Deutsche Thomson-brandt Gmbh

Heinz-Jorg Schroder

Yasuaki Morimoto

Christian Buchler

Friedhelm Zucker

Friedheim Zucker

The beam of light reflected from an optico-magnetic recorded medium is reflected by an optical pick-up onto one optical or another in accordance with the direction that the beam's plane of polarization is rotated in. A data signal is obtained from the difference in the photovoltages of the two photodetectors.

Pick-up for selectively reading and writing an optical recording medium

An optical pick-up for selectively reading and writing an optical and magneto-optical recorded medium, in which light projected on the recorded medium is reflected therefrom and directed onto one of two photodetectors, depending on the polarization of the light. The recorded medium has magnetic domains for storing data and a magneto-optical signal is generated from the difference between the two photo voltages from the two photodetectors. The magneto-optical signal represents the data stored in the magnetic domains. The recorded medium also stores data in pit forms, and an optical signal is generated from the sum of the photovoltages of the two photodetectors, to represent the data stored in the pit forms. The arrangement is suitable for reading out simultaneously the optical signal and the magneto-optical signal.

Optical pick-up selectively reading and writing an optical and

A tracking circuit for an optical scanner to return a light beam to a data storage track of a disk that was scanned by the light beam, after the light beam was deflected away as a result of an outside random shock or vibration. A difference amplifier generates a tracking error by taking the difference between two photovoltages. A directional logic circuit in the form of a D flip-flop determines which direction the light beam was deflected away from the data storage track that was scanned by the light beam. The light beam may skip storage tracks when it is deflected away from the track that was being scanned. The number of storage tracks that were skipped by the light beam, in this manner, are counted by an up-and-down counter, and this counter emits a control signal which is dependent on the state of the counter for deflecting the light beam back to the data storage track that was scanned. The counter output is applied to a control amplifier through a pulse shaper. The output of the difference amplifier in the form of the tracking error is applied to the control amplifier through a controllable switch that has a control input from the counter.

A tracking circuit for returning an optical beam to a track being

An optically-recorded medium in which a reflecting optomagnetic layer is applied to a transparent substrate layer. The recorded medium stores data magnetically and by pits. The magnetically stored data and the pit stored data are superimposed on each other, so that every spot and region on the recorded medium stores both magnetically stored data and pit stored data. The recorded medium is not divided into separate regions for magnetically stored data and pit stored data, and the magnetically stored data and pit stored data may be read out simultaneously by a single light beam.

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Marbach, Germany

Heinz-Jorg Schroder