Spatial misregistration in hyperspectral cameras. Lab characterization and errors in real-world images

摘要

Hyperspectral cameras capture images where every pixel contains spectral information of the corresponding small area of the depicted scene. Spatial misregistration - differences in spatial sampling between different spectral channels - is one of the key quality parameters of these cameras, because it may have a large impact on the accuracy of the captured spectra. Spatial misregistration unifies various factors, such as differences in the position of the optical point spread function (PSF) in different spectral channels, differences in PSF size, and differences in PSF shape. Ideally, there should be no difference in spatial sampling across the spectral channels, but in any real camera all these factors are present to some degree. This work shows the magnitude of the spectral errors caused by these spatial misregistration factors of different magnitudes and in various combinations, when acquiring hyperspectral images of real scenes. The spectral errors are calculated in Virtual Camera software, where high resolution airborne images of real-world scenes and several PSFs of different hyperspectral cameras are used as the input. The misregistration factors are simulated. Also, two different methods for quantifying spatial misregistration in the lab are tested and compared, using the correlation with the errors in the real-world scenes as the criterion. The results are used to suggest the best camera characterization approach, that would adequately predict spatial misregistration errors and allow reliable comparison of different hyperspectral cameras to each other.