Multiple-Pass Reflection Filter.
Patent, Filed 31 May 96, patented 2 Feb 99,
DEPARTMENT OF THE NAVY WASHINGTON DC
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An optical filter that uses multiple reflections to provide spectral bandpass filtering of ultraviolet, visible and infrared radiation with a very high transmission of wavelengths within a selected passband coupler with exceptional off-band rejection. The reflection filter uses dielectric-coated spherical reflections or mirrors manufactured with absorbing glass substrates. The multiple-pass feature of the reflection filter is achieved using a traditional long-path absorption cell such as a White Cell or Wilkes Cell. The light transmitted through the reflection filter is only that light which has undergone multiple reflections as the wavelengths of high mirror reflectivity reflect off the dielectric-coated substrates. All remaining light at wavelengths corresponding to high mirror transmission is attenuated by absorption in the mirror substrate. The degree of attenuation of light at wavelengths corresponding to high mirror transmission can be chosen simply by selecting an appropriate number of reflections in the multiple-pass reflection filter.
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