Effects of the Paraxial Approximation on Propagation Impulse Responses

A preliminary investigation generating a comparison of propagation impulse responses with and without the paraxial approximation is presented. The analysis is based on an angular spectrum interpretation for free-space optial propagation. A relative error between the two impulse reponses is evaluated and plotted. The results indicate that the relative error between responses does not continue to increase monotonically as the paraxial approximation becomes less valid. The relative error is peaked along a V shaped curve centered along the forward direction in the propagation plane.