WO2005081241A1

WO2005081241A1 - Optical information recording medium and information recording/reproduction device

Info

Publication number: WO2005081241A1
Application number: PCT/JP2005/002769
Authority: WO
Inventors: Shinya Abe; Shin-Ichi Tanaka
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2004-02-23
Filing date: 2005-02-22
Publication date: 2005-09-01
Also published as: JP2007213624A; TW200529210A

Abstract

There is provided an optical information recording medium characterized in that the medium includes an information recording layer capable of reproducing information by light irradiation and a substrate thickness information recording unit containing substrate thickness information. The substrate thickness information is a distance from the light incident surface of the medium to the surface of the information recording layer. When the optical information recording medium is, for example, a reproduction-dedicated disc, a reflection film (102) is arranged as an information recording layer. The substrate thickness is a distance from a cover layer (103) as the light incident surface to the surface of the reflection film (102) as the information recording layer. A BCA (Burst Cutting Area) arranged in the inner circumference of the optical information recording medium serves as a substrate thickness information recording unit where substrate thickness information is recorded by using a BCA mark (104) which is a barcode-shaped mark. Such substrate thickness information is recorded with a lower recording density than the other information.

Description

Specification

Optical information recording medium and information recording / reproducing device

Technical field

The present invention relates to an optical information recording medium including at least one information recording layer, and an information recording / reproducing apparatus for recording / reproducing information on / from the optical information recording medium.

Background art

Conventionally, the numerical aperture of a lens used for converging recording / reproducing light on an information recording layer of an optical information recording medium has been relatively small. The numerical aperture of a lens used for an optical information recording medium such as a CD (Compact Disk) or a DVD (Digital Versatile Disk) is small. Even a DVD using a lens with a larger numerical aperture than a CD is 0.6. Was. Here, in the optical information recording medium, assuming that the distance from the light incident surface to the surface of the information recording layer is referred to as the substrate thickness, the allowable error of the substrate thickness is determined by the optical design of the lens. For example, in a single-layer DVD provided with one information recording layer, the base material thickness is specified to be 0.6 ± 0.03 mm. If the thickness of the single-layer DVD substrate exceeds this range, the reproduction signal will deteriorate and the recording / reproducing accuracy will decrease.

[0003] In recent years, an optical information recording medium capable of recording information at a higher density than a DVD has been developed. For example, a BD (Blu-ray Disk) that realizes high-density recording by shortening the wavelength of the recording / reproducing light to 405 nm and increasing the numerical aperture of the lens for condensing the recording / reproducing light to 0.85 ) Has been commercialized.

[0004] When the recording / reproducing light is narrowed down by using a lens having a large numerical aperture, the thickness of the medium base material is designed to be thin in order to suppress the occurrence of aberration with respect to the tilt of the optical information recording medium. In the case of BD, the thickness of the base material is designed to be 0.1 mm in order to secure the margin for tilt as much as that of DVD.

[0005] However, when the numerical aperture of the lens is increased with high-density recording, the influence of spherical aberration caused by a change in the thickness of the base material increases. Therefore, an optical head used for high-density recording is provided with a mechanism for correcting spherical aberration. By this mechanism, even if the thickness of the base material is different from the specified value, the spherical aberration is corrected and a good recording / reproducing function is secured. it can.

[0006] When the optical information recording medium is disk-shaped, it is not easy to dynamically follow the deviation of the substrate thickness within one rotation of the disk, but the average substrate thickness between different disks is not easy. The deviation can be dealt with by correcting the spherical aberration at the beginning of the recording / reproducing operation.

Patent Document 1: Japanese Patent Application Laid-Open No. 2000-76705

Conventionally, when correcting spherical aberration, learning is performed while detecting a tracking error signal or an information reproduction signal before recording or reproducing information in order to detect the correction value. Needed. When a correction value is obtained by learning while detecting a signal as described above, it takes a long time to correct the spherical aberration. Therefore, it takes a long time to start up after setting the optical information recording medium in the device and then starting up. was there.

