| 摘要 |
An optical element includes a transparent substrate and an antireflection coating on the substrate. The antireflection coating includes an intermediate layer on the substrate, and an undulation layer that is formed on the intermediate layer and has a plurality of convexes arrayed with spacing shorter than a shortest wavelength. The undulation layer has a portion where refractive index increases from a light incident side to the substrate. The intermediate layer has a first layer closest to the substrate, and a second layer formed on the first layer. A refractive index n1 of the first layer, a refractive index n2 of the second layer, and a refractive index ns of the substrate satisfy the following conditional equations: 1.75≦̸ns≦̸2.20; n1<n2; and n1<ns. |
