Patent Application
20070230321
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2006-075691, filed Mar. 17, 2006, the entire contents of which are incorporated herein by reference.
1. Field
One embodiment of the present invention relates to a multi-layered optical disk capable of recording and reproducing information from a light incidence face side to a plurality of recording films, and an optical disk device carrying out the recording and reproduction.
2. Description of the Related Art
An optical disk that serves as an information recording medium is widely utilized as conforming to a DVD standard, the optical disk being capable of recording video image and music contents. This kind of optical disk includes: a reproduction only type, a write once type capable of recording information only one time; and a rewrite type or the like represented by an external memory or a recording video and the like of a computer. The optical disk conforming to a DVD standard has a structure in which two substrates each having a thickness of 0.6 mm (nominal) are bonded with each other, NA of an objective lens is 0.6, and a wavelength of a laser beam for use in recording/reproduction is 650 nm. In recent years, there has been expectation for increasing storage capacity. As a technique of increasing storage capacity, there are exemplified: shortening a wavelength of a light source; increasing the number of apertures of an objective lens; improvement of a modulation/demodulation technique; improvement of formatting efficiency; multi-layering and the like. In an HD DVD standard, recording density is remarkably improved using a blue laser having a wavelength on the order of 405 nm to increase a capacity; the NA of the objective lens is set to 0.65, thereby enabling affinity with a current DVD. However, for the purpose of a further increase of a capacity, the multi-layering of an information recording medium has been promoted.
In such a multi-layered information recording medium, with respect to specifically how large each layer should be, patent document 1 describes a relationship indicated by a predetermined formula among an error (tolerance) in thickness of a light transmission layer and a thickness and wavelength between recording layers (between intermediate layers); the number of apertures; and a refractive index.
However, in a conventional technique of patent document 1 (Jpn. Pat. Appln. KOKAI Publication No. 2004-71046), there has been a problem that, in order to carry out sufficient information separation in a plurality of recording apparatuses without producing a spherical aberration, no specific example is shown as to specifically how large a transparent substrate and an adhesive layer should be in values, respectively.
A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.
Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, an optical disk comprising: a substrate layer (11) having a refractive index of 1.50 to 1.70 and a thickness X (μm) equal to or greater than f (n)−13 μm; a first information layer (12) formed on the substrate layer; an adhesive layer (13) formed on the first information layer and having a thickness Y (μm) equal to or greater than 20 μm; and a second information layer (14) formed on the adhesive layer, wherein X+Y≦f (n)+30 μm and f (n)<X+Y/2 are satisfied and f (n) is given by the formula: f (n)=(A1×n3)(n2+A2)/(n2−1)(n2+A3)×1000 (μm), where “n” is a refractive index of the substrate layer; A1 is 0.26200; A2 is −0.32400; and A3 is 0.00595.
Now, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
(Configuration)
First, a configuration of an optical disk D according to an embodiment of the present invention will be described with reference to the accompanying drawings. As shown in
(Problems and Countermeasures)
In a multi-layered disk made of two or more layers, there is a problem that a reproduction signal quality is degraded due to a spherical aberration or due to leakage of a signal from a non-reproduction layer. In order to restrict the occurrence of the signal leakage (inter-layer crosstalk) from the non-reproduction layer while reproducing an information recording layer and the degradation of the reproduction signal quality, it is necessary to provide a sufficient thickness of an intermediate layer, and it is desirable that a thickness Y of an adhesive layer formed between a first information layer and a second information layer be 20 μm or more. However, if the sufficient thickness of the intermediate layer is provided, a distance up to the information recording layer greatly deviates from a distance at which a spherical aberration becomes minimal; and an influence caused by the spherical aberration becomes great. Thus, it is desirable that the thickness Y of the adhesive layer be 35 μm or less.
