Studies of Quantitative Methods for Imaging from Scattered Fields
Rept. for 8 Apr-30 Nov 1991,
LOWELL UNIV MA DEPT OF ELECTRICAL ENGINEERING
Pagination or Media Count:
A detailed analysis of the differences between first Born and Rytov approximations was carried out. In anticipation of the next phase of this project, namely to consider the inverse scattering problem for nonlinear medium, we have been studying the writing of structures into nonlinear media, specifically photorefractive crystals. This experimental and theoretical work has been direct toward writing structures with intense beams and reading with work beams, the partial erasure on reading being a problem. However, we have identified possible methods for storing information more permanently, which is important in its own right because of the widespread interest in these materials for optical data storage. Data sets from targets have now been taken using the bistatic procedure. This is much faster and avoids having to rotate the target to change the incidence angle and data are now available on concentric circular loci in k-space. This allows the data to be more uniformly spread in the Fourier domain and leads to improved interpolations of that data onto a Cartesian grid prior to taking the inverse Fourier transform. However, we are finding that the lack of data near the k-space origin leads to increased error in the interpolation, compared to data on arcs.
- Statistics and Probability