Experiments in long-distance holographic imagery

Long-range holographic experiments have been performed over distances as large as 12 km. Holograms and images of retroreflector and Scotchlite objects were obtained. The reference wave was supplied by a retroreflector placed next to the object, and the source of illumination was a Q-switched ruby laser. Resolutions obtained varied with atmospheric seeing conditions, ranging from 3 see of arc to 0.5 see of arc. The primary practical problem encountered was detector saturation, a consequence of the limited dynamic range of photographic film. The use of a low contrast developer only partially alleviates this problem.