a new differential technique for forming optical images using a synthetic aperture is introduced . this differential technique utilizes a single aperture to obtain unique phases that can be processed to produce a synthetic aperture image at points along a trajectory . this is accomplished by dividing the aperture into two equal “ subapertures ”, each having a width that is less than the actual aperture , along the direction of flight . as the platform flies along a given trajectory , a source illuminates objects and the two subapertures are configured to collect return signals . the techniques of the invention is designed to cancel common - mode errors , trajectory deviations from a straight line , and laser phase noise to provide the set of resultant phases that can produce an image having a spatial resolution corresponding to a synthetic aperture .