Simple optics that produce constant illuminance on a distant target

Abstract

Simple optics composed of a spherical lens and a conic mirror are described and the relation between the radius of the lens and height of the cone on far field illuminance performance is analyzed for a fixed exit aperture dimension. Ray sets for real LEDs were used to simulate the performance of the hybrid optics and it is shown that there are combinations of values for the lens radius and cone height for which the optic produces an approximately constant illuminance pattern on a distant target. The effects of varying the lens radius while keeping the cone height constant, and of varying the cone height while keeping the lens radius constant, are also presented, as these variations result in beams of varying angular spread. It is shown that a relatively course two parameter optimization can find near optimum solutions, where the optimization is carried out using ray sets of commercially available LEDs and the merit function is constant illuminance.