Circuit arrangement for clamping black level reference signals contained in a video signal sequence

摘要

A circuit arrangement is provided for clamping the black reference signals contained in a video signal sequence of an optical line scanner comprising a CCD sensor, using a video amplifier and a following analog- to-digital converter, and a memory controlled by the black reference signal for the control criterion that influences the video amplifier. A NOR gate is connected to all of the outputs of the analog-to- digital converter and the output of the NOR gate is connected to an input of a D flip-flop which is clocked by the black reference signal, and an integrator is connected to the output of the D flip-flop by way of a network and symmetrically driven with reference to its input voltage so that the output voltage of the integrator which decreases or increases in a ramp-like manner is added to the signal voltage of the line scanner at the input of the video amplifier.