With respect to an influence of the spherical aberration, in an HD DVD, a recording/reproducing optical system is designed to be optimal to record and reproduce an information recording layer over a substrate having a thickness of 0.6 mm. Thus, if the distance up to the information recording layer deviates from this optimal value, a beam spot is distorted and enlarged due to the influence of the spherical aberration, and then, a recording/reproduction signal is degraded. An allowable deviation from the optimal distance based on a result of simulation using a one-layered optical disk with a film free of light transmission property is obtained to be ±30 μm. In addition, when an access is provided to an information recording layer allocated to the depth with respect to a laser beam incident face, it is necessary for the laser beam to transmit a frontal information recording layer. However, in order to prevent light from being attenuated more than necessary, it is necessary to ensure a sufficient transmittance. Therefore, it is necessary to decrease the thickness of a recording film or a reflection film in the frontal information recording layer, and thus a reproduction signal quality is degraded.
Accordingly, it is desirable that the thickness X of a substrate layer be f (n)−13 μm or more and that the thickness of an adhesive layer formed between a first information layer and a second information layer be X+Y≦f (n)+30 μm and f (n)<X+Y/2 with respect to Y. In this manner, reproduction signal quality degradation due to a spherical aberration and signal leakage from a non-reproduction layer is reduced, making it possible to improve a recording/reproduction signal in the two information layers.
Here, the following formula is established:
f(n)=(A1×n3)(n2+A2)/(n2−1)(n2+A3)×1000 (μm), where “n” is a refractive index of the substrate layer; A1 is 0.26200; A2 is −0.32400; and A3 is 0.00595.
Reflection Index
Further, it is desirable that a reflection index from the first information layer or the second information layer be 3% to 10% with respect to a wavelength of a laser beam for carrying out recording/reproduction. If a reflection light quantity is small, an SN ratio becomes short on the side of a recording/reproducing apparatus, thus requiring a reflection index equal to or greater than 3%. However, at a high reflection index, a light quantity absorbed by a recording film decreases correspondingly, and recording sensitivity is lowered. In order to enable recording at an equal light quantity with respect to the two information layers, it is necessary for a reflection index to be 10% or less in an optical disk in which transmittance of the first information layer is 50% to 55%. In addition, if a reflection index difference between a reproduction layer and a non-reproduction layer is increased, the signal leakage from a layer in which a reflection index is high to a layer in which a reflection index is low becomes great. Thus, it is desirable that a reflection index difference between the two information layers be ±20% or less (in addition, it is preferable that the reflection index from the second information layer with respect to the reflection index from the first information layer be between 0.8 time to 1.2 times as an example). In addition, in the two-layered optical disk, tracking becomes unstable because the reflection index is lower as compared with a one-layered optical disk. In the case where a guide groove depth is shallow or deep, a push-pull signal becomes small. Thus, a guide groove depth of 25 nm to 80 nm (or 25 nm to 100 nm) is required in both of the first information layer and the second information layer to enable stable tracking. The guide groove width is required to be 0.4 μm or less for the purpose of high density recording.
Information Layer
At least one of the first information layer 12 and the second information layer 14 can be reversibly recorded/erased using light, and is equipped with a substrate, a recording film capable of reversibly changing an atomic sequence, a protective film, and a reflection film.
As the recording layer capable of reversibly changing the atomic sequence, it is preferable to use a phase change recording film such as a Ge—Sb—Te based alloy; a Ge—Sb—Bi—Te based alloy; a Ge—Bi—Te based alloy; a Ge—Sb—In—Te based alloy; a Ge—Bi—In—Te based alloy; a Ge—Sb—Bi—In—Te based alloy; a Ge—Sn—Sb—Te based alloy; an Ag—In—Sb—Te based alloy; an In—Ge—Sb—Te based alloy; or an Ag—In—Ge—Sb—Te based alloy. In the case where these materials are used, it is preferable to provide a film having a crystallization promoting function on one face or both faces of the phase change recording film. In addition, a dielectric material such as ZnS—SiO2 and a reflection layer material such as an Ag alloy or an Al alloy are used together in consideration of an environment resistance property or repetition recording property.
