Abstract: A beam controller for controlling a semiconductor laser provided in an optical recording/playback apparatus includes first and second current sources for driving the semiconductor laser at a low level (play-back mode) and/or at a high level (recording or erasing mode). The first and second current sources are controlled to have stable power automatically by a first and second auto-power circuits, respectively. The first and second auto-power control circuits include a sample-hold circuit which stores an output signal from a low-pass filter. This enables the beam controller to avoid the transition response problems of the low-pass filter. A switching circuit is also included to select either the stored low-pass filter signal on the present low-pass filter signal.

Abstract: An apparatus for reading an optical disk having tracks extending tangentially includes a driving device for moving at least one light spot. A signal which indicates a deviation of the light spot from one of the tracks and a second circuit produces acceleration and deceleration signals. The driving device is controlled to accomplish a track jump of the light spot in accordance with the acceleration and deceleration signals. The second circuit produces the acceleration signal when a track jump is to be initiated and produces the deceleration signal when the ratio of the level of the tracking error signal to the peak value of the tracking error signal becomes equal to a predetermined value.

Abstract: A method for manufacturing an optical memory element including the steps of disposing a resist film on a substrate, placing a photo-mask carrying a guide groove pattern on the resist film so as to position the photo-mask over a predetermined position of the substrate, forming a guide groove pattern latent image on the resist film, developing the guide groove pattern latent image formed on the resist film, conducting an etching operation through the developed guide groove pattern as to form guide grooves in the substrate, removing the resist film from the substrate, and disposing a recording medium layer on the substrate having the guide grooves formed therein.

Abstract: A disc clamping device comprises a disc base on which to set a disc and which has a spindle for rotating the disc, and a disc holding member movable in the axial direction of the spindle. The disc holding member comprises a portion for pressing a disc with a centering hub and a portion to be engaged with the center hole of a disc with no centering hub.

Abstract: A disk recording method in which recording is performed on a disklike recording medium having a radially coaxial or spiral recording track that is divided into a predetermined plural number of recording sectors each acting as a recording unit. A predetermined number of dedicated sectors are provided at a rear portion of the recording track so that the contents that are recorded in defective sectors of the recording sectors are alternatively assigned to the dedicated sectors.

Abstract: An automatic gain control device for use in an optical memory device has a circuit for producing an amplification control signal which is fed back to a gain control amplifier through a sample-hold circuit. A pulse train detection circuit is provided for detecting the pulse train indicating that the data stored are a on the optical memory device is being playedback. When the pulse train is detected, the sample-hold circuit is made inactive so that the amplification control signal is directly fed back to the gain control amplifier, and when the pulse train ends, the sample-hold circuit is made active to hold the amplification control signal obtained at the end of the pulse train and to produce the amplification control signal held in the sample-hold circuit.

Abstract: An analog signal switching device for use in an optical memory device having a recording/erasing mode and a mode other than the recording/erasing mode is disclosed. The switching device includes a source for producing a switch control signal which is HIGH during the recording/erasing mode and LOW during the mode other than the recording/erasing mode. An analog switch is provided for receiving a direct input analog signal and a held input signal and for providing as output the direct input signal during the LOW state of the switch control signal, and the held input signal during the HIGH state of the switch control signal by a switching operation.

Abstract: In an optical head of an optical memory device which records, reproduces or erases information onto or from a recording medium by applying a laser beam to the recording medium, a beam splitter is disposed in an optical path to conduct a portion of the laser beam emitted from a laser device to a light detector. In accordance with a detected value from this light detector, the influence of a stray beam generated in an optical system is removed from a servo error signal.

Abstract: A data modulation/demodulation system reproducing data that is divided and recorded in a plurality of blocks on a recording medium. The data modulation/demodulation system utilizes the steps of modulating the data by adding specified data bit patterns to the data bits of each block and reproducing the data which have been obtained by adding specified code bit patterns. The bit rows are independently demodulated by demodulation clocks which differ in phase. The demodulation bit pattern of the above code bit pattern which was added at the time of recording and the bit pattern which was demodulated by the different modulation clocks are compared with each other to determine which data is wrong. The correct demodulated data is selected according to this comparison and transmitted.

Abstract: An extra magnetic field positioning apparatus includes a motor which does not have stable points for defining the extra magnetic field. An encoder is provided which is rotated with the motor and individually has the information which indicates rotating displacement and the information which indicates rotating position. Further, a sensor detects the information indicating the rotating position recorded on the encoder, and another sensor detects the information indicating the rotating displacement recorded on the encoder.

