PURPOSE: To widen the dynamic range of light signals by making an image pickup element receive successively the quantity of light of an object at each different light emission time of a strobe light source, and after storing, adding the quantity of light.

CONSTITUTION: Controlling devices 9, 10 that irradiate the quantity of light for different light emission time in a fixed lighting time to an object successively are constituted by separately controlling a fixed lighting time of the strobe light source or providing a shading period during lighting of the strobe light source using the strobe light 8 as an illuminating light source and utilizing characteristic of the quantity of light of the strobe light source that changes in regard to the time of lighting. An optical image corresponding to the time of light emission controlled by the controlling devices is received by a solid-state image pickup element 4, and after storing successively in memories 14, 15, added to an adder 17 for addition.