TOMOGRAPHIC RECONSTRUCTION OF 2-D ABSORPTION-COEFFICIENT DISTRIBUTIONS FROM A LIMITED SET OF INFRARED-ABSORPTION DATA

The results of infrared absorption experiments, performed on a steady, nonreacting flow of methane and argon to test a new inversion method for tomographic reconstruction of spatially nonuniform distributions, are presented. The absorption coefficient distributions to be reconstr ucted are expressed as a weighted sum of Karhunen-Loeve eigenfunctions , formed by applying the Karhunen-Loeve procedure to a training set co ntaining a priori information regarding the distributions to be recons tructed. Reconstruction of asymmetric absorption coefficient distribut ions is accomplished by utilizing a set of laser absorption measuremen ts obtained using an infrared helium neon laser. Issues pertinent to t he practical application of the new inversion method, such as the cons truction of a training set using probe sampling, the effect of experim ental error, and the precise modeling of laser absoroption paths, are discussed. Reconstruction of absorption coefficient distributions from only 42 laser absorption measurements typically achieve normalized er rors of 10% or less over 80% of the domain.