The maximum resolution of a multiple-input multiple-output (MIMO) imaging system is determined by the size of the synthetic aperture. The synthetic aperture is determined by a coordinate shift using the relative positions of the illuminators and receive apertures. Previous methods have shown non-iterative phasing for multiple illuminators with a single receive aperture for intra-aperture synthesis. This work shows non-iterative phasing with both multiple illuminators and multiple receive apertures for inter-aperture synthesis. Simulated results show that piston, tip, and tilt can be calculated using inter-aperture phasing after intra-aperture phasing has been performed. Use of a fourth illuminator for increased resolution is shown. The modulation transfer function (MTF) is used to quantitatively judge increased resolution.

Multi-aperture coherent LADAR techniques can be applied to generate high resolution images. When setting up a system with multiple sub-apertures, misalignment of the sub-apertures causes the beams entering the sub-apertures to have mismatched optical path lengths, which will degrade the image resolution. Post-processing using image sharpening techniques to correct for piston phase, as well as other aberration corrections, require computing power and time. We study whether the processing time can be shortened by providing measured piston phase information to the image sharpening algorithms. Simulations are used to demonstrate the usefulness of piston phase measurements. Simulations are presented showing the benefits of piston phase measurements for two or more sub-apertures. The speed of convergence for the sharpening algorithm both with and without the piston phase measurements are compared for multiple sub-aperture imaging.

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