In addition, at least one of the first information layer 12 and the second information layer 14 may only carry out reversible recording using light. In this case, it is desirable for the information layer to contain an organic pigment material having light absorption in the range of laser beams to be used. As organic pigment materials, there are exemplified a cyanine pigment, a phthalocyanine pigment or the like (a description of a two-layered R pigment material is to be inserted). These materials are used together with a reflection layer material such as an Ag alloy, an Al alloy, or an Au alloy.
The substrate thickness and adhesive layer thickness can be measured by means of mechanical characteristic evaluation devices for optical disks. These evaluation devices can carry out measurement from a difference in light travel paths by utilizing a plurality of different wavelengths or by using a plurality of incidence angles at a single wavelength. In addition, the substrate thickness X (μm) and the adhesive layer thickness Y (μm) are optical disk intra-planar average values.
With respect to a recording/reproducing apparatus for carrying out recording/reproduction with respect to a two-layered optical disk according to the present invention, in addition to a current recording/reproducing apparatus, there is a need for a mechanism of identifying how many layers an inserted optical disk is made of; a mechanism of carrying out focusing on each layer; and a mechanism of carrying out recording/reproduction with respect to each of the focused information recording layers. In addition, a mechanism for spherical aberration correction may be required for an optical system depending on a situation.
In a two-layered disk that enables recording by using a disk structure and a disk manufacturing method, a material, and a recording/reproducing apparatus as described above, a good reproduction signal quality can be obtained from two information layers, making it possible to improve recording capacity.
(First Test Data:
First test data is intended to verify a proper value of the substrate thickness X while the adhesive layer thickness Y is fixed. That is, in a two-layered optical disk, a first information layer is required to form a film having light transmittance equal to or greater than 50% in recording/reproduction wavelength. Thus, using the film that meets this condition, there was verified an influence on a reproduction signal quality, the influence being caused by a spherical aberration. In this test, because a substrate with refractive index “n” of 1.60 is used as a substrate layer, f (n)=600 μm is established. In addition, an optical disk having only a first information layer was used in order to eliminate an influence caused by leakage of a signal from a non-reproduction layer.
With respect to the above two-layered optical disk, recording was carried out using an optical head having a wavelength of 405 nm and an NA of 0.65. The disk was rotated at a linear velocity of 6.6 m/s; a clock frequency was set to 64.8 MHz; and signals from 2T to 11T were measured by randomly recording them.
Therefore, the above influence can be avoided as long as the substrate thickness X 587 μm or more, and the reliability of a system described in the embodiments was successfully verified.
(Second Test Data:
Second test data is intended to verify that, in order to avoid an influence caused by a spherical aberration, a thickness Y of an adhesive layer is required to 20 μm or more by checking the influence caused by signal leakage from a non-reproduction layer.
Here,
Namely, from
In the third embodiment, assuming a case in which the first information layer is influenced by an spherical aberration, an influence of the thickness Y of the adhesive layer on the recording/reproduction characteristics of the first information layer was measured at the CNR and SbER under the same condition as that for the above test data, by defining the thickness X of the transparent substrate 11 as 583 μm. The CNR was obtained to be equal to or greater than 53 dB, regardless of the thickness Y of the adhesive layer in the same manner as the case in which there is no influence of the spherical aberration. The SbER showed no influence of the thickness Y of the adhesive layer unlike the case in which there is no influence of the spherical aberration, and was on the order of 1E-4 in thickness Y of any adhesive layer.
From these results of Comparative Example 1 as well, it is verified that the thickness X of the transparent substrate 11 is required to be 587 μm.
(Third Test Data:
Third test data is intended to verify that 600 μm<X+Y/2 is satisfied. An influence of the thickness X of the transparent substrate and the thickness Y of the adhesive layer is verified as to a case in which an influence is caused by a spherical aberration and a signal leakage from a non-reproduction layer obtained as the same condition as that for an actual two-layered optical disk.
