Abstract: Provided are an electric field read/write device and a method of driving an electric field read/write device. The method including an electric field read/write head comprising a resistance region disposed between a source region and a drain region and a writing electrode disposed on the resistance region, wherein the method includes: applying a controlling voltage to the writing electrode, wherein the controlling voltage is smaller than a threshold voltage which causes polarization of a recording medium, and reproducing data recorded in the recording medium according to change of an amount of a current flowing through the resistance region according to a polarization direction of electric domains of the recording medium.

Abstract: An optical reproducing apparatus connectable to optical pickups and a method of controlling an optical pickup thereof are provided. The optical reproducing apparatus measures resistance of an optical pickup on a port of a connection unit to which the optical pickup is connected, and determines the type of the optical pickup according to the measured resistance. Accordingly, optical reproducing apparatuses may be controlled according to the type of optical pickups, and manufactured using various optical pickups without checking the type of optical pickups, which allows convenient manufacturing of optical reproducing apparatuses.

Abstract: An information recording medium is provided that includes a recording portion (3), which is irradiated with a recording light or a reproducing light so that information is recorded or reproduced thereto or therefrom. The recording portion (3) contains a first phosphor and a photon-mode photosensitive material. The first phosphor has a property of absorbing a first light having a wavelength of ?1/n and then emitting a second light having a wavelength longer than that of the first light, where ?1 is a wavelength of the recording light. The photosensitive material absorbs the second light and then exhibits a change in an optical constant thereof. A n-photon absorption sensitivity of the first phosphor with respect to the recording light is greater than a n-photon absorption sensitivity of the photosensitive material with respect to the recording light, where n is an integer not less than 2.

Abstract: A control portion instructs supply of an offset voltage while a disk remains stopped at the time of start. While the disk remains stopped at the time of start, a differential operational amplifier detects a voltage difference between a first voltage supply line and a second voltage supply line. When the absolute value of the voltage difference output by the differential operational amplifier is equal to or lower than a prescribed threshold value, a failure determination portion determines that a spindle motor has shorted out.

Abstract: An optical drive apparatus includes: a phase-difference detection-signal generating unit that generates PEDr based on PEROd and PEFOd obtained by delaying a phase-lead output signal indicating a phase lead amount of DA with respect to DB and X that is changed to high at a timing at which NAND of the DA and the DB is changed from high to low and changed to low at a timing at which OR of the DA and the DB is changed from high to low, and generates PADr based on PAROd and PAFOd obtained by delaying a phase-lag output signal indicating a phase lag amount of the DA with respect to the DB by a predetermined time and the X; and a DPD signal generating unit that generates a phase difference signal indicating a phase difference between the DA and the DB based on the PEDr and the PADr, and generates a DPD signal based on the phase difference signal.

Abstract: According to one embodiment, single-sided dual-layer recordable disc 100 may be used. Information recording is performed by forming mark and space portions on data area DA using modulated laser power. Pp denotes the maximum laser power or peak power for forming the mark portion, and Pb denotes the bias power for forming the space portion. Power ratio Pb/Pp is calculated for each of recording layers L0 and L1. Information is recorded on any of the recording layers L0 and L1 based on the result of calculation. Here, the calculated power ratio Pb/Pp changes among the recording layers L0 and L1, thereby optimizing the recording condition for a multi-layer recordable optical disc within relatively short time.

Abstract: An optical disc drive having an optical pickup head emitting a light beam to an optical storage medium, detecting the light beam reflected from the optical storage medium, and outputting a signal based on the received reflected light, having a jitter measuring unit measuring jitter in signals output from the optical pickup head and having an evaluation unit determining from the measured jitter if the optical storage medium is good or defective. The jitter measuring unit measures jitter in a train of 3T or longer marks or spaces from an optical storage medium to which digital information is recorded as a train of marks or spaces of length kT based on a period T and an integer k of two or more.

Abstract: The invention relates to the field of optical information recording. In order to prevent abusive or fraudulent use of storage media, the invention provides a process for intentional degradation of information by application of a laser power below the normal power for reading information recorded in super-resolution on the media. This process relies on the surprising observation that a laser power below the super-resolution read power produces an irreversible degradation of the information recorded. This observation has been made with regard to media composed of a three-layer structure comprising an InSb or GaSb layer between two ZnS/SiO2 layers. Application for protecting sensitive data.

