WO2006088137A1

WO2006088137A1 - Recording medium, reproduction device and method, and computer program

Info

Publication number: WO2006088137A1
Application number: PCT/JP2006/302837
Authority: WO
Inventors: Eiji Muramatsu; Kazuo Kuroda; Akira Imamura
Original assignee: Pioneer Corporation
Priority date: 2005-02-18
Filing date: 2006-02-17
Publication date: 2006-08-24

Abstract

A recording medium (100) includes (i) a first recording layer (101: HD-DVD) having a signal plane which can be read by a first laser light (405 nm) of a first wavelength, (ii) a second recording layer (102: DVD) having a signal plane which can be read by a second laser light (650 nm) of a second wavelength, and (iii) an intermediate layer (103) arranged between the first recording layer and the second recording layer. The light reflection ratio of the intermediate layer for the first laser light is a value capable of detecting a focusing point position for the first recording layer. The light reflection ratio of the intermediate layer for the second laser light is a value not capable of detecting a focusing point position for the first recording layer.

Description

Specification

Recording medium, reproducing apparatus and method, and computer program

Technical field

[0001] The present invention relates to a technical field of a multilayer recording medium such as a two-layer optical disk, a reproducing apparatus and method for reproducing the recording medium, and a computer program. Background art

[0002] For example, in recording media such as CD-ROM (Compact Disc-Read Only Memory), CD-R (Compact Disc-Recordable), DVD-ROM, etc., it is described in Patent Documents 1 and 2, etc. As described above, a multi-layer or double-layer or multiple-layer optical disc in which a plurality of recording layers are stacked on the same substrate has been developed. More specifically, the two-layer type optical disc is positioned as the first layer on the most front side (that is, the side close to the optical pickup) when viewed from the irradiation side of the laser beam when played back by the playback device. It has a first recording layer, and further has a transflective film located on the far side (that is, the side far from the optical pickup force). As a second layer, a second recording layer is provided on the back side of the transflective film via an intermediate layer such as an adhesive layer, and a reflective film is further provided on the back side. Then, in a reproducing apparatus such as a CD player that reproduces such a two-layer type optical disc, the reproducing laser beam is condensed on the first recording layer to be recorded on the first recording layer. By reproducing the recorded information and condensing the laser beam on the second recording layer, the information recorded on the second recording layer is reproduced.

[0003] Focus pull-in to information recorded on each recording layer of such a two-layer type optical disc is realized by control of a focus servo. More specifically, when the objective lens in the optical pickup is moved closer to the optical disc, when the focus is in focus on the first recording layer, for example, the semi-transmissive reflective film of the first recording layer The focus error signal of the reflected light from is converged to “0”. When the objective lens is further raised and moved closer to the optical disk, the second recording layer is focused. In this case, the focus error signal of the reflected light from the reflecting film of the second recording layer is “0”. To converge. In this way, when the objective lens is moved in the direction closer to the optical disk, the first recording layer is moved to the first recording layer. Two S-shaped waveforms centered on the position of the objective lens (hereinafter referred to as “the in-focus position” of the first recording layer) and the in-focus position of the second recording layer, respectively, when they are aligned. A focused error signal (hereinafter referred to as “S-shaped signal”) is obtained (see Fig. 2 (b), etc. described later). Under the focus servo control using these two S-shaped signals, the focus of the first and second recording layers can be adjusted by moving the position of the objective lens up and down. .

[0004] Patent Document 1: Japanese Unexamined Patent Publication No. 2000-311346

Patent Document 2: Japanese Patent Laid-Open No. 2001-23237

Disclosure of the invention

Problems to be solved by the invention

[0005] However, the recording apparatus is provided with a recording layer having recording layers that can be reproduced by two different wavelengths by the same method as the reproduction of the recording medium such as the two-layer type optical disc as described above. When trying to reproduce, there is a possibility that it may be mistakenly recognized as a recording medium having a recording layer that can be reproduced by a single wavelength.

The present invention has been made in view of, for example, the conventional problems described above. For example, in a multi-layer recording medium such as a two-layer optical disk, the recording layer can be accurately determined by laser light. It is an object of the present invention to provide a possible recording medium, reproducing apparatus and method, and computer program.

