Color Variable Light Source Using Electrodeless Discharge

Abstract

Color variable pulsed Hg-Ne discharge lamp was invented and reported by Itatani's group in 1973. The color of Hg-Ne discharge was controlled by changing electron temperature by changing pulse frequency. Maya's group reported about color variable mercury fluorescent lamps using burst pulse and different type of phosphors. Kroesen's group proposed Hg-Ne color variable lamp using depletion effect. All these lamps use electrodes inside a tube. The authors propose a new type of color variable discharge lamp using inductively coupled plasma (ICP), electrodeless discharge. Color variable lamp using ICP is demonstrated. Just after starting discharge of Hg-Ne, the luminescent color of the lamp is red because of Ne emission. After that, the color changes gradually toward blue resulting from increase in mercury vapor pressure. When the color change stoppes and it is in the steady state with blue color, the color can be changed toward red by increasing input power. This is due to Ne emission resulting from increase in current density.