serving as a master is formed by plating.
e, and a substrate 11f is formed from the stamper 11e as shown in FIG. Then, as shown in FIG. 18D, the pit-forming surface of the substrate 11f is covered with a translucent Au film 11a, whereby the zero-layer substrate 11 is manufactured.

FIGS. 19A to 19D show a manufacturing process of the single-layer substrate 12. That is, FIG.
Indicates an exposure master 12b. This exposure master 12b
Is a method in which a resist 12d is applied to the surface of a glass substrate 12c and irradiated with light under the same exposure conditions as in the case of the 0-layer substrate 11 so that only the necessary portion of the resist 12d is left. Thereby, the depth of the pit of the manufactured one-layer substrate 12 is determined.

From this exposure master 12b, as shown in FIG. 19B, a stamper 12 serving as a master is formed by plating.
e, and a substrate 12f is molded from the stamper 12e as shown in FIG. Then, as shown in FIG. 19D, the pit formation surface of the substrate 12f is covered with an Al total reflection film 12a, whereby the one-layer substrate 12 is manufactured.

Thereafter, as shown in FIG.
By bonding the first and one-layer substrates 12 with the transparent adhesive 13 so that the reproducing surface distance is about 55 μm,
An optical disc 14 having a layer structure is manufactured. As described above, the optical disc 14 condenses laser light from the zero-layer substrate 11 through the objective lens 15 to select information recorded on the zero-layer substrate 11 and the one-layer substrate 12. It is designed to be read.

Incidentally, the above-mentioned zero-layer substrate 11 and one-layer substrate 12 are both manufactured based on the exposure masters 11b and 12b prepared under the same exposure conditions. For this reason, as shown in FIG. 21A, the case where the 0-layer substrate 11 before being bonded with the transparent adhesive 13 is reclaimed as a single plate is used, and as shown in FIG. The same reproduced signal amplitude characteristics can be obtained when the single-layer substrate 12 before bonding is reproduced as a single plate.

That is, as shown in FIG.
The pit formation surface of the layer substrate 11 (in this case, the translucent film 11
When the laser beam is condensed by the objective lens 15 on the Al total reflection film 11g instead of a), each reflected light of the longest land, the longest pit, the shortest land, and the shortest pit is obtained. Levels I14H, I14L, I3H and I3L
As shown in FIG. 2B, the longest land portion and the longest pit when the laser beam is condensed by the objective lens 15 on the pit forming surface of the single-layer substrate 12 covered with the total reflection film 12a. Light level I at the shortest lands, shortest lands and shortest pits
14H, I14L, I3H and I3L are equal to each other.

However, as shown in FIG. 22, a zero-layer substrate 11 having a translucent film 11a on the pit formation surface,
One-layer substrate 12 having pit formation surface provided with total reflection film 12a
And an optical disk 14 having a two-layer structure in which the two layers are adhered to each other with a transparent adhesive 13.
In the case where the information recorded in the shortest lands and the shortest pits of the 0-layer substrate 11 are respectively read as shown in FIG.
As shown in FIG. 3B, there is a problem that a difference Δ occurs between the reflected light levels I3H and I3L of the shortest land portion and the shortest pit portion of the one-layer substrate 12 as shown in FIG.

The reflected light levels I3H and I3L of the zero-layer substrate 11 and the reflected light levels I3H
H and I3L have a difference Δ, so that the 0-layer substrate 1
The amplitude characteristic of the reflected light level of 1 has a problem that the modulation factor M and the resolution D are smaller and the asymmetry A is shifted to the negative side as compared with the amplitude characteristic of the reflected light level of the one-layer substrate 12. Has occurred.

The reflected light level I3H of the 0-layer substrate 11
24, and the reflected light levels I3H and I3L of the one-layer substrate 12 cause a difference Δ, so that the optical disc reproducing apparatus changes the frequency characteristic of the equalizer circuit 19 to the characteristic indicated by reference characters a and b in FIG. It is necessary to switch to. In this case, the characteristic indicated by reference numeral a in FIG. 24 is the equalization characteristic corresponding to the reproduction of the zero-layer substrate 11, and the characteristic indicated by reference numeral b in FIG.
Are the equalization characteristics corresponding to the reproduction of the single-layer substrate 12.

