Research On Vibration And Dynamic 3D Shape Measurement Method Based On Coded Illumination

Visual measurement method has become a good choice for vibration monitoring and dynamic three-dimensional shape measurement,for its advantages of non-contact,strong adaptability,multi-point information acquisition and no weight or light weight of measuring points.This paper integrates single frame multi moment information acquisition,binary coding timing,information reconstruction for signal sparsity and projection illumination coding design,and proposes the visual dynamic measurement method based on coded illumination.Capture the high-frequency vibration with low-speed cameras and reconstruct the dynamic three-dimensional surface,realizing visual dynamic measurement.The main contents of this paper are as follows:（1）The binocular stereo vision imaging system and imaging principle are studied.The advantages and disadvantages of parallel optical axis system and intersection optical axis system are analyzed.The parallel optical axis system is selected and the devices are chosen.The vision measurement system is built and the calibration is finished.（2）A visual dynamic measurement method based on single frame coded illumination is proposed.This paper analyzes the principle of single frame coded illumination,studies the mask design and image process,and realizes the extraction of virtual feature points.The basic characteristics of the measurement system are explored:the stability of virtual feature points,the static and dynamic displacement resolution,and the cause of system error and its elimination method.The ability of the system in actual measurement is explored:the accuracy for low-frequency signal frequency measurement is tested,the number limit of single frame subframe extraction is analyzed,the best subframe number is found,the highest sampling frequency is confirmed,and the ability of multi-point different sampling frequency measurement is verified.The time resolution of the low-speed camera is extended,and the non-contact method adds spatial features to the object.It solves the problem of huge storage space and transmission bandwidth caused by the use of high-speed camera in dynamic measurement.（3）A compressed sensing method for visual dynamic measurement of single frame coded illumination is proposed.Combining compressed sensing with single frame coded illumination visual measurement method,the imaging process is analyzed.Through simulation analysis,the feasibility of the proposed method is confirmed,and it is found that the ₁l-norm spectral projection gradient algorithm is the more suitable reconstruction algorithm.The trigger signals of cameras and the projector are designed,the source of system error is found and the system error is eliminated,and the accuracy of the proposed method is tested.It makes full use of signal characteristics,reduces sampling frequency and the amount of data,and realizes compressed sensing in visual measurement.（4）A method combining down sampling vibration synchronous measurement and coded illumination is proposed.The stroboscopic light source commonly used in down sampling vibration synchronous measurement technology is replaced by digital projector,which plays the role of stroboscopic illumination and speckle coding.Several different types of digital speckle patterns are designed.The best type of digital speckle mask is found out by analyzing the mask pattern,disparity image quality and point cloud fitting results.The principle of down sampling vibration synchronous measurement and the setting of the camera and projector parameters are studied.The dynamic three-dimensional shape of high-frequency light sheet is recorded by low-speed cameras.