Non-threshold Windowed Fourier Filter Algorithm And Vortex Beams Used In Deformation Measurement

Electronic Speckle Pattern Interferometry (ESPI) has developed into non-contact, highsensitivity, real-time fast,3-d surface shape and deformation measurement. whole field,non-contact measurement techniques. The ESPI makes use of laser speckles in space or artificialspeckles sprayed on the specimen surface to implement the displacement and deformationmeasurement. Digital image processing is used to calculate the deformation phase. Electronicspeckle interference speckle fringe pattern is observed directly, We should get full phasedistribution of the deformation measurement. But there are a lot of speckle image noise, It is toodifficult to accurately extract the phase information. speckle fringe pattern filter processing isbecoming a hot spot of research.Vortex beam with spiral phase structure and determine the orbital angular momentum ofphotons, is a special kind of light field. It is widely used in optics micro manipulation, quantuminformation processing and data coding and other fields. In this paper, vortex beam is applied inoptics measurement. In this paper, the main contents are described as following:1. A review of the development of ESPI, and introduces the principle of ESPI in measurement.2. several kinds of electronic speckle fringe pattern filtering method are introduced in, Theirprinciple、advantages and disadvantages are compared and summarized.3. In order to reduce the speckle noise in phase distribution of deformation, a new windowedFourier transform algorithm that does not need to set a threshold in advance, callednon-threshold windowed Fourier filter algorithm is presented. Only optimum frequency in awindowed area is the aim of the new algorithm.The computing time is reduced. The principle ofthe algorithm is introduced. Experiment results of the fringe patterns show that the proposed algorithm has a better performance in reducing the speckle noise and has a high precision inphase calculation.4. Vortex beams used in deformation measurement is investigated theoretically in this paper.The plane beam is changed to vortex beam by the spatial light modulator in measuring theout-of-plane displacement. The interference fringe patterns are generated by vortex beam asreference light and plane beam as object light or the object light and reference light all vortexbeam interfered before and after the tested object deformed. The influence of interferencepatterns caused by the topological charge of the vortex beam is analyzed in the paper. Thedeformed interference fringe patterns are analyzed and the corresponding phase-maps arecalculated though phase shifting method. The phase results we measured are the same with thetheoretical value. It is found that the vortex beam could be used in out-of-plane displacementmeasurement. The experiment results show a new method in deformation measurement.