Patent ID: 7193780
Filing Date: 2007-03-20
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 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 thin film is provided with a first laminated portion, a second laminated portion that is adjacent to the first laminated portion, and a third laminated portion that is adjacent to 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 from the second laminated portion side, and the refractive indices of the low refractive index layers are substantially equal to the lowest refractive index of the low refractive index layers constituting the second laminated portion, and wherein the low refractive index layers of the first and second laminated portions have at least one of a low refractive index layer uniform portion in which the refractive indices are substantially uniform, or a low refractive index layer decreasing portion in which the refractive indices become gradually lower approaching the substrate.