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Optical Path

General Overview:

FTS New Diagram

The NIST Fourier transform spectrometer consists of a folded Michelson interferometer with the two mirrors replaced by cat's-eye retroreflectors. Each cat's-eye runs on a rail consisting of an oil bearing and linear motor. The cat's-eyes move in opposite directions along the rails, with the zero path difference being when both cat's-eyes are in the center. Each rail is 1 m long, giving a maximum possible path difference of 2 m, which in turn gives a maximum possible resolution of 0.0025 cm-1.

The wavelength range of the instrument is 200 nm to 5.5 µm, with various detectors and beamsplitters.

FTS Labeled

Photograph of spectrometer with vacuum chamber lifted away.