Study Of Electronic Shearography Speckle Pattern Interferometry

Speckle metrology is an important branch of optical measurement techniques.Speckle techniques make use of laser speckles formed in space or artificial specklesdeposited on the specimen surface to monitor displacement or to carry outdeformation measurement. In the past three decades, in addition to the study of theinherent properties of laser speckle fields, various speckle measurement techniquesare gradually developed such as Speckle Photography(SP) Speckle Interferometry(SI)and Speckle Shearing Interferometry(SSI) .They are widely applied in different fields.Electronic speckle pattern interferometry (ESPI), which uses fringe analysis fornondestructive deformation field measurements, has become an important techniquein the recent 20 years. Electronic Shearography Speckle Pattern Interferometry(ESSPI) is a new method which developed from Electronic speckle patterninterferometry (ESPI).The method has many advantages of the whole-fieldmeasurement, the simple optical road, the easy modulation and the low demand forenvironment. The phase-shifting method which is used in ESSPI can improve theprecision of the measurement greatly. So the phase-shifting method is used in NonDestructive Testing (NDT) widely.In this dissertation, Electronic Speckle-shearing Interferometry (ESSPI) and thephase-shifting technique are detailedly discussed. The main contents are described asthe following:1、The concept and the producing method of speckle is introduced.A review ofdevelopment of Speckle metrology is presented. 2、The main techniques, such as Electronic speckle pattern interferometry (ESPI) and Speckle-shearing Interferometry (ESSPI) are summarized.Principle of thephase measurement method is introduced. The principle, the method and thearithmetic of the phase-shifting technique is specially introduced.3、Because two shearing object beams travel in the same direction whenWollaston prism is used as image-shearing device in traditional speckle shearinginterferometry. It is difficult to realize phase-shifting technique by separating the twobeams. The phase-shifts method of the translating Wollaston prism can introduceadditional phase without separating the two beams. This paper gives the theoreticalanalysis of the method. The relationship between the displacement and additionalphase is offered. The errors of the output angle and the position of the prism in ESSPIare analyzed. The mathematic relationship and the figure of the relative error areoffered. A typical experiment about the method is carried out by using a centrallyloaded clamped circular plate. The result is offered. It shows that the method oftranslating Wollaston prism phase-shifting technique could effectively obtaindisplacement derivative field from fringe patterns of test object.4、Electronic speckle-shearing patten interferometry based on the square prism isprestended .This new shearing componen shearing principle is also introuduced .Thismethod has been proved to be feasible by a typical experiment using a centrallyloaded damped circular plate by compareing the results with those based on Wollastonprism show that thism new square prim can substitute Wollaston prim as a shearingcomponent. Comparing the two results,we can see the shearing effect of the squareprism is as well as Wollaston prism.5、The application of Electronic Speckle-shearing Interferometry (ESSPI) isintroduced.One side is the application in Non Destructive Testing (NDT) and itsdevelepment process is also given.On the other side is the analysis of stress and thestrain，at the same time,the theory of each direction strain is given.