Fig. 4: Vectorization and coded-aperture-related sensing matrix generation procedure.

a Illustration of the vectorization process. For a matrix A, vectorization means stacking the columns of A on top of one another; For a spectral cube of the input scene f(m, n, l), vectorization means stacking the vectorized 2D slice on top of one another. b Illustration of generating sensing matrix from colored coded aperture in SD-CASSI architecture. It consists of a set of diagonal patterns that repeat in the horizontal direction, each time with a unit downward shift M that accounts for dispersion. Each diagonal pattern is generated from the vectorized coded aperture pattern of a band. The block–unblock coded aperture is similar, just turning the color bands into black and white