| 摘要 |
PURPOSE:To enhance the luminous efficiency of a lamp by installing an under cover near the emission tube and making its part encircling an airtight space except areas through which the electrodes are led out transparent so that emissional output can be taken out. CONSTITUTION:An emission tube has a pair of main electrodes 2a and 2b in its ends and is charged with a rare gas, mercury and a metal halide. An outer tube 3 covers the emission tube, and is charged with nitrogen gas for example. A base 4 is connected to the upper end of the outer tube 3 and electrically connected to the electrodes 2a and 2b. An encircling part 1a forming the airtight space of the emission tube except areas through which the electrodes 2a and 2b are led out, has light-transmitting structure so that emissional output can be taken out. A light-transmitting body 6 covering the lower end of the emission tube is installed near its lower end. As a result, overcooling of the lower portion of the outer tube 3 caused by internal convection can be suppressed, thereby enabling the luminous efficiency of a lamp to be improved. |
