A photographic light is spectrally separated by a spectral prism 9 provided in an image-formation area R of the photographic light whose luminous flux is adjusted by a group of lenses 1a-1d for adjusting the luminous flux so as to image-form the photographic light. Respective lights spectrally separated by the spectral prism 9 are imaged by means of the imaging elements 2. An infrared-ray element of the photographic light whose luminous flux is being adjusted is eliminated by an infrared-ray cut filter 8. The infrared-ray cut filter 8 is advanced and retreated by a mechanism unit 14a between a position in an optica path of the photographic light and a position distant from the optical path. In the foregoing constitution, the infrared-ray cut filter 8 and the mechanism unit 14a are disposed in a luminous flux convergence area R of the photographic light whose luminous flux is being adjusted by the group of lenses 1a-1d.