Digital shearing laser interferometry for heterodyne array phasing

A laser radar using an array of heterodyne detectors offers the possibility of fine resolution angle-angle imaging. The heterodyne measurements, however, are subject to phase errors due to atmospheric turbulence and mechanical misalignment. A method is described that employs digital shearing of the heterodyne measurements as a means to remove phase errors. By this method large phase errors can be corrected without requiring a beacon or a glint. This digital shearing laser interferometry method was investigated theoretically and demonstrated via computer simulations which included photon noise and various types of phase errors. The method was also successfully applied to data collected in a simple laboratory experiment.