Pseudo-Monolithic Spatial Heterodyne Spectrometer Interferometer

High throughput IR spectrometer with no-moving parts and immunity to scene changes


Data ImageThe US Naval Research Laboratory has demonstrated a passive, broadband (8.4 to 11.2 µm), LWIR spectrometer with a resolving power of ~500 that has no moving parts, is immune to scene changes and has high throughput. It uses a compression assembly spatial heterodyne spectroscopy (SHS) interferometer (C-SHS) which employs precision spacers that result in a robust, self-aligning, economical assembly, and enables easy replacement of optical components.

The basic principle of spatial heterodyne spectroscopy is similar to a Fourier-transform spectrometer (FTS) in that it also features a beamsplitter which divides the incoming signal into two interferometer arms. However, in SHS, the latter terminate at fixed, tilted gratings that impose a wavelength-dependent tilt onto the diffracted wavefronts. After recombination at the beamsplitter and imaging onto a detector array, a complete interferogram can be recorded without using any moving parts.

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