Patent ID: 6961183
Filing Date: 2005-11-01
Classification: G02B

Abstract:
1. An optical filter comprising a substrate and a thin film that is formed on the substrate, wherein the thin film comprises low refractive index layers and high refractive index layers that have a higher refractive index than the low refractive index layers, the low refractive index layers and the high refractive index layers being alternately laminated from the substrate side, wherein in this thin film are further formed: a first laminated portion in which the refractive indices of the high refractive index layers gradually increase from the substrate side; a second laminated portion that is adjacent to the first laminated portion, and in which the refractive indices of the high refractive index layers are substantially the same as the highest refractive index from among the high refractive index layers constituting the first laminated portion; and a third laminated portion that is adjacent to the second laminated portion, and in which the refractive indices of the high refractive index layers gradually decrease from the second laminated portion side, wherein a high refractive index variation layer portion, in which the refractive index of the high refractive index layer is set so as to be lower than the other two high refractive index layers that are adjacent on both sides thereof via the low refractive index layers, is inserted into at least one of the first laminated portion through the third laminated portion.