PURPOSE: To decrease deposition possibly due to photochemical reaction using atmospheric air by a method wherein the gas for cooling down the title ultraviolet ray using device is passed through a cleaning region heated at specific temperature to be irradiated with the ultraviolet ray.
CONSTITUTION: A material gas led-in from a material gas intake port 7 is irradiated with ultraviolet ray in a temperature controlled gas flow path 4 and a depositing region 5 to produce a deposition on another depositing region 4. At this time, the material gas is cleaned up by removing the deposition component thereof. Thus, the cleaned up gas is used as the cooling down gas for the title ultraviolet ray using device 1. Besides, the cleanliness of the gas can be improved by repeatedly passing the gas through a gas flow path 4 via circulating gas flow path 8 to produce a deposition on the depositing region 5. Through these procedures, the presumable deposition due to photochemical reaction can be reduced. Accordingly, the deposition on an optical system can be decreased thereby enabling the service life to be lengthened.
OBARA HITOSHI
KUROIWA KEIJI
NAKAMURA MASAKI
