Compact acousto-optic processor for synthetic aperture radar image formation

A compact implementation of a real-time acousto-optic synthetic aperture radar (SAR) imager is described. The architecture generates SAR imagery by decomposing the required 2D integration into a cascade of two 1D integrations, in a manner similar to that used in computed tomography for medical imaging applications. To achieve low power consumption, the required integrations are performed in the analog optical domain, with a crossed Bragg cell configuration, using a combination of spatial and temporal integration of optical signals. The time integrating and space integrating modules of the architecture are coupled via a common path interferometer. Subimages are formed on a 2D CCD detector array that is rotated during image formation to avoid a computationally difficult digital interpolation operation. The complex-valued subimages are combined in a digital frame buffer for dynamic range enhancement before being displayed. To accommodate needed flexibility, the required filter functions are calculated in a digital controller and downloaded through the Bragg cells. Results of a laboratory demonstration are presented. Performance projections suggest that the architecture may offer an advantage over an all-electronic approach for high-resolution applications which are severely constrained in power consumption.<
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