Effect of keystone on coded aperture spectral imaging

Compared to conventional imaging spectrometry, coded aperture snapshot spectral imaging (CASSI) has the advantages of high throughput snapshot imaging etc. But because of the presence of the dispersive element, CASSI system suffers the effect of the same optical aberrations as traditional single slit spectrometer. To study the effect of keystone on signal acquisition, the model of spatial–spectral aliasing and the reconstructed result in CASSI system, combined with the principle of coded aperture spectral imaging and the reconstruction algorithm, the relative peak signal-to-noise ratio (PSNR) of the reconstructed image and the maximal error of the reconstructed spectral curve at different spectral band bending were calculated and analyzed. The experimental result showed that spectral band offset of the signal acquired by the detector will change the degree of spatial–spectral aliasing. Compared to the reconstructed results with no spectral band bending, distinct errors are exhibited when spectral band bending emerges. And the reconstructed spectral curve tends to be smooth on both sides of the spectral channel. In order to reconstruct the spectral cube with high accuracy, spectral band offset should be no more than half a pixel.