| 摘要 |
<p>The intention is to maintain the shape of the projection of the electrodes and the shape of the tip end optimally for a long time and to extend the lifetime of a discharge lamp. A lighting device lighting a high pressure discharge lamp wherein mercury is enclosed and a pair of electrodes is disposed opposite to each other in the interior of a discharge vessel made from quartz glass supplies alternating current such that an alternating current with a frequency (a basic frequency) at the time of the steady state lighting being selected from a range between 60 and 1000 Hz and a low frequency of a half cycle with a frequency being lower than the basic frequency are generated alternatingly, wherein the alternating current is supplied such that the waveform with one polarity of the low frequency appears consecutively at least two times. It is also possible to supply the alternating current such that the alternating current at the time of the steady state lighting and the low frequency being selected from a range from 5 to 200 Hz, which is lower than the basic frequency, are generated alternatingly, and the interval of the supply of the basic frequency is gradually increased and decreased with each specified time.</p> |
