Abstract: A thermoplastic resin composition with improved low-temperature impact strength and rigidity against heat, comprising (I) 10-40% by weight of a mixture of (a) 10-50% by weight of a propylene homopolymer and/or an ethylene-propylene block copolymer (an isotactic pentad fraction of a propylene homopolymer portion being 0.98 or above) and (b) 50-90% by weight of an olefin-based copolymer rubber, said mixture having been dynamically heat treated in the presence of an organic peroxide and a crosslinking agent, (II) 20-85% by weight of a propylene homopolymer and/or an ethylene-propylene block copolymer (an isotactic pentad fraction of a propylene homopolymer portion being 0.98 or above and a melt index of the propylene homopolymer portion being 30-150 g/10 min), and (III) 5-40% by weight of an inorganic filler.

Abstract: Disclosed is a tracking control apparatus for an optical disk. The optical head of the optical disk system generates a tracking error signal for servo tracking. The tracking error signal is also employed to judge whether the light spot is present in the tracking enable region of the disk. If the light spot is judged out of the tracking enable region, the optical head is moved inwardly or outwardly in the radial direction of the disk until the light spot is present in the tracking enable region to activate tracking servo.

Abstract: In an access control method, a light spot is formed on a disk and a track-crossing signal is detected from light reflected on the disk when the light spot crosses a track of the disk. A moving speed of the light spot is controlled by using the detected track-crossing signal to access the light spot in a radial direction of the disk in accelerating and decelerating modes. The access control method uses a precise driving device for slightly displacing the light spot in the radial direction of the disk, and a coarse driving device for greatly moving the light spot in the radial direction of the disk.

Abstract: In a closed-loop control system and a servo device of an optical disk unit, a loop gain can be suitably corrected by a simplified structure. A signal is added to a closed loop and a value having a correlation with a gain of the closed loop is measured in accordance with the added signal. The loop gain is changed such that the measured value is equal to a predetermined value. Therefore, it is possible to suitably correct the loop gain.

Abstract: In an information recorder, a low frequency region component of a tracking error signal is extracted by a digital filter in a track following mode. In a seek mode, an actuator for an objective lens is driven in accordance with a signal obtained by adding a value indicative of this low frequency region component to a speed error between moving and target speeds of a light spot. Driving force for canceling a displacement of the light spot caused by inclination and vibration of the information recorder is added to seek driving force for performing a seeking operation so that influences of the inclination and vibration of the information recorder can be compensated. Thus, the seeking operation can be performed stably and accurately in spite of the inclination and vibration of the information recorder and eccentricity of a disk.

Abstract: A jump pulse corrector has a level holding device for holding the voltage level of a tracking error signal after a constant time since a pulse signal was transmitted to a light spot moving device. The jump pulse corrector also has a pulse height correcting device for correcting a wave height value of the pulse signal such that the voltage level of the tracking error signal is equal to a predetermined level. The jump pulse corrector is suitably used in an optical disk unit. The pulse height value is corrected such that the voltage level of the tracking error signal is equal to the predetermined value after the constant time since the pulse signal was transmitted. Accordingly, when actuator constants, etc. are changed, a suitable acceleration of a light spot is obtained and a stable jumping operation of the light spot is performed after these changes.

Abstract: An optical disk device having a head for reading information from a disk having tracks of different pitches depending upon a radial position on the disk.

Abstract: Stable velocity control operations are made possible independent of a circuit constant or the like in digital circuit arrangement. A velocity controlling apparatus comprises a track cross detector, a counter for counting track cross pulses, a sampling device for periodically sampling an output of the counter, and a relative velocity detector for detecting a relative velocity between a light spot and tracks, based upon a difference between a currently sampled value and a prior value sampled by the sampling device prior to the sampling of the currently sampled value. The sampling device periodically samples the output of the counter to count the number of tracks crossed, and a velocity is detected based on the difference, whereby information on detecting velocity may be readily obtained in digital value and the control may be conducted with less errors.