That is,
Referring to
(Fourth Test Data:
The fourth test data is intended to specify a relationship between X+Y/2 when Y=20 μm and the reproduction characteristics after multi-track recording. That is,
In this manner, it is found that good recording/reproduction characteristics are obtained in the first information layer and the second information layer in the range of 600 μm<X+Y/2. As described above, in a recording type two-layered optical disk, by optimizing the thickness of the transparent substrate 11 and the thickness of the adhesive layer, the lowering of a reproduction signal quality due to a spherical aberration or due to signal leakage from a non-reproduction layer can be reduced to the minimum in the first information layer having light transmittance, enabling high density recording.
As a result, when a value of X+Y/2 is greater than 600, good reproduction characteristics can be obtained, making it possible to confirm that signal degradation can be avoided in f (n)<X+Y/2.
(Fifth Test Data:
Fifth test data specifies a reproduction characteristic radial tilt margin of the first information layer with respect to a two-layered optical disk when X=587 μm and X+Y/2=601 μm. That is,
In the sixth embodiment described above,
A second embodiment specifies that a guide groove of a first information layer 22 is provided on a transparent substrate 21 and that a guide groove of a second information layer 24 is provided on a substrate 25. Here, a guide groove is not provided in an adhesive layer 23.
That is, in
In addition, the guide grooves formed in these first and second information layers are capable of carrying out recording into only a guide groove that is closer to the laser beam incidence side. In addition, the guide grooves formed in these first and second information layers are capable of carrying out recording into only a guide groove that is distant from the laser beam incidence side. Similarly, it is preferable to carry out recording into both of the guide grooves formed in the first and second information layers.
A third embodiment specifies that a guide groove of a first information layer 32 is provided on an adhesive layer 33 and that a guide groove of a second information layer 34 is also provided on the adhesive layer 33. Here, a guide groove is not provided in a transparent substrate 31 and a substrate 35.
That is, the guide grooves provided in the first information layer 12 and the second information layer 14 in
In addition, the guide grooves formed in these first and second information layers are capable of carrying out recording into only a guide groove that is closer to the laser beam incidence side. In addition, the guide grooves formed in these first and second information layers are capable of carrying out recording into only a guide groove that is distant from the laser beam incidence side. Similarly, it is preferable to carry out recording into both of the guide grooves formed in the first and second information layers.
A fourth embodiment specifies that a guide groove of a first information layer 42 is provided on a transparent substrate 41 and that a guide groove of a second information layer 44 is provided on an adhesive layer 43. Here, a guide groove is not provided in a substrate 45.
That is, the guide groove provided in the first information layer 12 in
In addition, the guide grooves formed in these first and second information layers are capable of carrying out recording into only a guide groove that is closer to the laser beam incidence side. In addition, the guide grooves formed in these first and second information layers are capable of carrying out recording into only a guide groove that is distant from the laser beam incidence side. Similarly, it is preferable to carry out recording into both of the guide grooves formed in the first and second information layers.
A fifth embodiment specifies that that a guide groove of a first information layer 52 is provided on an adhesive layer 53 and that a guide groove of a second information layer 54 is provided on a substrate 55. Here, a guide groove is not provided in a transparent substrate 51.
That is, the guide groove provided in the first information layer 52 in
In addition, the guide grooves formed in these first and second information layers are capable of carrying out recording into only a guide groove that is closer to the laser beam incidence side. In addition, the guide grooves formed in these first and second information layers are capable of carrying out recording into only a guide groove that is distant from the laser beam incidence side. Similarly, it is preferable to carry out recording into both of the guide grooves formed in the first and second information layers. CL Sixth Embodiment:
A sixth embodiment specifies an example of an optical disk device for carrying out recording/reproducing processing operation of the two-layered optical disk described above.
In an optical disk device 110, a digital television having a recording function is shown while a tuner or the like is defined as a source. In addition, it is preferable that the optical disk device 110 be a hard disk recorder having tuner, recording functions and the like.
