Abstract: An elastic modulus according to the present embodiment includes a light source configured to generate light having a wavelength at which a material within a measurement target absorbs the light. An optical system causes the light to be passed through the measurement target at a desired aperture diameter and focuses the light on the material. A detector contacts the measurement target and detects an acoustic wave generated when the material absorbs the light. An operation unit calculates an elastic modulus of the material using a first acoustic-wave measurement value obtained in a case where the aperture diameter is a first diameter and a second acoustic-wave measurement value obtained in a case where the aperture diameter is a second diameter different from the first diameter.

Abstract: A tracking control is performed based on a first tracking error signal obtained from a first light beam reflected on an optical recording medium and a second tracking error signal obtained from a second light beam reflected on the optical recording medium. The first tracking error signal is corrected when recording information to or reproducing information from a first information recording layer that includes a first area facing an area on a second information recording layer with no information recorded and a second area facing an area on the second information recording layer with information recorded.

Abstract: An optical disk recording and reproducing apparatus includes a focus unit that focuses an irradiation light beam on an optical disk having data recording layers and tracks; a drive unit that changes a direction of the beam by moving the focus unit; a tilt control unit that detects a tilt amount of the optical disk, computes a control operation amount in a band wider than a rotation frequency of the optical disk based on the tilt amount, and controls the drive unit to move the focus unit based on the control operation amount. The tilt control unit holds a control state of the control at an immediate pre-state of an inter-layer jump in which the beam is moved to a different data recording layer or a track jump in which the beam is moved to a different track during the inter-layer jump or the track jump.

Abstract: A tracking control is performed based on a first tracking error signal obtained from a first light beam reflected on an optical recording medium and a second tracking error signal obtained from a second light beam reflected on the optical recording medium. The first tracking error signal is corrected when recording information to or reproducing information from a first information recording layer that includes a first area facing an area on a second information recording layer with no information recorded and a second area facing an area on the second information recording layer with information recorded.

Abstract: An optical disk recording and reproducing apparatus includes a focus unit that focuses an irradiation light beam on an optical disk having data recording layers and tracks; a drive unit that changes a direction of the beam by moving the focus unit; a tilt control unit that detects a tilt amount of the optical disk, computes a control operation amount in a band wider than a rotation frequency of the optical disk based on the tilt amount, and controls the drive unit to move the focus unit based on the control operation amount. The tilt control unit holds a control state of the control at an immediate pre-state of an inter-layer jump in which the beam is moved to a different data recording layer or a track jump in which the beam is moved to a different track during the inter-layer jump or the track jump.

Abstract: An optical recording/reproducing apparatus comprises a light beam emitting unit which emits a plurality of light beams to the recording medium, a photodetection unit which detects the reflected light beams and output detection signals, a detection signal selection unit which selects one of the detection signals according to one of a plurality of tracks which is selected in order to record or reproduce data, the tracks being formed on at least one of the land and the groove, and a tracking control unit which make one of the light beams trace the track which is selected in order to record or reproduce data, according to the selected detection signal.

Abstract: According to this invention, general addresses are given to a multi-layer information storage medium to facilitate handing of information. That is, it is possible to set generalized addresses for multiple information layers, and information indicating a condition for setting the general addresses, e.g., the contents of a disk ID zone in a rewritable zone of a lead-in area, is recorded on an information reproducing layer.

Abstract: An optical recording/reproducing apparatus comprises a light beam emitting unit which emits a plurality of light beams to the recording medium, a photodetection unit which detects the reflected light beams and output detection signals, a detection signal selection unit which selects one of the detection signals according to one of a plurality of tracks which is selected in order to record or reproduce data, the tracks being formed on at least one of the land and the groove, and a tracking control unit which make one of the light beams trace the track which is selected in order to record or reproduce data, according to the selected detection signal.

Abstract: According to this invention, general addresses are given to a multi-layer information storage medium to facilitate handing of information. That is, it is possible to set generalized addresses for multiple information layers, and information indicating a condition for setting the general addresses, e.g., the contents of a disk ID zone in a rewritable zone of a lead-in area, is recorded on an information reproducing layer.

Abstract: An optical disk used for writing and reading data in units of an error correction block containing a plurality of sectors by means of a light beam and comprising land and groove tracks arranged adjacent to one another and a plurality of emboss pits formed on a boundary between the land and the groove tracks to detect respective positions of the error correction blocks.

