Abstract: To produce a tracking error signal (28) precisely indicating a positioning error of an optical beam with respect to one of recording tracks in a radial direction of an optical disk (12), a compensation section (31-36) compensates for a subtracted signal produced by subtraction between first and second electric output signals of first and second sensors (23 and 24) which receive first and second partial beams reflected from the optical disk by irradiating the optical disk by the optical beam. In the compensation section, an added signal is produced between the first and the second electric output signals. When the added signal is greater than a predetermined reference level, a comparator produces a compared result signal of a high level. Otherwise, the comparator produces the compared result signal of a low level. A sample-and-hold circuit passes the subtracted signal therethrough while the compared result signal has the high level.

Abstract: Recording medium on which information is magneto-optically recorded is irradiated with a linearly polarized light beam. A light beam reflected from or passed through the recording medium is changed in phase by a wave plate. Through an analyzer the differently polarized components of the light beam from the wave plate are combined by aligning the polarizing directions of the light beam. The light intensities of the forward and backward parts of the moving direction of the recording medium in the far field of the light beam from the analyzer are detected by a photo detector. A difference between the detected signals of the forward and backward parts is generated to reproduce the information recorded on the recording medium. Furthermore, the light beam from the wave plate is splitted into two light beams linearly polarized in mutually orthogonal directions.

Abstract: A controller for moving a transducer between recording tracks, comprising a current driven actuator for accelerating and decelerating the transducer for determined periods, position and velocity detectors of the transducer at the end of deceleration, error signal generators for the final position and velocity, and circuitry for increasing or decreasing periods of acceleration and deceleration based on the error signals.

Abstract: An optical disk system comprising a head positioning system for positioning a head at a desired one of the tracks of an optical disk, and a tracking servo system for maintaining the head at the track by detecting a tracking error signal indicating deflection of the head from the track. In order to accurately position the head to the desired track, a track crossing signal deriving circuit derives an alternating signal component having a frequency corresponding to track crossing of the head from the tracking error signal as a track crossing signal. The track crossing signal is converted to a pulse signal which is counted to produce a counted number as a track crossing number. The track crossing number is compared with a desired track number previously set and a position error signal is produced. A head driving motor is driven until the position error signal becomes zero so that the head is correctly positioned at the desired track.

Abstract: A magneto-optical head for reading information from a recording medium, the head having a laser-based optical system that comprises two light paths, a first path from the source to and continuing through or reflecting from medium and a second path in a different direction which directs light from the medium to a detector. The second path includes a dual prism multiplying element (Wollaston prism) for dividing the reflected beam into three distinctly oriented beams, and a multi division photodetector for detecting a servo signal by the astigmatism method and an information signal by a differential polarization method.

Abstract: An optical information recording and reading apparatus checks the recording of information simultaneously with recording of said information by means of a recording laser beam by detecting a deflected portion of the reflected beam of the recording laser beam from an optical recording medium. An intensity differential signal is generated by monitoring different portions of the deflected portion of the reflected beam. The intensity differential signal is insensitive to intensity changes in the recording laser beam. The accuracy of the recorded information is determined by sensing the change of polarity of the intensity signal. An error signal is generated as a function of the polarity of the intensity differential signal to re-record information not recorded properly.

Abstract: A beam access apparatus for an optical disc system. The apparatus includes a lens position detector for generating a lens position signal indicating a position of the objective lens in a radial direction of the disc with respect to the optical head which is movable relative to the disc. The apparatus is operated in a head access mode in which the optical head is moved in the radial direction of the disc and the objective lens is caused to follow the movement of the optical head such that the objective lens is positioned at a predetermined location with respect to the optical head. The apparatus is also operable in a lens access mode wherein the objective lens is moved in the radial direction and the optical head is caused to follow the objective lens such that the objective lens is located at a predetermined position with respect to the optical head.

Abstract: A position control system has a motor for moving a movable member which is driven, at first, by a non-controlled signal. Responsive to a position error signal which represents a difference between a present position and a commanded position, and to a velocity signal which represents a velocity of the movable member, a deceleration signal is generated for positioning the movable member at the commanded position. When it exceeds a predetermined level, the deceleration signal is applied to the motor, instead of the non-controlled signal.

Abstract: A system for controllably driving a motor to place a movable element at a position indicated by a command signal from an external source produces, in response to a phase staggered incremental position signal pair, one and the other of two position pulse sequences at a time depending on an instantaneous angular velocity of the motor. Responsive to the command signal and the position pulses, a mode signal is produced to indicate a position control mode while a position error is within a predetermined range and otherwise a velocity control mode. Likewise, a signal is produced that represents at least one reference angular velocity and the position error during the respective modes. Responsive to the position pulses alone, gate pulses are produced either with two different pulse widths depending on the modes or with a single pulse width.