Therefore, in a description of an embodiment with reference to
In
In addition, the optical disk device 110 of
Further, the optical disk device 110 has an operating unit 132 that is connected to the control unit 130 via the data bus B, the operating unit receiving an operation of a user or an operation of a remote controller R. Here, the remote controller R enables an operation that is substantially identical to the operating unit 132 provided at a main body of the optical disk device 110 and enables a variety of settings such as a recording/reproducing instruction and an edit instruction from the hard disk drive unit 118 and the optical disk drive unit 119 or a tuner operation, settings of reserved image recording or the like.
(Basic Operation)
Recording Processing Operation
Now, an operation at the time of recording will be described in detail including another embodiment. As an input side of the optical disk drive 110, the communication unit 111 such as LAN is connected to an external device to make communication with a program information providing server or the like via a communication channel such as the Internet via a modem or the like, for example, or to download broadcast contents or the like. In addition, the BS/CS digital tuner unit 112 and the terrestrial digital/analog tuner unit 113 select a broadcast signal as a channel via an antenna, demodulates the selected signal, inputs a video image signal and a voice signal, and responds to various types of broadcast signals. For example, the above signals cover a terrestrial analog broadcast, a terrestrial digital broadcast, a BS analog broadcast, a BS digital broadcast, a CS digital broadcast and the like without being limited thereto. In addition, the above case not only includes providing only one element, for example, but includes a case of providing two or three or more terrestrial tuner units and BS/CS tuner units to function in parallel in response to a request for reserved image recording.
In addition, the communication unit 111 described previously, may be an IEEE1394 interface and can receive digital contents from an external device over a network. In addition, it is possible to receive a luminance signal, a color difference signal, a video image signal such as a composite signal, and a voice signal from an input terminal, although not shown. These signals are selectively supplied to the encoder unit 121 while an input is controlled by means of the selector 116 controlled under the control unit 130 or the like.
The encoder unit 121 has a video and audio analog/digital converter, a video encoder, and an audio encoder, the converter digitizing an analog video signal or an analog audio signal inputted by means of the selector 116. Further, this encoder unit also includes a subsidiary video image encoder. An output of the encoder unit 121 is converted into a predetermined MPEG compression format or the like, and then, the converted output is supplied to the control unit 130 described previously.
In addition, there is no need for the BS/CS digital tuner 112 or the like to be always incorporated, and it is also preferable that the tuner is externally provided via a data input terminal to supply a received digital signal to the encoder unit 121 or the control unit 130 via the selector unit 16.
Here, the equipment of
The signal editing unit 120 can carry out edit processing operations such as partially deleting video objects of a plurality of programs recorded in the hard disk drive unit 118 or the optical disk D or connecting objects of different programs.
Reproducing Processing Operation or the Like
Now, a processing operation of reproducing mainly recorded information will be described in detail including other embodiments.
The MPEG decoder unit 123 is equipped with a video processor for properly combining a decoded subsidiary video image on a decoded main video image, and then, superimposing and outputting a menu, a highlight button, subtitles or other subsidiary video image on the main video image.
An output audio signal of the MPEG decoder unit 123 is analogue-converted by means of a digital/analog converter, although not shown, via the selector unit 117 to be supplied to a speaker, or alternatively, is supplied to an external device via the interface (I/F) unit 127. The selector unit 117 is controlled by means of a select signal from the control unit 130. In this manner, the selector unit 117 is capable of directly selecting a signal having passed through the encoder unit 121 when a digital signal from each of the tuner units 12 and 13 is directly monitored.
The optical disk device 110 according to the present embodiment thus has comprehensive functions, and carries out recording/reproducing processing operation using the optical disk D or the hard disk drive unit 118 with respect to a plurality of sources.
A seventh embodiment specifies in detail an example of a standard of a two-layered optical disk that is the above described HD DVD.
