The resolution of an array sensor can be increased by projecting images of picture elements, which lie on the same scanning line, on a plurality of one-dimensional array sensors composed of a number of photoelectric transducers arranged with an equal interval in a row; and then subjecting picture signals, which have been output respectively from the array sensors, to a combination processing so as to obtain continuous picture signals. It is possible, without using any memory unit, to output picture signals with a resolution higher than that available from the use of a single one-dimensional array sensor, namely, with a resolution proportional to the number of a plurality of one-dimensional array sensors.