Abstract: An environmental load information of an information recording medium is recorded on the information recording medium so as to recycle or dispose properly an information recording medium, which is not necessary any more. The information recording medium comprises a main information area (102) for recording or reproducing information and a recording area (101) for environmental load information, which is recorded with an environmental load information of the information recording medium.

Abstract: An optical information recording and/or reproducing apparatus comprises: a focusing unit (11) which collects generated near-field light on an optical disc (1); a first detector (17) which receives light reflected by the optical disc (1) and outputs an electric signal according to the quantity of the received light; and a distance control circuit (22) which controls the distance between the focusing unit (11) and a light entrance surface of the optical disc (1), using the electric signal that is output from the first detector (17), and the optical disc (1) has at least N (N is an integer of 2 or greater) number of information layers, and a distance d0 from the light entrance surface to a first information layer which is most distant from the light entrance surface and a distance dn from the light entrance surface to an Nth information layer which is closest to the light entrance surface satisfy the relationship of dn?d0×(1/25).

Abstract: To provide a dye to be used for an optical recording medium excellent in both high speed recording characteristics and reproduction durability. A dye having an azo compound represented by the following formula coordinated to a metal ion: wherein the ring A represents a nitrogen-containing heteroaromatic ring containing a carbon atom and a nitrogen atom; X represents C—R1R2, an oxygen atom, a sulfur atom or N—R3, wherein each of R1, R2 and R3 which are independent of one another, represents a hydrogen atom, a linear or branched alkyl group, an aralkyl group, a cycloalkyl group, a linear or branched alkenyl group, an aryl group or an acyl group represented by —COR4, wherein R4 is a hydrocarbon group or a heterocyclic group which may be substituted; and the benzene ring B represents a benzene ring which may have a substituent(s), provided that adjacent substituents in the benzene ring B may be mutually bonded to form a ring.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: A beam applying method includes the steps of: rotationally driving an optical recording medium, in which a signal is recorded and reproduced by applying a beam thereto and which has a recording layer on which the signal is recorded, a polarization element formed below the recording layer, and a reflecting film formed below the polarization element; and applying a beam to the rotating optical recording medium through a half-wavelength plate that is rotationally driven with the rotation of the optical recording medium.

Abstract: A compound having a good durability against light and capable of producing desired liquid crystallinity after polymerization, and a polymerizable liquid crystal composition containing such a compound, are provided. Further, an optical element having a good durability against light, and an optical information writing/reading device employing such an element, are provided. A compound represented by CH2?CR1—COO—R2-Cy-Ph-R3—OCO—CR4?CH2. R1 and R4 are each preferably a hydrogen atom. R3 is preferably a C1-6 alkylene group wherein an oxygen atom is present or not present at an end of the group to be bonded to a cyclic group, and wherein some or all of hydrogen atoms bonded to carbon atoms in the group may be substituted by fluorine atoms; or an alkylene group wherein an oxygen atom is present at an end of the group to be bonded to a cyclic group.

Abstract: A mounting structure for an optical member comprising: an optical member; a holding member having the optical member mounted thereon; and a position adjustment member disposed between the optical member and the holding member, the position adjustment member configured to adjust a mounting position of the optical member.

Abstract: The core of the present invention is a method and an apparatus for transformation of matter parameters through optical way. In course of said method, a multilateral pattern inside a sample matter is created by means of a specific imaging beam emitted by a light emitting device. The most significant application of the suggested method is for writing on optic data storage media. Further application concerns the analysis of the above-mentioned optical parameters, i.e. reading data from the storage media.

Abstract: In a multilayer optical disc having information layers conforming to a plurality of different optical disc standards, because the type of each information layer is not recorded in the other information layers, in read and write operations by a compatible optical disc device conforming to a plurality of optical disc standards, every time the information layer being accessed changes, it has been necessary to read the type of the information layer and select a method of generating a tracking error signal adapted to the type of information layer, so access has taken time. In order to solve the above problem, in the optical multilayer disc according to the present invention, having information layers conforming to a plurality of different optical disc standards, in an area in one of the information layers, information about the other information layers is recorded. The time required to access the other information layers can be reduced by using this information to select a tracking error signal generating method.

