A noncrystalline film of As2S3 is used as a nonlinear recording material of the joint transform optical processor. Real time cross correlation between two transparencies is demonstrated using the optical processor. The authors observed cross correlation peaks between two photographs of identical words. The set-up can be applied to compare fingerprints.
"Joint Transform Real Time Optical Correlator Using A Noncrystalline Film Of As2S3", Proc. SPIE 0402, Three-Dimensional Imaging, (13 December 1983); doi: 10.1117/12.935556; https://doi.org/10.1117/12.935556