Three-dimensional Electronic Speckle Carrier Frequency Modulation And Deformation Measurement Technology

Speckle interferometry, with non-contact, full-field measurement, high sensitivity and high accuracy, has a wide application in research and industrial production. The rapid developments in electronics, computer and laser, greatly promote the development of speckle measurement, and make the technology moving in the direction of real-time, high-speed and automation.Among many practical applications of speckle measurement, a very important purpose is to measure the deformation of objects. Nearly two decades, ESPI has really become an important means of measuring the deformation fields. In many cases, the measured parameters have direct relations with the optical phase distribution. And ESPI also uses fringe analysis to achieve the non-destructive measurement of the deformation field. Several kinds of perfect phase measurement techniques have been applied in fringe analysis in ESPI. A lot of phase measurement methods have already existed, such as Heterodyne Method (HM), Temporal Phase-shifting Method (TPM), Spatial Phase-shifting Method (SPM), Fourier Transform Method (FTM) and Spatial Carrier Phase-shifting Method (SCPM) for carrier fringe patters.In this article, firstly, a brief of speckle interferometry is given, followed by phase measurement methods. Finally, two new technologies on deformation measurement were put forward.1,Three-dimensional ESPI based on large shearing blocky prismA new technology is proposed to measure three-dimensional deformation of the object, using by large shearing blocky prism. The principle of the technology and the characteristics of shearing were elaborated, as well as the difference from the traditional technology based on Wollaston prism.2,Three-dimensional ESPI with the technology of carrier modulation and three-dimensional displacement field for the deformationThe spatial modulation technique of fringe is applied in large-shearing ESPI technique, and the fringe modulation is achieved by using the rotated reference object. High-quality modulation stripes are acquired and the fringe analysis is carried on. On the other hand, the fringes of the modulation are demodulated by using Fourier transform, and three-dimensional displacement field for the deformation of objects were achieved.