Abstract: In an optical information storage medium reproduction apparatus (10) for reproducing an optical information storage medium including a plurality of information recording layers each including a recording mark having a length shorter than an optical system resolution limit, reproduction laser power for reading an information recording layer closest to a reproduction-laser-incident surface of the optical information storage medium is set to be lower than reproduction laser power for reading an information recording layer farthest from the reproduction-laser-incident surface but not lower than minimum reproduction laser power that satisfies a reproduction signal characteristic that the optical information storage medium reproduction apparatus (10) requires.

Abstract: An optical information recording medium (100) of the present invention includes an information layer (011) that allows information to be recorded thereon and reproduced therefrom by irradiation with a laser beam (040). The information layer (011) includes a reflective layer (002), a first dielectric layer (003), a recording layer (005) capable of undergoing a phase change by the irradiation with the laser beam (040) and a second dielectric layer (007) formed in this order from a side opposite to a laser beam incident side. The recording layer (005) contains Ge, Sb and Te. When Ge, Sb and Te contained in the recording layer (005) are represented by GexSbyTez in atomic number ratio, x, y, and z satisfy 0.39?x?0.48, 0.02?y<0.11, 0.40?z<0.56, and x+y+z=1. The recording layer (005) has a thickness of at least 10 nm but not more than 15 nm.

Abstract: A hologram recording apparatus (300) records record information into a hologram recording medium (100) on which a hologram recording layer (11) and a position information recording layer (13). The hologram recording apparatus is provided with: a first recording device (101) for recording the record information into the hologram recording layer; and a second recording device (121) for setting an area portion of the position information recording layer in a recorded state, the area portion of the position information recording layer corresponding to an area portion of the hologram recording layer in which the record information is recorded.

Abstract: An object of the invention is to improve the quality of a servo signal and a reproduction signal. Shape-wise thicknesses tr1, tr2, . . . , and trN of a cover layer and first through (N?1)-th intermediate layers of an optical recording medium having refractive indexes nr1, nr2, . . . , and nrN are converted into thicknesses t1, t2, . . . , and tN of the respective layers having a predetermined refractive index “no” which makes a divergent amount equal to a divergent amount of a light beam resulting from the thicknesses tr1, tr2, . . . , and trN, a difference DFF between the sum of a thickness “ti” through a thickness “tj”, and the sum of a thickness “tk” through a thickness “tm” is set to 1 ?m or more (where i, j, k, and m are each any positive integer satisfying i?j<k?m?N), and the thicknesses t1, t2, . . . , and tN are calculated by products of a function f(n) expressed by the following formula (1), and the thicknesses tr1, tr2, . . . , and trN: f(n)=?1.088n3+6.1027n2?12.042n+9.

Abstract: Optical recording mediums, and methods and systems for manufacturing optical recording mediums are provided. The optical recording medium includes a substrate on which a recordable layer and a reflective layer are formed. The reflective layer includes a predefined proportion of at least copper and zinc, wherein the predefined proportion is 50-75% copper and 15-45% zinc by mass. The recordable layer can either be formed over the substrate or the reflective layer, and is configured to record data. A protective layer is also formed over the reflective layer or recordable layer.

Abstract: An optical pickup apparatus includes a first objective lens having a low numerical aperture (NA) suitable for a low-density recording medium, a second objective lens having a high NA suitable for a high-density recording medium, a first light source to generate a short-wavelength optical signal to use the first and second objective lenses, a first photo-detector to receive an optical signal, which is generated from the first light source, is focused on a recording medium by the first and second objective lenses, and is then reflected from the recording medium, and a beam splitter to perform a division of the optical signal generated from the first light source, to direct some parts of the divided optical signal to the first objective lens, and to direct the other parts of the divided optical signal to the second objective lens.

Abstract: An optical pickup device which can improve heat radiation efficiency and an optical disk apparatus including the optical pickup device are provided. The optical pickup device having a base (110), a laser unit (141), an optical system (140) which propagates a laser beam, and an adjusting member (142) includes a heat radiation part (146) which is fixed to a heat radiation surface (141b) of the laser unit and which conducts heat from the heat radiation surface to the adjusting member. Therefore, heat generated by the laser unit is transmitted to the adjusting member and then the base through the heat radiation part to make it possible to efficiently perform heat removal for the laser unit.

