Control of adaptive optical elements for real-time wavefront phase
distortion compensation is a rapidly growing field of research and
technology development. Custom VLSI controllers and sensors are a
good match to the requirements of high resolution, real-time adaptive
optical systems. Crucial to adaptively correcting the wavefront is a
performance metric that can be directly evaluated from the acquired
image or received laser beam, to provide real-time feedback to the
controller adapting the wavefront. In this paper we introduce two
VLSI focal-plane sensors that supply image and beam quality metrics to
an adaptive controller that performs stochastic parallel perturbative
gradient descent on a spatial phase modulator in the control loop. For
imaging applications, we designed an image quality metric chip that
reports the high spatial frequency energy content of the received
image. For laser communications applications, we designed a beam
variance metric chip that calculates the compactness of the
transmitted or received beam as well as its centroid location. Both
sensor chips are fully functional and the beam variance metric chip
has been used in the feedback loop of an adaptive optics laser
receiver experiment.
