Helical boundary conditions allow the two-dimensional convolution matrix, , to be expressed as a one-dimensional convolution with a filter of length 2 Nx +1 that has the form
The structure of the finite-difference Laplacian operator, , is simplified when compared to equation ().(10) |
The 1-D filter can be factored into a causal and anti-causal
parts, and the matrix inverse can be computed by recursive polynomial
division (1-D deconvolution).