OPTICAL LOW-PASS FILTER

摘要

An infrared radiation is blocked by providing a coating layer (11) comprising high-refractive index and low-refractive index layers stacked alternately on a base material (10) in its light incident face. One of the high-refractive index layers is formed of an ITO film (11a) to enhance electroconductivity of the surface of the coating layer. Preferably, the outermost high-refractive index layer is formed of a transparent electroconductive material from the viewpoint of imparting electroconductivity to the surface of the coating layer to more reliably suppress the adherence of dust. Further, preferably, the sum total of thicknesses of the refractive index layers provided outside of the high-refractive index layer formed of the transparent electroconductive material is not more than 140 nm.