Abstract

The majority of lens designs can be subsumed under the imaging category, the purpose of which is an accurate rendering of the appearance of an object. Lenses have seen little use in the illumination field, where reflectors have predominated because of their lower cost and superior efficiency when used with conventional light sources. There has thus been little emphasis on the design of lenses for illumination, where the purpose is the fulfillment of a prescribed pattern of light distribution, and imaging of the light source is undesirable. Many of these prescriptions are for rectangular and other non-circular light patterns. Some important lighting prescriptions in today’s marketplace are for vehicular lamps, by the Society of Automotive Engineers, for ships, by the United States Coast Guard, and for traffic signals, by the Institute of Transportation Engineers. These are far-field prescriptions for an angular distribution of light. Illumination prescriptions for some nearby surface, such as the walls or ceiling of a room, can be transformed into intensity prescriptions.

© 1998 Optical Society of America