| 摘要 |
PROBLEM TO BE SOLVED: To precisely detect the occurrence of abnormal conditions in a laser oscillator which emits laser pulses. SOLUTION: The light intensity of the laser pulse emitted at a predetermined frequency is compared with a plurality of threshold intensities which have been set in advance, for counting a frequency at which the light intensity exceeds a threshold intensity, for each threshold intensity. The intensity range (minimum peak intensity range) in which the minimum value of peak intensity of laser pulse is present and the intensity range (maximum peak intensity range) in which the maximum value of peak intensity is present are detected, based on the number of emission pulses obtained for each of the threshold intensities as well as the number of reference pulses which is normally expected. Presence of abnormal operation of the laser oscillator is determined based on the fact whether they are within a predetermined intensity range. With this configuration, the information about a minimum value and maximum value of peak intensity and also the information about width of variation of peak intensity can be reflected, thereby the presence of abnormal operation of the laser oscillator is precisely determined. COPYRIGHT: (C)2010,JPO&INPIT
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