Amorphous ZnO:Al/ a-SixC1-x:H-p-i-n/Al optical imagers that use a small-signal scanning beam to read out the photogenerated carriers are presented. The effect of the image intensity on the sensor output characteristics (distortion, sensitivity and signal-to-noise ratio) are analysed for different sensor configurations (0.5 < x < 1). Results show that the sensitivity and the geometrical distortion are limited by the conductivity of the doped layers. A 75% image distortion reduction with a responsivity of 2 W/m (2) is obtained by decreasing the n-layer conductivity by one order of magnitude. An analysis of the image acquisition and representation is performed. A physical model supported by an electrical simulation gave insight into the methodology used for image representation.