Abstract: The multilayer optical recording medium with at least four or more recording and reading layers disposed one above the other has at least two or more recording and reading layer groups each including the recording and reading layers successively disposed one above the other. In adjacent recording and reading layer groups with an intermediate layer interposed therebetween, a recording and reading layer nearest a front side in the recording and reading layer group nearer a back side is higher than the higher value of the reflectances in a stacked state of two recording and reading layers nearest the back side in the recording and reading layer group nearer the front side.

Abstract: In a multilayer optical recording medium, it is an object to suppress generation of crosstalk while reducing an interlayer distance of recording and reading layers. In an optical recording medium including three or more recording and reading layers, a first distance, and a second distance greater than the first distance by 3 ?m or more are alternately defined as interlayer distances of recording and reading layers.

Abstract: Efficient recording and reading are achieved in an optical recording medium including servo layers and recording and reading layers. The optical recording medium includes: a first servo layer having a projection and a depression for tracking control that are formed in a first spiral direction; a second servo layer having a projection and a depression for tracking control that are formed in a second spiral direction opposite to the first spiral direction; and a plurality of recording and reading layers having a flat structure with no projection and depression for tracking control. Information is recorded on each of the plurality of recording and reading layers while tracking control is performed using the first servo layer or the second servo layer.

Abstract: A recording and reading system for a multi-layered optical recording medium includes: a multi-layered optical recording medium including a plurality of recording layers and a single servo layer; and an optical head. The optical head includes a recording and reading objective lens of a signal recording and reading optical system and a servo objective lens of a servo signal detection optical system that are disposed on a common actuator. The recording and reading objective lens is mounted on the common actuator through a minute-drive apparatus so as to be minutely driven in a focusing direction relative to the servo objective lens. When the servo objective lens is focused on the servo layer, a reading light beam is quickly focused on a target one of the plurality of recording layers.

Abstract: An optical recording and reading method is provided in which the information necessary for recording and reading layers is quickly acquired to reduce the seek time during reading and recording. The optical recording and reading method is used for an optical recording medium that includes a plurality of recording and reading layers and a servo layer. Information is recorded on or read from the recording and reading layers by irradiating them with a recording and reading beam while the servo layer is irradiated with a servo beam to perform tracking control. When information is recorded on the recording and reading layers, control information necessary for subsequent recording and reading to be performed on the recording and reading layers is recorded on the servo layer 18. When the subsequent recording or reading is performed, the control information on the servo layer is consulted, and then the recording or reading is performed on the recording and reading layers.

Abstract: A method for forming an information recording layer including a multilayer stack of reflection hologram layers modulated in the depth direction of a hologram material layer is provided. The method includes: generating a first pair of polarized coherent laser beams and a second pair of polarized coherent laser beams that are incoherent with the first pair; directing the first pair of polarized coherent laser beams to the hologram material layer from opposite sides thereof, respectively, such that the incident angles of the first pair are symmetric with respect to the hologram material layer; directing the second pair of polarized coherent laser beams to the hologram material layer from the opposite sides thereof, respectively, at incident angles different from the incident angles of the first pair; and forming the multilayer stack of reflection hologram layers according to the interference pattern of the first and second pairs of polarized coherent laser beams.

Abstract: In an optical recording medium, even when a plurality of recording and reading layers are stacked, deterioration in the recording and reading signal quality thereof is suppressed. Furthermore, the transfer rate thereof can be increased. When recording or reading information by means of light irradiation on or from an optical recording medium having a plurality of recording and reading layers which are stacked in advance or formed eventually, an optical recording and reading device includes: a first optical system for irradiating a first beam to recording and reading layers to be a first target to perform recording or reading of information; and a second optical system for irradiating a second beam to recording and reading layers to be a second target to perform recording or reading of information.

Abstract: An object of the present invention is to increase the number of stacked layers in a multilayer optical recording medium while simplifying the design of the multilayer optical recording medium. Provided is a multilayer optical recording medium 10 including at least four recording and reading layers from which information can be reproduced by light irradiation, the layers stacked through intermediate layers. The multilayer optical recording medium 10 includes the plurality of recording and reading layers that are continuous in order of stacking and includes at least one recording and reading layer group in which reflectance in a stacked state decreases from a near side of a light incident surface to a far side. A single-layer reflectance of the nearest recording and reading layer is set to 0.2% or more and less than 2.0%, and a light transmittance improvement process is applied to the light incident surface.

Abstract: An optical recording medium includes a recording and reading layer that is previously staked or formed afterward and has no concavo-convex pattern for tracking control, and a servo layer in which a concavo-convex pattern or a groove for tracking control is formed. Information can be recorded in the recording and reading layer while tracking is performed using the servo layer.

Abstract: An optical recording medium including recording and reading layers and a servo layer increases the recording capacity thereof. In the optical recording medium including the plurality of recording and reading layers and the servo layer, the servo layer has a groove and a land that can be used to perform tracking control with a long-wavelength servo beam. Information is recorded on the recording and reading layers with a recording and reading beam having a wavelength shorter than the wavelength of the servo beam. Recording marks are formed on the recording and reading layers while both the groove and land are tracked.

