Increasing the holographic matched filter information capacity

The advantage of a sampled Fourier hologram in enhancement of the number of characters included in a matched spatial filter in Vander Lugt correlator systems is shown in this paper. A sampled Fourier hologram can be easily obtained by inserting a sampling mask adjacent to the hologram during recording. When the sampling period in the recorded sampled hologram is matched to the object spectrum, according to the Whittaker-Shannon theorem, the resulting image does not suffer any loss of information content. However, the sampled hologram covers only a small part of the photographic plate, with the result that one can record many closely packed Fourier holograms on the same area of the plate and at the same working point of the H-D curve. Thus, sampling is used as a multiplexing technique. Sets of cross-correlation or autocorrelation images are generated in the output of the correlator system. The offset angle of the reference beam must be suitably selected to prevent overlapping of the sets of images.