Disclosure of the invention

[0008] The optical information recording medium of the present invention includes at least one information recording layer capable of reproducing information by irradiating light, and records substrate thickness information indicating substrate thickness information indicating the substrate thickness. It is characterized by further including a part. In the present invention, the thickness of the substrate refers to a distance from the light incident surface of the optical information recording medium to the surface of the information recording layer. In addition, the optical information recording medium of the present invention includes not only a read-only medium but also a recordable (write-once, rewritable) medium. When recording is possible, the information recording layer can record and reproduce information by irradiating light. The substrate thickness information recording section is formed, for example, on the information recording layer.

[0009] An information recording / reproducing apparatus of the present invention is an information recording / reproducing apparatus used for the optical information recording medium of the present invention described above, wherein the base material thickness information recorded on the optical information recording medium is recorded. A reproducing unit for reproducing, a correction value storing unit in which a correction value of the spherical aberration set according to the substrate thickness is stored in advance, and the substrate thickness information obtained by the reproducing unit, Correction value determining means for determining a correction value of spherical aberration using the correction value storage means, and spherical aberration correcting means for correcting spherical aberration using the correction value determined by the correction value determining means. Features.

Brief Description of Drawings

FIG. 1 is a perspective view, including a cross section, showing an embodiment of the optical information recording medium of the present invention. is there.

FIG. 2 is a schematic diagram showing a BCA (Burst Cutting Area) mark.

[FIG. 3A] FIG. 3A shows a sample (disc A) of an optical information recording medium having the configuration shown in FIG.

FIG. 7 is a waveform diagram of a reproduced signal obtained when reproducing the BCA.

[FIG. 3B] FIG. 3B is a waveform diagram of a reproduced signal obtained when BCA is reproduced for a sample (disc B) of the optical information recording medium having the configuration shown in FIG.

FIG. 4 is a block diagram showing an embodiment of the information recording / reproducing apparatus of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

[0011] In the optical information recording medium of the present invention, base material thickness information indicating the base material thickness is recorded. Therefore, when recording or reproducing information on or from the optical information recording medium of the present invention, first, the base material thickness information is read, and the spherical aberration of the device used for recording and reproduction is read in accordance with the read base material thickness information. It is possible to set a correction value. For example, the spherical aberration corrected by the correction value set in this way can be used as an initial value of learning for optimizing the spherical aberration. Conventionally, in order to obtain a correction value for spherical aberration, it was necessary to perform learning while detecting a tracking error signal or an information reproduction signal from the beginning.However, the optical information recording medium of the present invention does not require such learning. The time required for correcting spherical aberration can be reduced as compared with the case of. As a result, the time from when the optical information recording medium is set in the apparatus to when it is started can be reduced.

In the optical information recording medium of the present invention, it is preferable that the base material thickness information is recorded at a lower recording density and a lower recording density than other information recorded on the information recording layer. As a configuration for realizing such a low recording density, for example, the mark length of the recording mark used for recording the base material thickness information is set to be different from the recording mark used for recording other information recorded on the information recording layer. I'll make it longer. By recording the base material thickness information at a low recording density in this manner, for example, even if the spherical aberration does not match the base material thickness of the information recording layer on which the base material thickness information is recorded, It becomes possible to recognize the material thickness information. As a result, the substrate thickness information can be read out without performing tracking servo, so that the time required for correcting spherical aberration can be further reduced.

[0013] Further, the configuration of the optical information recording medium of the present invention provides information capable of reproducing information by irradiating light. The present invention is also applicable to a medium having a multilayer structure in which a plurality of information recording layers are provided. In this case, the information recording layer may include a plurality of information recording layers in which the substrate thickness information of the information recording layer is recorded. It is preferable that the substrate thickness information is recorded on the information recording layer located on the side of incident light. Note that the substrate thickness information recorded in this case may be information indicating the light incident surface power of the optical information recording medium and the distance to the surface of the information recording layer on which the substrate thickness information is recorded. desirable. Therefore, for example, when the base material thickness information is recorded on the information recording layer located closest to the light incident side, the recorded base material thickness information is the information located closest to the light incident side from the light incident surface of the medium. This is the distance to the surface of the recording layer. The information recording layer located closest (to the light incident side) from the light incident surface of the medium and the information recording layer located furthest (to the anti-light incident side) from the light incident surface of the medium first This is because the focus servo is used.