Means for solving the problem

[0007] (Recording medium)

In order to solve the above problems, the recording medium of the present invention has a first recording layer (HD-DVD) having a signal surface readable by a first laser beam having a first wavelength (blue LD (blue laser diode)), A second recording layer (DVD) having a signal surface that can be read by a second laser beam having a second wavelength (red LD (red laser diode)), and disposed between the first recording layer and the second recording layer An intermediate layer, and the light reflectance of the intermediate layer with respect to the first laser light (blue LD) is set to a value that enables detection of a focal point position with respect to the first recording layer, and the second laser light The light reflectance of the intermediate layer with respect to (red LD) is set to a value at which the in-focus position with respect to the first recording layer cannot be detected. [0008] According to the recording medium of the present invention, the first recording layer such as HD-DVD (High Definition-DVD), for example, has a first wavelength of the first wavelength, which is a wavelength in a blue LD (blue laser diode), for example. The signal surface is readable by the light. For example, a second recording layer such as a DVD has a signal surface that can be read by a second laser beam having a second wavelength, which is a wavelength in a red LD (red laser diode), for example.

In particular, in the present invention, an intermediate layer is disposed between the first recording layer (HD-DVD) and the second recording layer (DVD). The light reflectance of the intermediate layer with respect to the first laser light (blue LD) is set to a value that enables detection of the focal point position with respect to the first recording layer. The light reflectivity for the second laser beam (red LD) in this intermediate layer is set to a value that makes it impossible to detect the in-focus position with respect to the first recording layer. Therefore, the intermediate layer can retain the property of selectively transmitting or not transmitting light based on the wavelength in the laser light, that is, so-called wavelength selectivity.

[0010] With regard to wavelength selectivity, in detail, for example, when a desired first recording layer such as HD-DVD is irradiated with a first laser beam such as blue LD, the in-focus position is detected, That is, only one S-shaped signal centered on the in-focus position where the focus error signal converges to “0” is obtained only in the first recording layer, and it is possible to focus on the first recording layer. . More specifically, since the intermediate layer reflects the first laser beam, the first laser beam cannot reach the second recording layer. Therefore, since the first laser beam is reflected by the intermediate layer stacked on the first recording layer, only one S-shaped signal corresponding to the first recording layer can be detected. As a result, the reproducing apparatus recognizes the recording medium as a single-layer type recording medium that can be reproduced by the first laser beam, and has a relatively short wavelength, for example, with respect to the first recording layer disposed in front. For example, it is possible to read a recorded signal by irradiating a first laser beam for reproduction such as a blue LD.

On the other hand, when a desired second recording layer such as a DVD is irradiated with a second laser beam such as a red semiconductor laser via the first recording layer and the intermediate layer, the first recording layer The focal position cannot be detected in the layer, and the focal position is detected in the second recording layer. That is, only one S-shaped signal centered on the focal point where the focus error signal converges to “0” is obtained only in the second recording layer, and the second recording layer is focused. Is possible. More specifically, since the intermediate layer does not reflect the second laser light, the second laser light can reach the second recording layer via the first recording layer and the intermediate layer. Therefore, the second laser light is not reflected by the intermediate layer laminated on the first recording layer, but is reflected by the second recording layer, so that only one S-shaped signal corresponding to the second recording layer can be detected. . As a result, the reproducing apparatus recognizes the recording medium as a single-layer recording medium that can be reproduced by the second laser light, and has a relatively long wavelength with respect to the second recording layer disposed on the back side, for example. For example, it is possible to read a recorded signal by irradiating a second laser beam for reproduction such as a red LD. In the present invention, the sum of the light reflectance, the light transmittance, and the light absorptance in the predetermined layer is configured to be equal to 1.

[0012] If an intermediate layer that retains wavelength selectivity is not inserted, the reproducing apparatus simply identifies the recording medium from two S-shaped signals detected in the first recording layer and the second recording layer. May be mistaken for a reproducible recording medium by laser light of one wavelength

In contrast, according to the recording medium of the present invention, since the intermediate layer that retains wavelength selectivity is inserted, the first recording layer can be accurately discriminated by the first laser beam. . The second recording layer can be accurately discriminated by the second laser beam. In particular, the present invention is effective when the first recording layer and the second recording layer are close to each other and the accuracy of position control in an actuator that drives an objective lens using, for example, a position sensor is insufficient. is there.

In one aspect of the recording medium of the present invention, the light reflectance of the intermediate layer with respect to the first laser light (blue LD) takes a value between 0.4 and 0.8. 2 The light reflectivity for laser light (red LD) takes a value between 0.1 and 0.3.

[0015] According to this aspect, it is possible to further improve the reproduction quality in addition to the recording quality of the recording medium.

In another aspect of the recording medium of the present invention, the first wavelength is a wavelength of substantially blue to substantially blue-violet light, and the second wavelength is a wavelength of substantially red light.

