PURPOSE: To prevent the malfunction due to inverter light in a light receiving part by mounting a filter which is constructed by superimposing a visible light cut filter and an interference film filter cutting the light with longer wavelength than the infrared ray on a light receiving window hole in front of a light receiving module installed in the light receiving body.

CONSTITUTION: A filter F which is constructed by superimposing a visible light cut filter 2 and an interference film filter 3 cutting the light with longer wavelength than the infrared ray is mounted on a light receiving window hole 5 provided on a light receiving device 4 in front of a light receiving module 1 installed in the light receiving device 4. Thus, the visible light and inverter light can be cut by penetrating the only light with longer wavelength than the infrared ray.