[0014] In the optical information recording medium of the present invention, the base material thickness information may be recorded by a barcode mark. Here, the barcode-shaped mark means, for example, when the optical information recording medium of the present invention has a disk shape, has a shape that is long in the radial direction of the medium and is arranged in a plurality in the circumferential direction. That is.

[0015] The optical information recording medium of the present invention is also applicable to high-density recording using short-wavelength light for recording and reproduction and using a lens with a large aperture. At this time, the thickness of the base material is preferably 0.1 mm or less. Further, information may be reproduced by irradiation with light passing through a lens having a numerical aperture of 0.8 or more. If the optical information recording medium is a recordable medium, light that has passed through a lens having a numerical aperture of 0.8 or more can be used for recording.

According to the information recording / reproducing apparatus of the present invention, since the correction value of the spherical aberration can be determined using the base material thickness information recorded on the optical information recording medium, the time required for correcting the spherical aberration can be reduced. Can be shortened. Further, the information recording / reproducing apparatus of the present invention reproduces information recorded on an optical information recording medium with the spherical aberration corrected using the correction value determined by the correction value determining means as an initial value. Learning to optimize spherical aberration may be performed using the signal obtained by the above. This allows for more accurate spherical aberration correction. The

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)

An embodiment of the optical information recording medium of the present invention will be described. FIG. 1 is a perspective view including a cross section schematically showing the optical information recording medium of the present embodiment. The optical information recording medium of the present embodiment is a read-only disk, and a reflective film (information recording layer) 102 and a cover layer 103 are laminated on a substrate 101. As the substrate 101, for example, a polycarbonate substrate is used, and information is recorded by pits on the surface on the reflection film 102 side. The reflection film 102 is formed of, for example, an A1 alloy. Since the reproduction light enters from the cover layer 103 side, the cover layer 103 is formed of a transparent material.

[0019] An inner side of the optical information recording medium according to the present embodiment is provided with a BCA (Burst Cutting Area) in which identification information unique to the medium such as a serial number can be recorded. Information is recorded on the BCA as a barcode mark (hereinafter referred to as a BCA mark). This BCA mark can be formed overlapping the pit. In the present embodiment, a BCA is used as a base material thickness information recording unit, and in this area, a barcode shape having a long shape in the radial direction of the medium and a plurality of barcodes arranged in the circumferential direction is used. The base material thickness information is recorded by the mark 104. Note that the substrate thickness in this embodiment corresponds to the distance from the light incident surface of the medium to the surface of the reflective film 102, that is, the thickness of the cover layer 103.

The BCA mark 104 can be formed after laminating the reflective film 102 and the cover layer 103 on the substrate 101. For example, a rectangular YAG laser (the wavelength of the emitted light is 1064 nm, for example) can be used. Can be formed by irradiating the reflective film 102 with a pulse from the substrate 101 side based on a modulation signal modulated according to the substrate thickness information to be recorded, and rotating the optical information recording medium by a rotating mechanism in synchronization with the pulse irradiation. By such a method, the reflection film 102 at the portion irradiated with the pulse is removed, and the BCA mark 104 whose interval is modulated by the signal to be recorded is formed. The BCA mark 104 can be reproduced while focusing on the reflection film 102 using an optical head.

FIG. 2 is a schematic diagram showing the BCA mark 104. The BCA mark 104 in the figure Is hatched. The mark length of the BCA mark 104 corresponds to the width W of the BCA mark 104. In the present embodiment, width W of BCA mark 104 is approximately 8 μΐη. The interval between adjacent BCA marks 104 (mark interval) is set to 1, 2, 3 or 4 times the basic interval of 28.6 / im. By changing the mark interval in this manner, the base material thickness information is recorded.

[0022] The mark length of the BCA mark 104 formed as described above is longer than the mark length of other recorded information (here, the length of the pit formed on the substrate 101). Hiro, Therefore, the recording density of the BCA mark 104 is lower than the recording density of pits, which are other information recorded. Thus, even if the spherical aberration does not match the thickness of the base material, the optical head can be used to reproduce the BCA mark 104 and detect the recorded base material thickness information. Hereinafter, a specific example in which the BCA mark 104 is reproduced will be described.

