| 摘要 |
<P>PROBLEM TO BE SOLVED: To positionally stabilize an arc luminescent spot to prevent flickering in an ultra-high pressure discharge lamp containing sealed mercury of 0.20 mg/mm<SP>3</SP>or more. <P>SOLUTION: An alternating current having a frequency (FL) lower than a steady frequency (FH) is inserted periodically in an alternating current having the steady frequency. The frequency (FL) is set to a given minimum frequency (FLmin) when a lighting current value (IL) of the discharge lamp is smaller than a prescribed minimum (ILmin), and is set to a given maximum frequency (FLmax) when the lighting current value (IL) of the discharge lamp is larger than a prescribed maximum (ILmax). When the lighting current value (IL) of the discharge lamp is between the minimum (ILmin) and the maximum (ILmax), a frequency (FLsel) corresponding to the lighting current value (IL) is set selectively. The selectively set frequency (FLsel) has a greater width (ΔFL) change as the lighting current value (IL) increases. <P>COPYRIGHT: (C)2010,JPO&INPIT |
