To suppress a plurality of kinds of optical image components different in spatial frequency.

The optical low pass filter (13) is composed of a fiber bundle configured in such a way that a plurality of optical fibers (13a) are randomly arranged and bundled. When the arrangement pitch of the optical fibers (13a) is random like this, an optical image on an end surface (13A) is sampled at a random sampling pitch and then, projected to an end surface (13B). Thus, various spatial frequency components can be suppressed from the optical image after being projected. Incidentally, the range of the suppressed spatial frequencies corresponds to the range of the sampling pitch (=the range of the arrangement pitch).