[0023] For the optical information recording medium of the present embodiment, two types of samplers were prepared. One is a 22-nm-thick reflective film 102 made of A1 alloy and an ultraviolet-curing resin (UV resin) formed on a 1.1-mm-thick polycarbonate substrate 101 on which information is recorded by pits. A disk A in which a cover layer 103 having a thickness of 100 / im is laminated, and the other is a disk B similar to the disk A except that the thickness of the cover layer 103 is 75 / im. The width W of the BCA mark 104 recorded on the discs A and B was about 8 μm, and the mark interval was set to 1, 2, 3, or 4 times as long as the basic interval was 28.6 μΐη. . On the discs A and B, the random data force S having the shortest pit length of 0.149 μΐη and the track pitch of 0.35 μΐη are recorded on the base of the BCA mark 104 (the surface of the substrate 101).

[0024] BCA was reproduced from the above discs A and B using an optical head including a light source that emits laser light having a wavelength of 405 nm and an objective lens having a numerical aperture of 0.85. This optical head has a built-in beam expander that is placed between the light source and the objective lens. By changing the distance between the two lenses that make up this beam expander, spherical aberration is reduced. Will be corrected. When playing discs A and B, the optical head is set so that focus servo is performed on the reflective film 102 in a state where the thickness of the cover layer 103 is 100 xm, that is, when the base material thickness is 100 μm. I was Since the BCA mark 104 is a portion from which the reflection film 102 has been removed, the BCA mark 104 is reproduced as a portion having a low reflectance. FIG. 3A is a waveform diagram of a reproduced signal obtained when the BCA of the disk A is reproduced, and FIG. 3B is a waveform diagram of a reproduced signal obtained when the BCA of the disk B is reproduced. Since the spherical aberration of the optical head used for reproduction is set to be optimal at a substrate thickness of 100 / im, when the disk A is reproduced, the light is focused on the reflective film 102 to the minimum. It was. Therefore, in the disc A, the amount of reflected light was modulated by the pits recorded on the base of the BCA mark 104, and the pit information was reproduced as a large signal modulation in portions other than the BCA mark 104. Also, since the BC A mark 104 is recorded with a long mark length having a lower recording density than the pits, it is reproduced as a long low reflectance portion. For this reason, it was sufficiently detectable.

On the other hand, since the base material of the disc B has a thickness of 70 μm, light cannot be narrowed down on the reflective film 102 due to spherical aberration, and the light is blurred on the reflective film 102 to increase the spot size. Become. As a result, the pits recorded on the base of the BCA mark 104 appear relatively small with respect to the spot size on the reflective film 102, and the number of pits entering the spot increases. The signal modulation degree of the pit became small. On the other hand, the BC A mark 104 is recorded with a sufficiently long mark length, which has a lower recording density than the pit, so that even if the light is blurred, it is sufficient as a long low reflectance portion. It was detectable.

As described above, the BCA mark 104 can be detected even when the spherical aberration is not optimally corrected. For this reason, by recording the base material thickness information on the medium as the BCA mark 104, it is possible to detect the base material thickness information from the BCA mark 104 and set a spherical aberration correction value suitable for the medium. it can. In addition, an operation for optimizing conditions such as spherical aberration, focus, and tilt is performed to optimize the reproduction quality of the recorded signal. The time required to optimize spherical aberration is reduced by performing learning to optimize spherical aberration using the spherical aberration corrected using the corrected spherical aberration (corrected spherical aberration) as the initial value. it can

Also, since the BCA mark 104 can be recorded after forming the cover layer 103, the thickness of the cover layer 103 can be measured and the thickness can be processed into a BCA. Therefore, highly reliable substrate thickness information can be recorded. [0029] In the example shown above, but a thinner substrate thickness up to 75 _beta m, it is possible to detect the BCA marks 104 even when the thinner. The BCA mark 104 can be detected even in a state where the cover layer 103 is not provided.

For example, when the recording / reproducing light is narrowed down by using a lens having a large numerical aperture for high-density recording, the thickness of the base material in the medium is controlled in order to suppress the occurrence of aberration with respect to the tilt of the optical information recording medium. Is designed to be thin. When the thickness of the base material is reduced in this manner, a problem occurs in that the influence of the spherical aberration generated by the change in the thickness of the base material increases, and thus it is necessary to correct the spherical aberration. Therefore, applying the configuration of the present invention to a system such as a BD in which the numerical aperture of the lens is 0.85 and the thickness (base material thickness) of the force bar layer is S100 μm is particularly important. It is valid.

