Long-range holography field experiments

An active holographic and conventional imaging techniques were compared, with the images for both cases taken simultaneously at a range of 1 km. A 1-joule Q-switched ruby laser with a 1-m coherence length was used as the light source. To obtain both a conventional image and a holographic interference pattern simultaneously through one aperture, a beamsplitter and two cameras were mounted at the focus of a 36-cm-diameter telescope. Tests were conducted for several weeks, involving 257 exposures. At best, holographic imaging showed an improvement in resolution over conventional imaging by a factor of 2 but with a decrease in signal-to-noise ratio.