AIRWATCH: The collection optics

The Airwatch optical system is shown to have minimal resolution requirements (when compared to more standard imaging systems) while requiring both a large entrance aperture and a simple configuration. Several single and double element optical systems are discussed, and Fresnel lenses are shown to be a promising candidate for the Airwatch optical system. Design techniques of Fresnel lens systems are presented, and it is shown how complex Fresnel lenses systems can be modeled and analyzed using commercially available ray tracing programs. It is then demonstrated how the performance of the single element system can be improved through the use of a two element configuration. Specifically, focal surface curvature can be eliminated, and the field of view of a single aperture can be increased by switching to the two element design. Techniques for reducing the size of the focal surface are also discussed. Finally, current research efforts involving the construction of prototype Fresnel lens systems are explained.