The Perkin-Elmer 1700 Series FTIR Spectrophotometers* use a Michelson Interferometer in which the optical path difference is generated by rotary rather than linear motion as described by Sternberg and James'. The relative alignment of the interfering wavefronts is unaffected by any motion of the rotating assembly in all six degrees of freedom, while the OPD is generated by rotation about one axis. This configuration eliminates any need for dynamic alignment during scans and gives exceptional long term stability.
M. A. Ford,
A. R. Gee,
"Properties and Performance of A Rotary Scanning FTIR", Proc. SPIE 0553, Fourier and Computerized Infrared Spectroscopy, (20 December 1985); doi: 10.1117/12.970857; https://doi.org/10.1117/12.970857