The interference of two coherent images with a controlled phase difference between them is shown by using four-wave mixing in fluorescein-dye-doped boric acid glass and a liquid-crystal television spatial light modulator. We present results showing the digital optical exclusive OR operation with milliwatt optical power and an output that is compatible with CCD camera sensitivities.
S. A. Boothroyd, L. Chan, P. H. Beckwith, and J. Chrostowski, "Optical image subtraction in fluorescein-doped boric acid glass," Appl. Opt. 31, 4004-4009 (1992)