Thesis defense of Varvara CHILIAEVA

Thesis defense of Varvara CHILIAEVA, PhD student in the Imaging and Information group of the LCF, on Wednesday 6 December 2023 at 9:30am in the Auditorium of the Institut d'Optique Graduate School in Palaiseau, on the topic: "Study of performance limits of high étendue static Fourier transform spectrometry."

Abstract: "The fundamental element of a high-etendue Fourier transform hyperspectral imager is a lateral-shift interferometer producing rectilinear interference fringes, which are formed on the image itself. A sequence of instantaneous images is obtained by flying over the scene.  Once the images have been registered, the interferograms can be extracted, and thus a spectrum for each point in the scene. Such an instrument is characterized in particular by a large flux collection, and by the absence of any moving element, which makes it compact and robust. These hyperspectral imagers are therefore well suited for small platforms, particularly mini-satellites. However, due to the highly indirect measurement process, artifacts appear on hyperspectral images. In this thesis, two effects were studied in detail. The first is the optical transfer function. We have shown that, in the absence of field aberrations, a transfer function of the spectro-imaging system can be defined. Spatial frequencies are transmitted differently in the scanning direction and in the direction perpendicular to the scan, with a possible exceeding of the Nyquist frequency for spatial frequencies in the scanning direction. The second effect we studied was that of registration errors during interferogram reconstruction. We have shown that such errors cause crenellated artifacts on the edges of the scene elements. We quantified both spectral and spatial artifacts in the case of a single perturbation and a sinusoidal perturbation which describes residual microvibrations of the platform."