Research On In-plane Displacement Measurement Of Objects Based On Speckle Photography And Image Processing Technology

With the continuous development of optical technology and computer image processing technology,speckle photography has occupied a dominant position in many fields,especially in the field of material mechanics and engineering measurement.Speckle photography is often used to measure the in-plane micro displacement of the measured sample,and then some important parameters such as the heated deformation,Young's modulus and linear expansion coefficient of the object are obtained by computer technology.In addition to speckle photography,holography,speckle interferometry and optical lever method can also measure the tiny displacement of objects.However,in holography,complex wet processing is needed to obtain the speckle pattern,and in speckle interferometry,the interference between object light and reference light is needed to form the stray field.In optical lever method,the adjustment requirements of telescope are very strict,and the operation is rather troublesome,so it is inconvenient to apply to dynamic measurement.Speckle photography does not need reference light,which is not only simple in light path and convenient to operate,but also can be used for dynamic measurement.This paper mainly studies the measurement method and its application of speckle photography.According to the working principle of speckle photography and using image processing technology to measure the micro displacement in the object plane,the measurement range of this technology is explored,and the calculation error of this measurement method is analyzed.In order to improve the accuracy of speckle fringe spacing measurement,this paper also studies a variety of methods of image processing using Matlab,and compares and analyzes the processing results of enhancement,binarization,closing operation and skeleton extraction,and finds a group of schemes to make the fringe image quality better.The experimental results show that the measuring range of this technology is from 50?m to 140?m,which basically meets the requirements of general engineering measurement and mechanical experiment,and this technology has good accuracy,with the error within 9%.Finally,this paper combines speckle photography with image processing technology,and applies it to the measurement of in-plane micro displacement and thermal deformation of steel plate,lead plate and plastic plate.The experimental results show that the deformation of the steel plate is 28?m to 95?m when it is raised from 10? to 50?.When the lead plate is heated by 20? to 55?,the deformation of 42?m to 82?mmm is produced,while the plastic plate is easy to melt during heating.Experimental research shows that this research method is more suitable for the measurement of metal thermal deformation.