<title>Reflectors for efficient and uniform distribution of radiation for lighting and infrared based on nonimaging optics</title>

Abstract

A fundamental problem in illumination optics, with important applications for lighting and infrared heating, is to design reflectors that can concurrently fulfill two conditions: (1) maximum efficiency (all rays from the source reach the target); (2) uniform flux density on the target plane. The problem is difficult when the source is extended (rather than a point or a line) and when the reflector must be small compared to target distance and target size, i.e., when the field of view subtends a large angle. In general, an exact solution is impossible with a finite number of optical elements. To find practical solutions that approach the goal, we take the compound parabolic concentrator (CPC) of non-imaging optics as a starting point because it achieves the first condition by its very design. However, its flux density distribution falls off like cos3 ((theta) ) where (theta) is the angle from the normal of the aperture. To gain an extra degree of freedom for the design, we modify the CPC by introducing a gap between source and reflector. We present results for symmetrical configurations in two dimensions (troughlike reflectors) for flat and for tubular sources. For fields of view of practical interest (half angle in the range of 40 to 60 degree(s)), these devices can achieve minimum-to-maximum intensity ratios of around 0.7, while remaining compact and incurring low reflective losses.