PURPOSE: To eliminate difference of sensitivity due to positional conditions of picture elements, by making the arrangement of a collector part constituting one part of picture elements differ from the arrangement of a collector part of the other picture elements.

CONSTITUTION: As to the width in the main scanning direction of collector collars 6 being high concentration impurity regions positioning between picture elements, the width (a') of picture elements of end portions is made larger than the width (a) of other picture elements, and the picture elements are arranged so as to be adjacent to a base and an emitter. As the result, the efficiency that positive holes generated in the vicinity of collector collars 6 out of electron-hole pairs excited in an N- type epitaxial layer 2 are absorbed in a base region by diffusion becomes larger in picture elements of end portions than those of other regions. Since the signal output level of picture elements of the end portions becomes low as compared with other picture elements, the sensitivity is increased by using the change of positions of collector collars 6, and the difference of output levels is corrected.