Beamsplitter configuration for optical subtraction of self emission with Fourier transform spectrometer in dual input port mode

摘要

A four port scanning Michelson interferometer suppresses self-emission by using either a beamsplitter that is uncoated or a beamsplitter that has reflection enhancing dielectric coatings in the splitting and combining areas of the substrate on opposite sides of the substrate. Both beamsplitters are fabricated from infrared optical materials that have a predetermined absorptivity in a predetermined wavelength interval which is from 2 μm (5000 cm−1) to 13 μm (770 cm−1) in the infrared. The optical materials of the uncoated beamsplitter are selected from a group of materials made up of ZnSe, ZnS, CdS, CdTe, Silicon, Germanium or Diamond. The optical materials of the other beamsplitter are selected from a group of materials made up of KBr, KCl, NaCl, CsI, BaF, CaF and the like.

主权项

1. A four port Michelson interferometer comprising:
a first input port viewing a first field of view having spectral radiance and a second input port viewing a second field of view having spectral radiance; and a non-symmetrical single substrate beamsplitter assembly having first and second opposed faces, said non-symmetrical single substrate beamsplitter assembly arranged such that incident spectral radiance from both the first and second input ports are split at said first face of the non-symmetrical single substrate beamsplitter assembly and combined, after traversing separate optical paths, each of said separate optical paths containing a retro-reflector where at least one retro-reflector is movable in order to carry out Fourier transform spectral analysis on said second face of the non-symmetrical single substrate beamsplitter assembly, said Fourier transform spectral analysis comprising: said interferometer performing a direct optical subtractive comparison of the spectral radiance of said second field of view against the spectral radiance of said first field of view having complete absence or self-emitted spectral radiance of the four port interferometer.