The design, construction and performance of an incandescent light source with a transparent heat mirror

Abstract

We discuss the factors in the design of an economical incandescent light source using a filter envelope which directs heat back to the filament but allows light to be transmitted. Achievement of the necessary performance requires a new concept in the design of the lamp and a high-performance coating. The use of reactive sputtering to prepare dielectric-silver-dielectric filters into pressed glass semi-ellipses gives a 60% increase in luminous efficiency as compared with a standard unit.