Deutsche Thomson-brandt Gmbh

Friedheim Zucker

Yasuaki Morimoto

Christian Buchler

Steffen Lehr

Heinz-Jorg Schroder

Christian Buechler

A photodiode detection circuit is used to automatically identify a type of photodiode circuit connected to it. The photodiode circuit comprises at least a photodiode. Once the type of photodiode circuit has been identified by applying a current to it and evaluating a voltage occuring at an input of the detection circuit the photodetection circuit adapts itself to it, e.g. a reverse biasing voltage is/isn't applied to the photodiode of the photodiode circuit. The result is a photodiode detection circuit which uses a forward or a reversed biased photodiode. The photodiode detection circuit is now in a state to measure light falling on the photodiode. The detection circuit may be part of a light intensity monitoring and controlling circuit which allows to regulate the intensity of a laser beam in an optical disk reading/recording device.

Automatically adapting forward or reversed biased photodiode detection circuit

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

An optical pick-up for selective playback and recording on a magneto-optically recording medium, in which light is projected from a source onto the medium. The light is provided with a direction of a polarization, and is either reflected from the recording medium or is transmitted through the medium. The reflected or transmitted light becomes deflected onto a predetermined one of several photodetectors, depending on the direction of polarization of the light. The intensity of the reflected light or the transmitted light is held constant to minimize noise components that result from the optical properties of different recorded media as well as from the light. By holding the light intensity constant, moreover, precise readjustment to each of the different recording media that may be used, is not necessary.

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Villingen-Schwenningen, Germany

Friedheim Zucker