Development of 2-Lamp Type HID Headlighting System

This paper reports the development of 2-lamp type headlighting system using high-intensity-discharge (HID) light sources. HID or metal-halide light sources are attracting much attention these days for their highly efficient light emission, long life, low power consumption, and excellent color rendition. Balb manufacturers endeavor to develop HID light sources suitable for use in automotive lighting systems. A HID light source generates light by means of arc discharge excited in the electric-discharge tube. Unlike conventional filament bulbs, HID light sources cannot have two light-emitting sources within one tube. Consequently, HID headlighting systems so far developed are designed as 4-lamp type, which uses four HID light sources and four associated light-up electronics to operate them. The new system we have developed enables to incorporate HID light sources in 2-lamp type headlighting systems. In order to produce both upper and lower beams using a single HID light source, we adopted projector headlamp structure, where the distance between the lens and the shade to form lower beam is mechanically moved. In this paper, the concept of this new lighting system, its structure and photometric performance are described.