[0017] According to this aspect, a laser beam having a relatively short wavelength, such as a blue LD, can be applied as the first laser beam, and a relative wavelength, such as a red semiconductor laser, can be used as the second laser beam. In particular, a laser beam having a long wavelength can be applied.

[0018] (Reproducing device)

In order to solve the above problems, a reproducing apparatus of the present invention is a reproducing apparatus for reproducing the recording medium of the present invention described above (including various aspects thereof), wherein the first laser beam (blue), or Based on the output of the optical pickup means that irradiates the second laser light (red LD) and receives the reflected light, the first recording layer (HD-DVD) or the second recording medium based on the output of the optical pickup means. Based on the output of the optical pickup means, the first recording layer (HD-DVD) and the second recording layer (detection means for detecting the S-shaped signal indicating the in-focus position of the recording layer (DVD) Playback means for playing back information recorded on a DVD.

According to the reproducing apparatus of the present invention, first, when a recording medium is loaded, a seek operation is performed by the optical pickup means, and data reproduced by the decoder is acquired.

Subsequently, or when a host device isotropic reproduction command is input, the first or second laser light emitted from the optical pickup means is focused into a desired recording layer.

[0021] Next, the detection means is based on an output signal corresponding to the amount of light received from a detector that receives the reflected light beam provided in the optical pickup means, and is focused on the first or second recording layer. By detecting the S-shaped signal indicating the position, each recording layer can be properly identified.

Next, the reproducing means can reproduce the information recorded on each recording layer with the first or second laser beam corresponding to the first or second recording layer.

[0023] It should be noted that in the reproducing apparatus of the present invention, it is possible to appropriately adopt the same aspects as the various aspects of the recording medium described above.

[0024] (Reproduction method)

In order to solve the above problems, the reproducing method of the present invention is a reproducing method in a reproducing apparatus for reproducing the recording medium of the present invention described above (including various aspects thereof), wherein the first laser beam (blue) ) Or the second laser beam (red LD) and receiving the reflected light, and based on the output of the light receiving step, the first recording layer (HD-DVD) or the first recording layer 2 Based on the detection process for detecting the S-shaped signal indicating the focal position of the recording layer (DVD) and the output of the light receiving process, the first recording layer (HD-DVD) and the second recording layer ( A playback step of playing back information recorded on a DVD. [0025] According to the reproducing method of the present invention, various benefits similar to those of the reproducing apparatus of the present invention described above can be obtained.

[0026] Incidentally, in response to the various aspects of the reproduction apparatus of the present invention described above, the reproduction method according to the present invention can also adopt various aspects.

[0027] (Computer program)

In order to solve the above-described problems, a computer program according to the present invention is a computer program for reproduction control that controls a computer provided in the above-described playback device of the present invention (including various aspects thereof). The computer is caused to function as at least a part of the optical pickup means, the detection means, and the reproduction means.

[0028] According to the computer program of the present invention, if the computer program is read from a recording medium such as a ROM, a CD-ROM, a DVD-ROM, and a hard disk that stores the computer program and then executed by the computer, Alternatively, if the computer program is downloaded to a computer via communication means and then executed, the above-described playback device of the present invention can be realized relatively easily.

[0029] Incidentally, the computer program of the present invention can also adopt various aspects in response to the various aspects of the playback apparatus of the present invention described above.

[0030] In order to solve the above problems, a computer program product in a computer-readable medium is a program that can be executed by a computer provided in the above-described playback device (including various forms thereof) of the present invention. The command is clearly embodied, and the computer is caused to function as at least part of the optical pickup means, the detection means, and the reproduction means.

[0031] According to the computer program product of the present invention, if the computer program product is read into a computer from a recording medium such as a ROM, CD-ROM, DVD-ROM, or hard disk storing the computer program product, or For example, if the computer program product, which is a transmission wave, is downloaded to a computer via communication means, the above-described playback device of the present invention can be implemented relatively easily. More specifically, the computer program product comprises computer-readable code (or computer-readable instructions) that functions as the playback device of the present invention described above. May be.

[0032] These effects and other advantages of the present invention will become more apparent from the embodiments described below.

[0033] As described above, according to the recording medium of the present invention, the first recording layer, the intermediate layer, and the second recording layer are provided when viewed from the side irradiated with the laser beam. Therefore, in a recording medium such as a two-layer type optical disc that can be recorded at two different wavelengths, the recording layer can be accurately discriminated by at least the second laser beam.

