| 摘要 |
Optical filter with a thin film formed by laminating low refractive index layers (20) alternately from substrate side with high refractive index layers . The thin film is provided with first, second and third laminated portion (96-98;103,105,106). In the first laminated portion (96;103), the refractive indices of the high refractive index layers become gradually higher, while in the second laminated portion (97;105) the refractive indices of the high refractive index layers remain substantially equal to the highest refractive index of the high refractive index layers of the first laminated portion. In the third laminated portion (98;106), the refractive indices of the high refractive index layers become gradually lower. The lamination patterns of the laminated first, second and third portion are repeated twice or more (P1;P2), and the optical thickness of each lamination pattern is different.
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