Abstract: An optical information recording medium, which has recording layers that include substrates of the same thickness and that correspond to laser light at two difference wavelength, has excellent compatibility. An optical disk, in which recoding or reproduction is performed from one plane through the substrate, has two recoding layers, and the recording density of a first layer is different from the recording density of a second layer. First recording layer 101 and second recording layer 102 are stacked on substrate 1. The laser beam for recording or reproduction is incident through substrate 1. Structurally, the disk is formed by laminating two recording layers on the side opposite to the laser beam incident side. Intermediate layer 103 which is transparent to a second laser beam is formed between the first and second layers. Laser beam with different wavelengths is used to record or reproduce the first and second layers.

Abstract: Optical information recording and reproducing medium 10 has two recording layers of first and second recording layers 12 and 14, from a laser beam incident surface side. In each control area 21, recording layer management information containing at least information indicating recording states of a plurality of areas into which the inside of data recording area 22 of each recording layer is divided is recorded. When recording or reproducing is performed on the second recording layer 14, the recording layer management information is checked, and a laser beam output is changed based on a recording state of an area corresponding to the first recording layer 12.

Abstract: Optical information recording and reproducing medium 10 has two recording layers of first and second recording layers 12 and 14, from a laser beam incident surface side. In each control area 21, recording layer management information containing at least information indicating recording states of a plurality of areas into which the inside of data recording area 22 of each recording layer is divided is recorded. When recording or reproducing is performed on the second recording layer 14, the recording layer management information is checked, and a laser beam output is changed based on a recording state of an area corresponding to the first recording layer 12.

Abstract: An optical information-recording medium comprises (a) a disk-shaped substrate having a first main surface and a second main surface opposite to the first main surface; an incidence surface of the medium being located to be nearer to the first main surface than the second main surface; (b) a recording layer formed on the substrate; and (c) a signal generation layer formed on the substrate in such a way as to be nearer to the incident surface than the recording layer. The signal generation layer allows an incident light beam irradiated to the incidence surface to pass through and allows a reflected light beam from the recording layer to pass through. The signal generation layer includes a transmittance changing region having a transmittance with respect to the incident light beam different from its neighborhood, thereby generating a repeated transmittance change according to rotation of the medium.

Abstract: In a method of carrying out a recording operation and a reproducing operation to a data record medium, the data record medium contains a data area, and a system area containing at least one of record control data areas, in each of which record control data for user data recorded in the data area has been recorded. This method is achieved by extending a record control data area in a data area, and by recording a replica of the record control data containing a latest record control data in a predetermined replica record control data area of the data record medium when the record control data area is extended.

Abstract: Optical information recording and reproducing medium 10 has two recording layers of first and second recording layers 12 and 14, from a laser beam incident surface side. In each control area 21, recording layer management information containing at least information indicating recording states of a plurality of areas into which the inside of data recording area 22 of each recording layer is divided is recorded. When recording or reproducing is performed on the second recording layer 14, the recording layer management information is checked, and a laser beam output is changed based on a recording state of an area corresponding to the first recording layer 12.

Abstract: An information recording medium and an information reproduction apparatus that can substantially increase the capacity for recorded information. A preformat pit array 202 exists on the extension of the boundary between a concave portion 103 and a convex portion 104 and includes information on both sectors across the boundary. An adjustment pit array 201 precedes the preformat pit array 202 in the advancing direction of light that reproduces information recorded on an information recording medium. The information reproduction apparatus adjusts the amplifying rate so that the level of a signal from the adjustment pit array 201 becomes equal to a reference level required to reproduce the information correctly. The apparatus then uses this amplifying rate to correctly reproduce the information in the preformat pit array 202.

Abstract: There is disclosed an optical information recording medium having phase-change recording films whose the transmittance can be made substantially uniform irrespective of the presence or absence of recording. There are also disclosed methods for recording, reading, and erasing information well at a high density on such a medium. Each of the phase-change recording films other than the top one has a phase-change recording film for recording and erasing information by a phase change caused by illumination of laser light. A transparent upper protective film is formed on the phase-change recording film to protect the phase-change recording film mainly against thermal deformation during recording and erasing of information. A transparent lower protective film is formed under the phase-change recording film to protect the phase-change recording film mainly against thermal deformation during recording and erasing of information.

Abstract: An optical information-recording medium comprises (a) a disk-shaped substrate having a first main surface and an a second main surface opposite to the first main surface; an incidence surface of the medium being located to be nearer to the first main surface than the second main surface; (b) a recording layer formed on the substrate; and (c) a signal generation layer formed on the substrate in such a way as to be nearer to the incident surface than the recording layer. The signal generation layer allows an incident light beam irradiated to the incidence surface to pass through and allows a reflected light beam from the recording layer to pass through. The signal generation layer includes a transmittance changing region having a transmittance with respect to the incident light beam different from its neighborhood, thereby generating a repeated transmittance change according to rotation of the medium.

Abstract: A tracking groove comprising a land area and a groove area is previously provided on a substrate of an optical disk, and a prepit is previously provided on a boundary line between the land area and the groove area of the tracking groove. When information is recorded on both the land and groove areas, a half-split photodetector split into two parts by a splitting line perpendicular to the radial direction of the optical disk is used as a photoreceiver for receiving light reflected from the optical disk. The photoreceivers are switched so that light reflected from the prepit is reproduced as a signal in any one of the two photodetectors. This enables reproduction signals derived from light reflected from the prepit to be reproduced at a good S/N ratio, thus realizing an optical information recording apparatus which bas a simple construction and enables information to be recorded on both the land and groove areas.

