Abstract: A detrack detecting system for detecting deviation of the beam spot from the track in an optical recording/reproducing apparatus in which recording and reproducing of data are performed by irradiating optical beams onto an optical disc. Three beam spots are irradiated at positions on the optical disc which are away from each other by a predetermined distance. The reflected lights are respectively detected by three photodetectors whose photo sensitive surfaces are divided and tracking error signals are detected by a push-pull system. A tracking error signal obtained from the center beam spot of the three beam spots and tracking error signals obtained from other two beam spots are respectively added to obtain the first and second composite tracking error signals. Detracking state is detected based on the polarities of the first and second composite tracking error signals.

Abstract: An automatic servo gain control system for an optical disk player apparatus is capable of controlling an open-loop servo gain to be constant, regardless of parameter variations including variations in the optical head actuator gain. The system includes a gain control circuit that varies a gain for a first signal indicative of a positional relationship between the optical head and an optical disk based on a second signal providing light intensity information. The system further includes an oscillator that produces an output at a frequency within a servo frequency band of the optical head actuator and that is introduced into a servo loop via an operational amplifier. Signal values at an input side and an output side of the operational amplifier in the servo loop are compared so as to vary the gain for the first signal based on a difference between the input and output signal values.

Abstract: A linear motor comprising first and second magnetic members with first and second magnets secured to and cooperating respectively with the first and second magnetic members to form first and second magnetic circuits each having a magnetic gap formed therein, first and second driving coils mounted for integral movement with each other along the magnetic gaps and each including a driving coil winding wound in such a manner as to partially extend perpendicularly across a magnetic field produced in the magnetic gap by the first or second magnet and a velocity detecting coil winding wound in an overlapping relationship with the driving coil winding, the velocity detecting coil windings of the first and second driving coils being wound and connected to each other such that voltages induced in the velocity detecting coil windings of the first and second driving coils by external magnetic fields from a common magnetic field other than the magnetic fields produced by the first and second magnets are cancelled by each

Abstract: In an optical disk information recording and reproducing apparatus for writing and reading information to and from the optical disk using the optical disk as a record medium on which pre-grooves are formed and address signals are prerecorded on land sections among these pre-grooves presenting physical changes in the form, a servo circuit therein for executing tracking and/or focusing control is disclosed. In the servo circuit, by providing a switch for opening and closing control loops for said tracking and focusing control and by controlling said switch to open during reproduction of the address signals recorded on the address area of the optical disk, servo signals including noise due to pits presenting physical changes in the form on the address area are eliminated so as to establish tracking and/or focusing control. This serves to enable information writing and reading to and from the record area of the optical disk with high reliability and stability.

Abstract: An optical disc drive that employs a velocity feedback loop for detecting the moving velocity of an optical pickup, thereby to enable the optical pickup to seek a target recording track of an optical disc. The number of tracks to the target recording track is calculated on the basis of a signal derived from the optical pickup and a target velocity signal is supplied to the velocity feedback loop in accordance with the calculated result, whereby the moving velocity of the optical pickup can be controlled to become [0] at a timing (time point) at which the optical pickup reaches the target recording track.

Abstract: An actuator driving circuit for a servocontrol system comprises an amplifier for amplifying an error signal obtained in the servocontrol system to produce a driving signal supplied to the actuator, a power supply voltage source for producing a first power supply voltage and a second power supply voltage higher the first power supply voltage, a power supply voltage selector for selecting one of the first and second power supply voltages so as to supply the amplifier with the selected one of the voltages, and a level detector for detecting a specific portion of the error signal having such a level as to cause the amplifier to produce a portion of the driving signal having a level limited to be constant under a condition in which the first power supply voltage is supplied to the amplifier and for producing a detection output by which the power supply voltage selector is controlled to select the second power supply voltage in place of the first power supply voltage when the specific portion of the error signal is

Abstract: An optical disk recording and reproducing appartus is provided with a signal processing circuit in a focus servo circuit for suppressing a traverse signal which has a frequency determined by the pitch of pre-grooves and the transversely shifting speed of a laser beam spot and which modulates a focus error signal during a search mode operation. This signal processing circuit successfully avoids an influence of the traverse signal focus servo system and thus assures accurate focus on the control.

