Abstract: A method for reproducing write-once information from an optical disk. The disk includes a disk substrate and a recording layer on the disk substrate, the recording layer including a magnetic film with a magnetic anisotropy in a direction perpendicular to a surface of the magnetic film. Write-once information formed by first recording areas and second recording areas is stored in a pre-determined portion of said recording layer, the first and second recording areas having different magnetic anisotropies in a direction perpendicular to a surface of the magnetic film. The method includes irradiating linearly polarized laser light onto said pre-determined portion, and detecting a rotational change in a polarization orientation of light reflected from the optical disk or light transmitted through the optical disk, the rotational change being caused depending on which of the first recording area and the second recording area is irradiated with the linearly polarized laser light.

Abstract: An information recording/reproducing apparatus determines whether ejection of an optical disk stored in an optical disk drive or in a changer is allowed when receiving a command for ejecting the optical disk to the outside. The information recording/reproducing apparatus allows the optical disk to be ejected only when judging that the ejection is allowed. When judging that the ejection is not allowed, the information recording/reproducing apparatus rejects the ejection. Prohibition of ejection of an optical disk on which information whose copyright is to be protected has been recorded enables the use of the information for private hobby and at the same time prevents pirated versions or the like from being produced, thus realizing copyright protection.

Abstract: The optical recording medium of this invention includes: a first substrate having a first information surface; a semitransparent reflection film formed on the first information surface of the first substrate; a second substrate having a second information surface; a reflection film formed on the second information surface of the second substrate; and an adhesive layer for adhering the first substrate and the second substrate so that the first information surface and the second information surface face each other, wherein the thickness of the first substrate is 0.56 mm or more, the thickness of the adhesive layer is 30 &mgr;m or more, and the total thickness of the first substrate and the adhesive layer is 0.68 mm or less.

Abstract: The optical recording medium of this invention includes: a first substrate having a first information surface; a semitransparent reflection film formed on the first information surface of the first substrate; a second substrate having a second information surface; a reflection film formed on the second information surface of the second substrate; and an adhesive layer for adhering the first substrate and the second substrate-so that the first information surface and the second information surface face each other, wherein the thickness of the first substrate is 0.56 mm or more, the thickness of the adhesive layer is 30 &mgr;m or more, and the total thickness of the first substrate and the adhesive layer is 0.68 mm or less.

Abstract: A returning light beam emitted by a light source and reflected by an optical disk is separated by a half mirror, and partitioned and deflected at a hologram into a light beam passing a first region and a light beam passing a second region. The light beam passing the first region is received by a plurality of photo-detectors, and the aberration is detected by comparing the resulting signals. Based on the aberration detection, the aberration of an optical system can be reduced by driving an aberration correction element in real-time.

Abstract: A returning light beam emitted by a light source and reflected by an optical disk is separated by a half mirror, and partitioned and deflected at a hologram into a light beam passing a first region and a light beam passing a second region. The light beam passing the first region is received by a plurality of photo-detectors, and the aberration is detected by comparing the resulting signals. Based on the aberration detection, the aberration of an optical system can be reduced by driving an aberration correction element in real-time.

Abstract: A data transmission system for transmitting information data with a parity of an error correcting code for correcting an error in the information data. A read-out controller controls a transmitter to transmit information data and a parity so that each data component of the information data obtained by dividing the information data of one data block area into a plurality of data components and each parity component of the parity obtained by dividing the parity of one block area into a plurality of parity components are transmitted at intervals along each sector having a sector address. The sector is defined as an data area obtained by dividing one data block area of a predetermined data amount into a plurality of sectors each having an identical data amount.

Abstract: In an optical disc, an ID field contains a plurality of address information, and is preliminarily recorded in convex and concave signals, and is composed of two sets offset by about ½ track pitch toward the internal or external track direction adjacent to the guide track, an information recording field is composed of grooves and lands oscillating at a single frequency in the radial direction, and the grooves and lands alternate in every revolution of the guide track. When w bits of information are included in one period of oscillation, an information unrecorded field between the ID field and information recording field is arranged to have a length of w/10 bits or more and/or w bits or less, and therefore, when recording continuous information data such as video data, it is possible to record continuously by generating a clock securely from the oscillating signal, and moreover, the format efficiency is improved, so that a format of a larger capacity is achieved.

Abstract: The optical recording medium of this invention includes: a first substrate having a first information surface; a semitransparent reflection film formed on the first information surface of the first substrate; a second substrate having a second information surface; a reflection film formed on the second information surface of the second substrate; and an adhesive layer for adhering the first substrate and the second substrate so that the first information surface and the second information surface face each other, wherein the thickness of the first substrate is 0.56 mm or more, the thickness of the adhesive layer is 30 &mgr;m or more, and the total thickness of the first substrate and the adhesive layer is 0.68 mm or less.

Abstract: An optical disk storing write-once information usable for protecting the copyright of the software by preventing the duplication, unauthorized use, etc., of the software. In the optical disk, a recording layer (213) is formed on a disk substrate (211) with a dielectric layer (212) inbetween. Then, an intermediate dielectric layer (214) and a reflecting layer (215) are successively laminated upon the recording layer (213), and an overcoat layer (216) is formed on the surface of the reflecting layer (215). A plurality of BCA (one of write-once identification information systems) sections (220a and 220b) are recorded by lowering the vertical magnetic anisotropy of the recording layer (213). At the time of reproduction, the write-once information is detected from differential signals.

