Abstract: A disc player has a first array of pickup devices arranged in a line for reading information from a disc and a second array of pickup devices arranged in a parallel line. The pickup devices are each independently movable along their respective lines with the devices of the first line offset from the devices of the second line so as to form a zigzag pattern.

Abstract: A disc player includes: a plurality of pickup devices for reading information from a disc and a plurality of guide devices arranged radiately from a center of the disc, each for radially transferring one of the pickup devices. The guide devices are arranged so that each alternate pickup device is raised or lowered toward the inner circumferential portion of the disc.

Abstract: A disc player includes at least one pickup device, which includes a pair of objective lenses for reading information from a disc. The pair of objective lenses are independently movable in the radial direction of the disc by a magnetic field generated by a common magnet.

Abstract: A disc player includes: a plurality of pickup devices for reading information from a disc; and a plurality of guide devices having a longitudinal axis for transferring the pickup device, the longitudinal axis being directed in a direction rotated by a predetermined angle with respect to a radial direction of the disc.

Abstract: A PLL circuit, to which an input signal is inputted, is provided with: a voltage controlled oscillator for outputting an output signal; a control voltage generation circuit for generating a control voltage to lock phases of the input and output signals by a loop, and outputting the generated control voltage to a control input terminal of the voltage controlled oscillator; and a central frequency setting circuit for setting a central frequency, to which a frequency of the output signal is to be pulled-in, to the control voltage generation circuit.

Abstract: A record medium of disc type is recorded by a constant linear velocity. The record medium is reproduced by a reproducing apparatus, which reads the information from the rotated record medium into a buffer memory by a transmission rate corresponding to the number of rotation of the record medium and outputs the read information from the buffer memory to an external apparatus by a predetermined output rate.

Abstract: A PLL circuit, to which an input signal is inputted, is provided with: a voltage controlled oscillator for outputting an output signal; a control voltage generation circuit for generating a control voltage to lock phases of the input and output signals by a loop, and outputting the generated control voltage to a control input terminal of the voltage controlled oscillator; and a central frequency setting circuit for setting a central frequency, to which a frequency of the output signal is to be pulled-in, to the control voltage generation circuit.

Abstract: An optical disc recording apparatus for dividing an information record surface of an optical disc into a plurality of record zones and recording information at a data rate which differs for every record zone, is provided with: a drive device for rotationally driving the optical disc by a constant angular velocity; a frequency conversion device for converting a clock frequency of input clock data corresponding to record data inputted from the external which is to be recorded on the optical disc, to record clock data corresponding to the record zone to be recorded, and outputting the record clock data; a memory device for storing the record data by a timing corresponding to the input clock data, and outputting the record data on the basis of the record clock data; and a record device for recording the record data outputted from the memory device, to the optical disc.

Abstract: An opto-magnetic disk unit is constructed so that predetermined areas existing in the front of the unit recording areas can be detected. In addition, at least one of first and second saturation magnetizations are recorded on each of the detected predetermined areas. At the time of reproduction, signal processing on the output of the pickup is performed after a part of the output of the pickup corresponding to the one section of the predetermined area is clamped to a predetermined level. Also at the time of reproduction, gain controlling of a circuit for signal processing the output of the pickup may be performed based on the level difference between the signal read from a first saturation magnetization section and the signal read from a second saturation magnetization section. An opto-magnetic disk is also provided having recording areas including at least one of first and second magnetization saturation levels arranged in the front of the unit recording areas.

Abstract: An autochanger of writable discs automatically transfers a write-once optical disc between a disc accommodation unit and a recording/reading device where data is recorded into and read from the optical disc. In order to shorten a disc loading time, the latest defect management information is stored in a floppy disc and renewed when a new defective sector is found in the optical disc.

Abstract: An autochanger of writable discs automatically transfers a write-once optical disc between a disc accommodation unit and a recording/reading device where data are recorded into the optical disc and read from that. In order to shorten a disc loading time, address information of sectors in which the latest defect management information is stored is written into an erasable non-volatile memory IC and renewed when a new defect sector is found in the optical disc.

Abstract: In a finally recorded sector detecting system suitable for a write-once type optical disc device, an error correction code or error detection code provided for each index sector is utilized to detect a state of errors occurring in reproduced index signals, and a finally recorded index sector is determined from the state of errors thus detected.

