| 摘要 |
PROBLEM TO BE SOLVED: To provide a method capable of carrying out accurate laser durability evaluation of an optical element easily. SOLUTION: An excimer laser beam 16 from a laser beam source 1 passes through a forming optical system 2, an energy adjusting optical system 3, an aperture 4, and a beam splitter 5, and reference light 17 is received by a light quantity monitor sensor 9. Measuring light irradiates a sample 7 via a condensing optical system 6. The laser beam after transmitting the sample 7 and a sample holder 8 is diffused by the condensing optical system, thereby the transmission image of the sample 7 is enlarged and formed on a transmission image screen 10. A light receiving sensor group (array) 11 is arranged on the face of the transmission image screen 10, opposed to the light source, to measure the transmission image face while dividing it into small areas. The electric signals from the light receiving sensor group 11 are amplified by a preamplifier 12 to be inputted into a control computer 15 through an A/D converter 13.
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