Abstract: A sync signal detection apparatus is provided wherein a sync signal represents the top of recorded data. The sync signal includes a plurality of marks each having a different pattern from the pattern of any other mark. The apparatus is equipped with a circuit for sequentially detecting the patterns of the individual marks in a reproduction mode. Also, a circuit is provided generating a sync pulse at the top of the data in accordance with the address pattern of the mark after a predetermined number of marks are detected. The apparatus ensures accurate reproduction of the recorded data with a small number of bits and an increase in data reliability.

Abstract: An optical information recording and reproducing apparatus comprising: a circuit for focusing a light beam on a recording track of an optical disk having tracks formed spirally or concentrically; a circuit for recording the information on a track corresponding to the focused position of light beam on the track or reproducing information from on the track; a tracking control circuit for generating a tracking control signal for matching the focused position of the light beam with the track; a circuit for detecting deviation of the focused position of the light beam from the track and generating a deviation signal corresponding to the focused position of the light beam; a holding circuit for holding the deviation signal; a subtracting circuit for subtracting the held deviation signal from the tracking control signal; and a circuit for moving an objective lens for controlling the focused position of the light beam in response the output signal from the subtracting circuit.

Abstract: A beam controller for controlling a semiconductor laser included in an optical recording-play-back apparatus. The beam controller is comprised of first and second current sources for driving the semiconductor laser at a low level during a play-back mode and at a high level during an erasing mode. The first and second current sources are respectively automatically controlled by a first and second auto-power control circuit to provide stable power outputs.

Abstract: An optical disc apparatus provided with a recording correcting system for controlling variations in the recorded bit length. The recording correcting system may be controlled not only while the apparatus is put to work, but also during unoccupied times when the recording, reproducing, and erasing operations are not required from a higher level apparatus. Also, the controlling operation may be performed so that the value of the record correction may be renewed at proper time intervals. The repetition of the correction trial at the proper interval allows a time lapse after the apparatus power-supply is put to work to occur with no undesirable effects and the characteristic variation between respective discs during the disc exchange can be coped with.

Abstract: A tracking system for positioning a light spot onto a magneto-optic disc having a beam guide track preformatted thereon, includes a main light beam and two auxiliary light beams, and a circuit for switching between a low frequency component of a tracking error signal, detected by respective auxiliary light beam detectors, and a tracking error signal detected by a main light beam detector.

Abstract: A waveform processing circuit includes a switching circuit having first and second inputs and one output. The first input receives head portions and data portions contained in a reproduced signal from an optical head. The second input receives a level signal representing the level of the head portion or the level of the signal carrying the head portion. The switching circuit is switches between a first state in which the first input and the output are connected, and a second state in which the second input and the output are connected. A control signal producer produces a first control pulse indicating the presence of the data portion. The first control pulse is applied to the switching circuit for actuating the switching circuit to establish the first state when the first control pulse is present, and to establish the second state when the first control pulse is not present, so that the switching circuit continuously produces the signal having a level within the range of the head portion.

Abstract: An objective lens-driving unit comprising a lens supporting means for supporting the objective lens having an optical axis vertical to a recording medium on which light beams converge through the objective lens so as to attain optical recording, optical playing and optical erasing of information on the recording medium; at least one driving means for driving said lens supporting means in the tracking direction; a driving means for driving said intermediate supporting means in the focusing direction, wherein said tracking direction-driving means comprises a magnetic circuit that produces magnetic flux in the circumferential direction of the recording medium, and a tracking direction-driving coil that is positioned to cross a gap formed in the magnetic circuit to thereby receive an electro-magnetic force due to an interaction between the magnetic field of the magnetic circuit and the current passing through said coil, said tracking direction-driving coil being positioned within the excitation area of the magnet

Abstract: A method of manufacturing an optical memory element, which includes the steps of applying a first photo-resist layer onto a glass substrate for an optical memory element, laying a mask plate on the glass substrate applied with the first photo-resist layer, with the mask plate being prepared by covering a surface of a transparent substrate with metallic layers formed into a guide pattern configuration, irradiating ultraviolet rays onto the first photo-resist layer through the mask plate, transferring the guide patterns of the mask plate onto the first photo-resist layer, and engraving the guide patterns in the glass substrate by etching after developing the first photo-resist layer.

Abstract: An optical head for a magneto-optical disk, including a diaphragm for cutting at least an outer portion of a bundle of rays, which is provided in the course of an optical system of a signal detecting portion.

Abstract: A magneto-optical memory device includes a recording medium having a magnetic anisotropy in a direction perpendicular to the main surface thereof. A semiconductor laser is employed in an optical system of the magneto-optical memory device for reproduction purposes. A polarization beam splitter is disposed in the optical system. A multi coated dielectric thin-film is deposited on the reflection surface of the polarization beam splitter in order to establish a desired relationship between the reflection of the P-polarization component and the S-polarization component.