Abstract: A track counting device receives a tracking error signal from a light pickup element which is moving over a record medium having recording tracks thereon. A wave shaping circuit shapes the tracking error signal into a signal of rectangular pulses. A phase-locked loop (PLL) circuit receives the signal and compares it with a signal created by itself so as to synchronize a phase between two signals. The PLL circuit constantly effects the comparison to obtain the synchronized signal, so that it may provide information about the number of tracks crossed by the light pickup element apart from influence of surface conditions on the record medium such as a mirror finished surface and pits. A counter counts the number of tracks based on the synchronized signal.

Abstract: A tracking servo method in an optical disk drive unit has the steps of providing a signal in accordance with a different in voltage level between two signals respectively reproduced from a pair of tracking sample flags arranged in positions shifted by predetermined distances from a tracking center on an optical disk; setting the signal in accordance with the voltage level difference to a tracking error signal; and positioning a light spot on the optical disk in the tracking center using the tracking error signal. The tracking servo method further has the step of normalizing the tracking error signal by a signal indicative of a difference between an average value of the two reproducing signals and a signal reproduced from a sample flag approximately arranged in the tracking center on the optical disk.

Abstract: A focus offset correction method for optical information read/write device, the device comprising: a first amplitude detection circuit for detecting amplitude of a tracking error signal obtained from a record medium; a second amplitude detection circuit for detecting amplitude of an information reading signal; a tracking servo circuit for moving a laser beam to follow fluctuation of a track on the record medium; a focus servo circuit for controlling the laser beam so that a beam waist thereof is positioned on the record medium; and an offset adder for applying an offset to the focus servo circuit. The focus offset correction method comprises a first process for determining a range of the offset in which range an output from the first amplitude detection circuit always exceeds a predetermined value; and a second process for determining the offset which makes an output from the second amplitude detection circuit almost maximum.

Abstract: An optical disk apparatus comprises a plurality of heads for performing erasure of information from, record of information on, and reproduction of information from an optical disk. Each of the heads is movable in transverse to tracks on the optical disk for seek movement. Head drive system is provided for driving the heads so as to move the heads to a target track on the disk. The head drive system is adapted to apply for the seek movements of the heads a first drive force and a second drive force which is smaller than the first drive force to each of the heads in such a manner that when one of the heads is driven by the first drive force, the other heads can be driven by the second drive force only.

Abstract: A servo control system for an optical disk device which comprises a unit for scanning an optical disk by an optical spot converged and irradiated on the disk; a unit for feed back controlling position of the optical spot in a focussing direction; and a unit for feed back controlling position of the optical spot in a tracking direction. The system further comprises: a first and second optical detectors, each being divided to at least two detection areas; a multiplexer to which the detection areas are connected for time sharing the detection signals; an adder for adding up the detection signals output from one of the detectors; an A/D converter which converts the time shared signal output from the multiplexer to a digital signal using the added up signal as a reference thereof; and a logic circuit which is connected to the A/D converter and calculates from the digital signal output from the A/D converter to obtain digital error signals of focus and track.

Abstract: An electronic musical instrument is provided with a keyboard circuit, a voltage-controlled tone signal generating circuit arrangement and a sequencer for sequentially coupling memorized pitch voltage signals to the voltage-controlled tone signal generating circuit arrangement, thereby realizing automatic arpeggio performance. The sequencer is so connected as to receive a pitch determining voltage signal from the keyboard circuit at a given timing and is so arranged that the magnitudes of pitch voltage signals coupled to the tone signal generating circuit arrangement are shifted in accordance with the pitch determining voltage signal from the keyboard circuit, thus achieving transposition of arpeggio.

Abstract: A pitch bend apparatus for electronic musical instrument having a voltage-controlled oscillator that works as a tone generator is provided with a first variable resistor for operating the pitch bend as well as a second variable resistor for setting a varying width of pitch bend or a maximum amount of pitch deviation. The varying width of the pitch bend is controlled by connecting the first and second variable resistors into an amplifier circuit to control the gain thereof, or by controlling the voltage applied to the first variable resistor by means of the second variable resistor.