Tunable spatial heterodyne spectroscopy with a linear relationship between fringe frequency and wavenumber.

This paper presents a tunable spatial heterodyne spectrometer in which the fringe frequency exhibits a strict linear relationship with the wavenumber of incident light. We describe its optical implementation method, precise spectral inversion expression, and performance parameters, with theoretical validity verified through a simulation-based design example. Compared with conventional spatial heterodyne spectroscopy, it offers the same usable field-of-view and spectral resolution, while increasing the spectral range and eliminating the need for nonlinear data processing.