Deutsche Thomson-brandt Gmbh

Volker Politz

Hirohito Takagi

Friedrich Fueldner

Recording or playback devices for optical recording carriers have a servo control circuit which controls the tracking and the focus of an optical scanning unit 1 with reference to an error signal. According to the invention, the error signal is non-linearly amplified upstream of the servo controller, in order to process strong external mechanical effects, normally referred to as shocks, in such a way that the tracking and the focus are retained or adjusted. If there is a defect, such as a scratch on the disc etc., a defect detector and a linear amplifier connected in parallel with the non-linear amplifier are additionally used, the linearly amplified or non-linearly amplified error signal being fed to the servo controller as a function of the output signal of the defect detector. The sign of the error signal, which includes direction information, is retained in the case of the non-linearly amplified error signal.

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Isen, Germany

Volker Politz