PURPOSE: To reduce a temperature difference of a lamp in an axial direction caused by a forced exhaustion, enhance a rising time, and prevent a thermal deformation of a valve by a method wherein air led from the both, ends of a reflecting body to cool the reflecting body and a discharge lamp is forcibly exhausted by an air exhausting device, and the diameter of the valve of a discharge lamp at each end of 8 light emitting part is made smaller than that at the center part.
CONSTITUTION: When a fan 9 is driven, a space between a housing 1 and a reflecting body 2 is forcibly ventilated, whereby the housing 1 and the reflecting body 2 are cooled by the air. Outside air is led from slits 5, 5 formed on end plates 4, 4 attached on the longitudinal both ends of the housing 1. The air is sucked into a chamber 7 from slit-form air exhaustion ports 6 arranged on the top part of the reflecting body 2 in the longitudinal direction thereof through the inside of the reflecting body 2. In this manner, the air inside the reflecting body 2 is also forcibly exhausted. In the reflecting body 2, a mercury discharge lamp 20 is contained as an ultraviolet light source. The diameter of the lamp 20 at each end of a light. emitting part is made smaller than that at the center part.
SASAKI HIROMOTO
YONEZAWA AKIHIRO
