Research On The Key Technology Of Shadow Moire Measuring System Based On FPGA

Phase shadow moire 3D measuring profilometry has been paid much attention and studied because of its advantages such as non-contact,high measuring accuracy and low price,and has been widely used in the current optical 3D sensing measurement technology.The traditional phase shadow moire measurement system is based on the computer for image acquisition and processing,because the PC image measurement system has many functions,complex structure and large volume,which makes its method has a series of problems such as low acquisition rate,large power consumption.Moreover,due to the nature of the serial nature of the software,it is difficult to improve the real-time performance of its processing capacity for processing and calculation under the condition of large amounts of data,and it cannot leet the current industrial measurement requirements.Supported by the national natural science foundation of China,this paper proposes to establish a portable,efficient and reliable rapid moire measurement method.The main tasks are as follows:(1)firstly,the measuring principle of phase shadow moire is studied,the measuring device is set up,the measuring experiment is carried out,and then the deficiency of traditional shadow moire measuring device is analyzed.(2)a shadow moire 3D image processing method based on FPGA is proposed.With FPGA as the core,the image acquisition,storage and processing of moire shadow system are realized.The proposed method can complete the moire image acquisition,noise reduction and acquisition of initial phase information and phase unwrapping.Finally,the phase information is transmitted to the host computer to obtain the 3D topography of the measured object.(3)systematic calibration and 3D topography measurement experiments were carried out.A method of geometric parameter calibration of shadow moire based on stereo vision is proposed.This method does not need additional processing targets,but can automatically calculate the geometric structure parameters,which overcomes the problem of difficult calibration of geometric structure parameters existing in shadow moire technique.Experiments show that the proposed method is correct.(4)aiming at the phase shift misalignment error existing in moire shadow,a three-step-random phase shift algorithm was developed to reduce the phase shift error caused by mechanical motion.The algorithm is free from background interference,small computation and non-sinusoidal fringe pattern,and is easy to implement in many applications.Simulation and optical experiments verify the correctness of the method.(5)according to the measurement sensitivity in the measurement process,the causes of measurement error were analyzed,the structural parameter error was analyzed,and the error transfer process was analyzed by Monte Carlo method.The proposed method has made effective progress in phase extraction,phase unwrapping,structure parameter calibration and data processing.It has important practical significance and theoretical value for the research of shadow moire measurement system.However,the organic integration of the whole measurement system and the systematic error analysis need to be further developed to promote the practical application of the proposed method.