Abstract: An optical information processing element characterized by having a photoelectric and a memory layer provided with a function holding an electricity-conducting property which has been changed by radiation of light having a constant wavelength between electrodes at least one of which is provided with a light-transmitting property.

Abstract: An optical recording medium has a transparent substrate with a recorded pattern formed thereon and a saturable absorption dye containing layer disposed on the recorded pattern and containing at least a saturable absorption dye. The saturable absorption dye has a molecular extinction coefficient .epsilon. of 10.sup.4 or greater at the wavelength of reproducing light, and a relaxation time .tau. in the range of 1 ns.ltoreq..tau..ltoreq. 100 ns. A reflecting layer having a reflectivity of 70% or higher on an air boundary thereof may be disposed on the saturable absorption dye containing layer. The saturable absorption dye containing layer may have such a thickness that substantially minimizes the intensity of reflected light due to interference with respect to the intensity of the reproducing light. The saturable absorption dye may comprise a naphthalocyanine-based dye.

Abstract: An optical information medium providing a protective layer above an optically transparent substrate to protect a recording part, and can record information which is optically readable by means of laser beam. An aqueous printing ink-fixable, hydrophilic resin film is formed on the protective layer. Given letters and patterns can be printed easily and satisfactorily. Such letters and patterns are printable by means of, for example, an ink jet printer.

Abstract: An embodiment of the present invention is a process in which a polymer solution is spin coated onto a master data recording disk, such as glass substrate with photoresist images, before separating. After drying and forming polymer, a polymer membrane results which is a faithful reproduction of micron-sized optical recording features on the surface of the master. Such membrane is either peeled-off and mounted to a pellicle-like frame or first laminated to a stiffer, stronger substrate before peeling to support the duplicate.

Abstract: A method for making an optically readable medium containing a relief information track comprising the sequential steps of(a) laminating a dry photohardenable film to a surface of a transparent dimensionally stable substrate;(b) embossing the exposed surface of the photohardenable film with the relief information track by applying thereto under pressure a stamper die containing a reverse relief image of the information track;(c) passing actinic radiation through the transparent substrate and the photohardenable film to effect hardening of the photohardenable film while it is contact with the stamper die; and(d) separating the stamper die from the embossed photohardened film;The embossed film of the medium is made reflective by applying a reflective layer to either the photohardenable film prior to embossing or to the photohardened film subsequent to embossing.

Abstract: An optical memory is disclosed in which data is stored in an optical data layer capable of selectively altering light such as by changeable transmissivity or polarization. The data is illuminated by controllable light sources and an array of multi-surface imaging lenslets project the image onto a common array of light sensors. Data is organized into a plurality of regions or patches (called pages) in which each page contains a field of data spots that encode multiple states or levels of data by the amount of transmissivity or polarization of that spot. By selective illumination of each data page, one of the lenslets images the selected data page onto the light sensors. Light in the data image pattern strikes different ones of the arrayed light sensors, thereby outputting the multiple levels per spot in the form of electrical data signals that are A/D converted to digital.

Abstract: Described is an optical recording medium having a mixture or integrated layers of a metal and an oxide which react with each other under an exothermic reaction at a high temperature upon receiving an irradiation of a laser. The metal and the oxide are in a relation that the oxide has a standard enthalpy of formation higher than that of the oxide obtained by oxidizing the metal. An area irradiated with a laser spot is heated to a high temperature and the oxide at the area is reduced by the metal into a metal which changes in the optical constant and can be detected optically. The reduction reaction in an exothermic reaction generates a thermal energy in addition to the thermal energy of the irradiated laser. The optical recording medium of this structure can make the recording work more efficient. A manufacturing method of the optical recording medium and a recording method using the same are also disclosed.

Abstract: A photo-mask and a method of manufacturing a photo-mask, which includes the steps of applying a resist film onto a substrate of quartz, glass and the like, subjecting the resist film to light exposure and development to form a fine resist pattern, etching the mask substrate covered by the fine resist pattern, causing a non-light transmitting thin film of Cr, Ta, etc. to adhere thereon by vapor deposition, sputtering and the like, and removing the thin film on the resist pattern together with the resist film, thereby to form the photo-mask.

Abstract: An optical recording medium affording a maximum Kerr effect enhancement, yet exhibiting a good signal-to-noise ratio, includes, for example, a substrate, an interference layer, a tracking guide layer, and a recording layer which are successively formed one above the other in the stated order. The interference layer is made of a light transmissive material and has a refractive index that is larger than that of the substrate. The interference layer has a first portion etched to a predetermined depth (d) and a second portion having a predetermined thickness (D). The tracking guide layer is formed on the second portion of the interference layer in a predetermined pattern, e.g. spirally or coaxially, for obtaining a tracking signal for use in tracking servo. The thickness of the interference layer defined by D minus d is set substantially equal to (.lambda./4n)+M(.lambda./2n) where .lambda. is a wavelength of light for reading the information, n is a refractive index of the interference layer, and M is an integer.

Abstract: In a phase change optical disk wherein a first heat-resistant protection layer, an optical active layer showing a reversible phase change between a crystal state and an amorphous state, and a second heat-resistant protection layer are laminated on a substrate in this order, both of the first and the second heat-resistant protection layers are made of a mixture of a chalcogenide and a vitrification accelerating material. Further, a mixture ratio of the vitrification accelerating material in the second heat-resistant protection layer is larger than that in the first heat-resistant protection layer. Thereby, it becomes possible that the first heat-resistant protection layer has the mixing ratio which gives the refractive index value bringing suitable optical properties, while the second heat-resistant protection layer has the different mixing ratio which gives the thermal conductivity bringing suitable thermal properties.

Abstract: The invention discloses a CD-WO type optical recording medium which has a constitution obtained by successively laminating a recording layer, a metal reflection layer and a protective layer; is prepared by using in the recording layer a colorant having a melting point of 150.degree. to 300.degree. C., decomposition initiating temperature of 200.degree. to 350.degree. C., and .lambda. max of 720 nm; and has high sensitivity, low recording distortion and high durability. The colorant can be enhanced its effect by introducing halogen atoms.

Abstract: An optical data storage system comprises a multiple data surface medium and optical head. The medium comprises a plurality of substrates separated by a light transmissive medium. Data surfaces are located on the substrate surfaces. A layer of a dye material is deposited onto each of the data surfaces. The thickness of the dye layer determines the amount of reflectivity for each of the data surfaces.

Abstract: An azo metal chelate compound of an azo compound of the formula (I) with a metal: ##STR1## wherein A is a residue forming a heterocyclic ring together with the carbon atom and the nitrogen atom to which it is bonded, X is a residue forming an aromatic group together with the two carbon atoms to which it is bonded, R.sup.1 is an alkyl group which may be substituted, an aryl group which may be substituted, an alkenyl group which may be substituted, or a cycloalkyl group which may be substituted, Y is a hydrogen atom or a cation, and n is an integer of from 1 to 3.

Abstract: An optical information carrier comprising a substrate, an auxiliary layer bounded by dielectric layers, a thin reflection layer, a dielectric layer, a phase-change layer, a dielectric layer, a tight metal reflection layer and a protective layer. The information carrier is recordable and erasable by a laser-light beam and can be played in a conventional CD player. The auxiliary layer consists of selenium or AlGaAs, and has the property that the absorption increases substantially at temperatures above 70.degree. C. An information carrier comprising this auxiliary layer can be recorded with a lower laser power as compared to information carrier which does not comprise the auxiliary layer.

Abstract: An optical disc has a recording film with information recorded thereon, and a photochromic material film provided adjacent the recording film. The photochromic material film is made of a photochromic material. The photochromic material has a first state irradiated with reading light having a first wavelength. In the first state, the transmittance of the material is increased so as to enable reading of the recorded information. The photochromic material further has a second state irradiated with auxiliary light having a second wavelength, where the transmittance becomes low so as to disable the reading of the recorded information.

Abstract: An optical recording medium has a substrate and, provided thereon, a recording layer, a recording auxiliary layer that covers a given region on the surface of the recording layer on its side not facing the substrate, and a recording restraining layer that the covers the recording layer on its surface not covered with the recording auxiliary layer.

Abstract: Optical storage media based on ablative metals give improved stability and offer improved write-read characteristics when they are overcoated with inorganic oxide, nitride, carbide, hydride, oxynitride or carbohydride to a reflectivity of 40-80% at the media write/read wavelength. Preferably the metal and overcoat are applied by sputter-depositing.

Abstract: An optical recording medium includes in sequence a transparent substrate, a light-reflecting layer, a transparent intermediate layer and a light-absorbing layer. The light-reflecting layer and the light-absorbing layer are respectively formed as a layer of an organic coloring matter. The light-absorbing layer can cause deformation for recording information accompanied with a local charge in thickness of the transparent intermediate layer in response to a recording beam indicated to the light-absorbing layer through the transparent substrate.

