| 摘要 |
PURPOSE:To facilitate the start of discharge of a discharge lamp by providing a movable body on at least one part of a microwave cavity and by moving the movable body when starting the lamp so as to change the resonant frequency of the cavity. CONSTITUTION:When a power supply PS is turned on by a switch S, the voltage is applied to the filament and anode of a magnetron 1 through a transformer T, generating microwaves. Concurrently, the power supply PS is applied to operate a driving unit 19, thereby a movable section 101 starts to move immediately after the microwave output has appeared, and a metal mesh plate 7 is moved to the position of a line A of a cavity wall 4 aperture end in several msec to one sec, then stopping the driving unit 19 and the movable section 101 by detecting that both of them have got into contact with each other. When the movable section 101 is moved from the upper portion of the cavity wall 4 aperture end to the aperture end, the resonant frequency of a microwave cavity 11 formed with the cavity wall 4 and the metal mesh plate 7 is changed, and the resonant frequency coincides with the oscillation frequency of the magnetron 1 so that the electromagnetic field in the microwave cavity 11 becomes a resonant electromagnetic field, thus a discharge lamp 13 can be lit for sure. |
