Patent ID: 7312925
Filing Date: 2007-12-25
Classification: G02B

Abstract:
1. An optical filter formed by a substrate and a thin film that is formed on the substrate, wherein the thin film is provided with laminated portions having a first refractive index profile and a second refractive index profile, and wherein the first and second refractive index profiles are formed by laminating low refractive index layers whose refractive index is relatively low alternatingly from the substrate side with high refractive index layers whose refractive index is relatively high, and wherein the first refractive index profile and the second refractive index profile are continuous, and wherein each of the first refractive index profile and the second refractive index profile is represented by a first laminated portion, a second laminated portion that is laminated on the substrate side of the first laminated portion, and a third laminated portion that is laminated on the substrate side of the second laminated portion, and wherein in the first laminated portion, the refractive indices of the high refractive index layers become gradually higher approaching the substrate side, in the second laminated portion, the refractive indices of the high refractive index layers are substantially equal to the highest refractive index of the high refractive index layers constituting the first laminated portion, and in the third laminated portion, the refractive indices of the high refractive index layers become gradually lower approaching the substrate side, and wherein at least one of an optical thickness of the high refractive index layers in the first refractive index profile, an optical thickness of the low refractive index layers in the first refractive index profile, an optical thickness of the high refractive index layers in the second refractive index profile, and an optical thickness of the low refractive index layers in the second refractive index profile is different from the others.