Abstract: Simple design of a multilayer optical recording medium is achieved while suppressing interlayer crosstalk and confocal crosstalk in the multilayer optical recording medium. Simple recording and reading control by a recording and reading unit is also achieved. The multilayer optical recording medium includes at least three or more recording and reading layers deposited one above the other with intermediate layers interposed therebetween, and information can be read by light irradiation from the layers. The intermediate layers have film thicknesses of two types or less, and all the recording and reading layers except the recording and reading layer farthest from a light incident surface have substantially the same optical constant.

Abstract: The multilayer optical recording medium with at least four or more recording and reading layers disposed one above the other has at least two or more recording and reading layer groups each including the recording and reading layers successively disposed one above the other. In adjacent recording and reading layer groups with an intermediate layer interposed therebetween, a recording and reading layer nearest a front side in the recording and reading layer group nearer a back side is higher than the higher value of the reflectances in a stacked state of two recording and reading layers nearest the back side in the recording and reading layer group nearer the front side.

Abstract: The multilayer optical recording medium with six or more recording and reading layers disposed one above the other has at least two or more recording and reading layer groups. The recording and reading layer groups each include a plurality of recording and reading layers successively disposed one above the other. The reflectance of each of the recording and reading layers in a stacked state decreases in the order from a front side near a light incident surface toward a back side far from the light incident surface. A recording and reading layer nearest the front side among the recording and reading layers in the recording and reading layer group nearer the back side has a reflectance in a stacked state higher than that of a recording and reading layer nearest the back side among the recording and reading layers in the recording and reading layer group nearer the front side.

Abstract: Efficient recording and reading are achieved in an optical recording medium including servo layers and recording and reading layers. The optical recording medium includes: a first servo layer having a projection and a depression for tracking control that are formed in a first spiral direction; a second servo layer having a projection and a depression for tracking control that are formed in a second spiral direction opposite to the first spiral direction; and a plurality of recording and reading layers having a flat structure with no projection and depression for tracking control. Information is recorded on each of the plurality of recording and reading layers while tracking control is performed using the first servo layer or the second servo layer.

Abstract: An optical recording medium including recording and reading layers and a servo layer increases the recording capacity thereof. In the optical recording medium including the plurality of recording and reading layers and the servo layer, the servo layer has a groove and a land that can be used to perform tracking control with a long-wavelength servo beam. Information is recorded on the recording and reading layers with a recording and reading beam having a wavelength shorter than the wavelength of the servo beam. Recording marks are formed on the recording and reading layers while both the groove and land are tracked.

Abstract: A series of optical recording media is provided to reduce a burden on an optical pickup by introducing a standardized idea among a plurality of optical recording media. In the series of optical recording media, optical recording media are of a plurality of types, each optical recording medium including a plurality of planar recording and reading layers with no projections and depressions for tracking control, and a servo layer with projections and depressions for tracking control. The plurality of optical recording media have different numbers of stacked recording and reading layers. The plurality of optical recording media have different numbers of stacked recording and reading layers. The positions of the servo layers from the corresponding light incident surfaces are standardized among the plurality of optical recording media. The position of at least one recording and reading layer from the corresponding light incident surface is standardized among the plurality of optical recording media.

Abstract: An optical recording and reading method is provided in which the information necessary for recording and reading layers is quickly acquired to reduce the seek time during reading and recording. The optical recording and reading method is used for an optical recording medium that includes a plurality of recording and reading layers and a servo layer. Information is recorded on or read from the recording and reading layers by irradiating them with a recording and reading beam while the servo layer is irradiated with a servo beam to perform tracking control. When information is recorded on the recording and reading layers, control information necessary for subsequent recording and reading to be performed on the recording and reading layers is recorded on the servo layer 18. When the subsequent recording or reading is performed, the control information on the servo layer is consulted, and then the recording or reading is performed on the recording and reading layers.

Abstract: In a multilayer optical recording medium, it is an object to suppress generation of crosstalk while reducing an interlayer distance of recording and reading layers. In an optical recording medium including three or more recording and reading layers, a first distance, and a second distance greater than the first distance by 3 ?m or more are alternately defined as interlayer distances of recording and reading layers.

Abstract: A series of optical recording media is provided to reduce a burden on an optical pickup by introducing a standardized idea among a plurality of optical recording media. In the series of optical recording media, optical recording media are of a plurality of types, each optical recording medium including a plurality of planar recording and reading layers with no projections and depressions for tracking control, and a servo layer with projections and depressions for tracking control. The plurality of optical recording media have different numbers of stacked recording and reading layers, and the positions of the servo layers with respect to the corresponding light incident surfaces are standardized among the plurality of optical recording media.

Abstract: A reflection type hologram recording optical system is provided which implements a method for forming a light reflection hologram having uniform reflectivity. The method includes: focusing a first laser beam through one of a pair of objective lenses, the first beam satisfying the condition given by, 4?n/(NA)2<D, where ? (?m) is the wavelength of the first laser beam, NA is the numerical aperture of the pair of objective lenses, n is the average refractive index of the optical recording medium, and D (?m) is the thickness of the medium; allowing the first laser beam to interfere with a second laser beam within the optical recording medium, the second laser beam being focused through the other opposing objective lens; and allowing the optical recording medium and a flux of the laser beams to be displaced relative to each other, thereby forming a light reflection hologram having uniform reflectivity.