Abstract: In an optical disc system having a tracking actuator for driving a light spot on an optical disc in a radial direction thereof; a photodetector for detecting off-track information in respect of the light spot position; a circuit for driving the tracking actuator and track-jumping the light spot to an adjacent track; an acceleration pulse generating circuit for generating an acceleration pulse signal to accelerate the tracking actuator during a track jumping operation; a deceleration pulse generating circuit for generating a deceleration pulse signal to decelerate the tracking actuator during the track jumping operation; and a center detecting circuit for detecting a center position between adjacent tracks in response to an output signal of the photodetector, the optical disc system is characterized by including a switching device responsive to an output signal of the center detecting circuit for switching from the acceleration pulse signal to the deceleration pulse signal after a predetermined period of time

Abstract: A magneto-optic recording apparatus which has a magnetic field generator that applies a magnetic field with a constant direction to a magneto-optic recording information medium for overwriting information to improve accuracy of recording and reproducing information onto and from magneto-optic recording information medium and further has an auxiliary magnetic field generator that compensates a variation of intensity of a magnetic field generated by the magnetic field generator and applied to the magneto-optic recording information medium is disclosed as the first invention. Also, a magneto-optic recording apparatus which performs synchronous wave detection of the reflected light signals from the magneto-optic recording information medium and controls A.C.

Abstract: An optical disc having a plurality of information tracks, each information track having a servo field including a pair of wobbled pits and a clock pit. The distance between one of the wobbled pits and the clock pit in each servo field is selected such that the optical disc includes at least three different types of servo field. These differnt types of servo field appear in a predetermined sequence for every one or more contiguous information tracks. A driving apparatus for driving such an optical disc has a direction detecting circuit for detecting the moving velocity of a movable portion of an optical head, and a speed detecting circuit for detecting the relative velocity of the movable portion.

Abstract: An optical disc having a plurality of information tracks. Each information track having a data field including multiple data bytes and a servo field including a first servo byte having a pair of wobbled pits and a second servo byte having a clock pit. The byte length of at least one of the first or second servo bytes being longer than the byte lengths of the data bytes. The increased byte length providing for greater distance between the wobbled pits and the clock pit resulting in increased reliability in clock pit detection. An accessing apparatus for accessing such an optical disc including a phase-locked loop circuit with a frequency dividing ratio that varies in accordance with the various byte lengths.

Abstract: An apparatus in accordance with the present invention sequentially fixes the wavelength of a light beam irradiated from a light source whose oscillation wavelength sequentially varies to a plurality of different wavelengths to a recording medium to required wavelengths each capable of forming a hole at absorption spectrum of the recording medium, synchronizes timing of change of the wavelength of the light source with timing of recording or regenerating each bit of information, records the optical hole formed in a manner that each bit of information corresponds to the wavelength varying in sequence, and detects the formed hole to regenerate information.

Abstract: The present invention relates to apparatus and method for decoding a signal reproduced from an optical disc. The optical disc has a signal format for recording data from an original signal in a data area at the optical disc. The optical disc also has recorded thereon a clock signal having the same phase as the recorded data. During reproduction of the recorded signal from the optical disc, this clock signal is utilized to generate a delayed version of the reproduced data signal. This delayed signal is used to decode the reproduced data signal obtained from the optical disc, thereby enabling a phase shift of the reproduced clock signal to there produced data signal to be eliminated by circuit processing. During the recording on the data area of the optical disc, fixing data for setting phases of data reproducing recording clock and reproducing signal to optimum phases for decoding is recorded.

Abstract: An optical disc having a plurality of information tracks, each information track having a servo field including a pair of wobbled pits and the clock pit. The distance between one of the wobbled pits and the clock pit in each servo field is selected so that the optical disc includes at least three different types of servo field. These different types of servo field appear in a predetermined sequence for every one or more contiguous information tracks. A transducing apparatus for tranducing such an optical disc has a direction detecting circuit for detecting the moving velocity of a movable portion of an optical head, and a speed detecting circuit for detecting the relative velocity of the movable portion.

Abstract: When recording, reproducing or erasing data signal by illuminating a recording medium surface with a condensed light spot, a tracking sensor signal or a focusing sensor signal is detected from light reflected from the recording medium surface. The detected signal is subjected to current-to-voltage conversion, and the current-to-voltage conversion gain is switched by estimating reflected light power from the recording medium surface.

Abstract: An optical data medium driving apparatus which constitutes amplifiers for an output current signal of a photosensor including a plurality of current mirror circuits having different amplification factors in order to switch, in a wide range, the output current signal of the photosensor. The photosensor detects a quantity of the reflected light corresponding to a variation of the quantity of reflected light from an optical data medium having various characteristics. The output is obtained with high accuracy and in a wide band. A servo-circuit is used for an AGC circuit and normalizes a difference signal from each light receiving surface at a photosensor having a plurality of light receiving surfaces. An A/D converter is given the difference signal as an analog input signal and the sum signal as the reference input signal. The A/D converter outputs an offset binary type digital signal, thereby being inexpensive to produce, easy to be integrated having high function, and high in reliability.

Abstract: A servo system for controlling the position of an object in accordance with a servo signal, employing an A/D converter to normalize an error in the position of the object and to enable digital correction of any offset in the system and digital compensation for track jumping and drop outs.

Abstract: Disclosed in a system for recording, reproducing, and/or erasing information as recording pits on a recording medium. This medium has guide grooves for recording reproducing, and/or erasing the informatin signal. A condition whereby the value which is obtained by subtracting the groove width from the groove pitch is larger than a width of the recording pits is satisfied. A predetermined position for recording, reproducing, and/or erasing is set between the guide grooves. Alternatively, a condition whereby the width of a guide groove is larger than the width of a recording pit is satisfied. A predetermined position for recording, reproducing, and/or erasing is set on the guide groove.

Abstract: A semiconductor laser controller comprising an optical detecting circuit for detecting the output of a semiconductor laser, a first circuit for controlling the semiconductor laser driving current on the basis of a bottom output of the semiconductor laser detected by the optical detecting circuit, a detecting and holding circuit which detects the peak output at the start of the pulse modulation of the semiconductor laser and holds the peak output, and a second means for the feed-forward control of the modulated pulse amplitude of the semiconductor laser after the start of the pulse modulation, whereby the semiconductor laser controller is capable of restricting the change of the peak output of a semiconductor laser resulting from the variation of the quantization efficiency with temperature and passage of time, and stabilizing the peak output within a short time.

Abstract: An information recording and retrieval system, such as an optical system, for recording and reading signals, such as video signals and audio signals, on a recording medium provides improvement in the control of a moving part, such as an objective lens. In a first embodiment, reading of code signals is detected to disable the control of the moving part by the recorded code signals, recorded as discontinuities in a recording track, and to enable control by information signals, recorded as changes in reflectivity in the track, held by a holding circuit so that only recorded information signals operate the control to avoid control distrubances caused by differences in the recorded code and information signals. In another embodiment peak detecting circuits detect the minimum values of split detection signals for controlling the moving part; use of these minimum values for control avoids the control disturbances from the differences in signal reading during recording and reading modes.