Vehicle headlamp comprising a discharge lamp including an inner envelope and a surrounding shroud

摘要

This headlamp comprises a reflector and a discharge lamp comprising an inner envelope having a longitudinal axis coinciding with the optical axis of the reflector. The inner envelope includes a bulbous portion, a front leg extending along the optical axis from the bulbous portion toward the front of the headlamp, and a back leg extending along the optical axis from the bulbous portion toward the reflector. The discharge lamp further comprises a tubular shroud comprising a first hollow portion surrounding the front leg of the inner envelope, a second hollow portion surrounding the back leg of the inner envelope, and a bulbous portion between the two hollow portions. The bulbous portion of the shroud has a central longitudinal axis, and this central axis is upwardly offset by a small distance (e.g., at least about 0.5 mm) from the longitudinal axis of the inner envelope on which the discharge is located. The presence of this offset has been found to substantially increase the ratio of the seeing light to the glare light (i.e., the SGR) in the headlamp beam as compared to that present when there is no offset between these axes.