PURPOSE: To make it impossible to prevent generation of any flicker, transfer fringe and fringe without consuming wasteful electric power by intermittently lighting a discharge lamp with 2msec or less of a lighting time and 4msec or more of a non-lighting time.

CONSTITUTION: A rare gas discharge lamp is intermittently lighted with 2msec or less of a lighting time and 4msec or more of a non-lighting time. With 2msec or less of the lighting time, difference in ion density is not remarkable so as not to generate any fringe. When 4msec passes after putting off the lamp, the density distribution of the ion diffuses to an original uniform state. Therefore, even at such a lamp current value as to generate the fringe, the fringe is not generated by the effect of repeating 2msec or less of the lighting and 4msec or more of the non-lighting.