PURPOSE: To sufficiently suppress the high spatial frequency component of an object by an optical low-pass filter and to excellently prevent a spurious signal from being generated even when a semi-transparent mirror is inserted in an optical path.

CONSTITUTION: Image light L from the object is made incident on the semi-transparent mirror 2 through an image pickup lens 1. The image light Lb reflected on the mirror 2 is made incident on the image pickup surface of a color CCD solid image pickup element 5 through a 1/4 wavelength plate 9 and the optical low-pass filter 4. The light Lb reflected on the mirror 2 becomes the light having much linearly polarized light (vertically polarized light). However the vertically polarized light of the light Lb becomes the circularly polarized light by the plate 9. Thus, the high spatial frequency component of the object can be sufficiently suppressed by the filter 4 by utilizing birefringence and the spurious signal is excellently prevented from being generated.