| 摘要 |
PURPOSE:To moderately cool a high pressure discharge lamp and a reflector without adjusting an exhausting means which forcibly discharges air through an exhaust port whether a transmissive member exists or not, by providing a transmissive member attaching part which attaches the ultraviolet ray-transmissive member to close a light projection aperture part by an object to be irradiated and specifying the distance between the top part of a lamp tube body and the exhaust port. CONSTITUTION:A transmissive member 10 is arranged to close a light projection aperture 6 of a reflector 5 and consists of a light-transmissive plate 10, which intercepts inflow of gas and permits ultraviolet rays to pass through, and a frame member 10b which is engaged with the transmissive member attaching part, which is provided in the end part of a lower face aperture 2 of an enclosure 1 and consists of a U-shaped rail, and fixes the light-transmissive plate 10a. In this case, since a length L between the top part of the tube body and an exhaust port 7 is set to 0.7-1.1-fold tube body diameter D, the tube wall temperature of the tube body of a lamp 4 is kept within an allowable temperature range whether the transmissive member 10 exists or not, and a required ultraviolet output is obtained, and the reduction of the life of the lamp due to a failure in transmission of the lamp tube body is prevented.
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