| 摘要 |
PURPOSE:To prolong the service life of a lamp by switching a state that a constant-current is energized to a discharge lamp in unusing time as well as using time and state that a lower current than that of the using time is energized compared with the unusing time. CONSTITUTION:Light energy radiated from a discharge lamp 1 is condensed to other one point by a reflecting mirror. Subsequently, a current I is supplied to the discharge lamp 1 from a power source 6. The current I is controlled by a control part 7. A changeover switch 8 for switching a state that a constant- current is energized to the discharged lamp 1 at both the using time the unusing time and a state that a lower current than that of the using time is energized to the discharge lamp 1 at the unusing time is provided on the control part 7. In such a manner, the movement of the luminescent spot of the discharge lamp can be prevented. |
