| 摘要 |
PROBLEM TO BE SOLVED: To suppress evil effects on detecting operation of an acoustic resonance phenomenon by transitional change of a lamp voltage or change of a voltage level itself accompanied with changes of an oscillating frequency or a lighting frequency of a high frequency generating device. SOLUTION: A detecting means 19 detects the acoustic resonance phenomenon based on a lamp voltage value of a high brightness discharge lamp 18 only when energized by either one of the oscillating frequencies out of different oscillating frequencies (Fig. 2 (a)). Accordingly, it is hard to be effected by changes of a lamp voltage level generated by the transitional lamp voltage changes and differences of the frequencies generated at changing the oscillating frequency. Moreover, when the acoustic resonance phenomenon actually occurs, it surely detects the lamp voltage fluctuations at this time. COPYRIGHT: (C)2008,JPO&INPIT |
