Study On Phase Unwrapping Algorithm Of Non-contact Raster Projection

Over the past few years,the advancement of scientific and technological productivity coupled with the growing demand for social production has led to the widespread adoption of 3D shape measurement technology in various fields such as industrial manufacturing,cultural heritage preservation,and medical diagnosis.Notably,non-contact grating projection 3D measurement technology has emerged as a rapidly developing technology that boasts superior measurement accuracy and high reliability when compared to other measurement technologies.As the wrapped phase values in grating projection-based 3D surface measurement are usually acquired through the arctangent function,these values are confined within a specific interval.Hence,a phase unwrapping algorithm becomes necessary to unravel the wrapped phase and obtain accurate phase values.It is worth noting that there are problems of discontinuous phase and noise interference in the wrapped phase obtained in actual measurements.In order to achieve efficient and accurate 3D surface reconstruction using a non-contact grating projection-based 3D surface measurement system,this paper discusses research on improving the accuracy and efficiency of the phase unwrapping algorithm.The main work done is as follows:(1)Aiming at the problem of noise crosstalk in the parcel phase diagram,this paper classifies it as a problem to solve the influence of residual handicap,and proposed a method to locate the residual handicap position in the parcel phase diagram by using mask cutting technology,which effectively removes the interference of noise and residual handicap and improves the accuracy and precision of phase recovery.(2)Aiming at the problem of error transfer in the phase recovery path of the quality map guidance method,this paper proposed a quality guidance method that integrates residual characteristic information.In this method,the variance of phase derivative is taken as the initial mass graph,and the residual characteristic information is fused with the initial mass graph to obtain the improved mass graph.Based on the quality graph-oriented phase recovery method,the phase recovery process of the parcel phase diagram is carried out,and the absolute phase obtained is adjusted,so as to complete the three-dimensional topography reconstruction of the object.In the case of complex contour and noise crosstalk,the proposed method performs well in speed,accuracy and stability,especially in the case of anti-noise interference.(3)Aiming at the problems of low coding efficiency,complex decoding process,and coincidence of decoding order and truncation phase in the phase recovery of gray codeassisted multi-frequency phase shift method,a encoding and decoding strategy of mismatched terre gray code is proposed in this paper.This method significantly improves the coding efficiency and effectively solves the problem of phase order misjudgment.By this method,phase recovery can be more accurate and efficient.(4)Establishing a non-contact grating projection 3D measurement system.The methods mentioned above have been validated through numerous simulation experiments and actual measurement data experiments.The results of these experiments demonstrate that the two proposed phase unwrapping algorithms meet the measurement system’s efficiency and reliability requirements.