Abstract: The present invention provides an optical pickup device including: a light source for emitting light in a first wavelength range including a wavelength of 405 nm; an optical element for transmitting the light emitted from the light source and guiding the emitted light to an optical disc, and for transmitting light reflected from the optical disc and guiding the reflected light to a detector unit; a supporting member for supporting the optical element through an adhesive; a first light blocking member for blocking the light emitted from the light source from entering the adhesive when the optical element guides the emitted light to the optical disc; and a second light blocking member for blocking the light reflected from the optical disc from entering the adhesive when the optical element guides the reflected light to the detector unit.

Abstract: In a conventional multilayer optical disc, management information needs to be retrieved from the control area of its reference layer to find how many information layers there are in the optical disc. A multilayer optical disc according to the present invention has multiple information layers that are stacked one upon the other. The information layers include at least one layer on which layer number information, indicating its own place in the multiple information layers, and information about the total number of information layers included are both stored.

Abstract: An optical data recording medium, in which irradiation of a light beam is used for recording and/or reproducing data includes (i) a substrate having an a rise and/or a recess which are a light-incident surface, (ii) a reflective layer, provided on the light-incident surface of the substrate, for reflecting the light beam, (iii) a light absorption layer for converting, to heat, a light of the light beam to heat on the surface of the reflective layer, (iv) a reproducing layer, provided on the surface of the heat-light converting layer, having a transmittance that changes in accordance with a light intensity distribution of the light beam. The optical data recording medium is excellent in super-resolution property, and enables reproduction of a shorter mark length.

Abstract: In a multilayer optical disc having information layers conforming to a plurality of different optical disc standards, because the type of each information layer is not recorded in the other information layers, in read and write operations by a compatible optical disc device conforming to a plurality of optical disc standards, every time the information layer being accessed changes, it has been necessary to read the type of the information layer and select a method of generating a tracking error signal adapted to the type of information layer, so access has taken time. In order to solve the above problem, in the optical multilayer disc according to the present invention, having information layers conforming to a plurality of different optical disc standards, in an area in one of the information layers, information about the other information layers is recorded. The time required to access the other information layers can be reduced by using this information to select a tracking error signal generating method.

Abstract: In a multilayer optical disc having information layers conforming to a plurality of different optical disc standards, because the type of each information layer is not recorded in the other information layers, in read and write operations by a compatible optical disc device conforming to a plurality of optical disc standards, every time the information layer being accessed changes, it has been necessary to read the type of the information layer and select a method of generating a tracking error signal adapted to the type of information layer, so access has taken time. In order to solve the above problem, in the optical multilayer disc according to the present invention, having information layers conforming to a plurality of different optical disc standards, in an area in one of the information layers, information about the other information layers is recorded. The time required to access the other information layers can be reduced by using this information to select a tracking error signal generating method.

Abstract: A solid state image pickup device is provided which can reduce crosstalks between range finding photoelectric conversion elements (AF sensor) and photometry photoelectric conversion elements (AE sensor). The solid state image pickup device has an n-type epitaxial semiconductor region, a p-type first well region formed in the semiconductor region, a p-type second well region formed in the semiconductor region and electrically separated from the first well, an n-type first impurity doped region formed in the first well region and an n-type second impurity doped region formed in the second well, wherein a photometry photoelectric conversion element is formed by using the p-type first well region and n-type first impurity doped region, and a range finding photoelectric element is formed by using the p-type second well region and n-type impurity doped region.

Abstract: This invention directs to an optical disc assembly configured to receive an analyte which can be detected by a standard optical disc reader or an optical disc reader modified therefrom. The optical disc assembly may preferably be designed so that the optical disc reader can track the disc and detect the analyte concurrently and discriminably. The optical disc assembly contains or encodes optically readable features which are trackable by the optical disc reader and which have encoded speed information enabling the optical disc reader to rotate the optical disc assembly at a determinable speed. The optical disc assembly also includes an analyte section capable of receiving the analyte that can be detected by the optical disc reader.

Abstract: The invention relates to a master device which can be used in a method for producing a recording medium, a substantially spirally or concentrically running main track structure and at least one substantially spirally or concentrically running secondary track structure being formed on the master device, the secondary track structure being arranged on at least one side of the main track structure, the secondary track structure having discontinuities varying an optically detectable surface texture of the recording medium in such a way that at least first auxiliary information is represented on the recording medium.

