| 摘要 |
PROBLEM TO BE SOLVED: To provide filter structure in which a transparent band region is flat, a ripple is suppressed and excellent characteristics are realized. SOLUTION: An optical band pass filter has three or more steps of cavities 8 having two or more kinds of different structure on an optical substrate 1. The cavity 8 is constituted by alternatively arranging an optical thin film of high refractive index and an optical thin film of low refractive index different from each other in the refractive index at both sides of a spacer layer 2. When a central wavelength of the transparent band region is set to beλ, thickness of the spacer layer 2 is integral multiple ofλ/2. Further, there is a binding layer 3 consisting of a low refractive index film between respective cavities 8. When optical film thickness of the binding layer 3 is denoted by C, and P and Q respectively denote zero or above integer, at least two layers, out of a binding layer 2 satisfying a relation: 0.10λ+0.50λ×P≤C≤0.24λ+0.50λ×P and the binding layer 3 satisfying a relation: 0.26λ+0.50λ×Q≤C≤0.40λ+0.50λ×Q, are contained. COPYRIGHT: (C)2005,JPO&NCIPI
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