| 摘要 |
PROBLEM TO BE SOLVED: To enable optimum discharge timing to be constantly detected even if plasma impedance in a laser tube is changed with the lapse of time by monitoring the emission timing of discharge light with a specific wavelength that is collected outside laser beams. SOLUTION: A discharge light collecting unit 23 is placed inside a laser tube 21 where copper pellets 22 are disposed, with its optical axis oriented to the portion of the inside of the laser tube 21 where discharge light is most likely to be produced, whereby the discharge light produced within the laser tube 21 can be collected efficiently by means of a lens 25. Of light rays incident on the unit 23, the discharge light with a specific wavelength (e.g. emission line of 402.26 to 406.27nm) is captured by an interference fitter 28 and transmitted to a timing adjustment device as a timing monitor signal via an optical fiber 26. Thus even if plasma impedance inside the laser tube 21 is changed with time, the discharge timing of a laser can be monitored accurately since the emission timing of the discharge light with the specific wavelength coincides with the timing of laser oscillation with high precision. |
