Adaptive VLSI for active optics and imaging

Real-time correction of atmospherically induced phase distortion in wavefront propagation is one of the key problems facing laser communication and optical imaging. Newly developed wavefront phase corrector technology enables us to build adaptive optical systems that compensate these distortions online.; We explore stochastic optimization techniques for improving the performance of adaptive optical and imaging systems and their implementation in custom VLSI circuits. A “model-free” approach to system optimization, independent of the specifics of the problem, is robust to imprecision in the circuit implementation and fluctuations in the environment and offers a flexible choice of performance metric. These techniques were successfully applied to real-time correction of optical wavefront phase distortion and to nonuniformity reduction in CMOS imagers.; A custom VLSI chip implements a perturbative stochastic gradient optimization algorithm that directly controls liquid crystal array and MEMS mirror based wavefront phase compensators in real-time. The performance metric in the optimization is obtained from custom CMOS image-plane sensors that acquire images and compute beam and image quality metrics on-line. This work has resulted in the first hybrid VLSI/optical experimental system to combine adaptive integrated electronics with active optical elements for on-line microscale wavefront correction. Since the precision of the computed quality metric determines the overall system performance, we developed a stochastic nonuniformity correction technique to improve the quality of CMOS imagers and image-plane processors.; Experimental results from the stochastic controller, beam and image quality metrics, and nonuniformity correction chips and their successful integration into optical systems demonstrate that adaptive VLSI is a mature technology for active optics and imaging applications.