SBIR-STTR Award

Scatter from ground-based laser ports (weapons, communication systems, range finders) can be large enough that the laser location may be determined by detectors positioned well away from the beam. Port scatter can be reduced, but not eliminated, through the use of baffles to limit direct viewing of the laser optics. This document proposes developing a method to predict the scatter signal from laser ports given the design of the output optics and baffles. The method involves combining scatter data from known types of components (window, mirrors, lenses, baffles) with a ray tracing computer program that will follow scatter propagation through an optical system. Light that is scattered three or more times is ignored. The observer is assumed to be in the diffraction far field and the detector aperture large enough so that interference effects can be ignored. The object of phase i is to demonstrate feasibility by correctly predicting the port scatter from a simple he-ne laser, baffle combination.

The goal of this proposal is development of a model that predicts light scatter from laser port optis. The proposed model consists of three main software modules that calculate the specular beam and stray light levels as light propagates through the laser port optical system. The first module is a data base that manages angular scatter characteristics of individual optical components. Entry generation is by curve fitting to measured scatter data or by an analytical estimation technique using diffration and scattering codes along with component surface finish, material and quality standards. The second module is a ray-tracing program used for optical system description, design and alignment. The third module models scatter at the system level. Scatter as a function of angle from the output specular beam is calculated from given source specifications, system geometry and component scatter. Output can be utilized with detector and sensor information to predict the range and angles over which laser ports can be detected. Given the system scatter, the model can also be used to predict scatter from one component in the system, or to infer information about the laser source. Scatter from the atmosphere is modeled using available atmospheric scattering codes.