[0034] Further, according to the reproducing apparatus or method of the present invention, the optical pickup means or light receiving process, the detecting means or process, and the reproducing means and process are provided. Therefore, in a recording medium such as a two-layer type optical disc that can be recorded with two different wavelengths, the recording layer can be accurately discriminated by at least the second laser beam.

[0035] Furthermore, according to the computer program of the present invention, the computer is caused to function as the above-described playback device of the present invention. Therefore, it becomes possible to accurately determine the recording layer by using at least the second laser beam as a reproducing apparatus.

Brief Description of Drawings

FIG. 1 is a schematic plan view (FIG. 1 (a)) showing a basic configuration of an optical disc 100 according to an embodiment of a recording medium of the present invention, and a schematic cross section of the optical disc at a cutting plane “X”. It is a diagram (Fig. 1 (b)).

FIG. 2 is an enlarged cross-sectional view (FIG. 2 (a)) schematically showing a vertical cross section of a recording layer irradiated with laser light in an optical disc 100 according to an embodiment of the recording medium of the present invention, and a focus error signal. Is a graph (Fig. 2 (b)) that schematically shows the relationship between the position of one signal surface.

FIG. 3 is a graph showing light reflectance, which is a ratio of reflecting light, using wavelength as a parameter, in an intermediate layer constituting an embodiment of the recording medium of the present invention.

FIG. 4 is an enlarged cross-sectional view (FIG. 4 (a)) schematically showing a vertical cross section of a recording layer irradiated with laser light in an optical disc 100 according to an embodiment of the recording medium of the present invention, and a focus error signal. Is a graph (Fig. 4 (b)) that schematically shows the relationship between the position of the signal plane and other signal planes. [FIG. 5] —In the optical disc 200 according to the comparative example of FIG. 5, an enlarged cross-sectional view (FIG. 5 (a)) schematically showing a vertical cross section of a recording layer irradiated with laser light, and a focus error signal and ,

It is a graph (Fig. 5 (b)) that schematically shows the relationship between the positions of the two signal planes.

[FIG. 6] In an optical disc 300 according to another comparative example, an enlarged cross-sectional view (FIG. 6 (a)) schematically showing a vertical cross section of a recording layer irradiated with laser light, and a focus error signal and ,

It is a graph (Fig. 6 (b)) that schematically shows the relationship between the positions of the two signal planes.

FIG. 7 is a block diagram showing an overall configuration of an optical disk reproducing apparatus according to an embodiment of the present invention.

Explanation of symbols

100 optical disc

101 1st recording layer

101a HD—DVD signal side

102 Second recording layer

102a DVD signal surface

103 Middle layer

104 and 105 polycarbonate layers

500 playback device

502 Optical pickup

503 Spinneret Motor

504 head amplifier

510 Sum generation circuit

511 Pit data demodulator

512 pit data correction circuit

520 Push-pull signal generation circuit

521 Low-pass filter

522 servo unit

600 CPU

LB1 laser light (blue semiconductor laser) LB2 laser light (red semiconductor laser)

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described in each embodiment in order with reference to the drawings.

(1) Recording medium of the present invention

Hereinafter, with reference to FIG. 1 to FIG. 4, description will be given on embodiments of the recording medium of the present invention.

(1 1) Basic configuration

First, an outline of the basic configuration of an optical disc according to an embodiment of the recording medium of the present invention will be described with reference to FIG. Here, FIG. 1 (a) is a schematic plan view showing the basic configuration of the optical disk 100 according to the embodiment of the recording medium of the present invention, and FIG. It is a schematic sectional drawing of an optical disk.

As shown in FIG. 1 (a), the optical disc 100 has a disk shape having a center hole 10 and a diameter of about 12 cm, for example, like a DVD. However, it goes without saying that the shape and size are not limited to this, and various sizes and shapes may be adopted.

As shown in FIG. 1 (b), the optical disc 100 is a multilayer recording medium in which a plurality of recording layers such as a two-layer type are stacked.

Specifically, for example, when viewed from the side irradiated with two types of laser beams LB1 and LB2 (the lower side in FIG. 1 (b)), the first recording of the polycarbonate layer 104, for example, an HD-DVD or the like. The layer 101 includes an intermediate layer 103 that retains wavelength selectivity, for example, a second recording layer 102 such as a DVD, and a polycarbonate layer 105.

More specifically, the first recording layer 101 is a recording layer that can reproduce the recording mark by reflecting the laser beam LB1 that retains the reproduction power with a predetermined reflectance. Here, the laser beam LB1 according to the present embodiment is a laser beam having a relatively short wavelength such as a blue LD having a wavelength of 405 nm.

