Prism interferometer for a compact Fourier-transform spectroscope

As a step toward a field-use spectrometer based on Fourier-transform spectroscopy, we have developed a prism-scanning interferometer. It consists of a sliding triangular prism with two mirror surfaces attached to a fixed triangular-prism beam splitter. This design eliminates the effect of ambient air and simplifies alignment, which can otherwise be time consuming. It also halves the stage-moving distance, because the optical path difference is doubled, since both mirrors move while the sliding prism is scanning. We have tested the basic operation of the prototype and found that the spectral resolution and the wavelength scale agree well with our simple calculation.