Abstract: There is disclosed a recordable optical element that includes a recording layer. The element has a transparent substrate and on the surface of the substrate, a) a recording layer containing a light absorbing material and b) a light reflecting layer, the improvement wherein said light absorbing material has the structure: ##STR1## wherein; R is hydrogen, alkyl having from 1 to about 20 carbons, substituted or substituted aryl from about 6 to 10 carbon atoms;R.sub.1 represents hydrogen or an alkyl group of from 1 to about 6 carbon atoms;R.sub.2 represents a hydrogen, an alkyl group of from 1 to about 5 carbon atoms; SO.sub.2 R"' or SO.sub.2 NHR"' where R"' is an alkyl group from 1 to about 10 carbon atoms; an aryl group of from about 6 to 10 carbon atoms or a hetaryl group of from about 5 to about 10 carbon atoms or a halogen atom;R.sub.3 represents hydrogen, an alkyl group of from 1 to about 4 carbon atoms or a halogen atom;R.sub.4 represents alkyl group 1 to 10 carbon atoms; SO.sub.2 R"', SO.sub.

Abstract: A rotatable memory medium having a memory surface of ellipsoid surface defining two foci. A laser beam is directed to one focus and then reflected to the memory surface, and from the latter to the other focus where a sensor is positioned. The memory surface has a memory track of spiral shape, and the laser beam reflected to the memory surface is so reflected by a T-mirror, and the source of the laser beam remains stationary. The ellipsoid memory surface assumes a plurality of different shapes, such as one-half of an ellipsis on one side of a plane containing both foci, or generated about either an internal axis or an external axis.

Abstract: An optical recording medium comprises a transparent substrate, a recording layer containing at least one organic dye overlying the substrate, a metallic layer directly contacting and overlying the recording layer, a protective layer comprising at least one layer directly contacting and overlying the metal layer, a layered print portion comprising at least one layer directly contacting and overlying the protective layer, and said protective layer and said print portion satisfying the following relationship:.SIGMA.AiBi+.SIGMA.CjDj<3 (.mu.m) (1)where Ai (.mu.m) is a thickness and Bi is a curing shrinkage rate of the i-th protective layer, respectively, where i is an integer of 1 or more, Cj (.mu.m) is a thickness and Dj is a curing shrinkage rate of the j-th print portion layer, respectively, where J is an integer of 1 or more.

Abstract: High density optical information recording even at room temperature is achieved by control of the diameter of crystalline portions exhibiting quantum size effects of fine semiconductor particles distributed in a dielectric matrix, using the non-crystalline to crystalline phase transition of the fine particles. The quantum size effects mean that the optical properties of the medium depend on the diameter of the crystalline portions. Various methods of recording, reproducing and erasing information using this optical recording medium are possible. The invention is applicable to other optical devices.

Abstract: Optical storage media based on ablative metals give improved stability and offer improved write-read characteristics when they are overcoated with inorganic oxide, nitride, carbide, hydride, oxynitride or carbohydride to a reflectivity of 40-80% at the media write/read wavelength. Preferably the metal and overcoat are applied by sputter-depositing.

Abstract: A method of and an apparatus for writing and reading and/or erasing a multilayer record carrier (1) having a guide plane (2) and a plurality of recording planes (4) are described, using a guide beam (5) which cooperates with the guide plane (2) and a scanning beam (6) for at least writing in the recording planes (4). During writing the position of the scanning focus (36) formed by the scanning beam (6) is coupled to the focus (11) of the guide beam (5) which is actively controlled by using guide information which is present in the guide plane (2). During reading the scanning beam (6) is actively controlled by its own servosystem (20-28).

Abstract: An optical recording medium includes on the surface of a substrate a recording thin film, a thin film of dielectric material and a reflecting thin film in this order, characterized in that said recording thin film contains Ag, M and O or Fe, M and N, wherein M is at least one member selected from the group consisting of Ni, Ti, Co and Cu. The optical recording medium further includes between the substrate and the recording thin film and on the substrate a surface layer having a glass transition point lower than that of the substrate.

Abstract: The invention relates to a novel information recording medium and the recording of information thereon. The recording medium material possesses both retention and expansion characteristics suitable for use with optical recording, reading and erasing systems.

Abstract: An optical recording medium for pit length recording with excellent error rate and jitter value which has a transparent injection molded resin substrate, a recording layer containing a phthalocyanine dye of formula (1) overlying the substrate and a covering layer overlying the recording layer. Also, a method of optical recording by pit length recording with a focused laser beam using an optical recording medium as described above.