[0023]

As described above, in the conventional optical disk having a multilayer structure, there is a difference in the level of light reflected from the substrate constituting each layer, so that the characteristics of reproduced signals obtained from each substrate are not equal. There is a problem that. Also, for this reason, the optical disc reproducing device side
There is also an inconvenience that it is necessary to selectively switch the characteristics of the equalizer circuit for compensating the frequency characteristics of the reproduced signal.

Accordingly, the present invention has been made in view of the above circumstances, and provides an extremely good optical disk and a reproducing apparatus for the same, which can obtain substantially the same reproduction signal characteristics from the substrates constituting each layer. The purpose is to:

[0025]

An optical disk according to the present invention is formed by laminating a plurality of substrates on each of which information is recorded, and the information recording surface of each of the plurality of substrates is arranged from one side thereof. When the light is selectively condensed, the reflected light from the substrate on which the light is condensed is obtained from one surface side. The light reflected from any of the substrates is configured to be substantially equal in level when obtained from one surface of the optical disk.

Also, an optical disk reproducing apparatus according to the present invention comprises a driving means for rotating the above-mentioned optical disk, and a means for selectively condensing light from one surface of the optical disk to each information recording surface of a plurality of substrates. And an optical pickup for receiving reflected light reflected from the substrate on which the light is focused and obtained from one surface side of the optical disc and converting the reflected light into a reproduction signal.

According to the above arrangement, the reflected light from any one of the substrates is obtained from one surface of the optical disk so that the levels thereof are substantially equal to each other. As a result, substantially the same reproduction signal characteristics can be obtained from the substrate constituting each layer.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG.
21A and 21B, the same parts as those in FIGS. 21A and 21B are denoted by the same reference numerals. That is, FIG.
The pit depth P0 of the 0-layer substrate 11 shown in (a) is larger than the pit depth P1 of the 1-layer substrate 12 shown in FIG.
I try to make it deeper. Forming the pit depth P0 of the 0-layer substrate 11 deeper than usual is realized by increasing the thickness of the resist 11c in the manufacturing process shown in FIG.

In this way, as shown in FIG. 1A, the pit formation surface of the single-layer 0-layer substrate 11 before bonding (in this case, the total reflection of Al instead of the translucent film 11a) When the laser light is condensed by the objective lens 15 on the film 11g), the reflected light levels I14H and I3H of the longest land portion and the shortest land portion are as shown in FIG. The reflected light levels I14H and I3H of the longest land portion and the shortest land portion when the laser light is condensed by the objective lens 15 on the pit forming surface of the single-layer single-layer substrate 12 covered with the total reflection film 12a. And the reflected light level I14 of the longest pit portion and the shortest pit portion of the 0-layer substrate 11
L and I3L are higher than the reflected light levels I14L and I3L of the longest pit portion and the shortest pit portion of the one-layer substrate 12, respectively.
It is lower by the difference Δ. That is, the amplitude characteristic of the reflected light level of the zero-layer substrate 11 has a larger modulation factor M than the amplitude characteristic of the reflected light level of the one-layer substrate 12.

Therefore, as shown in FIG. 2, the zero-layer substrate 11 having a translucent film 11a on the pit formation surface and the one-layer substrate 12 having a total reflection film 12a on the pit formation surface are transparent. Optical disc 14 having a two-layer structure bonded with adhesive 13
In the case where the information recorded on the 0-layer substrate 11 and the 1-layer substrate 12 is selectively read by condensing a laser beam from the 0-layer substrate 11 side through the objective lens 15, FIG. As shown in FIG. 3A, the reflected light levels I14H, I14L, I3H, and I3L of the longest land, longest pit, shortest land, and shortest pit of the zero-layer substrate 11 are shown.
(B), the reflected light levels I14H, I14L, I3H, and I3L of the longest land, longest pit, shortest land, and shortest pit of the single-layer substrate 12 as shown in FIG.
Are equal to each other, and the reproduction signal characteristics of the 0-layer substrate 11 and the 1-layer substrate 12 can be equalized.

