Mitsubishi Denki Kabushiki Kaisha

Shigeo Hayashi

Masaharu Ogawa

Kunimaro Tanaka

Osamu Ito

Isao Watanabe

Keiji Nakatsu

Osamu Itou

An optical disc driving apparatus is provided for the access control system with respect to the optical disc, comprising emphasizing circuits which compensate for a decrease in the frequency response of a reproduced signal from an optical head and further comprising peak detection circuits for detecting envelopes of the output signals. The emphasizing circuits and peak detection circuits are not used for processing of the tracking servo sensor signal, therefore the compensation amount need not be accurately controlled. The characteristic of the reproduced signal of the optical disc is effectively utilized, thereby enabling the compensation amount to be used over a wider range from about a proper value to an excessive value. In addition, being able to use the compensation amount over a wider range results in a reduction in the number of separate stages of compensation.

Optical memory disc driving apparatus

A device for driving and controlling an optical head by forming a spot of a light beam on an optical disk having a plurality of tracks and detecting light from the spot reflected on the optical disk by a pair of optical detectors disposed in the head. This device has: a head actuator for moving a movable portion of the optical head in the radial direction of the disk; a speed detector for detecting the track-crossing speed of the spot from outputs from the optical detectors; a reference speed generator for generating, while accessing to a target track, a reference moving speed signal in accordance with the distance to the target track obtained from the outputs from the optical detectors, the movable head portion being moved on the basis of the reference moving speed signal so that the speed of the movable portion decreases at a position near the target track before the light beam spot reaches this track; a speed error detector for obtaining the difference between outputs from the reference speed generator and the speed detector; and a magnification change circuit adapted for amplifying the outputs from the reference speed generator and the speed detector by a predetermined multiplying factor when the distance between the light beam spot and the target track, or the crossing speed of the spot, becomes smaller than a predetermined value, the magnification change circuit also being adapted for outputting the difference obtained by the speed error detector after multiplying it by the reciprocal of the multiplying factor. The head actuator is driven on the basis of the output from the error detector so as to control the speed of the movable head portion.

Device for driving and controlling optical head for use in optical disk

A power conversion system includes an inverter for transforming d.c. power into high-frequency a.c. power, a high-frequency transformer for changing the voltage and isolating the input and output power lines, and a rectifier which rectifies the transformer output in synchronism with the inverter output and in timing relationship so that the averaged voltage waveform of the rectified output is sinusoidal.

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Amagasaki, Japan

Shigeo Hayashi