A method of performing a DFT (discrete Fourier transform) or a DFT derived transform
on data, comprising: providing spatially modulated light having spatial coherence,
said spatially modulated light representing the data to be transformed; Fourier
transforming said spatially modulated light, using an at least one optical element;
and compensating for at least one of a scaling effect and a dispersion effect of
said at least one optical element, using an at least one dispersive optical element.