Abstract: A clock of a predetermined frequency is generated on a basis of clock information contained in a read signal. Sample values obtained by sampling the read signal in response to the clock are sequentially converted into digital data, and the thus obtained digital data are held in a first data holding means and then second data holding means in response to the clock for a time corresponding to the clock. The digital data and the output data from the second data holding means are added, and the addition output bits are multiplied by a predetermined constant by inserting a selected number of zero bits as upper significant bits, and shifting the addition output bits by the selected number of zero bits. Data corresponding to the difference between the multiplied output and the output of the first data holding means is obtained, and the thus obtained difference output is demodulated in response to the clock.

Abstract: A read-out information signal processing circuit having a switching device for relaying the read-out information signal read-out from a recording medium in an optical recording and reproducing system. The read-out information signal relayed by the switching device is supplied to an A/D converting circuit through DC interrupt means. The switching device is turned off during the recording period. Thus, the variations of DC level supplied to the A/D converting circuit at the transient time from a recording mode to a reproducing mode can be prevented and the dynamic range of A/D converting circuit can be effectively used.

Abstract: A photoelectric converting circuit including a light-receiving element which produces a current signal corresponding to the amount of light incident upon it and a current-to-voltage converting circuit which converts the current signal to a voltage signal. The circuit is characterized in that the current signal is supplied to the current-to-voltage converting circuit through an active circuit which exhibits a low input impedance. In preferred embodiments, the active circuit is a common-base transistor circuit in which an emitter current is supplied to the light-receiving element and a collector voltage is outputted as an output signal.

Abstract: A phase-locked loop circuit (PLL) to which a phase-synchronization signal is intermittently supplied, both of the natural angular frequency of the PLL and the damping factor of the same are so determined as to prevent a phase difference produced at the next sampling point from exceeding the linear property range of a phase comparator even when the extraneous electrical disturbance enters the PLL. In addition, when the level of a clock control signal supplied to a variable frequency oscillator which varies the clock signal of the PLL in phase and frequency exceeds a predetermined value, the level of the clock control signal is limited to the predetermined value. As a result, it is possible to prevent the output signal of the phase difference from having any discontinuity.

Abstract: A disc drive control system for controlling the drive of a disc carrying a binary digital signal incluring a clock information of a predetermined frequency wherein the digital signal includes an information signal portion of an information to be recorded and synchronizing signal portions which includes successive maximum periods of inversion. The system includes a detection means for detecting the period of the successive maximum periods of inversion of the synchronizing signal and producing a detection signal, and a control means for producing a control signal of disc drive means which control signal is produced in accordance with the detection signal prior to a period in which the control signal is produced in accordance with a reproduced clock signal, whereby eliminating a problem that the driving speed of the disc may be controlled in accordance with an erroneously reproduced clock signal.

Abstract: A signal waveform equalizing circuitry for compensating for the distortion of a signal picked up from a magnetic recording medium by means of a magnetic head, including a first network having the transfer function of (1-BS) and a second network made up of passive elements having the transfer function of a multiplication of the transfer function (1+AS) and the transfer function having the integration function, wherein said first and second networks are serially connected. Thus, the circuitry having an overall transfer function which is a multiplication of transfer functions expressed by (1+AS) and (1-BS) respectively (A, B being a constant, and S being j.omega. while .omega. is angular frequency) and a transfer function having an integration function is realized using relatively simple circuit configuration.

Abstract: In a system for optically reading out information recorded on a recording medium, the focus servo device includes an object lens supported by a resilient support member and a focus servo loop. The focus loop includes a driving current generating means for generating a driving current of a cylindrical coil of a focus actuator connected to the object lens in accordance with an output signal of a pickup means which includes the object lens. The improvement is that the dc loop gain of the focus servo loop is substantially raised to infinity, so as to reduce the magnitude of the focus error signal which is required to produce the driving current of the cylindrical lens for moving the object lens against the resilient force of the support member. Further, the focus servo device is characterized by a phase retarding circuit for reducing the amount of the phase rotation at the higher frequency range so as to assure the stability of the operation of the focus servo loop.

Abstract: A disc drive control system for controlling the drive of a disc carrying a binary digital signal including clock information of a predetermined frequency wherein the digital signal includes an information signal portion to be recorded and an synchronizing signal portion which includes successive maximum periods of inversion (transitions). The system includes a detection means for detecting the period of the transition of the synchronizing signal and producing a detection signal, (frame sync servo signal) disc a control means for producing a disc drive control signal for controlling a disc drive means. The drive control signal is produced in accordance with the detection signal prior to a period in which the drive control signal is produced in accordance with a reproduced clock signal (playback clock and playback frame sync signals), whereby eliminating the problem that the driving speed of the disc may be controlled in accordance with an erroneously reproduced clock signal.