Neutral density (ND) filter

摘要

A thin-film-type ND filter which attenuates the amount of light transmission is formed on a transparent substrate by using two or more types of metallic oxide having a refractive index n and an attenuation coefficient k which are in the range of 1.0 to 3.0 in the wavelength region of the visible region, making it possible to obtain flat transmittance characteristics.