Real-time coherent phased array image synthesis and atmospheric compensation testing

Developments in imaging technology for aircraft-based systems are moving in the direction of sparse, dis- tributed aperture arrays which are conformal to the shape of the air vehicle. These modular arrays can provide resolution capabilities similar to large monolithic telescope apertures without the associated weight and required aircraft structural modications. A key challenge of such a system is to accomplish the imaging function without requiring an elaborate optical relay system to bring the receive channels together on a single focal plane array (FPA). To overcome this challenge, phased array imaging systems rely on coherent imaging through holographic detection of the complex optical eld such as spatial-heterodyne imaging, which requires a digital processor to synthesize the combined imagery. This approach also allows atmospheric compensation to be included digitally in the image synthesis processing thereby eliminating any latencies due to phase modulation hardware in the subaperture module. To support testing of phased array imaging systems, we have constructed a GPU-based image processor capable of real-time (1 kHz) image synthesis including low-order atmospheric compensation. Using this processor and the IMAGE testbed at UD/LOCI, we demonstrate the eectiveness of our processor and phasing algorithm during scaled testing of a Hex-7 aperture array. We show image synthesis and compensa- tion results from laboratory testing where atmospheric turbulence eects have been induced with phase wheels at varying positions along the propagation path.