Abstract: Disclosed is an information recording medium which, when inserted into a recording/reproducing device, can be run in an updated state intended by a disc supplier since a recordable layer can be specified as a layer to be run first. For example, in an optical disc including an L1 layer which is a read-only recording layer and an L0 layer which is a recordable layer, layer specifying information for specifying the L0 layer in priority to the L1 layer is recorded as an information recording layer to be run first when the optical disc is inserted into the optical disc device which carriers out recording or reproduction of information with respect to the optical disc.

Abstract: In an optical disc (100) having a plurality of recording layers, layer specifying information is recorded for specifying a recording layer to be run first when the optical disc (100) is inserted into an optical disc device (1) which carries out recording or reproduction of information with respect to the optical disc (100). Therefore, a recording layer intended by at least a disc supplier can be run first. In the optical disc (100) including an L1 layer which is a read-only recording layer and an L0 layer which is a recordable layer, layer specifying information for specifying the L0 layer in priority to the L1 layer is recorded as the information recording layer to be run first when the optical disc (100) is inserted into the optical disc device (1) which carries out recording or reproduction of information with respect to the optical disc (100).

Abstract: An optical disk has a lead-in region provided at the inner circumference side and a user region provided at the outer circumference side. Pit string 3 of pits of different depths is formed in the lead in region. Light beam reflected from the pit string is detected by detector and TPP and RF signals are output by differential amplifier and addition amplifier. A ternary signal is restored from pits based on the TPP and RF signals. Information is recorded by pits of the same depth in the user region. Recording information in the depth direction in the lead-in region increases the recording capacity thereof. The information recorded in the depth direction in the lead-in region cannot be transferred to a user region of another optical disk.

Abstract: An optical disk has a lead-in region provided at the inner circumference side and a user region provided at the outer circumference side. Pit string 3 of pits of different depths-is-formed-in-the-lead-in-region. Light beam reflected from the pit string is detected by detector and TPP and RF signals are output by differential amplifier and addition amplifier. A ternary signal is restored from pits based on the TPP and RF signals. Information is recorded by pits of the same depth in the user region. Recording information in the depth direction in the lead-in region increases the recording capacity thereof The information recorded in the depth direction in the lead-in region cannot be transferred to a user region of another optical disk.

Abstract: On an optical disk, a string of a plurality of pits having two different depths is formed. Quantity of light reflected from the pit string is detected by a photoreceptor element, and based on the detected quantity of reflected light, a pit depth detecting unit detects depth of each pit. Based on the detected quantity of reflected light, a servo signal generating unit generates a tracking servo signal. An output control unit supplies the generated tracking servo signal when a pit of such depth that is to be reproduced is tracked, and holds and supplies an immediately preceding tracking servo signal when a pit of different depth is being tracked, based on the result of detection by the pit depth detecting unit.

Abstract: On an optical disc including a substrate on which pits having at least two different depths are formed, main information is recorded by the shape of the pits and additional information is recorded by the depth of the pit. It is possible to reverse polarity of a tangential push-pull signal dependent on the depth of the pit, and therefore it becomes possible to record information utilizing the depth of the pit. This improves recording density of the optical disc. Further, when information of the optical disc is to be copied, the information recorded by the depth of the pit cannot be copied. Therefore, unauthorized reproduction can be prevented.

Abstract: An optical disk has a lead-in region provided at the inner circumference side and a user region provided at the outer circumference side. Pit string 3 of pits of different depths is formed in the lead-in region. Light beam reflected from the pit string is detected by detector and TPP and RF signals are output by differential amplifier and addition amplifier. A ternary signal is restored from pits based on the TPP and RF signals. Information is recorded by pits of the same depth in the user region. Recording information in the depth direction in the lead-in region increases the recording capacity thereof. The information recorded in the depth direction in the lead-in region cannot be transferred to a user region of another optical disk.

Abstract: On an optical disc including a substrate on which pits having at least two different depths are formed, main information is recorded by the shape of the pits and additional information is recorded by the depth of the pit. It is possible to reverse polarity of a tangential push-pull signal dependent on the depth of the pit, and therefore it becomes possible to record information utilizing the depth of the pit. This improves recording density of the optical disc. Further, when information of the optical disc is to be copied, the information recorded by the depth of the pit cannot be copied. Therefore, unauthorized reproduction can be prevented.

Abstract: On an optical disc including a substrate on which pits having at least two different depths are formed, main information is recorded by the shape of the pits and additional information is recorded by the depth of the pit. It is possible to reverse polarity of a tangential push-pull signal dependent on the depth of the pit, and therefore it becomes possible to record information utilizing the depth of the pit. This improves recording density of the optical disc. Further, when information of the optical disc is to be copied, the information recorded by the depth of the pit cannot be copied. Therefore, unauthorized reproduction can be prevented.

Abstract: An optical device to control the output power of a laser on recording and reproduction without expensive high-speed circuits is provided. The optical disk device of the present invention comprises monitor portion for monitoring the power of laser light, averaged light quantity calculating portion for calculating the averaged light quantity of the power of the laser light, memory portion for memorizing the averaged light quantity, error quantity calculated portion for calculating the difference between the output signals of the averaged light quantity calculating portion and the memory portion, and laser power control portion for controlling the power of the laser light in response to the output signal from the error quantity calculating portion.

