Abstract: A circuit arrangement is composed of a first adder whose first output is assigned to the digitized output signals of the photosensors and a second input connected to the outputs of a white level memory, and a second adder at whose input side the currently stored white level are linked with the correction signal and which reads the resultant signal back into the white level memory, the comparator following the first adder which, dependent upon the threshold level derived from maximum and average blackening values of the output signal of the first adder supplies a black signal or a white signal. A correction signal derived from a plurality of influencing variables serves for white level correction, the correction signal supplying a white level increment/decrement for delivery into the white level memory dependent on a carry signal that appears or, respectively, that does not appear at the first adder.

Abstract: 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.

Abstract: An editing arrangement for character recognition has a binary coded character stored in a X/Y-addressable image signal memory from which signals are first read out column-by-column, whereby a first character shadow is formed from the result by projection of successive columns respectively comprising black points onto the character base line. The stored character pattern is then repeatedly read out in accord with a scanning at positive and/or negative oblique angles relative to the Y-axis until as minimum character shadow is produced. The scanned pattern yielding this minimum character shadow is then selected for further evaluation of the character.