A rapid-light miniature metal halide lamp

Abstract

A metal halide lamp shows higher intensity, greater luminous efficacy and longer life as compared with an incandescent lamp. However, a few minutes are needed for it to reach full light output after ignition. This limits the application of the metal halide lamp. A rapid-lighting miniature 35 W metal halide lamp has been developed to extend its applicability. The following technology is applied: A ceramic heater of 30 W operating power is mounted next to the arc tube. The arc tube is heated immediately before or at the time of starting to gain light output rapidly. New electrodes for the discharge tube have been developed; these carry a high current input during starting. The starting pulse waveform starting pulse is in two parts. A short pulse of very high voltage breaks through the arc gap. A long low-voltage pulse, then builds up the arc discharge between the electrodes. Radioisotopes are added to the arc tube to produce initiating electrons which enable the electrode gap to break down instantly. This lamp can emit over 75% of its rated light output immediately after being switched on, if the arc tube has been preheated for at least 10 min. This can be useful for video camera lights or vehicle headlamps.