Next, a second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 4A shows a pit row formed on the one-layer substrate 12, and FIG. 4B shows a pit row formed on the zero-layer substrate 11. In this pit row, the shortest pit portion having a length of 3T and a length of 14T
And the longest pit portion. Then, the width W0 of the pit formed on the zero-layer substrate 11 shown in FIG. 4B is set to be larger than the width W1 of the pit formed on the one-layer substrate 12 shown in FIG. I have. Forming the width W0 of the pits of the zero-layer substrate 11 wider than usual is as shown in FIG.
Is realized by increasing the exposure power for the resist 11c in the manufacturing process shown in FIG.

According to such a configuration, as shown in FIG. 5A, the pit formation surface of the single-layer 0-layer substrate 11 before bonding (in this case, Al is used instead of the translucent film 11a). The reflected light levels I14H and I14L of the longest land portion and the longest pit portion when the laser beam is condensed by the objective lens 15 on the total reflection film 11g) are as shown in FIG. The total reflection film 1 of a single-layer single-layer substrate 12
When the laser light is condensed by the objective lens 15 on the pit forming surface covered with 2a, the reflected light levels I14H and I14L of the longest land portion and the longest pit portion are equal to 0.
The reflected light levels I3H and I3L of the shortest land portion and the shortest pit portion of the layer substrate 11 are the reflected light levels I3H and I3L of the shortest land portion and the shortest pit portion of the one-layer substrate 12, respectively.
Than the difference Δ. In this case, the amplitude characteristic of the reflected light level of the zero-layer substrate 11 becomes deeper so that the asymmetry A shifts to the positive side, that is, becomes deeper than the amplitude characteristic of the reflected light level of the one-layer substrate 12.

For this reason, as shown in FIG. 6, the zero-layer substrate 11 having a pit-forming surface provided with a translucent film 11a and the one-layer substrate 12 having a pit-forming surface provided with a total reflection film 12a are transparent. Optical disc 14 having a two-layer structure bonded with adhesive 13
In the case where the information recorded on the 0-layer substrate 11 and the 1-layer substrate 12 is selectively read by condensing a laser beam from the 0-layer substrate 11 side through the objective lens 15, FIG. As shown in FIG. 7A, the reflected light levels I14H, I14L, I3H and I3L of the longest land, the longest pit, the shortest land and the shortest pit of the zero-layer substrate 11 are shown.
(B), the reflected light levels I14H, I14L, I3H, and I3L of the longest land, longest pit, shortest land, and shortest pit of the single-layer substrate 12 as shown in FIG.
Are equal to each other, and the reproduction signal characteristics of the 0-layer substrate 11 and the 1-layer substrate 12 can be equalized.

As described above, the deterioration of the asymmetry A can be corrected by making the size of the pits on the zero-layer substrate 11 larger than the pits on the one-layer substrate 12.
As means for making the size of the pits of the zero-layer substrate 11 larger than that of the pits of the one-layer substrate 12, there is a method shown in FIGS. 8 and 9 in addition to changing the width of the pits. First, FIG. 8A shows a pit row formed on the one-layer substrate 12,
FIG. 2B shows a pit row formed on the 0-layer substrate 11. This pit row shows the shortest pit portion having a length of 3T and the longest pit portion having a length of 14T.

The length L0 of the pit formed on the zero-layer substrate 11 shown in FIG. 8B is larger than the length L1 of the pit formed on the single-layer substrate 12 shown in FIG. Is set longer. In this case, the recording densities of the zero-layer substrate 11 and the one-layer substrate 12 are the same. The formation of the pit length L0 of the zero-layer substrate 11 longer than usual can also be realized by increasing the exposure power for the resist 11c in the manufacturing process shown in FIG.

FIG. 9A shows a pit row formed on the one-layer substrate 12, and FIG. 9B shows a pit row formed on the zero-layer substrate 11. This pit row shows the shortest pit portion having a length of 3T and the longest pit portion having a length of 14T. Then, the one-layer substrate 12 shown in FIG.
The width W1 of the pit formed on the 0-layer substrate 11 shown in FIG.
0 and the length L0 are set large. Again, 0
The recording densities of the layer substrate 11 and the single layer substrate 12 are the same.
Then, the width W0 and the length L of the pit of the zero-layer substrate 11 are obtained.
Forming 0 larger than usual can also be realized by increasing the exposure power to the resist 11c in the manufacturing process shown in FIG.