Abstract: A composition of materials having ferromagnetic, piezoelectric, and electro-optical properties is disclosed. In the preferred embodiment, the composition of materials comprises a first layer of Pb.sub.(1-x-y) Cd.sub.x Si.sub.y, a second layer of Se.sub.(1-z) S.sub.z, and a third layer of Fe.sub.(1-w) Cr.sub.w, where x, y, z and w are values within the ranges of 0.09.ltoreq.x.ltoreq.0.11, 0.09.ltoreq.y.ltoreq.0.11, 0.09.ltoreq.x.ltoreq.0.11 and 0.18.ltoreq.w.ltoreq.0.30. Additionally, each of the layers contain at least one of the elements of Ag, Bi, O, and N. A random-accessible, non-volatile memory built using the invented composition of materials is also disclosed. This memory provides for storing two independent bits of binary information in a single memory cell.

Abstract: This optical recording medium is constructed by a substrate, a protecting film, an optical recording material layer, a light reflecting layer and a protecting layer sequentially laminated with each other. The substrate is made of a transparent material. The protecting film is made of transparent optical hardening resin. The optical recording material layer has a transparency reversibly changed in accordance with temperature. The optical recording material layer is formed by an optical recording material in which an organic low molecular substance of higher saturated fatty acid such as stearic acid or behenic acid, etc. is uniformly dispersed in a transparent resin base material composed of thermoplastic resin such as vinyl chloride resin, etc. as a high molecular compound.

Abstract: A WORM optical disk that not only has a sufficiently improved reflectance to permit the setting of higher RF signal levels but that also permits the setting of higher levels for the tracking error signals to insure consistent performance in operation. This WORM optical disk of the present invention comprises a substrate 1 that has grooves 2 formed in its surface and that is coated with a dye film 3 which, in turn, is coated with a reflecting film 4, wherein the part of the dye film 3 which is formed on the lands 5 of the substrate 1 and a portion of that part of the dye film 3 which is formed in the grooves 2 are subjected to irradiation to effect color fading in the irradiated dye regions.

Abstract: An optical recording medium of a single plate type capable of recording comprises a transparent resin substrate having a groove of 900-1800 .ANG. in depth and 0.3-0.6 .mu.m in width, a recording layer containing a dye overlying the substrate, a reflective layer overlying the recording layer and a protective layer overlying the reflective layer, the thickness of the recording layer being 800-1250 .ANG. at the groove portion and 500-1100 .ANG. at the land portion.

Abstract: By using an information recording medium comprising at least a substrate and an information recording film which is mounted on the above substrate and changes the physical property under irradiation of a recording energy beam, wherein the surface of the information recording area of the above substrate is uneven, both surfaces of the above recording film are also uneven, and an inorganic protective layer is provided in contact with the surface of the above recording film opposite to the above substrate, fine recording points can be formed stably without complicated control of the recording power and recording waveform so that an optical disk unit can record data simply in high density.

Abstract: A recording layer 3 including shape-memory alloy thin films 311, 312 and a hydrogen storage alloy thin film 32, a dielectric thin film 4, and a reflective thin film 5 are stacked on a surface of a substrate 2 in the described order. Irradiation of recording light causes the hydrogen storage alloy thin film 32 to release hydrogen gas and contract in volume at the same time, creating a space 321 in the film. The shape-memory alloy thin films 311, 312 are deformed by the gas pressure in space 321, allowing space 321 to enlarge its thickness. Upon exposure to erasing light, shape-memory alloy thin films 311, 312 tend to restore their shape prior to deformation, applying pressure to the hydrogen gas in space 321 so that the hydrogen gas is occluded again and space 321 is substantially extinguished. Reversible release and occlusion of hydrogen gas enables to rewrite the recording information.

Abstract: A medium comprises a reading layer, a memory layer and a writing layer. The reading layer, the memory layer and the writing layer are exchange-coupled to each other to form a three-layered structure. The medium satisfies the following condition at room temperature and during reproduction:i) 2M.sub.SR H.sub.CR t.sub.R <.sigma..sub.WR1 ;ii) 2M.sub.SR H.sub.CR t.sub.R +2M.sub.S1 H.sub.C1 t.sub.1 >.sigma..sub.W12 ;iii) Hb<(.sigma..sub.WR1 /2M.sub.SR t.sub.R)+H.sub.CR,where t.sub.R is a film thickness of the reading layer, t.sub.1 is a film thickness of the memory layer, M.sub.SR is saturation magnetization of the reading layer, M.sub.S1 is saturation magnetization of the memory layer, H.sub.CR is a coercivity of the reading layer, H.sub.C1 is a coercivity of the memory layer, .sigma..sub.WR1 is an exchange coupling force between the reading layer and the memory layer, .sigma..sub.W12 is an exchange coupling force between the memory layer and the writing layer, and Hb is a recording magnetic field.