Further, in the present embodiment, only the read-only optical information recording medium has been specifically described. However, the present invention is not limited to this, and is applicable to a recordable write-once or rewritable optical information recording medium. However, the same effect can be obtained by recording the substrate thickness information on the information recording layer using a means such as a BCA mark.

[0032] Further, in the present embodiment, the base material thickness information is recorded as a barcode mark in the BCA, but is not limited to this, and may be recorded in another area of the information recording layer. Also, the mark shape is not limited to this, and may be another shape. At this time, it is preferable to record the base material thickness information using a mark shape that is lower than the recording density of other information recorded on the optical information recording medium.

[0033] The area for recording the base material thickness information is not limited to the information recording layer. For example, even on the cover layer or in the cover layer, if the area can be detected using an optical head, the place is not limited. Not limited.

[0034] Further, in the present embodiment, an optical information recording medium having a single-layer structure provided with only one information recording layer has been described. However, an optical information recording medium having a multilayer structure provided with a plurality of information recording layers has been described. It may be your body. In the case of an optical information recording medium having a multi-layered structure, first, because of focus servo shading, the thickness of the base material information is recorded in the information recording layer located closest to the light incident side or the information recording layer located closest to the opposite light incident side. It is preferably recorded. Further, the substrate thickness information recorded at this time is recorded from the light incident surface of the medium. Desirably, the distance to the surface of the information recording layer.

(Embodiment 2)

An embodiment of the information recording / reproducing apparatus of the present invention will be described. FIG. 4 is a block diagram showing a main configuration of the information recording / reproducing apparatus of the present embodiment. The optical information recording medium 201 set in the information recording / reproducing apparatus shown in FIG. 4 has the same configuration as the optical information recording medium described in the first embodiment.

The information recording / reproducing apparatus according to the present embodiment includes a spin-doner motor 202 for rotating a set optical information recording medium 201, and a semiconductor laser. An optical head (reproducing means) 203 for recording information by condensing the information on the layer and obtaining a reproduction signal from the reflected light; a moving mechanism 204 for moving the optical head 203 in the radial direction of the optical information recording medium 201; A focus control circuit 205 for controlling the optical head 203 based on a focus error signal generated from the reproduction signal, and a tracking control circuit for controlling the optical head 203 based on a tracking error signal generated from the reproduction signal 206, a reproduction signal processing unit 207 for processing an information reproduction signal included in the reproduction signal, and a correction value storage unit (correction value storage means) 208 for storing a spherical aberration correction value set according to the thickness of the base material. When A system control unit (correction value determination unit) 209 that determines a correction value of spherical aberration using a correction value storage unit 208 from base material thickness information obtained when the BCA of the optical information recording medium 201 is reproduced; A spherical aberration control circuit (spherical aberration correcting means) 210 for correcting the spherical aberration of the optical head 203 based on the correction value determined by the control unit 209. The spherical aberration control circuit 210 also controls the spherical aberration of the optical head 203 at the time of learning to optimize the spherical aberration using the spherical aberration corrected based on the base material thickness information as an initial value. The system control unit 209 has a function as a correction value determining unit for determining correction of spherical aberration, and further includes an entire system including an optical head 203, a focus control circuit 205, a tracking control circuit 206, and a spherical aberration control circuit 210. Is controlling.

[0037] The operation of correcting spherical aberration in the information recording / reproducing apparatus of the present embodiment will be briefly described.

First, after setting and rotating the optical information recording medium 201 on the spindle motor 202, the optical information recording medium 201 is irradiated with a laser beam for information reproduction by the optical head 203. this At this time, first, the BCA of the optical information recording medium 201 is focused and irradiated with a laser beam to read out the substrate thickness information. The reading of the base material thickness information is performed by processing the information reproduction signal obtained from the reflected light from the optical information recording medium 201 by the optical head 203 in the reproduction signal processing unit 207, and converting the obtained base material thickness information signal into a system. This is performed by taking it into the control unit 209.

