Optical computing in synthetic aperture radar

In a synthetic aperture radar system, an aircraft moving along a very straight path continually emits successive microwave pulses. All the echoes which return during this period can be processed as though a single antenna as long as the flight path had been used. This large 'synthetic' aperture provides not only a high gain but also a very high resolving power. The microwave generator provides also a reference wave. The reflected signals and the reference wave generate a complex interference pattern which is equivalent to a hologram in one dimension. The processing of microwave holograms as obtained with a side-looking radar yields photos of extremely good detail. Applications of similar concepts in the sonar field are also explored.