| 摘要 |
<P>PROBLEM TO BE SOLVED: To maintain proper light transmittance over a long time. <P>SOLUTION: An optical system comprises a plurality of optical elements, a means for holding spaces between optical elements in atmospheres different from the external environment, and a means for arbitrarily adjusting the moisture concentration in each of the atmospheres. <P>COPYRIGHT: (C)2007,JPO&INPIT |
