LIGHTING DEVICE

PROBLEM TO BE SOLVED: To suppress illuminance unevenness caused by unevenness or the like of surface temperature in a high pressure discharge lamp in which a discharge lamp is installed in the interior of the outer tube, the inner radius of the outer tube and the outer radius of the discharge tube are nearly the same, and at least one part of the outer tube and the discharge tube contacts. SOLUTION: The high pressure discharge lamp 10 is constituted of the discharge tube 11 and the outer tube 20 and lighted up when AC voltage is applied to a pair of electrodes 16 of the high pressure discharge lamp 10 from a feeder part 1. Upon lighting, by circulating a cooling water W in a cooling water flow passage 65, the high pressure discharge lamp 10 is cooled. The feeder part 1 lights up the lamp 10 by driving an inverter with a drive signal of a stationary lighting frequency f1. Before illuminance unevenness occurs, the drive signal is switched to the drive signal of a lower frequency f2 which can solve illuminance unevenness, and the feeder part 1 lights up the lamp 10. By this arrangement, non-uniform density distribution of positive ion caused during stationary lighting can be solved, and illuminance non-uniform distribution can be suppressed. COPYRIGHT: (C)2010,JPO&INPIT