Patent ID: 9158039
Filing Date: 2015-10-13
Classification: G02B

Abstract:
1. An optical element having an anti-reflection film formed on a substrate, wherein the anti-reflection film comprises: a first layer formed on the substrate; a second layer formed on the first layer and consisting of a material different from that of the first layer; and a third layer formed on the second layer and consisting of a concave-convex structure, wherein, when a wavelength defining a refractive index is 550 nm, the substrate has a refractive index in the range of from 1.65 to 2.20, the first layer has a thickness in the range of from 30 to 70 nm and a refractive index in the range of from 1.52 to 1.82, the second layer has a thickness in the range of from 10 to 50 nm and a refractive index in the range of from 1.40 to 1.58, and the third layer has a thickness in the range of from 200 to 300 nm and the refractive index of the third layer changes from a value in the range of from 1.40 to 1.58 toward 1.0, and wherein the third layer comprises, in order from the second layer: