Abstract: An optical disc having a track pitch of 0.85 .mu.m, a shortest pit length of 0.49 .mu.m, a pit depth of 100 nm, and a pit width of 0.35 .mu.m is rotate at a linear velocity of 2.4-2.8 m/s such that the same is optically reproduced by a laser beam having a wavelength of 635 nm which is converged to a spot size of 0.9 .mu.m by an objective lens having a numerical aperture of 0.6. Accordingly, data is read from the optical disc at a transfer rate of 5.6 Mbps.

Abstract: An optical pickup device provides ultraresolving prism between a semiconductor laser and an objective lens so as to reduce light intensity at around a cross sectional center of a laser beam, thereby generating ultraresolution thereon. An optical detector is disposed at a signal detecting position where the laser beam reflected by an optical disk is converged. The optical detector has a detecting element for receiving a main lobe and a pair of detecting elements for receiving a pair of side lobes. A peak of a shielding portion of the prism is inclined to a track center of the optical disk so that the side lobes are oppositely shifted from the track center. Thus, tracking error signals are obtained on the basis of detected signals in the side lobes.

Abstract: An optical disc having a track pitch of 0.85 .mu.m, a shortest pit length of 0.49 .mu.m, a pit depth of 100 nm, and a pit width of 0.35 .mu.m is rotated at a linear velocity of 2.4-2.8 m/s such that the same is optically reproduced by a laser beam having a wavelength of 635 nm which is converged to a spot size of 0.9 .mu.m by an objective lens having a numerical aperture of 0.6, Accordingly, data is read from the optical disc at a transfer rate of 5.6 Mbps.

Abstract: An apparatus is disclosed that reproduces data recorded on a recording medium having a plurality of pits formed in the medium that stores the data. The medium is designed to be compatible with an information reproducing apparatus having a lens with a first numerical aperture NA1 for focusing a laser beam of a first wavelength .lambda.1 on the recording medium. The apparatus of the present invention comprises a laser generator for generating a laser beam of a second wavelength .lambda.2 and a lens having a second numerical aperture NA2 for focusing the laser beam from the laser generator. The second wavelength .lambda.2 of the laser beam and the second numerical aperture NA2 of the lens are set to satisfy the relationship: (.lambda.2/NA2)<(.lambda.1/NA1).

Abstract: An optical pickup device provides an ultraresolving prism between a semiconductor laser and an objective lens so as to reduce light intensity at around a cross sectional center of a laser beam, thereby generating ultraresolution thereon. An optical detector is disposed at a signal detecting position where the laser beam reflected by an optical disk is converged. The optical detector has a detecting element for receiving a main lobe and a pair of detecting elements for receiving a pair of side lobes. A peak of a shielding portion of the prism is inclined to a track center of the optical disk so that the side lobes are oppositely shifted from the track center. Thus, tracking error signals are obtained on the basis of detected signals in the side lobes.

Abstract: A high density optical disc having a track pitch of 0.85 .mu.m, a shortest pit length of 0.49 .mu.m, a pit depth of 100 nm, and a pit width of 0.35 .mu.m is rotated at a linear velocity of 2.4-2.8 m/s such that the same is optically reproduced by a laser beam having a wavelength of 635 nm which is converged to a spot size of 0.9 .mu.m by an objective lens having a numerical aperture of 0.6. Accordingly, data is read from the optical disc at a transfer rate of 5.6 Mbps.

Abstract: The present track counter circuit is employed for a disk player of three-beam type. The track counter circuit includes a pickup having three sensors, two differential amplifiers, two zero cross detectors, an OR circuit and a counter. The first sensor is divided into two, and receives light reflected from a beam spot formed by a main beam. The outputs of the two sensor portions are applied to a first differential amplifier, the output of which is applied to a first zero cross detector. A second sensor receives light reflected from a beam spot formed by a sub beam, and a third sensor receives light reflected from a beam spot formed by another sub beam. The outputs of the second and third sensors are applied to a second differential amplifier, the output of which is applied to a second zero cross detector. The outputs of first and second zero cross detectors are applied to the OR circuit, and the counter counts crossing pulses therein in response to the OR output.