[0043] The second recording layer 102 is a recording layer capable of reproducing the recording mark by reflecting the laser beam LB2 having the reproducing power with a predetermined reflectance. In the second recording layer 102, Alternatively, a total reflection film capable of reflecting the laser beam LB2 may be laminated. Here, the laser beam LB2 according to the present embodiment is a laser beam having a relatively long wavelength such as a red laser beam having a wavelength of 650 nm, for example.

[0044] The intermediate layer (wavelength selection layer) 103 has a characteristic that the reflectance with respect to laser light of one wavelength is relatively high, and the reflectance with respect to laser light of another wavelength is relatively low. Long selectivity is maintained.

[0045] The polycarbonate layers 104 and 105 may be configured to have a thickness of 0.6 mm, for example.

(1 2) Recording layer discrimination method

Next, with reference to FIG. 2 to FIG. 4, a method for discriminating the recording layer of the optical disc according to the embodiment of the recording medium of the present invention will be described. FIG. 2 is an enlarged cross-sectional view (FIG. 2 (a)) schematically showing a vertical cross-section of the recording layer irradiated with laser light in the optical disc 100 according to the embodiment of the recording medium of the present invention. Fig. 2 (b) is a graph that schematically shows the relationship between the focus error signal and the position of one signal surface. FIG. 3 is a graph showing the light reflectivity, which is the ratio of reflecting light, with the wavelength as a parameter, in the intermediate layer constituting the embodiment of the recording medium of the present invention. In FIG. 3, the vertical axis indicates the light reflectance, and the horizontal axis indicates the wavelength. FIG. 4 is an enlarged sectional view (FIG. 4 (a)) schematically showing a vertical section of a recording layer irradiated with laser light in the optical disc 100 according to the embodiment of the recording medium of the present invention, and a focus error. It is a graph (Fig. 4 (b)) that schematically shows the relationship between the signal and the position of other signal planes.

As shown in FIGS. 2A and 2B, when the desired second recording layer 102 is irradiated with the laser beam LB2, the focus error signal converges to “0”. As a result, only one S-shaped signal centered on the in-focus position is obtained, and the focus can be adjusted to the DVD signal surface 102a included in the second recording layer 102. This is because, as described above, the intermediate layer 103 (“wavelength selection layer”) that retains wavelength selectivity is inserted between the first recording layer 101 and the second recording layer 102. This intermediate layer 103 retains so-called wavelength selectivity, which is a characteristic that the reflectivity for laser light of one wavelength is relatively high and the reflectivity for laser light of another wavelength is relatively low. Yes. Specifically, as shown in “Point A” in FIG. Therefore, the light reflectance for the laser beam LB2 having a wavelength of 650 nm is set to be relatively small. Accordingly, the laser beam LB2 passes through the intermediate layer 103, reaches the DVD signal surface 102a, and is reflected, so that only one S-shaped signal corresponding to the DVD signal surface 102a can be detected.

As a result, the playback apparatus correctly recognizes the optical disc 100 as a single-layer DVD, and has a relatively long wave with respect to the DVD signal surface 102a included in the second recording layer 102 disposed on the back side. It is possible to read a recorded signal by irradiating a long reproduction laser beam LB2, such as a red LD.

On the other hand, as shown in FIG. 4, when the desired first recording layer 101 is irradiated with the laser beam LB1, the focus position where the focus error signal converges to “0” is the center. Only one S-shaped signal is obtained, and the focus can be matched with the HD-DVD signal surface 101a included in the first recording layer 101. This is because, as described above, the intermediate layer 103 that retains wavelength selectivity is inserted between the first recording layer 101 and the second recording layer 102. Specifically, as indicated by “Point B” in FIG. 3, the light reflectance of the intermediate layer 103 with respect to the laser beam LB1 having a wavelength of 405 nm is set to be relatively large. Therefore, since the intermediate layer 103 reflects the laser beam LB1, the laser beam LB1 cannot reach the second recording layer 102. Accordingly, since the laser beam LB1 is reflected by the intermediate layer laminated on the 110-0 ¥ 0 signal surface 101 &, only one S-shaped signal corresponding to the HD-DVD signal surface 101a can be detected.

As a result, for example, when the reproduction laser beam LB1 such as blue LD is irradiated onto the HD-DVD signal surface 101a included in the first recording layer 101, the reproduction laser beam LB1 Since the optical disc 100 is correctly recognized as a single-layer HD-DVD and is included in the first recording layer 101 disposed in front, the optical disc 100 is included in the first recording layer 101 disposed in front. The recorded signal can be read by irradiating the HD-DVD signal surface 101a with a reproduction laser beam LB1 having a relatively short wavelength, such as a blue LD.

