Photorefractive Crystal Compresses Dynamic Range Of Image

Experiment shows dynamic range of spatial variations of illumination within image compressed by use of photorefractive crystal. In technique, photorefractive crystal placed in optical path at some stage preceding video camera, photographic camera, or final photodetector stage. Provided brightness of parts of scene vary as slowly as or more slowly than photorefractive crystal responds, effect exploited to provide real-time dynamic-range compression to prevent saturation of bright areas in video or photographic images of scene, helping to preserve spatial-variation information in such images.