Abstract: An object of the present invention is to remove a laser beam source noise in an optical disc device. An optical disc device comprises: a laser beam source which outputs a laser beam, a reproducing signal beam-receiver which receives a signal beam from an optical disc and generates a reproducing signal, a beam-source monitoring beam-receiver which detects the laser beam from the laser beam source, and a beam splitter which divides the laser beam from the laser beam source into the beams to the reproducing signal beam-receiver and to the beam-source monitoring beam-receiver; an output signal from the beam-source monitoring beam-receiver being used for removing a noise contained in the reproducing signal from the reproducing signal beam-receiver through a noise cancellation calculation.

Abstract: An optical disc system includes a disc recording unit for recording an information signal on an optical disc by switching irradiation power of laser light to be applied to the optical disc in accordance with the information signal. The disc recording unit includes a semiconductor laser; a laser-power controlling circuit for outputting a laser-driving-current instruction signal; a recording-pulse generating circuit for outputting a laser-modulation timing pulse; a laser driving circuit for generating a laser driving current in accordance with the laser-driving-current instruction signal and the laser-modulation timing pulse; and a correction-data storage for storing as correction data the shift between the laser-modulation timing pulse and the pulse position of the laser driving current.

Abstract: A laser driving apparatus for a light source of an optical head apparatus includes a laser, a laser driving circuit, and a radio frequency current generation circuit for generating a radio frequency current to be superimposed on the drive current. The laser driving apparatus further includes a current monitor circuit, an optical detector for detecting an optical output of the laser; a selection circuit for selecting either of non-superimposing or superimposing the radio frequency current on the drive current, an APC circuit for controlling the optical output of the laser at a constant level, and a control circuit. The control circuit controls the amplitude of the radio frequency current on the basis of current values of the drive current on non-superimposing and superimposing or detection values of the optical output of the laser on non-superimposing and superimposing.

Abstract: A tilt servo apparatus which can correct a tilt error at a high speed and with high precision irrespective of a magnitude of the tilt error even if a response speed of a liquid crystal device decreases is provided. An amount of change and an increase/decrease of a signal intensity are detected by changing a correction value of a tilt error correcting arrangement by a first correction width, and a correction width of the correction value and a correcting direction are determined on the basis of the detection result. When the amount of change of the signal intensity is smaller than a predetermined amount of change, the correction width is changed to a second correction width which is smaller than a first correction width. When it is larger than the predetermined amount of change, the correction width is changed to a third correction width larger than the first correction width. The correction width is also determined in accordance with a change in environmental temperature.

Abstract: The light intensity of a light beam emitted from a light source is appropriately controlled when the light beam is transmitted through a variable optical coupling efficiency device in an optical head. During a read mode, the light beam from the light source is incident on an optical disk at an intensity relatively weaker than that of the light source. By switching the optical coupling efficiency of the variable optical coupling efficiency device between a write mode and a read mode, the light intensity directed to an optical recording medium is substantially varied from the write mode to the read mode. This arrangement eliminates the need for substantially increasing the optical output power ratio of the light source of write power to read power.

Abstract: A liquid-crystal tilt servo apparatus in which a reference voltage generating circuit is unnecessary for a liquid-crystal driving circuit and which has a simple circuit configuration and high reliability is realized. The liquid-crystal driving circuit has a DC removing circuit for removing a DC component of a driving signal generated on the basis of a tilt error correction control signal from a control unit and supplying a resultant signal to a liquid crystal device.

Abstract: An object of the present invention is to remove a laser beam source noise in an optical disc device.

Abstract: A focusing bias adjusting apparatus in an optical recording medium playing apparatus, in which a focusing bias adjustment is executed to remove an offset component in a focusing error signal based on each output signal of a split type photodetector in an optical pickup and, thereafter, a tilt adjustment is executed to an optical system so as to maximize a read signal serving as a sum signal of the output signals of the photodetector in order to compensate a tilt angle which is defined by a normal at the irradiating position of a laser beam from the optical pickup on the recording surface of an optical recording medium and the optical axial direction of the laser beam. When the tilt adjusting operation of the optical system of the optical pickup is performed after completion of the focusing bias adjustment, the focusing bias adjustment is executed again.