Next, a correction value of the spherical aberration according to the thickness of the base material is determined. The system control unit 209 determines the correction value of the spherical aberration based on the obtained base material thickness information using the correction value storage unit 208 in which the relationship between the base material thickness and the correction value of the spherical aberration is stored. Information on the determined correction value is taken into the spherical aberration control circuit 210.

Next, the spherical aberration control circuit 210 corrects the spherical aberration of the optical head 203 based on the determined spherical aberration correction value.

After that, learning for optimizing the spherical aberration is performed using the corrected spherical aberration as an initial value. The learning is performed, for example, as follows.

For example, after correcting the spherical aberration of the optical head 203 using the above initial value, the correction value of the spherical aberration is changed based on the information reproduction signal obtained from the reflected light from the optical information recording medium 201, A correction value that maximizes the information reproduction signal amplitude is searched for. Further, the jitter (fluctuation) of the information reproduction signal is detected, and the correction value is finely adjusted so as to minimize the jitter. When there is a correlation between the amplitude of the tracking signal and the spherical aberration, a tracking signal may be used instead of the information reproduction signal.

According to the information recording / reproducing apparatus of the present embodiment as described above, the time required for correcting spherical aberration can be reduced.

Industrial applicability

[0044] The optical information recording medium and the information recording / reproducing apparatus according to the present invention provide a high-density recording such as a BD in which recording / reproducing is performed using a lens having a thin base material and a high numerical aperture. The present invention can be effectively applied to a medium or an information recording / reproducing apparatus for recording / reproducing information on / from such a high-density recording medium.

Claims

The scope of the claims

[1] An optical information recording medium including at least one information recording layer from which information can be reproduced by light irradiation, based on a distance from a light incident surface of the optical information recording medium to a surface of the information recording layer. In the case of material thickness,

An optical information recording medium further comprising a base material thickness information recording section on which base material thickness information indicating the base material thickness is recorded.

[2] The optical information recording medium according to claim 1, wherein the base material thickness information recording section is formed on the information recording layer.

3. The optical information recording medium according to claim 1, wherein the base material thickness information is recorded at a lower recording density than other information recorded on the information recording layer.

4. The optical information recording according to claim 1, wherein a mark length of a recording mark used for recording the base material thickness information is longer than a recording mark used for recording other information recorded on the information recording layer. Medium.

[5] A plurality of information recording layers capable of reproducing information by irradiating light are provided, and the information recording layer located closest to the light incident side or located closest to the non-light incident side of the plurality of information recording layers is provided. 2. The optical information recording medium according to claim 1, wherein the base material thickness information recording portion is formed on the information recording layer to be formed.

[6] The base material thickness information recording section is formed with the base material thickness information recording section, and the base material thickness information is recorded on an information recording layer. An optical information recording medium according to claim 1.

7. The optical information recording medium according to claim 1, wherein the base material thickness information is recorded by a barcode-shaped mark.

[8] The optical information recording medium according to claim 1, wherein the thickness of the base material is 0.1 mm or less.

[9] The optical information recording medium according to claim 1, wherein information is reproduced by irradiating light having passed through a lens having a numerical aperture of 0.8 or more.

[10] An optical information recording medium including at least one information recording layer capable of reproducing information by light irradiation, wherein a distance from a light incident surface of the optical information recording medium to a surface of the information recording layer is determined by a thickness of a base material. In that case, the base material thickness on which the base material thickness information indicating the base material thickness is recorded An information recording / reproducing apparatus used for an optical information recording medium further including an information recording unit.

Reproducing means for reproducing the base material thickness information recorded on the optical information recording medium; and a correction value storing means in which a correction value of spherical aberration set according to the base material thickness is stored in advance;

Correction value determining means for determining a spherical aberration correction value using the correction value storage means, based on the base material thickness information obtained by the reproducing means;

Spherical aberration correcting means for correcting spherical aberration using the correction value determined by the correction value determining means,

An information recording / reproducing apparatus characterized by including:

Using the spherical aberration corrected using the correction value determined by the correction value determining means as an initial value, the spherical aberration is calculated using a signal obtained by reproducing information recorded on the optical information recording medium. The information recording / reproducing device according to claim 10, wherein learning for optimization is performed.