Abstract: An optical disk recording and reproducing apparatus is provided with an element in a servo system circuit, which element is provided high response characteristics to run out frequency. Output of the element is monitored for detecting whether a disk is defective.

Abstract: A system and method for accessing tracks for an optical disc apparatus are disclosed in which when a light spot is jumped toward a target track, an acceleration pulse is applied across a fine tracking actuator to accelerate the fine tracking actuator for a predetermined period of time, a relative speed of the light spot to the tracks of the optical disc is detected though a detection of a period of a traverse signal outputted due to a movement of the fine tracking actuator, and a control signal corresponding to the relative speed is used to control the movement speed of the fine tracking actuator. Therefore, before the end of a track jump, a constant relative speed can be achieved such that a smooth tracking servo can be carried out. Consequently, an access time to access the target track can be shortened.

Abstract: A light beam control arrangement for an optical disc apparatus in which a tracking servo control for a light beam projected onto an optical disc is performed in accordance with a tracking error signal and a reproduced information signal is obtained from a record track in the optical disc upon which the light beam impinges, which comprises a differentiation circuit for differentiating one of the tracking error signal and the reproduced information signal to produce a differentiation output signal, a phase detection circuit for phase-detecting the differentiation output signal with the other of the tracking error signal and the reproduced information signal to produce a detection output signal, a low pass filter circuit for producing a DC output signal having a level varying in response to an amplitude of the detection output signal, and a signal mixing circuit for mixing the DC output signal with the tracking error signal so that the DC output signal is used, in addition to the tracking error signal, for the t

Abstract: A control circuit operating with a pulse-width modulated signal which is operative to control a driving circuit portion provided therein for driving a unit to be driven so as to operate in accordance with a pulse-width modulated control signal and in which an analog control signal is provided with a first DC voltage level at a biasing circuit portion (15), a triangular or saw-toothed waveform voltage signal which is obtained from a reference voltage producing circuit portion (17) with an amplitude varying in response to variations in a power supply voltage is superposed on both a second DC voltage level higher than the first DC voltage level and a third DC voltage level lower than the first DC voltage level, and a driving circuit portion (32) provide for driving a unit to be driven (43) is controlled with first and second pulse-width modulated control signals obtained from a level comparing circuit portion (30, 31) in which the level of the analog control signal provided with the first DC voltage level is com

Abstract: A driving apparatus for a recording medium includes a motor for driving a recording medium, a preset counter for counting either of a reference clock signal and a signal provided by multiplying a reproduced synchronizing signal, the preset counter being reset in response to a synchronizing signal in a reproduced signal when the reference clock signal is counted and being reset in response to a reference synchronizing signal when the signal which is provided by multiplying the reproduced synchronizing signal is counted, and a circuit for producing an analog electrical signal corresponding to a time interval during from a time when a count value of the preset counter reaches its preset value to a reset time of the preset counter, wherein the motor is so controlled by the analog electrical signal that the moving speed of the recording medium relative to a pickup is made constant.

Abstract: A servo system for controlling a motor rotation to rotate a disc having thereon information modulated in run length limited code is disclosed, which includes a circuit for counting the number of pulses of the maximum transition interval in the information reproduced from the disc, a loop for controlling the motor rotation at a constant linear velocity in response to the output of the counting circuit, a phase comparator for digitally phase-comparing a phase information signal of the signals reproduced from the disc with a reference signal having a frequency N times that of the phase information signal at every N times and a loop for controlling the phase of the motor through the output of the phase comparator.

