Research For Electronic Speckle Pattern Interferometry Testing Technology

Electronic Speckle Pattern Interferometry is short for ESPI, which is a modern optical measurement technology. ESPI is the combination of laser technology, video technology, computer image processing technology, holographic interferometry and speckle interferometry technology. It is widely used in Nondestructive Testing (NDT), optical rough surface displacement, deformation measurement, vibration analysis, and other fields.The paper outlines the development of the speckle pattern interferometry technology and the application of ESPI in nondestructive testing. The origin of speckle and the basic theory of speckle measurement are analyzed, we focuses on the reference beam ESPI experimental system, which is used in the paper.According to the speckle interference fringe pattern with a large number of noise features, the fringe information extraction has been studied on the basis of denoise algorithm. After the processing of filtering, binarization, refining, fitting, the content stripes skeleton map can be obtained, further analysis can be continued. The out-of-plane displacement of specimen is measured with the experimental system. The information of interference fringes is extracted. After image and date processing, we can obtain 3-D reconstruction of the specimen surface displacement.In the field testing of industrial environment, the disturbance can cause ESPI to be instable, double-pulsed ESPI improves stability by reducing exposure time and spacing. The advantages of double-pulsed ESPI are analyzed.But the double- pulsed ESPI pattern is generated by adding, The pattern's quality is poor and fringes are immersed in the low-frequency noise. The double-pulsed ESPI system is studied in this paper. Because of limitations of conditions, we use CW-laser to simulate the sum of double-pulsed ESPI patterns, and we design a suitable filter system to get better fringes, and the resulting conclusions fully are applicable to the double-pulsed ESPI.ESPI has a wider range of applications in NDT of composite materials. In this paper, ESPI experimental system is used in nondestructive testing of honeycomb structure composite material, as the starting point for research. We imitated several flawed specimens to come to the preliminary results of the testing.