Next, a third embodiment of the present invention will be described in detail with reference to the drawings. FIG. 10A shows a pit row formed on the single-layer substrate 12, and FIG.
The pit row formed on the layer substrate 11 is shown. In this pit row, the shortest pit portion having a length of 3T and a length of 14T
T indicates the longest pit portion. In this case, FIG.
The linear density of the pits formed on the zero-layer substrate 11 shown in FIG. 3B is set lower than the linear density of the pits formed on the single-layer substrate 12 shown in FIG. This zero-layer substrate 11
The linear density of the pits is made lower than usual by making the length T corresponding to one bit of the recorded information longer than usual during the exposure of the exposure master 11b in the manufacturing process shown in FIG. To form a pit portion.

In this way, as shown in FIG. 11A, the pit formation surface of the single-layer 0-layer substrate 11 before bonding (in this case, total reflection of Al instead of the translucent film 11a) The reflected light levels I14H, I14L, and I3H of the longest land, the longest pit, and the shortest land when the laser light is focused by the objective lens 15 on the film 11g) are shown in FIG. As shown in (), the longest land portion, the longest pit portion, and the shortest portion when the laser beam is condensed by the objective lens 15 on the pit formation surface of the single-layer single-layer substrate 12 covered with the total reflection film 12a. Each reflected light level I of land
Similarly to 14H, I14L and I3H, the reflected light level I3L of the shortest pit portion of the zero-layer substrate 11 is lower than the reflected light level I3L of the shortest pit portion of the one-layer substrate 12 by a difference Δ. In this case, the amplitude characteristic of the reflected light level of the zero-layer substrate 11 has a higher resolution D than the amplitude characteristic of the reflected light level of the one-layer substrate 12.

Therefore, as shown in FIG. 12, a zero-layer substrate 11 having a pit-forming surface provided with a translucent film 11a and a one-layer substrate 12 having a pit-forming surface provided with a total reflection film 12a, An optical disk 14 having a two-layer structure bonded with a transparent adhesive 13 is focused on a laser beam from the side of the zero-layer substrate 11 via an objective lens 15 to form a zero-layer substrate 11 and a one-layer substrate 12.
When the information recorded on the 0th layer substrate 11 is selectively read, as shown in FIG. 13A, the reflected light of the longest land portion, the longest pit portion, the shortest land portion, and the shortest pit portion of the 0-layer substrate 11 are obtained. Levels I14H, I14L, I3H and I3
L, and the reflected light levels I14H, I14L, I3H and I3 of the longest land, longest pit, shortest land and shortest pit of the one-layer substrate 12 as shown in FIG.
L are equal to each other, and the 0-layer substrates 11 and 1
The reproduction signal characteristics with the layer substrate 12 can be made equal.

Next, a fourth embodiment of the present invention will be described in detail with reference to the drawings. FIG. 14A shows a pit row formed on the single-layer substrate 12, and FIG.
The pit row formed on the layer substrate 11 is shown. In this pit row, the shortest pit portion having a length of 3T and a length of 14T
T indicates the longest pit portion. In this case, FIG.
The linear density of the pits formed on the zero-layer substrate 11 shown in FIG. 14B is set lower than the linear density of the pits formed on the single-layer substrate 12 shown in FIG. a)
The width W0 of the pits formed on the zero-layer substrate 11 shown in FIG. 3B is set to be larger than the width W1 of the pits formed on the single-layer substrate 12 shown in FIG.

As described above, by setting the linear density of the pits formed on the zero-layer substrate 11 lower than usual and setting the width W0 of the pits formed on the zero-layer substrate 11 larger than usual, It becomes possible to correct both the deterioration of the resolution D and the deterioration of the asymmetry A.

That is, in the above-described first to third embodiments, when the depth of the pit of the 0-layer substrate 11 is increased, the deterioration of the modulation factor M of the amplitude characteristic of the reflected light level is corrected. And the case where the deterioration of asymmetry A of the amplitude characteristic of the reflected light level is corrected by increasing the size of the pits of the 0-layer substrate 11, and the linear density of the pits of the 0-layer substrate 11 is reduced. The case where the degradation of the resolution D of the amplitude characteristic of the reflected light level is corrected has been described. However, the three types of elements of the pit depth, the pit size, and the pit linear density are optionally combined. To make the 0-layer substrate 11
Needless to say, the reproduction signal characteristics of the first and second layer substrates 12 may be made equal.

