| 摘要 |
PURPOSE:To provide a stable characteristic in cosmic environment as well by providing an IR interference filter on at least one of the outside surface of the interference plates used in a Fabry-Perot interferometer thereby enabling modulation of the IR light having a required wevelength band without adding any IR filter. CONSTITUTION:Parallel flat plates 31, 32 which are transparent to IR light and of which the opposed inside surfaces having >=24% reflectivity are formed on germanium or silicone plates. The plates 31, 32 are disposed in parallel, via a spacer 33. An antireflection film is formed on each outside surface of the plates 31, 32 to minimize a reflection loss. An IR interference filter 34b manufactured by forming thin films 34', 34'' having a prescribed IR transmission characteristic on both surfaces of an IR transmittable base plate of germanium or the like is fixed, via an annular space 35, to the plate 31. When a voltage is impressed on the spacer 33, the thickness thereof changes and the space between the plates 31, 32 changes as well, resulting in a change in the IR transmittance characteristic. The IR light in the wavelength region selected by the filter 34 is thus intermitted according to the voltage applied on the spacer 33. |
