Research On Portable Deformation Measurement System Based On Digital Speckle

Digital speckle correlation method can realize non-contact and high precision measurement,so it is widely used in experimental mechanics and chemical analysis and other related fields.Most of the methods use computer to process and calculate the related image of the object to be measured at home and abroad,so they can not really achieve portable real-time measurement.A portable real-time measurement system based on the digital speckle correlation method is studied in this paper,which is used to measure the in-plane micro-displacement when the object is deformed.In this paper,a research scheme of portable measurement system is proposed,and the related algorithms used in the system are studied,and a correlation calculation method which can reduce the calculation error is proposed.The influence of calculation window size on correlation coefficient and calculation error is analyzed,and the optimal calculation window size is found.The ARM embedded system is proposed to replace the computer for image processing and related measurement.The laser ranging module and angle measurement module are used to complete the calibration of different distances,and the measurement function is completed by the screen key operation control system.In order to eliminate the system jitter caused by the button operation,a speckle APP was studied.The mobile phone can use it to control system for remote measurement by connecting WIFI.Research shows that increasing the power of the correlation coefficient formula can not only effectively avoid falling into the local maximum in the whole pixel search,but also reduce error of subpixel calculation,which can reduce the calculation error by 21.66%.The prototype is 196mm×132mm×50mm in size,1.008 kg in weight and 2.6h in endurance.The final test data shows that the system can measure at different distance within 50 m.The measurement accuracy is higher than 0.2mm within 10 m and the measurement error is less than 5%.The single direction calculation time is about 3s and the whole field calculation time is about 12 s.