Non-Imaging Optics Design Using Genetic Algorithms
Ian E. Ashdown · Journal of the Illuminating Engineering Society · 1994
Introduction In the past, luminaires were designed using a combination of ray-tracing techniques and hard-won experience_ Designing reflectors and lenses by hand was a time-consuming and arduous task_ While designs could be quickly evaluated using red-green diagrams, e_g_, Elmer, IO and other shortcuts, a complete photometric performance analysis required tracing hundreds of rays using a calculator, pencil, and paper_ It was often easier to build a prototype and measure its performance_ A designer's successes and failures eventually led to a sixth sense regarding luminaire design-or early retirement_ The advent of computers in the late 1940s allowed designers to quickly trace thousands of rays_ Other design approaches such as finite element radiative transfer (radiosity) techniques could also be employed_ Designers of imaging optical systems were quick to adopt this new technology_ It has taken us several decades longer, but we now have commercial software such as Lighting Technologies's FiELD and Lighting Sciences's CAD-LITE to analyze our nonimaging luminaire designs_ The ability of these programs to accurately predict a design's photometric distribution makes them invaluable design analysis tools_ Notice the adjective analysis_ These programs must trace millions of rays or calculate flux transfers between thousands of reflector elements if they are to generate accurate predictions_ Either approach takes time: hours or even days on even the fastest desktop computers_ As useful as these programs are, they are too slow to be used as interactive design tools_ We must still rely on trial-and-error experimentation and hard-won experience for our design ideas_ We could create an interactive luminaire design tool by tracing a limited number of rays, sufficient only to determine an approximate photometric distribution_ We don't need the features of a commercial product; a serviceable tool can be created within a computer-aided drafting program such as Autodesk's AUTO CAD by using its script language facilities, in