Abstract: In an optical information recording and/or reproducing apparatus, information is recorded by applying a beam of light to an optical recording medium and/or the recorded information is reproduced by receiving the reflected light of a beam of light applied to the optical recording medium by a photosensor divided into a plurality of sections. The apparatus has a subtractor for subtracting a plurality of signals from the photosensor divided into a plurality of sections, dividing means for dividing a part of a photocurrent from the photosensor into a predetermined frequency component and a predetermined high frequency component, amplifying means for amplifying the signal of the low frequency component and the signal of the high frequency component produced by the dividing means, an adder for adding the both signals amplified by the amplifying means, and a divider for dividing a subtraction signal obtained by the subtractor by an addition signal obtained by the adder to thereby normalize a servo signal.

Abstract: An information recording and/or reproducing apparatus comprises a head section to record and/or reproduce information onto/from an information recording medium having a shape other than a circular shape, holding device for holding the information recording medium and rotating the medium, moving device for moving the holding device in a predetermined direction, detecting device for detecting a rotating position of the information recording medium held to the holding device, and control device for controlling movable guide device in correspondence to a signal from the detecting device.

Abstract: There is disclosed an information recording disk, and a method and apparatus for information recording and reproduction, enabling secure tracking and full utilization of the recording capacity. For this purpose, a spiral or concentric track divided into plural sectors is provided with servo signals for detecting tracking error, by an integral number per sector, and the number is made different between the tracks in the radially inner area of the disk and those in the outer area. The disk is rotated at a constant angular velocity, and the tracking error is detected by the servo signals with a first clock signal of a constant frequency, while the information recording and/or reproduction is conducted with a second clock signal having a frequency higher for the tracks in the outer area of the disk.

Abstract: An optical information recording medium includes a recording surface formed by a recording layer provided on a substrate, the recording surface being provided with parallel information tracks each divided into plural blocks, each of which is formed by a data area for information recording and a servo area for forming prepits for tracking signal detection, wherein the data area has a separating part the height of which is different from that of the information track and which is provided between information tracks adjacent to each other, and the difference in height is equal to or larger than the thickness of the recording layer, and wherein the servo area is not provided within the separating part.

Abstract: An optical information recording apparatus includes a recording device for condensing a light beam into a spot-like shape, the light beam having been intensity-modulated between at least two levels which are not zero, scanning the light beam on a recording medium and recording information thereon; a detector for detecting a signal indicative of the position error between the light beam spot and the medium in the focusing direction perpendicular to the surface of the medium or the tracking direction in a plane parallel to the surface of the medium which is perpendicular to tracks formed on the medium; a servo device for correcting the position error on the basis of the detected signal; a device for varying the gain of the servo device in conformity with the intensity level of the light beam for producing a gain output; and a device for sampling and holding the gain output as the intensity of the light beam shifts between different levels.

Abstract: A position detecting device includes a: generator for generating a plurality of phase-shifted signals which are alternately changed in accordance with changes in position or angle of a movable member; a selector for selecting one of the plurality of signals; supplier for supplying a variable level signal; adder for adding a signal selected by the selector and the variable level signal from the signal supplier and outputting a sum signal as a position detection signal; a detector for detecting a phase of the selected signal; and a controller for switching the signal selected by the selector and changing a level of the variable level signal from the signal supplier in accordance with an output from the phase detector.

Abstract: An apparatus for applying a light beam to an optical recording medium having tracks provided thereon and effecting at least one of recording and reproduction of information includes a light source emitting the light beam, an optical system for directing the light beam emitted from the light source to the medium, a device for receiving the light flux reflected by or transmitted through the medium and detecting a tracking error signal indicative of the deviation between the applied position of the light beam and a track, a tracking servo for moving at least a portion of the optical system on the basis of the tracking error signal and correcting the applied position of the light beam, a detector for detecting abnormality of tracking servo from the velocity of the moved portion of the optical system.

Abstract: An optical information processing apparatus comprises an optical head having an optical system contained in a frame and effecting at least one of recording and reproduction of information by applying a light beam condensed by the optical system to a recording medium, a detector for detecting at least one of a tracking signal and a focusing signal, a controller for moving at least a portion of the optical system in accordance with at least one of the tracking signal and the focusing signal, a detector for detecting the postion of the moving portion of the optical system relative to the frame, a position controller for controlling the moving portion so as to be held in a predetermined position, on the basis of the output signal of the position detecting detector, a detector for detecting the abnormality of at least one of the tracking and focusing controls, and a switching device for alternatively operating the tracking and focusing controller and the position controller and rendering the tracking and focusing

Abstract: Disclosed are optical information reproducing method and apparatus wherein an information carrying member having an information pattern recorded thereon is irradiated by plural light beams which are spaced from each other in the direction of tracing of the information pattern, the light beams modulated by the information pattern are simultaneously and independently photoelectrically converted, and a predetermined operation is effected relative to the outputs obtained by the photoelectric conversion to thereby generate a reproduction signal with respect to the recorded information.

Abstract: There is disclosed an information recording and reproducing apparatus which is provided with a disk-shaped recording medium having a recording face allowing information recording and reproduction from both sides; a recording head positioned at a side of the recording face to record information thereon; a reproducing head positioned at the other side of the recording face to reproduce information recorded on the recording face; and a rotary drive unit for independently driving at least two of the disk-shaped recording medium, recording head and reproducing head about a same axis and in the circumferential direction of the recording medium.

Abstract: A tracking error signal is detected by irradiating an information pattern recorded on an information carrying member with first and second light beams, the second light beam being incident on the information carrying member at a position which is spaced from the incidence position of the first light beam at least in the direction orthogonal to the tracing direction of the information pattern, the light beams modulated by the information pattern being independently photoelectrically converted, an envelope-detection being effected with respect to the outputs obtained by the conversion, and on the basis of the output signals formed by the envelope-detection, the tracking error signal being produced.