The Research Of Measure In-plane Small Displacement By Using Digital Speckle Photography

In engineering testing and material mechanics testing, there is often need tomeasure in-plane tiny displacement of the object, such as young’s modulusmeasurement and linear expansion coefficient of determination, etc. These parametersin engineering and scientific research have an important meaning, measurement methodusually have holographic and speckle interferometry, the optical lever method, etc.Method of holographic and speckle interferometry optical path is complex, even has ahigh requirement on the environment. The adjustment of the optical lever method in thetelescope can be time-consuming and troublesome, also not conducive to dynamicmeasurement. Digital speckle photography compared with the methods of holographicand speckle interferometry, the technology does not need the reference light, the lightpath is greatly simplified, but slightly lowers precision. Compared with the optical levermethod, the operation is simple and can be used for dynamic measurement, faster andprecision higher.This topic is the study of the use of matlab-based digital speckle photographywithin the plane of measurement of tiny displacement, the main research work include:1, For domestic and foreign research status of speckle photography and theprinciple of speckle photography is introduced in detail, puts forward system design:adopt ccd-array record speckle graph, using MATLAB software to collect speckleimage processing, extraction stripe center line and get stripe cycle, displacement isobtained by calculation.2, According to the design scheme to build measuring light path, complete inMATLAB for the observed speckle fringe spacing extraction.3, Design test platform, the use of optical bench with a spiral micrometerimplement precise control of the actual displacement of the object to be tested throughthe experiment under different displacement measure system of multiple sets of validdata, the measurement results will be compared with the actual displacement analysis,the system measuring accuracy and measuring range are obtained.4, The system was applied to measurement of young’s modulus.After experimental test, this system has realized the accurate measurement of tinydisplacement in surface, has the good stability and accuracy of measurement. Thesystem measurement error is below4.5%, measurement range from0.05mm to0.3mm, can meet the requirements of general mechanics experiment and engineering detectionfor small displacement measurement. Compared with other measurements, the systemhas a light path is simple, easy to operate, fast data processing, the characteristics ofhigh measuring precision.