Abstract: A driving apparatus for a recording medium which includes a motor for driving a recording medium, a preset counter for counting either of a reference clock signal and a signal provided by multiplying a reproduced synchronizing signal, the preset counter being reset in response to a synchronizing signal in a reproduced signal when the reference clock signal is counted and being reset in response to a reference synchronizing signal when the signal which is provided by multiplying the reproduced synchronizing signal is counted, and a circuit for producing an analog electrical signal corresponding to a time interval during from a time when a count value of the preset counter reaches its preset value to a reset time of the preset counter, wherein the motor is so controlled by the analog electrical signal that the moving speed of the recording medium relative to a pickup is made constant.

Abstract: In an apparatus for reproducing, from a record disc, audio information recorded in the form of a pulse code modulation (PCM) in a run length limited code, a reproduced signal derived from the rotated record disc, for example, by a pick-up in the form of photo detector in the case of optical recording and reproducing, is compared with a first reference level or signal to provide an output signal corresponding to the reproduced signal and having portions of opposite polarities, the interval between transitions from one to the other of the opposite polarity portions of the output signal is detected for providing a corresponding detecting signal, a velocity servo circuit compares the detecting signal with a second reference signal which corresponds, for example, to a maximum transition interval when the record disc is driven at a predetermined linear velocity at the location scanned by the pick-up, so as to produce a corresponding velocity control signal for maintaining the record medium at such predetermined lin

Abstract: Apparatus for reproducing from a record disc a run length limited PCM audio signal comprises an optical transducer which reproduces the PCM audio signal from the record disc; a waveform shaping circuit for producing an output signal corresponding to the reproduced PCM audio signal and having portions of opposite polarities so that the output signal includes a plurality of transition intervals; a clock pulse generator for generating clock pulses having a constant frequency higher than the bit frequency of the output signal; a counter for detecting the period of each transition interval of the output signal by counting the number of clock pulses generated during each detected transition interval of the output signal; a NAND gate for determining, during each of at least one predetermined period selected to be longer than the period ##EQU1## if the number of the clock pulses counted by the counter during each detected transition interval in each longer predetermined period corresponds to a predetermined number of

Abstract: An information signal reproducing apparatus for reproducing from a disc having recorded thereon a pulse code modulated (PCM) signal which is modulated in a run length limited code is disclosed, in which a reproduced signal is compared with a threshold voltage by a comparing circuit so as to be converted in waveform, a maximum or minimum transition interval of the signal with the waveform converted is detected, and a counter is used to control the threshold voltage in such a manner that a positive polarity part and a negative polarity part of the maximum or minimum transition interval will be equal to each other.

Abstract: A switching regulator includes a chopper circuit and a DC-DC converter. A switching signal for use with the chopper circuit is derived from an inverter portion of the DC-DC converter so as not to use an external pulse oscillator. A DC voltage feedback circuit is provided from the output of the DC-DC converter to the chopper circuit so as to stabilize the DC output signal of the DC-DC converter. Alternatively, the DC voltage feedback is provided from an output of the chopper circuit.

Abstract: In a DC-AC inverter having a switching circuit connected between DC input terminals and being controlled by pulses from an oscillation transformer to provide an AC output from which voltage and current feedbacks are applied to the transformer for maintaining oscillation thereof; the core of the oscillation transformer is formed, in part, of a core material having a large saturation magnetic flux density and, in part, of a core material having a high Curie temperature so as to provide the inverter with both a high efficiency and a stable oscillation frequency. The DC-AC inverter is particularly suited to be included in a DC-DC converter constituted by applying the AC output of the inverter to a suitable rectifying and smoothing circuit.

Abstract: An inverter includes a pair of switching elements operated by control signals from a signal generator to take two-position action in the same phase or in opposite phases, and a coupling transformer to couple the control signals so that ON actions or ON and OFF actions of the switching elements are synchronized with each other more precisely than circuits of the past have been able to provide.