Geometrical-spreading and ray-caustic decomposition

The computation of the geometrical-spreading (GS) factor and the number of caustics is in general considered to be the most fundamental step in order to compute zero-order ray solutions for elementarywave Greens functions. Here, a new factorization method is described which establishes both quantities recursively along the ray segments into which the total ray can be subdivided. As a. consequence of the proposed method, the point-source GS factor and the number of ray caustics along the total ray can be decomposed into (a) point-source GS factors of the ray segments and (b) Fresnel zone contributions at the ray-segment connection points.