| Electronic Speckle Pattern Interferometry （ESPI） refers to the method of usingoptoelectronic devices to record the speckle image of the object before and after deformationand then applying digital processing to the image, which is generally used for object in-planeand out of plane deformation measurement. What is directly measured using the electronicspeckle interference is the speckle streak image. To further obtain the object deformationinformation, we need to get stripe phase information of each point in the fringe pattern, andthe commonly used phase method includes the Fourier transform method and the method ofphase shift.Rectangular filter window is used to filter out the primary spectrum in thefrequency domain by the traditional Fourier transform method. As s result, the wrapped phaseobtained contains a certain amount of noise and the fringe contrast is relatively low, whichaffect the precision of image processing. This paper presents a polygonal filter window,which can reduce the effect of noise, improve the fringe contrast of the image, so as to obtainmore accurate experimental results.Optical Vortices are special kinds of optical field, whose phase distribution formis exp il, where l is called the topological charge number, and each quantum photon hasdetermined orbital angular momentuml.Optical Vortices are widely used in the fields suchas optical micro manipulation, quantum information processing, optical informationtransmission and so on. Currently, the methods to generate Optical Vortices mainly includethe method of liquid crystal spatial light modulator and the spiral phase plate method,etc.Whether we can use other methods to produce Optical Vortices or apply Optical Vorticesto object deformation measurement is still a significant subject that people constantlyexplore.In this article, we present an innovative way to generate Optical Vortices utilizingspiral zone plate, and apply Optical Vortices to deformation measurement, which provides anew approach to deformation measurement using electronic speckle interference. There are three parts in this article.The first part gives a brief introduction to the historical development process of ESPI aswell as the basic theories of ESPI.In the second part, we discuss the principle of spatial filtering，frequency domainfilteringand several other filtering methods to calculate the wrapped phase.，and discussedthe advantages and disadvantages of various methods As well as the applicable scope.Considering the question that the noise interference can be easily produced when using therectangular filter window in the process of calculation of wrapped phase with traditionalFourier Transform, we design the polygonal and the circular filter window.With the help ofMATLAB, I implement filtering on the deformation fringe of object in the experiment, usingrectangular, polygonal and circular filtering window respectively. And then I discuss Signal toNoise Ratio (SNR) of the image after filtering.It turns out that in view of the different shapespectrum diagram, the SNR of the obtained wrapped phase diagram can get least while theimage quality can be the best when adopting the polygonal filter window which is mostsuitable to the spectrum shape.In the third part, we introduced the developing situation of the vortex beam, anddiscussed the various methods to obtain vortex beam, such as holographic calculationmethod,spiral phase plate method,spatial light modulator method, etc.Further more, a methodis put forward, which is designed to produce vortex beams through parallel light enteringspiral zone plate. We simulate the process of calculating the deformation with electronicspeckle interference making use of the vortex beam as object beam or reference beam.Experimental results show that Optical Vortices can be used in deformation measurement ofobject, and the deformation fringe pattern can be modulated by changing the topologicalcharge number, which provides a new method for deformation measurement. |
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