Abstract: An optical data recording medium utilizing reversible inter-crystalline-amorphous phase changes for recording, reproducing and erasing data as phase changes of a recording film caused by laser beam irradiation. The medium is formed by a lamination of a transparent substrate having tracking guide grooves for laser beam tracking, a base film formed on the substrate, a first protective film formed on the base film, a phase change type recording film formed on the first protective film, a second protective film formed on the recording film, and a reflecting film formed on the second protective film. Thus formed, the medium improves the over-writing characteristics of phase change type optical discs and permits high density recording.

Abstract: There is provided an apparatus for optical recording, reproducing and erasing data into or from a recording medium, including an optical head for recording, reproducing or erasing data into or from a recording medium by emitting a light to the recording medium, the optical head including at least an objective lens and a laser diode, a sensor for sensing a thickness of the recording medium, and a focal distance compensator for varying a focal distance of the light in accordance with a thickness sensed by the sensor, the focal distance compensator including a convex lens located between the objective lens and the laser diode and designed to be able to located in or out of an optical path. In accordance with the above-mentioned apparatus, a thickness of a recording medium is readily measured by the sensor, and the focal distance compensator adjusts a focal distance of a light emitted from the light source in accordance with the measured thickness of a recording medium.

Abstract: The optical disk writing system disclosed is one in which a data written on an optical data writing medium is verified essentially simultaneously with the writing on the medium. The written data is verified by detecting a timing of the light irradiated on the medium and by measuring return light doses at a rise and a fall of the light irradiated on the medium and comparing the doses thereof with predetermined reference values. The medium used is one which uses a phase transition reversible between a crystal state and an amorphous state for writing/reading/erasing of data on a data writing film and includes, a first protective film, a phase transition type data writing film, a second protective film, a reflection film formed in this order on a transparent substrate.

Abstract: Disclosed are an optical information recording medium for recording, reproducing and erasing information by emitting laser light with a wavelength in vacuum of .lambda., which has: a transparent substrate through which the laser light can be transmitted; a high refractive-index layer which is formed on the transparent substrate; a guide groove for tracking which is formed on the high refractive-index layer; and a recording layer which is formed on the guide groove for tracking; wherein a width W of the guide groove for tracking and a refractive index n.sub.a of the high refractive-index layer are so set that the following relation: W>.lambda./(2xn.sub.a) is obtained, and an optical information recording medium for reproducing information by emitting laser light with a wavelength in vacuum of .lambda.

Abstract: The optical phase difference between reflected laser light from the crystalline and the amorphous part of a phase change recording layer is established as 180 degrees .+-.5 degrees. The ratio between the light absorption factor when the phase change recording film is in the crystalline condition to that when it is in the amorphous condition is set to within the range 0.9 to 1.1. With the wavelength of the laser light used as .lambda., the optical depth of a guide groove formed on the substrate is set to within the range .lambda./9 to .lambda./6. With the wavelength of the laser light used in the range 635 nm to 650 nm, the depth of the guide groove is in the range 40 to 70 nm. In an optical disk such as this, when seen from reflected light, the groove region of a groove during playback and land region of the groove during playback are optically equivalent.

Abstract: The optical disk writing system disclosed is one in which data written on an optical data writing medium is verified essentially simultaneously with writing on the medium. The written data is verified by detecting a timing of the light irradiated on the medium and by measuring return light doses at rise and fall of the light irradiated on the medium and comparing the doses thereof with predetermined reference values. The medium uses a phase transition reversible between a crystal state and an amorphous state for writing/reading/erasing of data on a data writing film, and includes a first protective film, a phase transition type data writing film, a second protective film, and a reflection film, formed in this order, on a transparent substrate.

Abstract: An optical disk includes a transparent rigid substrate, a phase change rewritable optical recording medium formed on the transparent rigid substrate, a transparent spacer formed on the phase change rewritable optical recording medium and having a grooved surface for storing information, and a reflecting layer formed on the grooved surface of the transparent spacer. The grooved surface of the transparent spacer and the reflecting layer form a read-only recording medium.

Abstract: An optical information recording medium includes a transparent substrate, a first protection film, a recording film, a second protection film, a dielectric film, and a dielectric reflective film. The first protection film is formed on the transparent substrate. The recording film is formed on the first protection film to record and erase information by causing a reversible phase change between a crystalline state and an amorphous state upon being irradiated with a laser beam, and reproduce recorded information by detecting a change in optical nature accompanying the phase change in the recording film. The second protection film is formed on the recording film to protect the recording film together with the first protection film. The dielectric film is formed on the second protection film and has a refractive index lower than a refractive index of the transparent substrate.

Abstract: A phase change type optical disk includes a transparent substrate, a recording layer, a first transparent protection layer, a reflective layer, and a transparent interference layer. The recording layer is formed above the transparent substrate to cause a reversible phase change between a crystalline state and an amorphous state. The recording layer causes a phase change upon being irradiated with a laser beam, thereby recording, reproducing, and erasing information. The first transparent protection layer is formed on the recording layer to protect the recording layer. The reflective layer is formed above the recording layer to reflect light transmitted through the recording layer and causes the reflected light to be incident on the recording layer. The transparent interference layer is formed between the first protection layer and the reflective layer to cause light beams reflected by the reflective layer to optically interfere with each other.

Abstract: A signal information recorded on a recording layer formed on a phase-change type optical disk is reproduced as a phase change. Laser light emitted from a laser light source is collimated to a reference light by a lens. The reference light is divided by a beam splitter into a first reference light and a second reference light. The first reference light is directed through a condenser lens to the recording layer of the optical disk. A reflection light from the recording layer is directed through the beam splitter and a second condenser lens to an optical detector. The second reference light is passed through a phase difference plate, a reflection mirror, the phase difference plate, the beam splitter and then through the second condenser lens to the optical detector as a phase shifted reference light.