| 摘要 |
In a discharge lamp lighting apparatus comprising a short arc type discharge lamp and a power supply unit, a relation of the natural frequency fe (Hz) of the electrodes, the ripple frequency fd (Hz) of the alternating current that is supplied to the discharge lamp, and the ripple power Pr (W) of the alternating current, satisfies a formula: Pr ≤  f e - f d  · ( - 0.13 × Vh Va + 3.0 ) , wherein the volume of the electrode head portion is represented as Vh and the volume of the segment of the electrode axis portion that projects into the arc tube is represented as Va. When the alternating current supplied to the discharge lamp satisfies the formula, it is possible to prevent or control damage in the electrode axis portion, since vibration produced in the electrodes during lighting of the discharge lamp is small even if the discharge lamp is lighted for a long time.
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