Offset, Linear and Quadratic Scene-Change Artifact Comparison in Fourier-Transform Spectroscopy of a Target with Sharp Spectral Features.

Observations of time-varying scenes using a Fourier-transform spectrometer can produce scene-change artifacts in the measured spectra. These artifacts typically appear as oscillations in the spectra and are often mistaken for noise. Interferogram-offset scene-change artifacts arise from an incorrect interferogram offset estimate. The error is Fourier-transformed and superimposed onto the measured spectrum. The recently developed smooth offset correction method removes these artifacts. Prior to this work, this correction method had only been applied to spectrally smooth targets. Concerns have been raised regarding its application to targets with structured spectra. In addition to the interferogram-offset scene-change artifacts, higher-order artifacts are predicted to be significant for structured spectra. Linear scene-change artifacts occur when a target moves with constant velocity through the field of view, and quadratic scene-change artifacts occur when a target moves with constant acceleration. These artifacts are largest near abrupt spectral transitions. Despite this, the higher-order artifacts remain relatively small and have minimal impact on spectral accuracy. We conclude that, after smooth offset correction, the remaining scene-change artifacts can be ignored when examining spectrally smooth targets such as notch filters.