| 摘要 |
PURPOSE:To obtain a stable laser output continuously over a long time by a method wherein the degree of cleanliness inside a light path is always monitored and a clean gas is supplied according to the detection result by using a monitor. CONSTITUTION:When a laser beam is passed through light paths 17, 17 during a laser oscillation operation, it is scattered by dust particles existing inside the light paths 17, 17; scattered light caused by the dust particles is always monitored by using detectors 28, 28. When the air inside the light paths 17, 17 is contaminated to a certain extent, the intensity of the scattered light detected by using the detectors 28, 28 exceeds a set value which has been set in advance in a reference-signal generation circuit 30. When the intensity of the scattered light exceeds the set value, a start signal is input to a compressor 25 from a comparison operation circuit 29. When the compressor 25 starts operating, the clean air which has passed a filter 24 is fed to the light paths 17, 17 and the contaminated air is discharged to the outside from an evacuation pipe 26. When the light paths 17, 17 are filled with the clean air, a stop signal is output to the compressor 25 from the circuit 29. |
