Development of High Energy-Conserving Incandescent Lamps

In close agreement with theoretical prediction, model energy conserving incandescent lamps have been produced which conserve 55 percent of the energy compared with a clear lamp of the same lumen output at the same filament temperature. This result was obtained with an optically ground and polished envelope internally coated with a multilayer heat mirror. Theoretical predictions employed a computer calculation which included the spectral variation of the filament emissivity and the heat mirror-reflection-induced-shift in the spectral output of the filament.