Abstract: A focus jump control apparatus of a player for playing a multilayer recording disc surely achieves a focus jump. This apparatus includes: a focusing servo loop for allowing a focal point to trace a recording surface in accordance with a focusing error signal by using a focusing actuator to displace the focal point of read light to a disc in the optical axial direction; and a tracking servo loop for allowing the focal point to trace disc tracks. A loop opening/closing control unit opens/closes focusing/tracking servo loops in response to an instruction and closes the focusing servo loop when the movement of the focal point from one of the recording surfaces to the other. During the movement of the read light focal point, the closing state of the tracking servo loop is maintained. Jump driving means generates a drive signal of the actuator to move the focal point from one of the recording surfaces to the other based on the error signal under the opening/closing control of the focusing/tracking servo loops.

Abstract: A focus control apparatus for a multilayer optical recording medium which performs an appropriate focus jump on a multilayer optical recording medium. This focus control apparatus implements such focus jump control as to temporarily release a focus servo on one layer of a loaded multilayer optical recording medium, shift the focus position of read light on another target layer and then restart the focus servo on the another target layer, detects an ambient temperature, sets a drive signal condition according to the temperature detection output, and moves the focus position of the read light under the set drive signal condition.

Abstract: A carriage controller for a multi-layer disc which is capable of performing a stable carriage control during reproduction of a multi-layer disc of the opposite recording scheme. A tracking error signal is relayed by an equalizer, and a carriage motor is driven in accordance with an output signal of the equalizer. An information reading direction on a layer of a disc on which a pickup reads information is detected, and an equalizer characteristic is set in the equalizer in accordance with the detection result.

Abstract: An optical disk player for obtaining a read data signal by the use of laser light beams incident on an optical disk, wherein any laser noise component included in the read data signal due to wavelength and power variation in the light beam incident on the optical disk can be suppressed efficiently and completely.

Abstract: An output current from the anode side of one photo-diode PD1 of two photo-diodes PD1, PD2 and an output current from the cathode side of the other photo-diode PD2 which serves as an in-phase signal with respect to the first mentioned output current are added in terms of current to convert an added current thus obtained into a voltage signal by a current/voltage converter 1. Thus, circuit such as summing amplifier, etc. can be omitted and this light signal detection circuit is only required to have one circuit/voltage converter 1. As a result, noise at the time of reproduction of a magneto-optical signal can be reduced while holding the circuit scale down to small size. Thus, S/N ratio of the reproduction signal is improved, thus, making it possible to improve, e.g., the error rate in the digital system to much degree. Accordingly, improvements, in reliability /information desity/transmission rate(speed) can be made.

Abstract: An output current from the anode side of one photo-diode PD1 of two photo-diodes PD1, PD2 and an output current from the cathode side of the other photo-diode PD2 which serves as an in-phase signal with respect to the first mentioned output current are added in terms of current to convert an added current thus obtained into a voltage signal by a current/voltage converter 1. Thus, circuit such as summing amplifier, etc. can be omitted and this light signal detection circuit is only required to have one circuit/voltage converter 1. As a result, noise at the time of reproduction of a magneto-optical signal can be reduced while holding the circuit scale down to small size. Thus, S/N ratio of the reproduction signal is improved, thus, making it possible to improve, e.g., the error rate in the digital system to much degree. Accordingly, improvements, in reliability /information desity/transmission rate(speed) can be made.

Abstract: In a three-spot tracking control system for a multi-layer optical disc, stray light of the signal-reproducing main beam from a layer other than the layer being reproduced leaks into first and second photodetectors receiving the reflected beam of two auxiliary tracking controlling beams to render the tracking operation unstable. In order to overcome this drawback, a first photodetector detects one auxiliary reflected beam from one or the other of the information signal layers of a double-layer optical disc. The second photodetector detects the other reflected auxiliary beam from the information signal layer. A first upper envelope detector detects the upper envelope signal of the reflected auxiliary beam. A second upper envelope detector detects the upper envelope signal of the detection signal of the other reflected auxiliary beam. A first subtractor subtracts the detected output by the first upper envelope detector 6 from the detection signal of the first photodetector.

Abstract: A processing circuit for an optical reproduction signal provided with a signal generating unit for dividing an optical reproduction signal output from a photo detector and including a plurality of signal components into a plurality of signals having frequency regions corresponding to the respective plurality of signal components and performing current/voltage conversion on the divided optical reproduction signals and a correcting unit for adding the results of the current/voltage conversion of the signal components to correct the results of the current/voltage conversion.