Operating apparatus of discharge lamp

摘要

An operating apparatus of a discharge lamp for operating the discharge lamp having an arc tube defining a discharge space includes: generation means for generating a first waveform signal having a frequency component of an acoustic resonance frequency exciting a mode which straightens an arc discharge, a center line of a waveform of the first waveform signal being maintained at a fixed level; and modulation means for modulating the first waveform signal periodically so that a polarity of the center line of the first waveform signal changes alternately at a modulation frequency which is lower than the acoustic resonance frequency, and generating a modulated signal. A modulation depth alpha / beta , where alpha is a peak-to-peak amplitude of the first waveform signal and beta is an effective value of an amplitude of the modulated signal, is set at such a value that a sealed material in the arc tube is prevented from adhering to a center portion of the arc tube in substantially a strip shape.