| 摘要 |
PURPOSE:To prevent the characteristics of transmittivity of the wavelength selective means such as the filler from changing by a method wherein cooling means, by which the temperature rise of the wavelength selective means is suppressed, are provided. CONSTITUTION:Just the part of the specific wavelength of the cool light is made to incide in an optical integrator 6 by the wavelength selective means such as a filter 4 and the component of the other unnecessary wavelengths of the cool light is absorbed in the filter 4. At that time, air-cooling units 5 are provided on the periphery of the filter 4 and the whole surface of the filter 4 is uniformly cooled by spraying the cooling gas from the units 5 on the whole surface thereof. So that the temperature rise of the filter 4 is suppressed and the transmittivity of the filter can be prevented from changing. |
