| 摘要 |
PURPOSE:To make it possible to produce double spots stably by magnetically isolating a plurality of filament coils corresponding to the filaments of a discharge lamp from each other in preheating transformers. CONSTITUTION:Preheating transformers 21, 22 are provided for applying filament voltages to filaments 4A, 4B of a discharge lamp 4 for producing double spots, and a plurality of filament coils n1, n2 in the preheating transformers 21, 22 corresponding to the filaments 4A, 4B of the discharge lamp 4 are isolated from each other magnetically. If a lamp current goes through the filament coil n1, n2, therefore, effects are not given to the other filament coil n2, n1. Double spots are thus produced stably for the filaments 4A, 4B. |
