| 摘要 |
PURPOSE:To control the temperature of the coolest point and make the luminescent color of a light-emitting tube variable by varying the position of a field application coil relative to that of the light-emitting tube around the outer periphery of which the field application coil is wound. CONSTITUTION:When a high frequency current is applied to a coil 11, a light- emitting tube 10 emits light and then the coolest point is located at a point A. A driving device 14 is actuated and the light-emitting tube 10 is raised rela tive to the coil 11 and then an arc (not shown) comes close to the coolest point A and the temperature of the point A is raised. As the temperature of the coolest point is raised, the steam pressure of sealed materials NaI, TlI and InI is raised in the order of NaI, TlI and InI and the amount of steam of Na which evaporates least is increased and the red components of the luminescent color of the tube are increased. When the position of the tube 10 is lowered relative to the coil 11, the arc is distant from the coolest point A and the temper ature of the coolest point is lowered and the amount that Na and Tl evaporate is decreased and the green components of the luminescent color of the tube are decreased. The luminescent color of the tube is thus varied by varying the position of the light-emitting tube 10 relative to the coil 11. |
