The pattern recognition of 16 levels gray image with iterative exposure schedule in Zn:Fe:LiNbO_3

摘要

An iterative method designed by angle multiplexing holographic storage is introduced to determine exposure schedule for multiplexing storage in Zn(2mol.%):Fe(0.03wt.%):LiNbO_3 crystal. In this experiment, 60 holograms were recorded in the same location of the crystal with 2mJ/cm~2 incident exposure energy per hologram (0.7s exposure time at 2.8mW/cm~2 total incident intensity). And the self-correlation peaks of holograms were collected by CCD. We found that the cumulative grating strength of correlation peak versus exposure energy could be fitted to be a sixth-order polynomial, and made use of an iterative expression to calculate the exposure schedule for 60 holograms. The correlation recognition of 99 pictures with 16 levels gray is completed and the accuracy is 100%, while an appropriate exposure schedule is used to store the two-dimensional holograms.