Abstract: The optical recording medium of this invention includes: a first substrate having a first information surface; a semitransparent reflection film formed on the first information surface of the first substrate; a second substrate having a second information surface; a reflection film formed on the second information surface of the second substrate; and an adhesive layer for adhering the first substrate and the second substrate so that the first information surface and the second information surface face each other, wherein the thickness of the first substrate is 0.56 mm or more, the thickness of the adhesive layer is 30 &mgr;m or more, and the total thickness of the first substrate and the adhesive layer is 0.68 mm or less.

Abstract: An optical disk and a method for storing write-once information usable for preventing the illegal copies. The optical disk comprises a disk substrate, and a recording layer having a magnetic film disposed on the disk substrate. The optical disk stores write-once information formed by first recording areas and second recording areas and the write-once information being different for each disk. The second recording areas are formed as a plurality of stripe-shaped marks that are oblong in a radial direction of the disk by irradiating laser light based on a modulation signal of the write-once information in the pre-determined portion of the recording layer, in a manner that a magnetic anisotropy in a direction perpendicular to a surface of the second recording areas is smaller than a magnetic anisotropy in a direction perpendicular to a surface of the first recording areas.

Abstract: An optical information processing apparatus includes: an optical head for radiating a light beam onto an information storage medium and generating a reproduction signal from the light beam reflected an/or diffracted from the information storage medium, the information storage medium carrying optically readable information recorded thereon; a transportation member for causing a relative movement of the optical head with respect to the information storage medium; and a signal processing circuit for receiving the reproduction signal generated by the optical head and processing the reproduction signal.

Abstract: One or more optical discs, each having a ROM field having information with a length of at least one track formed in convex and concave pit rows, and a rewritable field capable of rewriting the information with a length of at least one track, an information unrecorded field having a length of at least one track located between the ROM field and rewritable field, the rewritable field having a spiral or concentric guide track oscillating in a radial direction, the ROM field having spiral or concentric convex and concave pit rows, and at least a part field at the rewritable field side of the information unrecorded field has a transition field having a spiral or concentric guide track oscillating in the radial direction continuously or intermittently and a track pitch To of the ROM field and a track pitch Tw between grooves and lands of the rewritable field have values such that To>Tw.

Abstract: The optical recording medium of this invention includes: a first substrate having a first information surface; a semitransparent reflection film formed on the first information surface of the first substrate; a second substrate having a second information surface; a reflection film formed on the second information surface of the second substrate; and an adhesive layer for adhering the first substrate and the second substrate so that the first information surface and the second information surface face each other, wherein the thickness of the first substrate is 0.56 mm or more, the thickness of the adhesive layer is 30 .mu.m or more, and the total thickness of the first substrate and the adhesive layer is 0.68 mm or less.

Abstract: In an optical disc, an ID field contains a plurality of address information, and is preliminarily recorded in convex and concave signals, and is composed of two sets offset by about 1/2 track pitch toward the internal or external track direction adjacent to the guide track, an information recording field is composed of grooves and lands oscillating at a single frequency in the radial direction, and the grooves and lands alternate in every revolution of the guide track. When w bits of information are included in one period of oscillation, an information unrecorded field between the ID field and information recording field is arranged to have a length of w/10 bits or more and/or w bits or less, and therefore, when recording continuous information data such as video data, it is possible to record continuously by generating a clock securely from the oscillating signal, and moreover, the format efficiency is improved, so that a format of a larger capacity is achieved.

Abstract: The optical recording medium of this invention includes: a first substrate having a first information surface; a semitransparent reflection film formed on the first information surface of the first substrate; a second substrate having a second information surface; a reflection film formed on the second information surface of the second substrate; and an adhesive layer for adhering the first substrate and the second substrate so that the first information surface and the second information surface face each other, wherein the thickness of the first substrate is 0.56 mm or more, the thickness of the adhesive layer is 30 .mu.m or more, and the total thickness of the first substrate and the adhesive layer is 0.68 mm or less.

Abstract: A data transmission system for transmitting information data with a parity of an error correcting code for correcting an error in the information data. A read-out controller controls a transmitter to transmit information data and a parity so that each data component of the information data obtained by dividing the information data of one data block area into a plurality of data components and each parity component of the parity obtained by dividing the parity of one block area into a plurality of parity components are transmitted at intervals of each sector having a sector address. The sector is defined as an data area obtained by dividing one data block area of a predetermined data amount into a plurality of sectors each having an identical data amount.

Abstract: A digital modulation apparatus applies a method for converting data words to runlength-limited code words using plural conversion tables. The data words are converted to code words that significantly suppress the low frequency component of the final nonreturn-to-zero inverted signal.This digital modulation apparatus includes ROM tables for storing plural conversion tables containing the runlength-limited code words corresponding to the data words; end-runlength memories and evaluators for determining whether the runlength-limit constraints are satisfied in the interconnection between two consecutive code words when the data words to be converted are supplied; and a DSV controller for storing each of the code words that can be selected from two conversion tables to buffer memories when the runlength-limit constraints are satisfied, and selecting the code words wit the greatest effect suppressing the low frequency component in the obtained signal when the code words are NRZI converted.

Abstract: A data transmission apparatus for transmitting an original data has a converter for converting the original data to sequential data codes. The data code is formed by a combination of HIGH level binary codes and LOW level binary codes. The maximum length of a continuous binary codes of one level, such as HIGH level, in the data codes is limited to T.sub.max, e.g., to 14T, in which T is a unit length representing one binary code, and the minimum length of a continuous binary codes of one level, such as HIGH level, in the data codes is limited to T.sub.min, e.g., 3T. A generator generates a synchronization code. The synchronization code is formed by a combination of HIGH and LOW level binary codes. The synchronization code comprises an identifier having a continuous binary codes of one level, such as HIGH level, with a predetermined length 16T which is 2T greater than T.sub.max. An inserter inserts the synchronization code intermittently in the sequential data codes.