Microscale adaptive optics:: wave-front control with a μ-mirror array and a VLSI stochastic gradient descent controller

The performance of adaptive systems that consist of microscale on-chip elements [microelectromechanical mirror (V-mirror) arrays and a VLSI stochastic gradient descent microelectronic control system] is analyzed. The mu -mirror arrays with 5 X 5 and 6 X 6 actuators were driven with a control system composed of two mixed-mode VLSI chips implementing model-free beam-quality metric optimization by the stochastic parallel perturbative gradient descent technique. The adaptation rate achieved was near 6000 iterations/s. A secondary (learning) feedback loop was used to control system parameters during the adaptation process, further increasing the adaptation rate. (C) 2001 Optical Society of America.