Abstract: A recording medium, a recording/reproducing apparatus, and a recording/reproducing method are disclosed. The apparatus uses the number of record layers contained in a recording medium and a multi-wavelength light source including a plurality of optical signals having different wavelengths, and irradiates an optical signal emitted from a light source on each recording medium according to wavelengths of the light beams. As a result, the apparatus can effectively gain access to the recording medium including a plurality of record layers, such that it can simultaneously record/reproduce data in/from the recording medium.

Abstract: A data reading/writing head reading/writing data from/to a ferroelectric recording medium by using an electric field effect, includes a semiconductor body having a first plane on which an air bearing pattern is formed and a second plane crossing the first plane. A sensing unit is located on the second plane and reads data written to the ferroelectric recording medium, wherein the second plane is separated from the first plane, and a floating gate is disposed on the sensing unit, wherein an end of the floating gate extends to the first plane to guide an electric field from the ferroelectric recording medium to the sensing unit.

Abstract: An electric field sensor includes a substrate having a low resistive semiconductor layer doped with a high-density dopant as the top layer of the substrate, a high resistive semiconductor layer doped with a low-density dopant, the high resistive semiconductor layer located at a partial area on the low resistive semiconductor layer, and a conductive layer located on the high resistive semiconductor layer, wherein a change of an electric field is detected by a change of a current flowing through the low resistive semiconductor layer, the high resistive semiconductor layer, and the conductive layer.

Abstract: A system controlling recording on an optical disc is provided. A first counter performs a bit count according to provided channel bit clock signals. A second counter performs a sector count responsive to the bit count obtained by the first counter. The Land/Groove switch predicts machine uses the result of bit count and sector count to predict the land/groove switch point. The processor uses the physical ID (PID) to determine the track type of a sector at which a recording operation initiates. The power controller determines a recording power for the recording operation according to the Land/Groove switch predict machine.

Abstract: Universal multimedia distribution, storage, and playback systems, devices, and methods are disclosed herein. A media distribution kiosk located at a retail establishment provides a user with access to a multitude of different forms of digital multimedia that may be purchased and downloaded onto a portable media transporter device. The portable media transporter device may then be inserted into a media storage and playback device that is capable of transcoding and storing the media on a hard disk drive. Additionally, the media storage and playback device is capable of transcoding, storing, and playing information residing on various other media formats such as DVD (movies, audio, gaming software), CD, and memory cards. Digital rights management (DRM) security measures employed at the kiosk and at the transporter and storage/playback devices ensure the integrity of the media transferred to the user.

Abstract: An optical information recording and reproducing method for recording or reproducing information by irradiating pulsed laser diode light from a laser diode (LD) light source in which the resistance value of the LD light source is measured in an operating state, the measured LD light source resistance value is compared with a target resistance value, and the LD light source is heated when the LD light source resistance value is higher than the target resistance value, in order to maintain the LD light source resistance at a specified value or less.

Abstract: According to the present invention, multiple space bitmaps (SBMs #0 and #1 30) are provided for the user data area of each recording layer. A disc management structure update unit including one of those space bitmaps and a disc definition structure (TDDS 32) and having a size of one block is written on a management information area (TDMA 17). As a result, data including the disc definition structure (TDDS 32) can always be arranged in the first block at the top of the management information area (TDMA 17).

Abstract: According to an embodiment, a storage medium includes a transparent resin substrate having a concentric or spiral groove and a recording film formed on the groove on the transparent resin substrate, a recording mark being formed by irradiation of a laser beam, wherein a reproduction durability count in a case where reproduction is continuously carried out by a laser beam is 1,000,000 or more.

Abstract: An information storage medium according to the present invention has n information storage layers (where n is an integer and n?3), on which data can be written with a laser beam and which are stacked one upon the other. Each of the n storage layers has a test write zone for determining the recording power of the laser beam. When those n layers are counted from the one that is located most distant from the surface of the medium on which the laser beam is incident, there is a bigger radial location difference between the outer peripheral end of the inner one of the test write zones of ith and (i+1)th information storage layers (where i is an integer that satisfies 2?i?n?1) and the inner peripheral end of the other outer test write zone than between the outer peripheral end of the inner one of the test write zones of jth and (j+1)th information storage layers (where j is an integer that satisfies 1?j?i?1) and the inner peripheral end of the other outer test write zone.

