Comparison of reconstruction-algorithm performance for optical-phase tomography of a heated air flow

Abstract

Lenore McMackin Air Force Research Laboratory, VSSS 3550 Aberdeen Avenue SE Kirtland Air Force Base New Mexico 87117-5776 Abstract. An existing high-speed optical tomography system built at the Air Force Research Laboratory uses Hartmann wavefront sensors to obtain the optical path projections necessary for two-dimensional tomographic reconstruction of the temperature (or equivalently the index of refraction) in a heated jet of air. Conventional optical tomography algorithms require optical-path-length projection data obtained at a number of angles through the flow. However, Hartmann sensors detect the first derivative of the path length. Conventional reconstruction algorithms thus require integration of the measured gradients. New iterative algorithms can reconstruct directly from the measured gradients. Using computer simulation, we compare the accuracy of reconstructions made directly from optical-path-length gradients with the accuracy of reconstructions based on the optical path length obtained by integrating gradient measurements for several iterative tomographic algorithms employing local and global basis functions. For a data-limited tomography system, our studies have shown that accuracy of reconstructions depends on both the choice of algorithm and the structure of the flow under observation. © 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)01603-2]