We have experimentally demonstrated a single-beam interferometer that effectively subtracts an exponentially weighted history of the input from the current value, thus functioning as a novelty filter. The single-beam interferometer uses signal depletion due to noise amplification (fanout) in a specially cut crystal of photorefractive BaTiO3. To demonstrate its real-time operation we used a Hughes liquid-crystal light valve to convert a video image into a phase- and/or amplitude-modulated input signal. Potential applications of this interferometer include image-clutter removal, motion detection and tracking, edge enhancement, and image time differentiation.
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