(Parameters of Two-Layered Disk)
With reference to
Similarly, a use wavelength and an NA value of an objective lens are indicated with respect to the one-layered structure and the two-layered structure. In addition, as (A) numeral values in a system lead-in region and a system lead-out region, and further, as (B) numeral values in a data lead-in region, a data region, a middle region, and a data lead-out region, there are shown, with respect to the one-layered structure and the two-layered structure: a data bit length; a channel bit length; a minimum mark/pit length (2T); a maximum mark/pit length (13T); a track pitch; and a value of a physical address setting method.
Further, with respect to the one-layer structure and the two-layered structure, there are shown: an outer diameter of an information storage medium; a total thickness of the information storage medium; a diameter of a center hole; an internal radius of a data region DTA; an outer radius of the data region DTA; a sector size; ECC; an ECC block size; a modulation system; an error correctable error length; and a linear velocity.
Further, with respect to the one-layered structure and the two-layered structure, a channel bit transfer rate and a user data transfer rate are shown as numeral values in (A) the system lead-in region and the system lead-out region, and further, as numeral values in (B) the data lead-in region, the data region, the middle region, and the data lead-out region.
(Wobble Structure of Two-Layered Optical Disk)
Now, with reference to the accompanying drawings, a description will be given here in detail with respect to HD DVD that is a two-layered optical disk according to the present invention, and in particular, primarily with respect to a wobble structure and features thereof.
Next, the inside of wobble data units #0560 to #11571 is composed of a modulation region 598 for 16 wobbles and no-modulation regions 592 and 593 for 68 wobbles, as shown in
When the control moves from the no-modulation regions 592 and 593 to the modulation region 598, an IPW region serving as a modulation start mark is set by using four wobbles or six wobbles. Then, a wobble data region as shown in (c) and (d) on
In a wobble address region 610, a 3-address bit is set at 12 wobbles. Namely, a 1-address bit is composed of continuous 4 wobbles. As described above, the present embodiment employs a structure in which address information is assigned after dispersed every 3-address bit. If the wobble address information 610 is intensively recorded in one site in the information storage medium, when dust or scratch adheres to a surface, all information becomes difficult to be detected. As described in the present embodiment, there is an advantageous effect that wobble address information 610 is assigned after dispersed every 3-address bit included in one of the wobble data units 560 to 576; information collected every integer-multiple address bit of the 3-address bits is recorded; and, even in the case where it is difficult to detect information contained in one site due to influence of dust or scratch, another item of information can be detected.
As described above, the wobble address information 610 is assigned in a dispersed manner and the wobble address information 610 is completely assigned every 1-physical segment, thus making it possible to identify address information every physical segment. Therefore, when the information recording/reproducing apparatus provides an access, it is possible to know a current position in units of physical segments.
By employing an NRZ technique according to one embodiment, a phase does not change in continuous 4 wobbles in the wobble address region 610. Utilizing this feature, the wobble sink region 580 is set. That is, a wobble pattern that cannot be generated in the wobble address information 610 is set with respect to the wobble sink region 580, thereby making it easy to identify a layout position of the wobble sink region 580. The present embodiment is featured in that a 1-address bit length is set at a length other than 4 wobbles at a position of the wobble sink region 580 with respect to the wobble address regions 586 and 587 that configure 1-address bit with continuous 4 wobbles. That is, in the wobble sink region 580, as shown in (a) and (b) on
(1) wobble detection (wobble signal judgment) can be stably continued without distorting a PLL relating to a slot position of a wobble carried out at a wobble signal detecting unit; and
(2) detection of the wobble sink region 580 and modulation start marks 561 and 582 can be carried out more easily due to a shift of an address bit boundary position carried out by the wobble signal detecting unit. In addition, the present embodiment is also featured in that the wobble sink region 580 is formed in a 12-wobble cycle, and a length of the wobble sink region 580 is caused to coincide with a 3-address bit length. In this manner, detection easiness of a start position of the wobble address information 610 (layout position of the wobble sink region 580) is improved by assigning all of the modulation regions (for 16 wobbles) contained in one wobble data unit #0560 to the wobble sink region 580. This wobble sink region 580 is assigned to a first wobble data unit in a physical segment. In this manner, there occurs an advantageous effect that the wobble sink region 580 is assigned at a start position in a physical segment, making it possible to easily sample a boundary position of the physical segment merely by detecting a position of the wobble sink region 580.
