Patent ID: 7230746

Claim:
A diffraction specific computer generated holographic display for replay of a hologram into an image volume, said image volume having a plurality of image volume points, said display comprising: at least one spatial light modulator (SLM) to which diffraction data is written to produce a diffraction pattern thereon, wherein the diffraction pattern is notionally divided into a plurality of hogels and each hogel is divided into a plurality of points; image calculation means for calculating diffraction data which is independent of the image to be displayed, relating each image volume point to each hogel by performing pre-processing steps and for using at least some of said diffraction data in image replay steps, said pre-processing steps comprising the steps of: i) calculating a plurality of sample values at a plurality of sample points on each hogel, said sample values representing a calculated curved wavefront radiating from each image volume point to each hogel; ii) calculating a set of complex spatial frequency coefficients from the sampled values and storing said set for said image replay steps; said image replay steps comprising the steps of i) defining a three-dimensional image to be replayed by said display by selection of a sub-set of image volume points; and ii) summing a sub-set of said stored set of complex spatial frequency coefficients corresponding to said sub-set of image volume points; writing means for writing a diffraction pattern to the corresponding hogel on the SLM calculated from the summed set of spatial frequency coefficients; and a light source for illuminating the SLM so as to project curved, real wavefronts from said SLM to said image volume.