| 摘要 |
By stacking films whose refractive index differs, there is formed an optical filter which reflects light in a predetermined wavelength band for separation. The films whose refractive index differs are stacked by varying the film thickness. As a result, there is formed a filter comprising a low refractive index region having a physical thickness of dL and an equivalent refractive index of nL* and a high refractive index region having the physical thickness of dH and the equivalent refractive index of nH* alternately stacked. The equivalent optical film thicknesses are set to 1/(4.lambd0) or 1/(2.lambd0), whereby it is possible to reflect light having a narrow band of wavelengths with a wavelength lambd0 being centered for separation.
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