We describe a new approach to controlling the deformable mirror in beam projection systems operating in conditions of strong scintillation. Under the conditions of interest, two-way propagation is required to create the light used for wavefront sensing. In this situation, the beacon can subtend an angle that is many times larger than the isoplanatic angle. Our approach uses a nonlinear optimization-based technique to determine the deformable mirror (DM) figure which optimizes an image sharpness

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... metric. This correction is applied to the outgoing laser beam with the goal of concentrating most of the laser's power on a small area of the target. The optimization algorithm chosen for this purpose is the simultaneous perturbation stochastic approximation (SPSA). Our results show that using phase-only conjugation with nonlinear optimization of an image sharpness metric can provide an improvement in encircled energy performance compared to phase-only conjugation with only linear Hartman wavefront sensor processing.