As shown in (c) and (d) on
For reference, the following contents of the wobble address information 610 in the rewrite type information storage medium shown in (a) on
Physical segment address 601
(2) Zone address 602
(3) Parity information 605
(4) Unity region 608
(a) on
As shown in (b) and (c) on
Layer number information 722 in the write-once type information storage medium shown in (b) on
when “0” is set, “L0 layer” (frontal layer at the laser beam incidence side) in the case of a one-sided 1 recording layer medium or a one-sided 2 recording layer;
when “1” is set, “L1 layer” of a one-sided 2 recording layer (layer on the depth side of the laser beam incidence side).
Physical segment sequence information 724 indicates a layout sequence of relative physical segments in the same physical segment block. As is evident in comparison with (a) on
A data segment address 725 shown in (b) on
In a CRC code 726 shown in (b) and (c) on
In the write-once type information storage medium, a region equivalent to the remaining 15 address bits is assigned to a unity region 609, and the inside of 5 wobble data units from 12th to 16th data units is wholly obtained as NPW (modulation region 598 does not exist).
A physical segment block address 728 shown in (c) on
The physical segment sequence information 724 represents the sequence of the physical segments in 1 physical segment block, “0” is set with respect to the first physical segment, and “6” is set with respect to the last physical segment.
The embodiment shown in (c) on
The inside of the segment information 727 is composed of type identification information 721 and a reservation region 723.
The present embodiment is featured in that the type identification information 721 is assigned immediately after the wobble sink region 580 in (c) on
(Method for Measuring Wobble Detection Signal)
With reference to a flow chart shown in
Next, in step ST02, a linear velocity is adjusted by changing a rotation frequency of a disk so that a wobble signal frequency is set at a predetermined value.
In the present embodiment, a predetermined value of a signal frequency of a wobble is set to 697 kHz because an H format is used.
Now, a description will be given with respect to a example of measuring a maximum value (Cwmax) and a minimum value (Cwmin) of a carrier level of a wobble detection signal.
A wobble phase between the adjacent tracks changes depending on a track position because the write-once type storage medium according to the present embodiment uses a CLV (Constant Linear Velocity) recording system. In the case where there has been a coincidence in wobble phase between the adjacent tracks, a carrier level of a wobble detection signal becomes the highest, and then, the maximum value (Cwmax) is obtained. In addition, when the wobble phase between the adjacent tracks is reversed in phase, the wobble detection signal becomes the lowest under the influence of a cross talk of the adjacent tracks, and the minimum value (Cwmin) is obtained. Therefore, in the case where tracing is carried out from the inner periphery to the outer periphery along a track, the magnitude of a carrier of a wobble detection signal to be detected fluctuates at a 4-track cycle.
In the present embodiment, a wobble carrier signal is detected on a 4 by 4 track basis, and then, the maximum value (Cwmax) and the minimum value (Cwmin) on a 4 by 4 track basis is measured. Then, in step S03, a pair of the maximum value (CWmax) and the minimum value (Cwmin) is stored as data of 30 or more pairs.
Next, using the computing formula below, in step ST04, a maximum amplitude (Wppmax) and a minimum amplitude (Wppmin) are computed from an average value of the maximum value (Cwmax) and the minimum value (Cwmin).
In the formula below, R represents a terminated resistance value of a spectrum analyzer.
Now, a description will be given with respect to a formula of computing Wppmax and Wppmin from the values of Cwmax and Cwmin.
In a dBm unit system, 0 dBm=1 mW is defined as a reference. Here, a voltage amplitude Vo when power Wa=1 mW is obtained is as follows:
Therefore, Vo=(R/1000)1/2 is obtained.
