Hyperspectral imager for the mid-infrared spectral range using a single-mirror interferometer and a windowing method

In this paper, we present a static imaging Fourier transform spectrometer (sIFTS) for the mid-infrared spectral range. The system employs imaging optics, a single-mirror interferometer, and an uncooled broadband microbolometer array. As the hyperspectral data cube is acquired using a windowing method, a comparatively high light throughput in a spectral range from 2600 cm⁻¹ to 800 cm⁻¹, respectively 3.8 µm to 13 µm is achieved. The spectral resolution is 12 cm⁻¹, and the spatial resolution amounts to 16 lp/mm, corresponding to a resolution of 62.5 µm at a design wavelength of 10.6 µm. As the employed spectrometer, in contrast to scanning Fourier transform infrared (FTIR) spectrometers, contains no moving parts, the measurement rate is mainly limited by the detector read-out and is currently 25 Hz. After an evaluation of the spatial resolution by both simulations and experimental results, the spatially resolved transmission spectra of a sample containing different polymer films are recorded and compared to a laboratory FTIR spectrometer. Thereby, the acquired spectra show good agreement. As the system combines both a spectrometer with low internal light loss and a windowing technique allowing high etendue, the presented hyperspectral imager shows significant potential especially for the mid-infrared.