Michihiro Tsuchihashi

A High Pressure Sodium Lamp with Improved Color Rendition

We have developed a new type of retrofit HPS lamp which achieves the improved color rendering properties, general C.R.I. 50–60 with higher luminous efficacy of 105–130 lm/W (220 W-660 W), and can be operated on the conventional mercury lamp ballast by a bimetallic starter unit in the outer bulb. High pressure xenon as a inert gas was effective to obtain the new lamp, lowering total thermal conductivity of the arc. New sealing glass mainly composed of Al2O3 and CaO which had superior stabilities to the high temperature sodium and newly designed electrodes which improved the voltage rise of the lamp during operation were useful to realize this lamp.

Improvement of the Luminous Efficacy in Sc-Na Halide Lamps and Development of Direct Retrofit type Sc-Na Halide Lamps for Operation with Mercury Lamp Ballasts

In this paper we will first discuss improvement of the luminous efficacy in Sc-Na halide lamps without special modification of the arc tube configuration and secondly, development of direct retrofit Sc-Na halide lamps for operation with high pressure mercury lamp choke ballasts. To attain a higher lamp efficacy, we studied the influence of the arc tube length-diameter ratio on additive segregation and lamp efficacy, and then determined the optimum additive composition for a set aspect ratio of the arc tube. To operate Sc-Na halide lamps on mercury lamp ballasts, we studied the use of a neon-argon mixture as a starting gas together with a special starting mechanism to prevent ballast overheating and facilitate starting.

Electrode Phenomena in Metal Halide Lamps

This paper describes the role of emission materials on electrodes in metal halide lamps. In scandium-sodium and dysprosium-thallium metal halide lamps, emission materials such as Sc2O3 and Dy2O3 have been used, respectively compared with pure tungsten electrodes. Further, investigationa for the reactions between electrodes, additive halides and a silica envelope were conducted on discharge lamps containing ScI3 or DyI3.