FIG. 15 shows an example of an optical disk drive for recording and reproducing image data and audio data on and from the optical disk 14 described above. That is,
The optical disk 14 is driven to rotate by the disk motor 16. An optical head device 24 is arranged so as to face the signal recording surface of the optical disk 14.

The optical head device 24 is used for the optical disc 14
By irradiating the laser beam to the signal recording surface of
Writing data to the optical disk 14 and the optical disk 1
The optical disk 14 selectively reads data from the optical disk 4, and is supported so as to be movable in the radial direction of the optical disk 14.

Here, the reproducing operation will be described first. Data read from the optical disk 14 by the optical head device 24 is applied to a modulation / demodulation / error correction processing unit 25.
Supplied to The modulation / demodulation / error correction processing unit 25
Using the track buffer memory 26, the optical head device 2
4 is subjected to demodulation processing and error correction processing.

The modulation / demodulation / error correction processing unit 2
5 is MPEG data
(Moving Picture Image Coding Experts Group) is supplied to the encoder decoder 27. The MPEG encoder / decoder 27 uses a frame memory 28 to perform MPEG decoding on the image data supplied from the modulation / demodulation / error correction processing unit 25.

Thereafter, the image data obtained from the MPEG encoder / decoder 27 is supplied to a video encoder / decoder 29, subjected to a video decoding process, and taken out from an output terminal 30. Audio data among the data output from the modulation / demodulation / error correction processing unit 25 is supplied to an audio encoder decoder 31, subjected to audio decoding processing, and extracted from an output terminal 32.

Next, the recording operation will be described. First,
The image data supplied to the input terminal 33 is supplied to a video encoder decoder 29, subjected to a video encoding process, and then supplied to an MPEG encoder decoder 27. The MPEG encoder / decoder 27 uses a frame memory 28 and a video encoder / decoder 29
Is subjected to an MPEG encoding process.

The audio data supplied to the input terminal 34 is supplied to the audio encoder / decoder 31 and subjected to audio encoding processing. And the above M
The image data output from the PEG encoder decoder 27 and the audio data output from the audio encoder decoder 31 are supplied to a modulation / demodulation / error correction processing unit 25.

The modulation / demodulation / error correction processing unit 25 uses the track buffer memory 26 to perform a modulation process for recording and an error correction code adding process on the input image data and audio data. . Then, the data output from the modulation / demodulation / error correction processing unit 25 is recorded on the optical disk 14 via the optical head device 24.

The disk motor 16, modulation / demodulation
Error correction processing unit 25, MPEG encoder decoder 2
7. The video encoder decoder 29 and the audio encoder decoder 31 are MPU (Micro Processing Uni
The operation is controlled by t) 35. In addition,
The present invention is not limited to the above embodiments, and can be variously modified and implemented without departing from the scope of the invention.

[0052]

As described in detail above, according to the present invention,
It is possible to provide an extremely good optical disk and a reproduction apparatus for the same, which can obtain substantially the same reproduction signal characteristics from the substrates constituting each layer.

[Brief description of the drawings]

FIG. 1 is a view shown for explaining a first embodiment of the present invention;

FIG. 2 is a diagram showing an optical disc having a two-layer structure according to the first embodiment.

FIG. 3 is a view shown for explaining a reflected light level in each layer of the optical disc.

FIG. 4 is a diagram shown to explain a second embodiment of the present invention;

FIG. 5 is a view for explaining a main part in the second embodiment.

FIG. 6 is a diagram showing an optical disc having a two-layer structure according to the second embodiment.

FIG. 7 is a view for explaining a reflected light level in each layer of the optical disc.

FIG. 8 is a diagram shown to explain a first modification of the second embodiment.

FIG. 9 is a view shown to explain a second modification of the second embodiment.

FIG. 10 is a view for explaining a third embodiment of the present invention;

FIG. 11 is a view for explaining main parts according to the third embodiment;

FIG. 12 is a diagram showing an optical disc having a two-layer structure according to the third embodiment.

FIG. 13 is a view for explaining a reflected light level in each layer of the optical disc.

FIG. 14 is a view for explaining a fourth embodiment of the present invention;

FIG. 15 is a block diagram showing an example of a disk drive device for recording and reproducing data on an optical disk.

