To prevent dust from flowing into a housing part accompanying cooling air, to prevent the contamination of an optical means and to miniaturize a blowing means by arranging a photoelectric conversion means and a cooling means on the outside of the housing part.

A first mirror base 10, a second mirror base 11 and a condensing lens 12 are arranged inside a frame body 1. On the outside of the frame body 1, a CCD unit 16 and a cooling fan 17 which is the blowing means, etc., are arranged. The dust-proof member of sponge or the like is held between metal sheets, where a CCD sensor which is the photoelectric conversion means is fixed and the sticking of the dust to the light-receiving surface side of the CCD sensor is prevented. Thus, the cooling air from the fan 17 efficiently cools the CCD sensor and heat generation components on a sensor board, the dust included in the cooling air does not reach the mirror bases 10 and 11, and the condensing lens 12 and good images are obtained at all times.