Next, a relationship between a wobble amplitude Wpp [V] and a carrier level Cw [dBm] monitored by the spectrum analyzer is obtained as follows. Here, Wpp is a sine wave, and thus, when the amplitude is represented as an effective value, it follows:
Wpp−rms=Wpp/(2×21/2)
Cw=20×log(Wpp−rms/Vo) [dBm] is obtained.
Therefore, it follows:
Cw=10×log(Wpp−rms/Vo)2
When log in the above formula is converted, it follows:
Now,
Next, a (I1-I2) signal that is a track shift detection signal detected by an optical head shown in (a) on
A description will be given with respect to an internal structure of an optical head that exists in an information recording/reproducing unit. As shown in (a) on
The optical detector 1025 is composed of an optical detection cell 1025-1 and an optical detection cell 1025-2. A difference between signals 11 and 12 detected from the respective detection cells 1025-1 and 1025-2 can be obtained, and then, these signals are inputted to a wobble signal detecting unit, although not shown. As shown in (a) on
When a track loop is turned ON, a bandwidth of a wobble frequency is higher than a tracking bandwidth, and thus, a wobble signal is detected from an optical head. Here, when wobble phases of pre-grooves between the adjacent tracks are equal to each other, the maximum amplitude of Wppmax is obtained. When the wobble phase is reversed, a wobble signal amplitude is lowered under the influence of a cross talk of the adjacent tracks, and the minimum amplitude is obtained as Wppmin.
In the present embodiment, a contrivance is made so as to specify a condition between the maximum amplitude (Wppmax) and the minimum amplitude (Wppmin), and enable more stable wobble detection. That is, the wobble signal detecting unit is designed so that, even if the amplitude value of the wobble detection signal changes up to a maximum of 3 times, a signal can be stably detected. In addition, it is desirable that a change rate of an amplitude of a wobble detection signal be equal to or smaller than ½ under the influence of a cross talk.
Therefore, in the present embodiment, an intermediate value thereof is taken, and a value obtained by dividing an allowed maximum value of a wobble signal by a minimum value of the wobble signal (Wppmax÷Wppmin) is set to be 2.3 or less.
In the present embodiment, the value of (Wppmax÷Wppmin) is set to be 2.3 or less, whereas it is possible to stably detect a signal even if the value of (Wppmax÷Wppmin) is 3 or more in view of the performance of the wobble signal detecting unit. In addition, in the case of carrying out wobble detection with high precision, the value of (Wppmax÷Wppmin) can be 2.0 or less. The wobble amplitude of the pre-groove region 1011 is set so as to meet the conditions described above.
In the case where a track loop is turned OFF as shown in (b) on
Now, with reference to
In step ST11, a signal of (I1-I2) obtained from an optical head shown in (a) on
In step ST12, an amplitude value is measured on a track by track basis in response to a low-pass filter output, and 30 or more samples are accumulated.
In step ST13, (I1-I2) pp is obtained by taking an average of the samples obtained in step ST12.
A wobble signal detecting unit, although not shown, detects a wobble signal and detects a track shift detection signal by using the same detector circuit. The wobble signal detecting unit, although not shown, detects the wobble signal and the track shift detection signal, thereby making it possible to process (share) two works by one detector circuit, and thus, making it possible to promote circuit simplification.
(Method for Measuring NBSNR)
Now, with reference to a flow chart shown in
Now, a description will be given with respect to a reason why a square circuit (1033 in
Thus, when a wavelength of a wobble detection signal shown in (a) on
On the contrary, as shown in (b) on
One skilled in the art can achieve the present invention in accordance with a variety of embodiments described above. Further, it would be obvious to one skilled in the art to conceive a variety of modified examples of these embodiments. The present invention can be applied to a variety of embodiments even if one does not have any inventive capability. Therefore, the present invention covers a broad range without departing from the disclosed principle and novel features, and is not limited to the embodiments described above.
While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-075691 | Mar 2006 | JP | national |
