| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical element having an antireflection film having excellent incident angle characteristics with respect to a substrate having a high refractive index.SOLUTION: The optical element has an antireflection film 100 formed on a substrate 10 that is transparent in a wavelength range to be used. The antireflection film includes an intermediate layer 20 formed on the substrate, and a fine rugged structure 30 formed on the intermediate layer and having a plurality of projections with a pitch shorter than the shortest wavelength in the wavelength range to be used. The rugged layer includes a portion where the refractive index continuously increases from 1.0 in a direction from an incident side of light toward the substrate. The intermediate layer includes a first layer closest to the substrate and a second layer formed on the first layer. Refractive indices ns, n1 and n2 of the substrate, the first layer and the second layer, respectively, at a wavelength of 550 nm satisfy 1.75≤ns≤2.20, n1<n2 and n1<ns. |
