The Signal Reception And Processing Of Laser Ultrasonic Detection Based On Digital Holography

Non destructive testing(NDT) is an indispensable technology in the rapid development of the industry. Laser ultrasonic testing is a new type of detection method.Laser ultrasonic testing technology is the use of ultrasonic penetration ability and the advantages of optical non-contact detection of ultrasonic vibration signal. To realize the nondestructive testing of the tested workpiece. The method is especially suitable for remote detection in harsh environment. So it is an indispensable subject to study the laser ultrasonic testing, and it has the significance of engineering value.Firstly, this topic is based on the theory of laser ultrasonic testing, this paper describes the principle of ultrasonic excitation and the principle of signal reception in the laser ultrasonic testing system. Focus on the Engineering application of more thermal elastic mechanism. Secondly,in recent years at home and abroad are summarized in detail using laser ultrasonic detection technology. The detection principle, advantages and disadvantages of various techniques are analyzed and studied;According to the requirements of the project put forward a new optical detection method---Based on digital holographic theory of laser ultrasonic testing.In this paper, the functional relationship between the interference fringes and the ultrasonic vibration induce phase difference is obtained by the theoretical deduction.Using CCD receiving surface twice whether loaded ultrasonic vibration of holographic interference fringe image. By the MATLAB software programming to be received two images respectively through numerical representation.The two images of the reconstructed image are overlapped and interfered, to test whether the defects in workpiece by judging the interference fringes changes.The feasibility of the detection theory is proved theoretically.In particular, the interference beam angle, optical path difference, intensity ratio parameter is optimized and obtained A set of experimental parameters suitable for the design of the system a set of experimental parameters suitable for the design of the system.Finally, a set of laser ultrasonic testing system is set up, and the engineering application of aerospace aluminum plate and glass fibre for defect detection, The interference fringe pattern is obtained by the algorithm;Then in the MATLAB programming environment, the image filtering, denoising, enhancement and other columns of the image processing. Clear interference fringe patterns are obtained. Thechange of interference fringes is analyzed by using the ultrasonic vibration signal on the surface of the tested aerospace aluminum plate and glass fibre to analyze the interference fringes. It verifies the feasibility of the theoretical derivation, and provides a theoretical reference for the research of laser ultrasonic testing, and it has a certain value of engineering application.