PURPOSE: To output an optical signal having high uniformity by switching a case when a testing optical signal is made to made to form an image on an image pickup device to be tested through a condensing lens and an image forming lens from a light emitting lamp, and a case when said signal does not pass through these lens systems.

CONSTITUTION: A lens system 21 constituted of a condensing lens 14, a test chart 15 and an image forming lens is capable of moving mechanically to switch a case when it is inserted between a light emitting lamp 11 and an image pickup device to be tested, and a case when it is not inserted as shown in the figure. Accordingly, when uniform light is irradiated to the image pickup device to be tested, and the lens system 21 can be moved to shift from a signal path, therefore, uniform light required for the image pickup surface of the image pickup device to be tested is given by luminous flux having an extremely small solid angle, in the luminous flux emitted from the light emitting lamp 11, and the various characteristic tests of the image pickup device can be executed with high accuracy.