Abstract: An optical recording/reproducing method employs a recording laser beam having a first output and a first wavelength, and a reproducing laser beam having a second output lower than the first output and a second wavelength shorter than the first wavelength. A disk-like recording medium is irradiated with the recording and reproducing laser beams by use of an objective lens having an NA of about 0.55 so that a small mark equal to or smaller than about one fourth of a spot size optically defined from the wavelength of the recording laser beam and the NA of the objective lens is formed on the recording medium by a recording characteristic of the recording medium and a shielding plate provided in an optical system for irradiation with the laser beam. Two-dimensional recording is performed as a recording system to arrange marks at lattice points of a two-dimensional lattice which extend in a track direction and a track radius direction.

Abstract: An optical recording/reproducing method and apparatus using an optical recording medium in which grooves and lands are formed on a substrate, information recording areas are formed in association with both the groove and land, and having a flat address area. First and second address pits are disposed in the address area and satisfy predetermined requirements. An optical spot is irradiated on the optical recording medium and a reflected beam from the optical recording medium is detected which includes detection of an address pit so as to form an address pit readout signal. An address is detected on the basis of the address pit readout signal, wherein an amplitude of a first readout signal obtained from the first address pit is sampled and held and compared with an amplitude of a second readout signal obtained from the second address pit, which is sampled and held. The irradiation position of the optical spot is controlled in accordance with a result of the comparison.

Abstract: A super high density optical disk apparatus is obtained by using an exchangeable recording medium having a recording capacity of at least 1.5 Gb/in.sup.2 in an optical recording and reading apparatus for recording or reading at least using a laser beam or by using one of means which can record on a recording medium only once and means which can record at least two times repeatedly as recording means to be used.

Abstract: An optical recording/reproducing method employs a recording laser beam having a first output and a first wavelength, and a reproducing laser beam having a second output lower than the first output and a second wavelength shorter than the first wavelength. A disk-like recording medium is irradiated with the recording and reproducing laser beams by use of an objective lens having an NA of about 0.55 so that a small mark equal to or smaller than about one fourth of a spot size optically defined from the wavelength of the recording laser beam and the NA of the objective lens is formed on the recording medium by a recording characteristic of the recording medium and a shielding plate provided in an optical system for irradiation with the laser beam. Two-dimensional recording is performed as a recording system to arrange marks at lattice points of a two-dimensional lattice which extend in a track direction and a track radius direction.

Abstract: Learning marks are recorded in a learning region preceding a data recording region of the track. The positions of information recording lattice points are staggered by one lattice point between two contiguous tracks. At reading of recorded information, a two-dimensional information leakage amount is detected by the reproduced signals from a learning mark preceding a target information recording lattice point on a track, and from the information recording lattice points immediately before and after the learning mark in question. The equalization coefficients are calculated from leakage amount thus obtained. The crosstalk present in a reproduced signal for the target lattice point is removed by using this equalization coefficients and a pair of reproduced signals from intermediate lattice points which are located immediately before and after the current lattice point and which are not used to record information marks.

Abstract: In an optical disk recording medium having grooves and lands formed on a substrate and information recording areas formed in association with both the groove and the land, prepits are disposed on a virtual extension of the boundary between a groove and a land, the prepits being disposed to satisfy such requirements that the prepits are disposed on both sides of a virtual extension of the center line of a groove, that the prepits are disposed on both sides of a virtual extension of the center line of a land, that the prepits do not exist on both sides of a position on the center line of the groove, and that the prepits do not exist on both sides of a position on the center line of the land.

Abstract: An optical disk device having a light source for emitting light, focusing optics for radiating and focusing the light onto an optical recording medium, a photo-detection system for photoelectrically transforming reflected light from the optical recording medium, a reproduction circuit for reproducing information recorded on the optical recording medium by using an electric signal from the photo-detection system, phase control optics for changing the phase of the reflected light, a readout control circuit for controlling the quantity of the phase change of the phase control optics, and a learning control circuit for calculating the optimum value of the phase change quantity by monitoring the output signal of the reproduction circuit while changing the quantity of the phase change by the readout control circuit. Thus, information can be reproduced from a recording medium having high recording density without crosstalk.

Abstract: An optical information reproducing method, for optically reproducing information recorded on a recording medium, irradiates the recording medium with a laser beam and detects the light returning from the recording medium. When the diffracted light returning from the recording medium is detected, the optical intensity distribution of the diffracted light is detected by a plurality of detectors to produce a plurality of signals, and the signals are calculated to produce a reproduced signal for detecting the information.

Abstract: An optical disk device which improves the S/N ratio of reproduced signals and increases the recording density on it. Pulsed reproducing light is projected onto the data detection points on the optical disk medium to reproduce the data. This enables the reproduction of signals of large optical intensity without raising the temperature of the recording layer. A servo region is irradiated with DC light to form channel clocks from the PLL.

Abstract: An optical recording apparatus includes an optical system to focus a beam of light onto an optical recording medium; a laser source to generate the beam; a laser driver that modulates the output of the beam according to digital information to be recorded; and a controller that performs control in such a way that the average power per unit recording time of the beams used to record digital information "1" (or "0") and digital information "0" (or "1") onto the recording medium are virtually equal, and so that the peak power of the beams used to record the digital information "1" (or "0") and the digital information "0" (or "1") differ from each other.

