The usability of tungsten halogen lamps as secondary standards of luminous intensity

Tungsten halogen lamps are widely used as sources of radiant intensity because of their compactness and long life. Little is known, however, about their usefulness as secondary standards of radiant intensity. What is unknown is the polar distribution of the emitted light. If it is irregular in space, it may be possible to use a frosting as a means of providing for a more uniform distribution. In addition, use of a black sleeve over the lamp may be used to control emitted light, and also control the temperature of the lamp. To perform the experiment, a lampholder was designed and constructed, which allows the lamp to be moved on its horizontal and vertical axis. The lampholder was set up on an optical bench along with a foot-candle meter, for lamp testing. Using this set up a clear lamp, and lamps frosted by mechanical buffing and acid treatement were tested for direction characteristics. A black sleeve was designed and constructed and tested with the machine frosted lamp. Experimentation shows favorably tward the fact that a machine frosted lamp can be used as a secondary standard