As a result of the above, according to the optical disc of the present example, it is possible to accurately determine the recording layer at least by the laser beam LB2. Note that the first and second recording layers are close to each other. In this case, the present invention is effective.

[0051] (2) Examination of effects of the recording medium of the present invention

Subsequently, referring to FIGS. 1 to 4 described above in conjunction with FIGS. 5 and 6, the operational effects of the embodiment of the recording medium of the present invention will be examined. FIG. 5 is an enlarged cross-sectional view (FIG. 5 (a)) schematically showing a vertical cross section of the recording layer irradiated with laser light in the optical disc 200 according to one comparative example, and a focus. Fig. 5 (b) is a graph that schematically shows the relationship between the error signal and the position of the two signal planes. FIG. 6 is an enlarged cross-sectional view (FIG. 6 (a)) schematically showing a vertical cross section of a recording layer irradiated with laser light in an optical disc 300 according to another comparative example, and a focus error signal. Fig. 6 (b) is a graph that schematically shows the relationship between the position of the two signal planes.

First, the effects of the recording medium according to the present invention will be examined based on the following five conditions (i) to (V).

That is, in the optical disc 100 according to the present embodiment, (i) the DVD signal surface 102a included in the second recording layer 102 such as a DVD is irradiated with a red LD having a relatively long wavelength. By means of this, it is possible to detect S-shaped signals.

[0054] (ii) The reflectivity for laser light of one wavelength is relatively high, and the reflectivity for laser light of other wavelengths is relatively low. It is inserted between the first recording layer 101 and the second recording layer 102.

(Iii) The recording density is high! The first recording layer 101, the intermediate layer 103, and the first recording layer are arranged from the front side so that the recording layer is arranged on the front side when viewed from the side irradiated with the laser beam. Arranged in the order of 2 recording layers 102.

[0056] () For example, the 110-0 \ 0 signal surface 101 & included in the first recording layer 101 such as 110-0 \ 0 may be irradiated with a red LD having a relatively long wavelength. The S-shaped signal cannot be detected.

[0057] (V) For example, in the HD-DVD signal surface 101a included in the first recording layer 101 such as HD-DVD, from the reflected light generated by irradiating the blue LD having a relatively short wavelength, S-shaped signal can be detected.

[0058] If only the condition (ii) is not satisfied among the above-mentioned five conditions (i) to (V), Considering this with reference to FIG.

[0059] As shown in FIG. 5 (a), a reproduction laser beam LB2 having a relatively long wavelength, such as a red LD, is included in the first recording layer 101, such as an HD-DVD. When the HD-DVD signal surface 101a is irradiated, the first S-shaped signal can be detected on the HD-DVD signal surface 101a by the reproduction laser beam LB2. Further, the reproduction laser beam LB 2 passes through an intermediate layer 203 such as a transflective layer that does not retain the wavelength selectivity characteristic, and is, for example, applied to the DVD signal surface 102a included in the second recording layer 102 such as a DVD. As a result, the second S-shaped signal can be detected on the DVD signal surface 102a.

Therefore, for example, a playback device such as a DVD player cannot be distinguished from two S-shaped signals detected in a recording medium 300 such as a two-layer DVD. Specifically, as shown in FIGS. 6 (a) and 6 (b), a DVD signal surface 301a included in the first recording layer 301 such as a DVD and a second recording layer 302 such as a DVD, for example. S-signals can be detected respectively on the DVD signal surface 302a included in the.

Therefore, the playback apparatus misrecognizes the optical disc 200 as a dual-layer DVD, and is relative to the HD-DVD signal surface 20 la included in the first recording layer 201 disposed in front. For example, a reproduction laser beam LB2 such as a red LD, which has a long wavelength, is irradiated to read a recorded signal. However, the HD-DVD signal surface 201a can be read only by irradiation with a reproduction laser beam LB1, such as a blue LD. As a result, the playback apparatus may determine that the optical disk is non-standard, for example, which cannot be recognized, and eject it. As described above, since the optical disc 200 is erroneously recognized as a two-layer DVD by the reproducing apparatus, for example, the second recording layer corresponding to the reproducing laser beam LB2 by irradiation with the reproducing laser beam LB2 such as a red LD. The DVD signal surface 202a included in 202 cannot be read.

