Simplified measurement of point spread functions of hyperspectral cameras for assessment of spatial coregistration

In multi- and hyperspectral imaging, spatial coregistration of the point spread functions (PSFs) of all bands within each pixel is critical for the integrity of measured spectra. There is a need to define a standardized method for characterizing coregistration error. We propose a method that estimates PSFs from the product of line spread functions (LSFs) recorded in two orthogonal directions. Coregistration is then evaluated according to the PSF difference metric [T. Skauli, Opt. Expr. vol. 20, p. 918 (2012)]. Experimental results on two pushbroom hyperspectral cameras show good correspondence with measurements based on the full PSF, provided that LSF scan directions are aligned with axes of symmetry in the optics. Even a maximally unfavourable choice of scan directions gives meaningful estimates of coregistration error. The proposed method may have potential as a standard for coregistration characterization.