Abstract: On an optical disc including a substrate on which pits having at least two different depths are formed, main information is recorded by the shape of the pits and additional information is recorded by the depth of the pit. It is possible to reverse polarity of a tangential push-pull signal dependent on the depth of the pit, and therefore it becomes possible to record information utilizing the depth of the pit. This improves recording density of the optical disc. Further, when information of the optical disc is to be copied, the information recorded by the depth of the pit cannot be copied. Therefore, unauthorized reproduction can be prevented.

Abstract: Featured is a recording and reproducing method of a magneto-optical recording medium including a recording layer for recording thereon information magneto-optically and a readout layer which has in-plane magnetization at room temperature and where a transition occurs from in-plane magnetization to perpendicular magnetization as temperature raises. The method includes projecting a light beam onto such a magneto-optical recording medium so as to form a perpendicularly magnetized area in the readout layer by duplication of the magnetization of said recording layer to the area. In further embodiments, the recording medium further includes an intermediate layer made of non-magnetic film formed between the readout and recording layers and the readout and recording layers are composed of rare-earth transition metal alloys such as TbFeCo (recoding layer) readout layer, made of GdFeCo (readout layer).

Abstract: A magneto-optical recording medium is composed of a base which has a property that a light can be transmitted therethrough, a readout layer formed on the base, which has in-plane magnetization at room temperature, whereas, a transition occurs from in-plane magnetization to perpendicular magnetization as the temperature thereof is raised and a recording layer formed on the readout layer for recording information magneto-optically. A recording and reproducing method and the optical head are designed for the magneto-optical recording medium. By the recording and reproducing method using the optical head, information recorded at high density can be reproduced.

Abstract: A magneto-optical head device includes a light source, an objective lens which condenses a light beam emitted from the light source, an auxiliary lens which converts an effective numerical aperture of the light beam condensed by the objective lens to irradiate a recording medium with the light beam, and a magnetic reproducing head which is integrated into the auxiliary lens. The magneto-optical head device can thus be decreased in size and information can be reproduced from both surfaces of a disk since the magnetic reproducing head is integrated into the auxiliary lens. Further, when a thermomagnetic recording medium is employed as the recording medium, the magneto-optical head device can reproduce information recorded at a high track density and a high line density.

Abstract: In an optical recording medium in which marks are allowed to be written at grooves and information has been recorded beforehand in the form of prepits, the depth of the grooves, Dg, and the depth of the prepits, Dp, satisfy the following relationships, respectively: Dg<&lgr;/8n, and &lgr;/8n<Dp<&lgr;/4n where &lgr; is a wavelength of light to be used for recording/reproducing of information signals, and n is an index of refraction of the substrate of the optical recording medium.

Abstract: In an optical recording medium in which marks are allowed to be written at grooves and information has been recorded beforehand in the form of prepits in a prepit area, the medium is constructed so that the groove width, Wg, the land width, Wl, and the prepit width, Wp, satisfy the relationships of either Wl<Wg, and Wp<Wg, or Wl>Wg, and Wp>Wg. Alternatively or additionally to the above, a sum of lengths of pit-presence portions in the prepit area is larger than a sum of lengths of pit-absence portions in the prepit area.

Abstract: Featured is a recording and reproducing method for recording and reproducing information on and from a recording medium. The medium includes a base having a property that a light can be transmitted therethrough, a readout layer formed on the base, which has an in-plane magnetization at room temperature, whereas, a transition occurs from in-plane magnetization to perpendicular magnetization as temperature rises and a recording layer formed on said readout layer for recording thereon information magneto-optically. A groove for guiding a light beam is formed on a readout layer side of the base and a groove width is set substantially equal to a land width formed between grooves. The recording layer on the grooves and the recording layer on lands are used in recording and reproducing information.

Abstract: An optical recording medium capable of obtaining a large reproduced signal from the recoded mark, a large reproduced signal of a pre-pit and a large tracking signal both in an area of the grooves and an area of the pre-pits, which provides a sufficient time allowance for switching tracking to that suitable for the area of the grooves or to that suitable for the area of the pre-pits. An optical recording medium comprising a substrate whereon tracks each comprising at least of writable grooves and pre-pits deeper than or equal to the grooves are formed and areas of a relatively shallow pits are each provided between an area of the deep pits and an area of the grooves. The depth Dg of the grooves, the depth Dsp of the shallow pits and the depth Ddp of the deep pits satisfy the following conditions: Dg<&lgr;/(8n), &lgr;/(8n)<Ddp<&lgr;/(4n) and Dg≦Dsp<Ddp. Tracking method is switched over in the shallow pit area when recording or reproducing information on the optical recoding medium.

Abstract: Light emitted from a light source is converged by an objective lens, and an auxiliary lens increases an effective numerical aperture to project the light on a recording medium. The temperature of a recording mark recording on the recording medium is increased by the projection of the light, and saturation magnetization which is in accordance with the information is generated, thus generating magnetic flux. There is a reproducing magnetic layer, which is provided on the auxiliary lens. Magnetization generated on the reproducing magnetic layer has an effect on the polarization direction of the reflected light at the reproducing magnetic layer. Reflected light from the reproducing magnetic layer reaches a photodetector to generate a reproduced signal.

Abstract: In an optical recording medium in which marks are allowed to be written at grooves and information has been recorded beforehand in the form of prepits, the depth of the grooves, Dg, and the depth of the prepits, Dp, satisfy the following relationships, respectively: