| 摘要 |
PURPOSE: To restrain reaction between a light emitting tube constitutive material and light emitting metal of a discharge lamp, and lengthen the service life by making electric potential of a conductive member arranged around an electrode higher than average electric potential of a discharge lamp electrode. CONSTITUTION: Electric potentials V101 and V102 of electrodes 101 and 102 change in a rectangular wave shape, and its average value becomes [-(Vc+Vd)/2)] when electric potentials of output teminals (c and d) of a DC power source 3 are denoted by (-Vc and -Vd), and are equal to discharge arc average electric potential of a discharge lamp 1. Here, electric potential of a conductive member 105 equal to GND electric potential is equal to the electric potential (-Vd), and is higher than the average electric potential of the electrodes 101 and 102. Therefore, an electric field proceeding to a discharge arc from a tube wall is generated inside the lamp 1, and since a metallic ion turned into a cation proceeds to the discharge arc, it becomes more distant from the tube wall of the lamp 1, and devitrification can be prevented. Therefore, devitrification reaction of quartz glass of the lamp 1 can be restrained, and the service life can be lengthened. |