FIG. 16 is a view for explaining an optical disk having a general two-layer structure.

FIG. 17 is a block diagram showing a measuring system for measuring the jitter of a reproduction signal of the optical disc.

FIG. 18 is a view for explaining the manufacturing process of the zero-layer substrate of the optical disc.

FIG. 19 is a view for explaining the manufacturing process of the single-layer substrate of the optical disc.

FIG. 20 is a diagram showing an optical disc having a two-layer structure in which the zero-layer substrate and the one-layer substrate are attached to each other.

FIG. 21 is a view for explaining reflected light levels when the 0-layer substrate and the 1-layer substrate are each reproduced as a single plate.

FIG. 22 is a view for explaining a reproducing operation of an optical disc having a two-layer structure in which the zero-layer substrate and the one-layer substrate are bonded to each other.

FIG. 23 is a view for explaining a reflected light level in each layer of the optical disc.

FIG. 24 is a view for explaining switching of the frequency characteristic of the equalizer circuit in the reproducing apparatus for the optical disc.

[Explanation of symbols]

 11: 0 layer substrate, 12: 1 layer substrate, 13: transparent adhesive, 14: optical disk, 15: objective lens, 16: disk motor, 17: optical pickup, 18: preamplifier circuit, 19: equalizer circuit, Reference Signs List 20: data slice circuit, 21: output terminal, 22: PLL circuit, 23: output terminal, 24: optical head device, 25: modulation / demodulation / error correction processing unit, 26: track buffer memory, 27: MPEG encoder decoder, 28 ... Frame memory, 29: Video encoder decoder, 30: Output terminal, 31: Audio encoder decoder, 32: Output terminal, 33, 34: Input terminal, 35: MPU.

Claims (15)

[Claims] 1. A plurality of substrates on each of which information is recorded are laminated, and light is selectively condensed from one surface side to each information recording surface of the plurality of substrates. And, in the optical disk having a multilayer structure in which the reflected light from the substrate on which light is collected is obtained from the one surface side, the reflected light from any of the substrates on which light is collected,
An optical disk characterized in that the levels are substantially equal to each other in a state obtained from one surface side of the optical disk. 2. The optical disk according to claim 1, wherein the plurality of substrates are configured such that pits formed on an information recording surface thereof have different depths from each other. 3. The pit formed on the information recording surface of the substrate is configured to be deeper as the substrate is closer to one surface of the optical disk.
An optical disc as described. 4. The optical disk according to claim 1, wherein the plurality of substrates are configured such that pits formed on an information recording surface thereof are different from each other. 5. The optical disk according to claim 4, wherein the size of the pit formed on the information recording surface of the substrate is increased as the substrate is closer to one surface of the optical disk. . 6. The optical disk according to claim 4, wherein the pits formed on each of the information recording surfaces of the plurality of substrates have different widths from each other. 7. The optical disk according to claim 4, wherein the pits formed on each of the information recording surfaces of the plurality of substrates have different lengths. 8. The optical disc according to claim 4, wherein the pits formed on each of the information recording surfaces of the plurality of substrates have different widths and lengths. 9. The optical disk according to claim 1, wherein the plurality of substrates are configured such that the linear density of pits formed on the information recording surface thereof is different from each other. 10. The optical disk according to claim 9, wherein the linear density of pits formed on the information recording surface of the substrate decreases as the substrate is closer to one surface of the optical disk. . 11. The plurality of substrates are configured such that pits formed on an information recording surface thereof have different linear densities and sizes from each other.
An optical disc as described. 12. The optical disk according to claim 1, wherein the plurality of substrates are configured such that pits formed on the information recording surface have different depths and sizes from each other. 13. The optical disk according to claim 1, wherein each of the plurality of substrates is configured such that a depth and a linear density of a pit formed on an information recording surface thereof are different from each other. 14. The optical disk according to claim 1, wherein the plurality of substrates are configured such that the depth, size, and linear density of pits formed on the information recording surface thereof are different from each other. . 15. A driving means for rotating the optical disk according to claim 1, wherein light is selectively condensed from one surface side of the optical disk to each of the information recording surfaces of the plurality of substrates. An optical pickup for receiving reflected light reflected by the substrate and obtained from one surface side of the optical disc and converting the reflected light into a reproduced signal.