Radar tomography for the generation of three-dimensional images

Abstract

Computer-aided tomography is normally a process by which a 2D cross-sectional image of an object is obtained by illuminating it from many different directions in a plane. For the case of radar imaging, microwave energy reflected by the object is processed to produce an image which maps the object's radar cross-section (RCS) density into the image plane. Each observation provides a 1D projection of the RCS density. The Fourier slice theorem states that the Fourier transform (FT) of each projection is equal to the functional value of the 2D FT of the RCS density along a related projection. By accumulating the FT of many 1D projections, it is possible to accumulate a sample representation of the FT of the RCS density. The image can then be obtained using the backprojection algorithm by taking the inverse FT of the sampled transform function. The authors extend the tomographic technique to the generation of 3D images from 1D range profiles. It is seen that the Fourier slice theorem, the backprojection image generation algorithm, and the backprojected function are useful concepts in the interpretation of 3D imagery. Point spread functions (PSFs) for various radar and observation parameters are illustrated.