Multidither Adaptive Algorithms
Abstract
Various analytic and experimental algorithms that can reduce the beam distortions caused by thermal blooming were investigated. A 19-element beryllium deformable mirror was used in the DARPA/RADC Coherent Optical Adaptive technique system to perform the experimental compensation studies. Using this system, both spatial and temporal algorithms employing zonal multidither and modal multidither using Zernike polynomials have been studied. A major result from this work is the identification of certain algorithms which can compensate for thermal blooming. The specific algorithms involved and the degree of correction achieved depended on the blooing scenario studied. Experimental results indicated that standard zonal system gave blooming correction over a larger set of parameters than did the Zernike polynomial system. This is believed to result from cross coupling and limited Zernikes - both caused by poor representation of the actual Zernike by the deformable mirror. Sequencing studies, both analytic and experimental, showed no preferred sequences but did indicate that focus and/ or astigmatism always dominated the correction. Numerical studies employing multidither coherent optical adaptive techniques, function maximization, and phase-conjugate algorithms were performed. Function maximization gave better correction than either of the other two. Servo convergence time was varied on the multidither system with the results indicating no change in correction.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1977
- Accession Number
- ADA040247
Entities
People
- M. L. Minden
- Richard C. Lind
- S. Hansen
- T. A. Nussmeier
Organizations
- HRL Laboratories