Abstract
An energy conserving incandescent lamp which the infrared reflective film has been studied.
This lamp can be called the heat mirror lamp, because it has an envelope internally coated with a multilayer heat refl ective mirror such as consisting of Ti02-Ag-Ti02.
A theoretical formula which led the luminous efficacy and the energy conserving ratio of the lamp could be found.
Those are depend on the spectral transmittance and reflectance of the heat mirror, the spectral emissivity of the radiator and the geometrical factor of the lamp components.
In case of the spherical envelope lamp with tungsten coiled coil filament at the center, a geometrical factor of 0.63 has been experimentally obtained, and the luminous efficacy of 27 lm/W can be expected by using the Ti02-Ag-Ti02 film coated lamp.
An experimental luminous efficacy of the lamp with a bulb internally coated with a thin gold film almost coincides with the results of theoretical calculations.