[0062] In contrast, according to the recording medium of the present invention, since the five conditions (i) to (V) are satisfied, a two-layer type optical disc or the like that can be recorded at two different wavelengths respectively. In the recording medium, it is possible to read out the DVD signal surface 202a included in the second recording layer 102 by irradiation with the reproduction laser beam LB2.

That is, for example, a playback laser beam LB1 such as a blue LD is included in the first recording layer 101. — When the DVD signal surface 101a is irradiated, the reproduction laser beam LB1 hardly or completely transmits the intermediate layer (wavelength selection layer) 103. Single-layer HD-For playback of, for example, a blue LD, which is correctly recognized as a DVD and has a relatively short wavelength with respect to the HD—DVD signal surface 101a included in the first recording layer 101 placed in front. The recorded signal can be read out by irradiating the laser beam LB1.

As a result of the above, according to the optical disc of the present example, it is possible to accurately determine the recording layer at least by the laser beam LB2.

[0065] Power! For example, when the reproduction laser beam LB2 such as a red LD is irradiated to the second recording layer 102 via the first recording layer 101, the reproduction laser beam LB2 is an intermediate layer (wavelength selection layer) 1 Since 03 is transmitted with a transmittance of approximately 70 to 95%, the S-shaped signal is hardly or completely detected from the HD-DVD signal surface 101a included in the first recording layer 101.

As a result of the above, the playback apparatus correctly recognizes the optical disc 100 as a single-layer DVD, and is relatively long with respect to the DVD signal surface 102a included in the second recording layer 102 disposed on the back side. It is possible to read a recorded signal by irradiating a reproduction laser beam LB2, such as a red LD, having a wavelength. In particular, the present invention is effective when the first recording layer and the second recording layer are close to each other and, for example, the position control accuracy in the actuator that drives the objective lens using a position sensor is insufficient. is there. More specifically, as shown in the upper part of FIG. 5 (a), the signal surfaces are very close to each other, for example, within several tens of micrometers, compared to a case where the signal surfaces are separated by about 0.6 mm, for example. In some cases, the present invention is effective.

[0067] (3) Playback device

Next, with reference to FIG. 7, an optical disk reproducing apparatus according to an embodiment of the present invention will be described. FIG. 7 is a block diagram showing the overall configuration of the optical disk reproducing apparatus according to the embodiment of the present invention.

[0068] The playback device 500 includes an optical disc 100, an optical pickup 502, a spindle motor 503, a head amplifier 504, a sum generation circuit 510, pit data, which constitute an example of the "playback means" and "optical pickup means" according to the present invention. Demodulation circuit 511, pit data correction circuit 512, buffer 513, interface 514, push-pull signal generation circuit 520, low-pass filter 521, servo unit 522, and CPU (Central Processing Unit) 600 It is.

[0069] On the optical disc 100, pit data DP synchronized with the first clock signal CK1 is recorded by the length of the recording mark 20. The first clock signal CK1 of the RF playback signal component is the RF playback signal component of the optical disc 100 that fluctuates at a substantially constant period according to wobbling or unreadable embossing, as described in the various embodiments of the optical disc 100 described above. Therefore, it is a signal that can be generated by the playback apparatus 500, and is generated by the pit data recovery circuit 511 in this embodiment. In this embodiment, the recording mark 20 can be interpreted as a pit, and the track is constituted by this pit row.

More specifically, the reproduction apparatus 500 includes an optical pickup 502 that irradiates the reproduction beam to the optical disc 100 and outputs a signal corresponding to the reflected light, and a spindle motor 503 that controls the rotation of the optical disc 100. Servo unit 522 is provided. The servo unit 522 is supplied with a first clock signal CK1 and a pit synchronization signal SYNCp. The servo unit 522 executes a spindle servo that controls the rotation of the spindle motor 503, a focus servo that is a relative position control of the optical pickup 502 with respect to the optical disc 100, and a tracking servo in synchronization with these signals.

The optical pickup 502 includes a laser diode that irradiates a reproduction beam and a quadrant detection circuit (not shown). The quadrant detection circuit divides the reflected light of the reproduction beam into four areas 1A, 1B, 1C, and ID shown in the upper part of FIG. The head amplifier 504 amplifies each output signal of the optical pickup 502, and a divided read signal la corresponding to the area 1A, a divided read signal lb corresponding to the area IB, a divided read signal lc corresponding to the area 1C, and the area The divided read signal Id corresponding to the ID is output. Here, for example, a focus error signal by the astigmatism method is detected (see FIG. 2B, etc.).

[0072] The sum generation circuit 510 adds the divided read signals la, lb, lc, and Id, and serves as an adder circuit that outputs the sum read signal SRF. The total read signal SRF is a signal indicating the length of the recording mark.