Abstract: Optical storage media based on ablative metals give improved stability and offer improved write-read characteristics when they are overcoated with inorganic oxide, nitride, carbide, hydride, oxynitride or carbohydride to a reflectivity of 40-80% at the media write/read wavelength. Preferably the metal and overcoat are applied by sputter-depositing.

Abstract: A writable recording medium having reduced jitter, improved performance on repeated reproduction, improved light resistance, and sensitivity controllability is disclosed, in which a light-absorbing layer thereof contains (D-1) a cyanine dye having an absorption band in the wavelength region of light for recording or reproduction, (D-2) a cyanine dye having an absorption band in a shorter wavelength region than that of cyanine dye (D-1) and having a smaller absorption than that of cyanine dye (D-1) in the wavelength region of light for recording or reproduction, (Q-1) a quencher for preventing photo-deterioration of cyanine dyes, and (Q-2) a quencher selected from an azo compound and a diphenylamine compound, the weight ratio of cyanine dye (D-2) to cyanine dye (D-1), taken as .alpha., being from 1 to 3, the weight ratio of quencher (Q-1) to quencher (Q-2), taken as .beta., being from 0.

Abstract: A recording medium comprises a recording layer, a birefringent layer, and a reflecting layer. The recording layer is formed of a material whose optical rotatory power is alterable such that in one state no optical rotatory power is present and, in a second state, optical rotatory power is present. Information is recorded in the recording layer by selectively altering the state of the recording layer. The birefringent layer is formed of a material having constant birefringence without regard to the state of the recording layer. The reflecting layer reflects a light beam transmitted through the recording layer and the birefringent layer to reintroduce the beam into the birefringent layer and the recording layer. A method of reproducing information from this recording medium applies a polarized light beam to the recording medium and detects change of the polarized state of the polarized light beam reflected from the recording medium, thereby reading the information recorded in the recording layer.

Abstract: An optical recording medium having at least a pair of recording films which have a predetermined light absorption distribution and have steep absorption end slopes which are closer to each other. The difference between the wavelengths of recording or reproduction lights for these two recording films may be close to about 50 nm. A common optical system may be used for recording or reproduction operation for the two recording films, whereby the optical system may be simplified.

Abstract: The DRAW type optical recording medium which can record optical information by forming information pits in the recording layer by irradiation of an energy beam such as laser beam, and yet can reproduce the information immediately after writing without requiring any step of developing processing after writing of information. The optical recording medium includes a recording layer (3) for forming information pits through the occurrence of physical deformation by irradiation of an energy beam and a sensitizing layer (4) for augmenting the physical deformation in the recording layer (3) laminated on a support (2). By the presence of the sensitizing layer, recording sensitivity is improved and also stability of the medium with lapse of time becomes excellent.

Abstract: A technique of an optical card having high information recording density. A specially superior writing characteristic is required for an additional recording optical card among optical cards. In the case where the optical card of additional recording type is closed, reduction in the writing characteristic is observed. In this invention, a sensitizing layer (50), which serves as escape for molten recording material at writing, is provided in rear of an optical recording section (30), so that an optical card is produced which is superior in both environmental resistance and writing ability. The sensitizing layer (50) is made of self-oxidizable or thermoplastic resin and an absorbing agent dispersed in the resin. The absorbing agent cooperates with the resin not only to improve a writing characteristic, but also to improve design ability and reading ability of the card.

Abstract: An optical disk having a warp preventive film for preventing the warp of the substrate which does not exfoliate for a long period by forming the warp preventive film on a textured area on the substrate surface with a minute embossment, and a method of manufacturing the optical disk by controlling the plasma etching condition for forming a textured area for reinforcing the bonding force of the warp preventive film on the substrate surface, so that the warp preventive film being bonded after forming the textured area may not exfoliate for a long period.