Abstract: Information about a variation ratio of the recording power sensitivity, which varies depending on whether another recording layer is recorded or unrecorded, is recorded onto a disc control information area (DI) in advance. Moreover, based on this recording-power-sensitivity variation information, recording-power compensation is performed. The corresponding recording-power compensation method is classified into three types: (1) type in which the recording is performed by judging the recorded/unrecorded states of another layer, (2) type in which, instead of judging the recorded/unrecorded states of another layer, the recording is performed using an intermediate power of the optimum powers for both of the recorded/unrecorded states, and (3) combination of (1) and (2).

Abstract: An optical recording method for recording information by irradiating an optical disc medium with a modulated write pulse train of laser light variable over a plurality of power levels such that a plurality of marks are formed on the optical disc medium, edge positions of each of the marks and a space between adjacent two of the marks being utilized for recording of the information.

Abstract: An optical disc having a region with pre-recorded data and a recordable region, a method of fabricating the disc, a stamper for forming a disc master, and a recording device for use with the disc are disclosed. Data recorded in the recordable region may be used for activation of the disc, providing unique identification or enhancing program content on the disc.

Abstract: An optical recording medium includes a main-information area in which a metal reflection film is formed on a substrate where a row of pits is formed as main data, and a sub-information area in which is recorded medium identification information, which is used to identify the optical recording medium individually, by removing the metal reflection film partially and forming a plurality of reflection-film removed areas. Information is reproduced by irradiating the metal reflection film with a beam of light. In the sub-information area, a row of pits or a guide groove is formed on the substrate, and a track pitch of the row of pits or the guide groove is at least 0.24 ?m wide and at most 0.45 ?m wide.

Abstract: In an optical pickup device 3, a supporting base 18 that has a main-shaft bearing 6a with two concentric round holes to pass a main shaft 7 through is formed out of a synthetic resin. On the other hand, an optical base 19, which has a sub-shaft bearing 6b to pass a sub-shaft 8 through and which supports a light emitter 11, a beam splitter 12, a collimator lens 13 and a photodetector 17, is formed by metal die casting process. And a pickup frame 6 is formed by bonding the supporting base 18 and the optical base 19 together with an adhesive.

Abstract: The optical storage medium comprises a substrate layer, and a data layer having a mark/space data structure with data arranged in tracks on the substrate layer, wherein between neighboring tracks alternatingly a groove section or a land section without a groove is arranged. The tracks, groove sections and land sections may be arranged by providing a single spiral, two spirals, or four spirals on the optical storage medium. The optical storage medium is in particular an optical disc comprising a nonlinear layer with a super-resolution structure arranged above the data layer.

Abstract: A laser diode read driver is described. A first transistor operative for producing a first voltage in response to receiving a first current signal. A first resistor is coupled between the first transistor and a low voltage supply. A first transconductor having a first input is coupled to receive the first voltage, wherein the transconductor produces a second current signal in response to differences between signals received on the first input and a second input. A second transistor is coupled to the second input, and operative for producing a third current signal in response to receiving the second current signal. A third transistor is coupled to the second transistor and the second input, the third transistor operative for producing an output current signal in response to receiving the third current signal, wherein the first transistor is scaled to the first transistor by the inverse of a gain factor.

Abstract: According to one embodiment, a write-once type information storage medium comprises an organic dye based recording material having sensitivity at a wavelength of 405 nm and at a recording wavelength in the range of 600 nm to 700 nm, wherein, when absorbance of a maximum absorption wavelength in the vicinity of 405 nm is defined as 1, the absorbance is 5% or more at any wavelength in the range of 600 nm to 700 nm.

Abstract: An information recording medium, comprising N number (N is an integer fulfilling N?3) of information layers on which information is recordable, and allowing information to be recorded on each of the information layers and allowing information recorded on each of the information layers to be reproduced by being irradiated with laser light. The N number of information layers include an N'th information layer, an (N?1)th information layer, an (N?2)th information layer, . . . a second information layer and a first information layer sequentially located from a laser light incidence side. A reflectance of the N'th information layer is RN, and a reflectance of an M'th information layer (M refers to every integer fulfilling N>M?1) is RM.