STROMVERSORGUNG FUER STRAHLUNGSQUELLEN VON FREQUENZ-ANALOGEN OPTISCHEN SENSOREN.

摘要

The current supply for providing a modulation signal with a periodically modulated constant amplitude uses a variable resistance (12b) in series with an LED or semiconductor laser (12a). Part of the light output of the latter is supplied to a reference detector (14a), e.g. a photodiode, coupled in a feedback loop for the current through the LED or laser (12a). The variable resistance (12b) pref. comprises a photoresistive illuminated by a controlled light source (17b), a hot conductor heated by a heating resistance, or a motor driven potentiometer. The resistance is adjusted to obtain a constant rise time for the modulation signal.