| 摘要 |
PROBLEM TO BE SOLVED: To prevent the center wavelength of the spectrum of an oscillation laser beam from fluctuating during exposure by using reference light even if light to be detected is a fluorine molecule F2 laser beam. SOLUTION: When light to be detected is a fluorine molecule F2 laser emission beam, at least one emission beam out of carbon C, iron Fe, sodium Na, fluorine F, magnesium Mg, aluminum Al, argon Ar, calcium Ca, scandium Sc, chromium Cr, manganese Mn, nickel Ni, copper Cu, germanium Ge, arsenic As, bromine Br, or platinum Pt whose wavelength is close to the fluorine molecule F2 laser emission beam and whose light intensity is at least a constant is used as a reference beam. |
