Nec Corporation

Mitsuya Okada

Shuichi Ohkubo

Tatsunori Ide

Masaki Itoh

Masaki Itou

Masaki Nakano

Masatsugu Ogawa

Toshiaki Iwanaga

Masashi Kubota

Hideki Tanabe

Takeharu Shibatoko

Syu-Ichi Ohkubo

Syuichi Ohkubo

Optical information recording and reproducing mediumhas two recording layers of first and second recording layersand, from a laser beam incident surface side. In each control area, recording layer management information containing at least information indicating recording states of a plurality of areas into which the inside of data recording areaof each recording layer is divided is recorded. When recording or reproducing is performed on the second recording layer, 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

Optical information recording and reproducing medium

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.

Optical information-recording medium and optical information recording/reproducing method

An information recording medium and an information reproduction apparatus that can substantially increase the capacity for recorded information. A preformat pit array exists on the extension of the boundary between a concave portion and a convex portion and includes information on both sectors across the boundary. An adjustment pit array precedes the preformat pit array 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 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

Information-recording medium and information reproducing apparatus

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. A foundation interference film is formed under the transparent lower protective film to adjust the transmittance of the phase-change recording film for the laser light.

Optical information recording medium and methods for recording, reading, and erasing information thereupon

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.

Optical information recording apparatus, optical recording medium, and

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.

Optical recording media

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. Hence, it is always possible to properly record, reproduce and erase data into or from a recording medium.

Apparatus for optically recording data into a disc

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. The thickness of the first protective film is set such that, of three reflectivities of the data writing film respectively in crystal, amorphous and melted states, the reflectivity in the crystal state and the reflectivity in the melted state are made different from each other, and the reflectivity in the amorphous state and the reflectivity in the melted state are made different from each other. A high speed writing operation can be carried out and an overwrite operation can be completed in one time disk rotation.

System and method for simultaneously verifying optical data writing and

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&gt;.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., 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 concave-convex pit which is formed on the high refractive-index layer; and a reflection layer which is formed on the concave-convex pit; wherein a width W.sub.p of the concave-convex pit and a refractive index n.sub.a of the high refractive-index layer are so set that the following relation: W.sub.p &gt;.lambda./(2xn.sub.a) is obtained.

High density optical information recording medium using high refractive

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. For this reason, it is substantially the same as the case in which the optical phase difference between the reflected laser light from the crystalline part of the recording film and the reflected laser light from the amorphous part of the recording film is zero, this making it possible to achieve consistency in the signal levels between land playback and groove playback. As a result, it is possible to perform double track density recording and mark edge recording.

Phase change optical disk and a method for recording and playbacking

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. The thickness of the first protective film is set such that, of three reflectivities of the data writing film respectively in crystal, amorphous and melted states, the reflectivity in the crystal state and the reflectivity in the melted state are made different from each other, and the reflectivity in the amorphous state and the reflectivity in the melted state are made different from each other. A high speed writing operation can be carried out and an overwrite operation can be completed in one disk rotation time.

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.

Single-substrate multi-layer optical disk for read-only storage and

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. The dielectric reflective film is formed on the dielectric film and has a refractive index higher than the refractive index of the transparent substrate.

Optical information recording medium

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. Light transmitted through the recording layer is multiple-reflected between the reflective layer and an interface between the interference layer and the first protection layer.

Re-writable phase change type optical disk with suppressed recording

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. At an input end of the optical detector, the reflection light and the phase-shifted reference light interfere with each other and the signal information having substantially no phase jitter is obtained at an output of the optical detector.

Growing community of inventors

Tokyo, Japan

Mitsuya Okada