Sony Corporation

Honda Motor Co., Ltd.

Yasuo Sasaki

Munekatsu Fukuyama

Kazuo Kurihara

Yutaka Soda

Tetsuo Sekiya

Koji Fukumoto

Kenji Araki

Kimihiro Saito

Noriaki Nishi

Kazuyoshi Horie

Kazuhiko Okamatsu

Akira Hasegawa

Kohjiro Minakami

A tracking servo device for use with an optical disc apparatus includes a photodetector unit having a plurality of photodetectors each of which is split in association with the direction of tracks formed on the optical disc, and a tracking error generating unit for finding the difference in outputs from at least two of the photodetectors of the photodetector unit for generating a tracking error signal. The tracking servo device also includes a first correction unit for removing an offset produced in the tracking error signal when the tracking servo is on, and a second correction unit for removing an offset produced in the tracking error signal when the tracking servo is off. The tracking servo device also includes a switching unit for selecting the first correction unit or the second correction unit when the tracking servo is on or off, respectively, for producing a tracking error signal freed of the offset component, and an offset holding unit for holding an offset component extracted by the second correction unit. The tracking servo device further includes a control unit for controlling the holding time of the offset component in the offset holding unit.

Tracking servo apparatus for optical disc

A recording/reproducing apparatus for a magneto-resistive (MR) head having a playback amplifier, including a capacitor for a dc feedback low-pass filter for do feedback to an initial-stage transistor, and a differential amplifier (gm amplifier), and a switching device for the gm amplifier and for the initial-stage amplifier operable at the time of recording/playback switching. The timing of the switching device is deviated for shortening the switching time interval. To this end, an output of the initial-stage transistor of a playback amplifier for a MR head is compared to reference voltage Vref by a gm amplifier and the low-pass filter is constituted by transconductance gm of the gm amplifier and the capacitance of the capacitor, with the dc output of the gm amplifier being fed back to the base of the initial-stage amplifier. The delay in switching time by the charging of the capacitor caused by the difference in the rise time of the initial-stage transistor and the gm amplifier is deviated by the control signal from a control circuit to control the initial-stage transistor and the gm amplifier.

Reproducing circuit for a magnetic head having a variable gain amplifier

A recording/reproducing apparatus for a magneto-resistive (MR) head having a playback amplifier, including a capacitor for a dc feedback low-pass filter for dc feedback to an initial-stage transistor, and a differential amplifier (gm amplifier), and a switching device for the gm amplifier and for the initial-stage amplifier operable at the time of recording/playback switching. The timing of the switching device is deviated for shortening the switching time interval. To this end, an output of the initial-stage transistor of a playback amplifier for a MR head is compared to reference voltage Vref by a gm amplifier and the low-pass filter is constituted by transconductance gm of the gm amplifier and the capacitance of the capacitor, with the dc output of the gm amplifier being fed back to the base of the initial-stage amplifier. The delay in switching time by the charging of the capacitor caused by the difference in the rise time of the initial-stage transistor and the gm amplifier is deviated by the control signal from a control circuit to control the initial-stage transistor and the gm amplifier.

Reproducing circuit for a magnetic head incorporating the

A small size, high performance optical pickup device using a light reception/emission element (laser coupler) and more particularly, an optical pickup device which is capable of excellent recording and reproduction for a magnetic optical recording medium. A prism disposed over optical detectors is made of double refractive crystal material. An optical detector for receiving extraordinary ray is formed at a position laterally deviated corresponding to so-called walk-off of the extraordinary ray. Tracking error signal is detected depending on a distribution of intensities of spots formed by reflective beams on respective optical detectors.

Optical pickup device and disk player apparatus

A tracking error detecting circuit including a light receiving unit divided into a plurality of light receiving sensors; a push-pull signal detecting circuit detecting the push-pull signal based on the difference of the amount of the reflected light received by the sensors; a compulsory offset cancellation circuit for removing the input offset signal from the detected push-pull signal; an offset component detecting circuit for detecting an offset component in accordance with the push-pull signal based on an amplitude of the wobbling component of the groove; a cancellation signal detecting circuit for finding an offset cancellation signal with respect to the push-pull signal an offset cancellation circuit for finding a tracking error signal by removing the offset cancellation signal from the push-pull signal; and a parameter determining means for determining the parameter to be referred to at the cancellation signal detecting circuit based on an offset component detected at the offset component detecting circuit by the movement of an optical pick-up and the offset signal input to the compulsory offset cancellation circuit for suitably removing this offset component from the push-pull signal.

Tracking error detecting circuit in disc-shaped recording medium

A thin-film magnetic head, a magnetoresistance effect magnetic head and an MR inductive head are disclosed. The thin-film magnetic head has one of thin-film magnetic cores stacked on a substrate and formed of two magnetic films and a non-magnetic film held between them, with a current flowing through the thin-film magnetic core in the direction of hard axis thereof. The magnetoresistance effect magnetic head has one of a pair of shield cores having a magnetoresistive element between them formed of two magnetic films and a non-magnetic film held between them, the magnetoresistive element being electrically connected to the shield core, with a sense current flowing through the shield core. The current flowing through the one shield core via the magnetoresistive element is preferably an AC of decrement amplitude for demagnetizing the shield core along with a DC sense current. Also, this current preferably flows in the direction of hard axis of the shield core so that magnetic properties of the shield core are stabilized or demagnetized by the magnetic field generated in the direction of easy axis. The MR inductive head has a second thin-film magnetic core as a common magnetic body of an MR head and an inductive head on one substrate, formed of two magnetic films and a non-magnetic film held between them, with a current flowing through the second thin-film magnetic core in the direction of hard axis thereof.

Growing community of inventors

Kanagawa, Japan

Yasuo Sasaki