STRESS WAVE DETECTING DEVICE FOR ELEMENT AREA AND DETECTING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To remove the influence of noise generated from a whole device and to realize a high accurate measurement by irradiating a laser beam on a local element area surface of a fixed substance and detecting a motion speed at the area surface by Doppler effect. SOLUTION: A first incident laser 3 of an instrumentation laser output device 1 is incident on a first light wave guide 4 and a second incident laser 5 of a heating laser output device 2 is incident on a second light wave guide 6. The laser 5 emitted from a tip end opening 7 of the light wave guide 6 irradiates a local heat input area surface 8 to heat-input. The laser 3 emitted from a tip end opening 9 of the light wave guide 4 irradiates around the center point of the local heat input area 8 and reflects. A modulated laser L Doppler- modulated enters from the tip end opening 9 to a frequency analyzer 12 through the light wave guide 4 and a return path. A portion of the laser 3 and the returning modulated laser L are Doppler-interfered at an interference optical system by the frequency analyzer 12 and the strength of a light by the interference is measured and calculated to obtain a motion speed spectrum of the local heat input surface 8 based on the Doppler effect of the laser 3.