| 摘要 |
PROBLEM TO BE SOLVED: To provide a transmissivity measurement method and a transmissivity measuring instrument for highly accurately measuring a change in transmissivity of an optical material caused by illumination of ultraviolet or vacuum ultraviolet light. SOLUTION: The optical material under measurement is illuminated for a prescribed period of time with outgoing light from an ultraviolet or vacuum ultraviolet light source. Then, movable mirrors are put on the optical axis of the outgoing light, before and behind of the optical material when viewed from the light source, thereby interrupting the illumination of the outgoing light to the optical material. At the same time, measurement light having substantially the same wavelength as the outgoing light is launched from a light source for the measurement light. The measurement light is caused to pass through the optical material and then let into a measurement light detector for measuring intensity of the measurement light to measure the transmissivity of the optical material. COPYRIGHT: (C)2006,JPO&NCIPI
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