Abstract: An optical information recording medium comprises tracks having information recorded thereon as a mark portion where information is readable by irradiation of a light beam and a non-mark portion, wherein a first track whose optical phase difference between the mark portion and the non-mark portion is about .lambda. (1/4+k/2) and a second track whose optical phase difference between the mark portion and the non-mark portion is about .lambda. (1/8+m/4)(k and m are integers of 0 or more) are alternatively arranged when a wavelength of the optical beam is set to .lambda..

Abstract: An optical recording apparatus that rewrites recorded information on a modified constant angular velocity type phase change optical disk by overwriting using at least a recording light beam, erasing light beam and off-pulse light beam irradiation. The apparatus comprises a semiconductor laser for irradiating the optical disk with the light beam and a control unit for controlling the intensities P1, P2 and P3, wherein P1>P2>P3, of the light beam with which the optical disk is irradiated and their irradiation periods .tau.1 and .tau.3 to obtain a relation of{(P2-P3).times..tau.3}/{(P1-P2).times..tau.1}=below 1.

Abstract: An optical recording apparatus which records information by irradiating an optical recording medium with a light beam of a first intensity P1 for an irradiation period .tau.1 so as to form an amorphous state area in the recording medium, with a light beam of a third intensity P3 during an irradiation period .tau.3 and with a light beam of a second intensity P2 so as to form a crystal state area in the recording medium optical recording medium includes an information recording area provided for recording the recording information and a recording condition recording area provided for recording a recording condition. The recording condition recording area is provided on one of an outer circumference side and inner circumference side of the information recording area. The recording condition recording area stores recording condition data representing the intensities P1, P2, P3 (P1>P2>P3) and irradiation periods .tau.1, .tau.

Abstract: An optical recording and readout system comprises a first optical system for projecting a plurality of optical beams onto a phase-change optical disk, a second optical system for picking out the reflected light from the optical disk, a optical sensor for sensing the reflected light picked out by the second optical system, and a signal generating circuit for producing an information signal from the output signal from the optical sensor, wherein the phase-change optical disk contains a data area containing land tracks and groove tracks on both of which user information is recorded, the land tracks and groove tracks being formed on the data area alternately, and a header area in which header information is recorded in the form of prepit rows every other track with respect to the tracks including the land and groove tracks.

Abstract: An optical disk apparatus includes a semiconductor laser for emitting a light beam, and an automatic power control or APC circuit for driving the laser. A compound prism structure is optically coupled to the laser in an optical head section, and defines a first optical path for causing a front laser light to be projected onto a rotating optical disk and guiding a reflected light therefrom toward a first photodetector, and a second optical path for guiding a part of the reflected light toward a second photodetector. An output signal of the first photodetector is used to generate a reproduced information signal. An output signal of the second photodetector is fed back to the APC circuit as a front light monitor signal. A part of a laser control signal internally generated in the APC circuit is supplied through a wiring line to a noise reduction circuit as a laser noise monitor signal.

Abstract: A magneto-optical information storage medium includes a substrate, a recording layer formed on the substrate and having an axis of easy magnetization extending in the direction perpendicular to its surface, a nonmagnetic layer formed on the recording layer, and a bias layer, formed on the nonmagnetic layer, for generating bias magnetic field H.sub.B (T) in accordance with a temperature. The magnetization of the recording layer is reversed by bias magnetic field H.sub.B (T) in first and second magnetization reversal temperature regions T.sub.W and T.sub.E (T.sub.W >T.sub.E). Information is recorded on such a magneto-optical information storage medium by radiating a first laser beam having a first power level for heating an irradiated portion to a temperature in region T.sub.W. In addition, information erasing is performed by radiating a second laser beam having a second power level which is lower than the first power level and heats an irradiated portion to a temperature in region T.sub.E.

Abstract: To reduce the size and thickness of a magnetooptic head, a single hollow cylindrical permanent magnet magnetized in the radial direction thereof is arranged at the center of a condenser lens. The axial component of the magnetic flux is available for an external magnetic field required for recording and erasing operations, while the radial component of the magnetic flux is available for a magnetic field required for focusing operation in cooperation with a cylindrical focusing coil arranged coaxially with the cylindrical magnet.

Abstract: To minimize the size and thickness of a magnetooptic head, a plurality of permanent magnets are arranged symmetrical with respect to the center of a condenser lens in such a way that the magnetic flux extends in both axial and radial directions of the condenser lens or that the same magnet poles are confronted each other. The axial magnetic flux is available for external magnetic field required for recording and erasing operations; while the radial magnetic flux is available for a magnetic field required for focusing and tracking operation is cooperation with focusing and tracking coils. In addition, part of the radial magnetic flux is available for lens position detection in cooperation with Hall elements to generate a lens position signal.