Abstract: For use with an optical disk having a plurality of reference marks Mk arranged at intervals of P in the radial direction and deviant marks Hx (x=1, 2, . . . ) arranged so as to deviate in at least two different phases in the radial direction from the reference marks Mk, an optical disk tracking control method comprising the steps of: generating tracking error signals A, B, . . . with at least two different phases obtained by addition and subtraction on combinations of the light quantity signal corresponding to the reference mark Mk and the light quantity signals corresponding to the deviant marks Hx; and positioning the data tracks at intervals of P/4 or less in the radial direction based on the tracking error signals A, B, . . . .

Abstract: A super high density optical disk apparatus is obtained by using an exchangeable recording medium having a recording capacity of at least 1.5 Gb/in.sup.2 in an optical recording and reading apparatus for recording or reading at least using a laser beam or by using one of an element which can record on a recording medium only once and another element which can record at least two times repeatedly as recording elements to be used.

Abstract: A variable readout signal with at least one reference level to obtain digital data having two or more values. Based upon demodulated digital data, a standard level having two or more values is caused to change following the level of a readout signal having two or more values, and the reference level is changed based upon the change of the standard level.

Abstract: In a three-dimensional recording and reproducing apparatus having a recording medium including a plurality of recording layers stacked on a substrate and an optical system for converging a light irradiated from the substrate side on each of the plurality of recording layers to three-dimensionally record and reproduce information, the following equation is satisfied:.lambda./4.ltoreq.(1/8NB)(1/NB.sup.2 -1)NAF.sup.4 .DELTA.dwhere.lambda.: Wavelength of the light;NB: Refractivity of the substrate 3;NAF: Numerical aperture of a focus lens 8 for converging a light;.DELTA.d: Positional range in the optical axis direction in which exists a recording layer on which the light is to be converged.A light spot is focused on each layer of the multi-layer structured disc to record and reproduce highly reliable data in a high density.

Abstract: An optical disk device which uses a light spot for reproducing data, including photodetector, a decoder, and a non-linear equalizer provided between the photodetector and the decoder for correcting non-linear distortions in a reproduced signal from an optical disk. The non-linear equalizer includes a linear equalizer and a decision feedback equalizer provided after the linear equalizer. The non-linear equalizer includes a detector for detecting a signal on the basis of the output of the linear equalizer with the output of the detector being input to the decision feedback equalizer, the output of which is input to the detector along with the output of the linear equalizer in an additive manner.

Abstract: An information recording/reproducing method is disclosed for an information recording/reproducing apparatus including a recording medium having a disk-like shape, a unit for rotating the recording medium at a constant angular velocity, a unit for recording code information so that the bit length of the code information becomes approximately constant with respect to a radial position on the recording medium, a unit for modulating the code information to be recorded to form a modulated signal, and a recording unit for forming in the recording medium a localized recording region having a different physical property with respect to an unrecorded region, the recording unit being controlled by the modulated signal so that the code information is recorded to correspond to the edge of the recording region, wherein the bit rate of the code information to be recorded changes depending on a location on the recording medium, and a part of each of a recording characteristic of the apparatus and a reproducing characteristi

Abstract: An optical recording medium on which information is recorded by irradiating the medium with a light spot to cause a characteristic change of an actual reflection factor, the optical recording medium including grooves of different optical depths which extend in a direction in which the light spot is moved relative to the medium and which are alternately and periodically formed in a direction perpendicular to the relative movement direction of the light spot so that a plurality of grooves thereof can be covered by the light spot, and mark recording regions provided on the flat surfaces between the grooves, the pitch of the flat surfaces between the grooves being selected to be substantially half the diameter of the light spot, thus increasing the recording density and preventing the cross-talk. A method and apparatus for reproducing the information recorded on the medium are provided.

Abstract: An optical information recording/reproducing method includes that information is recorded on a rotary disk in an optically discriminative form, a light emitted from a light source is focused on the surface of the disk to form a light spot, the information is scanned with the light spot relative thereto in a rotating direction of the disk, and a reflection light or transmitting light from the disk is collected by an optical system to record or reproduce the information.

Abstract: An information recording medium includes an information recording layer on which at least information is to be recorded by irradiating light, and a light transmission restricting layer which has a plurality of nonlinear transmission characteristics or nonlinear reflection characteristics for the intensity of the light irradiated and which has an optical material for restricting the transmission or reflection of the light according to the respective characteristics when the light is irradiated onto the information recording layer. An information recording and reproducing unit uses the information recording medium and includes an information recording position setting unit for deciding a position at which information is to be recorded on the information recording medium by detecting a direction of an easy magnetization axis.

Abstract: A method and an apparatus for recording and reproducing information for use with an optical disk apparatus in which a pit edge recording method is used. According to the pit edge recording method, the leading edge and the trailing edge of a hole pit or a record domain generated during a recording operation are dealt with as information. During the recording, the recording pulse width and the recording power are corrected, and during the reproduction, the variation in the edge position is corrected.