| 摘要 |
A cover detection unit is disposed in a cover which is opened and closed when changing a lamp, said cover detection unit detecting whether the cover is open. If the cover is opened when in a power off state, cover open/close information which indicates that the cover is opened is saved by an information retaining unit which has an auxiliary power source. A control unit measures and saves a lamp use time when the lamp is lit, and acquires, updates, and saves a lamp voltage for each of a prescribed time interval. If the cover open/close information which is saved in the information retaining unit indicates that the cover is open when the power is switched back on from the power off state, the control unit acquires the lamp voltage which is detected when the power is switched back on, and determines that the lamp has been changed if the acquired lamp voltage is lower than the lamp voltage which is saved prior to the power being switched off. |