Abstract: A disk cartridge includes a main body of the cartridge having an opening or its major surface by which the signal recording surface of an optical disk accommodated in the main body is exposed to outside and an aperture formed on the lateral surface orthogonal to the major surface of the main body for enabling the optical disk to be inserted into and taken out of the cartridge for disk exchange. The disk cartridge also an opening/closing member which is rotatably supported by the main body by pivot pins provided at its one end for engaging in recesses in the aperture in the main body, for opening and closing the aperture and, which is provided at its other end with a resilient arm having a retaining end pawl engageable with a mating retaining section in the main body. By actuation of the opening/closing member, the aperture in the main body is opened or closed to permit exchange of the optical disk.

Abstract: The invention discloses a method and an apparatus for creating optical disc recordings by forming pits having ideal shapes. These ideally shaped pits are improvements in the technology of disc mastering, due to the manufacturing and data playback advantages that are inherent in the ideally shaped pits. A disc substrate has a very thin partially reflective layer applied to the surface of the optical disc upon which data will be recorded. The substance used to make the partially reflective layer is normally considered opaque in more commonly occurring thicknesses. However, the partially reflective layer, is created to be so extremely thin that it becomes partially optically transparent. The partially reflective layer then has spin coated, thereon, an optically active lamina to enable the recording of data on the disc by laser means in the form of pits.

Abstract: An information recording disk formed from two substrates with a stepped central opening for receiving a hub within the stepped recess of at least one of the substrates is provided. In one embodiment, the central aperture of the first substrate is larger than the central aperture of the second substrate to form the stepped recess. In another embodiment, at least one substrate has a stepped surface defining a central aperture and a hub structure is mounted within this stepped recess to reduce overall thickness of the disk.

Abstract: An information recording medium comprises a recording layer including a mixture of organic polysilane and oxo metallic phthalocyanine pigment. Information is recorded by adding heat or light to the recording layer. In a method for recording information onto the information recording medium, a decoloring reaction of oxo metallic phthalocyanine pigment is used which is caused by heating the recording layer to a temperature equal to or higher than a pyrolyzing point of organic polysilane.

Abstract: An information recording disc including a plurality of disc substrates (2), at least one of which has a recording medium containing layer (1), two pieces of hubs mounted over the center hole of said disc substrates on both sides thereof, each hub having a portion to be inserted into said center hole and a flange portion to cover a portion of said disc substrate in the vicinity of said center hole, and an adhesive layer (13, 14) formed between said hubs and said disc substrates and between said two hubs. An adhesive layer (7) laminates the substrates (2a, 2b) to one another.

Abstract: An optical information recording medium is composed of a substrate, and a recording layer formed on the substrate, the recording layer including (a) a first recording layer, (b) an intermediate, and (b) a second recording layer, which are successively overlaid on the substrate, the first recording layer containing as the main component an organic dye having a peak of spectral reflectivity near the wavelength of a light beam for the recording and reproduction of information, the intermediate layer being transparent to the light beam for recording and reproduction of information, and containing a material having a refractive index smaller than the refractive index of the second recording layer, and the second recording layer containing as the main component an organic dye having a peak of spectral absorbance near the wavelength of the light beam for recording and reproduction of information, and having a thickness by which a maximum reflectivity is exhibited.

Abstract: The invention relates to the reading of optical disks in which the recording is performed in volume in separate layers. Reading a bit recorded within the layers gives a signal with a background noise from all the adjacent bits illuminated by the read beam. In order to eliminate this background noise, the read beam is modulated in position about the bit to be read, either horizontally or vertically with respect to a recording level. The background noise remains unchanged but the signal from the bit being read becomes a periodic signal.

Abstract: The apparatus includes optical recording media each of which includes a single plate substrate with recording layers and spiral grooves formed on both sides of the substrate and which are available for recording and reproduction or for recording, erasing and reproduction via irradiation with laser beams. Both surfaces of the recording media are available for simultaneous access, and a plurality of thin floating-type optical heads are provided to irradiate laser beams onto the recording media. The optical heads are respectively provided at each side of the recording media and float, responsive to rotation of the recording media, above the respective surfaces of the recording media at a distance of at most hundreds of microns. The combination of these optical recording media and optical heads makes it possible to stack plural pairs thereof within an ultra-thin space, thus greatly improving the on-line capacity of the optical recording apparatus.

Abstract: An optical information recording medium is composed of a transparent substrate, a recording layer provided on the substrate, which is transparent with respect to a light beam for reproducing information recorded in the recording layer, a reflection layer provided on the recording layer, and an anti-reflection layer provided on the back side of the substrate opposite to the recording layer. The anti-reflection layer is composed of a plurality of overlaid layers, and at least one of the layers being a transparent electroconductive layer and the other layers are transparent insulating layers.