Detection of Imitative Defect by Non-Contact Inspection Method Using Laser

Abstract

This paper describes non-contact inspection method using lasers and development of experimental setup.
An ultrasonic wave is generated when Q switched YAG laser is focussed on the surface of metal. Relations between the ultrasonic amplitude and the focussed laser density are measured and the optimum condition is found experimentally. Wave form detected by ultrasonic transducer is compared with wave form detected by experimental setup. Characteristic of demodulator and frequency characteristics of band path filter in experimental setup are adjusted to be same wave forms. Consequently, the ultrasonic echo of a small hole in a test metal can be observed.