The pit data demodulating circuit 511 reproduces the pit data DP based on the total read signal SRF and generates the first clock signal CK1. More specifically, the pit data demodulation circuit 511 assigns the reproduced pit data DP with the pit synchronization signal SYNCp as a reference position. Demodulation is performed using a fixed table to generate reproduction data. For example, when EFM modulation is adopted as a modulation method, processing for converting 14-bit pit data DP into 8-bit reproduction data is performed. Then, a descrambling process for rearranging the order of the reproduction data according to a predetermined rule is executed, and the processed reproduction data is output.

The reproduction data obtained in this way is supplied to the pit data correction circuit 512, where it is subjected to error correction processing, interpolation processing, etc., and then stored in the notper 513. The interface 514 sequentially reads the data stored in the buffer 513, converts it into a predetermined output format, and outputs it to an external device.

Push-pull signal generation circuit 520 calculates (la + Id) (lb + lc) and generates a push-pull signal. The component (la + ld) corresponds to the regions 1A and 1D on the left side with respect to the reading direction, while the component (lb + lc) corresponds to the regions 1B and 1C on the right side with respect to the reading direction. The value of the push-pull signal represents the relative positional relationship between the playback beam and the pit.

The push-pull signal is output to the servo unit 522 via the low-pass filter 521. The servo unit 522 performs tracking control based on the push-pull signal.

The CPU 600 is connected via a bus (not shown) or the like, and controls the entire playback device 500 by giving instructions to each circuit or means. Usually, software for operating the CPU 600 is stored in a memory (not shown) or the like.

In the above-described embodiment, the power described for the optical disc 100 as an example of the recording medium and the player related to the optical disc 100 as an example of the playback apparatus. The present invention is not limited to the optical disc and the player. The present invention can also be applied to various recording media compatible with high-density recording or high transfer rate, and players thereof.

[0079] The present invention is not limited to the above-described embodiments, but can be appropriately changed within the scope of the claims and the entire specification without departing from the gist or concept of the invention which can be read, and a recording medium with such a change Further, a playback apparatus and method, and a computer program for playback control are also included in the technical scope of the present invention. Industrial applicability

[0080] A recording medium, a playback apparatus and method, and a computer program according to the present invention are examples. For example, it can be used for a multilayer recording medium such as a two-layer optical disk, and can also be used for a playback device such as a DVD player. Further, the present invention can be used for a playback device or the like that is mounted on or can be connected to various computer devices for consumer use or business use, for example.

Claims

The scope of the claims

[1] a first recording layer having a signal surface readable by a first laser beam having a first wavelength;

A second recording layer having a signal surface readable by a second laser beam having a second wavelength; and an intermediate layer disposed between the first recording layer and the second recording layer

With

The light reflectivity of the intermediate layer with respect to the first laser light is a value that enables detection of a focal point position with respect to the first recording layer,

The recording medium according to claim 1, wherein a light reflectance of the intermediate layer with respect to the second laser light is set to a value at which a focal point position with respect to the first recording layer cannot be detected.

[2] The light reflectance for the first laser light in the intermediate layer takes a value between 0.4 and 0.8, and the light reflectance for the second laser light is 0.1 to 0. The recording medium according to claim 1, wherein the recording medium takes a value between three.

[3] The first wavelength according to claim 1, wherein the first wavelength is a wavelength of substantially blue to substantially blue-violet light, and the second wavelength is a wavelength of substantially red light. recoding media.

[4] A playback device for playing back the recording medium according to claim 1,

An optical pick-up means for irradiating the first laser light or the second laser light and receiving the reflected light;

Detecting means for detecting an S-shaped signal indicating a focal point position of the first recording layer or the second recording layer based on an output of the optical pickup means;

Reproduction means for reproducing information recorded on the first recording layer and the second recording layer based on the output of the optical pickup means;

A playback apparatus comprising:

[5] A playback method in a playback apparatus for playing back the recording medium according to claim 1,

A light receiving process for irradiating the first laser light or the second laser light and receiving the reflected light;

A detection step of detecting an S-shaped signal indicating a focused position of the first recording layer or the second recording layer based on an output of the light receiving step; A reproducing step of reproducing the information recorded in the first recording layer and the second recording layer based on the output of the light receiving step;

A playback method comprising:

A reproduction control computer program for controlling a computer provided in the reproduction apparatus according to claim 4, wherein the computer is at least one of the optical pickup unit, the detection unit, and the reproduction unit. A computer program characterized by functioning as a part.