David Gerwe (Boeing Directed Energy Systems), Michael Johnson (Boeing Directed Energy Systems), Brandoch Calef (Boeing Laser Technical Services)
Keywords: Imaging
Abstract:
Phase diversity techniques infer wavefront phase aberrations of an imaging system directly from the image data by processing of a set of two or more images with deliberately induced additional aberrations (usually defocus). This is a non-linear inverse problem that is typically solved by iteratively determining the aberration that maximizes an objective function or by iteratively applying a set of constraints. The robustness of these techniques can be severely degraded by local minima that start to appear and increase in density with increasing wavefront aberration strength. Local minima severely limit the dynamic range of wavefront aberration levels for which diversity techniques can serve as a reliable wavefront sensing method using the processing approaches currently in practice. This paper explores mechanisms behind the local minima and characterizes their density and spacing as dependent on SNR and wavefront aberration level. The performance of a global optimization method is compared to a single gradient search for robust WF estimation accuracy.
Date of Conference: September 16-19, 2008
Track: Imaging