Research On 3D Measurement Technology Based On Encoded Structured Light

As a non-contact,active 3D measurement method,structured light 3D measurement technology has the advantages of non-destructive,high-efficiency,low-cost,high reliability,and is widely used in the fields of cultural relic reconstruction,medical imaging,industrial measurement,mould manufacturing and so on.The time-coded structured light method requires no scanning and has a high measurement efficiency,and it has become a research hotspot in the field.In 3D measurement technology,the design of coded pattern has become the main breakthrough point for improving 3D measurement technology.In this regard,this paper mainly improves the measurement speed and measurement accuracy of 3D measurement by designing the coding pattern.The main research contents are as follows:(1)The mathematical model of the 3D measurement system is analyzed and studied,and the system calibration is realized.Using the Zhang Zhengyou calibration method to calibrate the camera;the projector is considered as a reverse camera.First,the ray equations and plane equations of the projection point are obtained.The 3D coordinates of the projection point are obtained by the line surface intersection method,Then the calibration method is used to calibrate the projector with the same method as camera calibration.The calibration error is reduced by re-projecting the extracted corner points,and the calibration results meet the requirement of measurement accuracy.(2)The two-gray-level Gray code encoding and decoding method and gray level two value method are studied.Based on this,the coding and decoding process of multi-gray level Gray code and the grayscale multivalued image processing are realized.The advantages and disadvantages of multiple grayscale Gray code are analyzed.The sinusoidal phase shift coding method commonly used in 3D measurement is analyzed.In order to solve the complexity of the sine phase shift decoding process,a trapezoidal phase shift intensity ratio method using simple linear operation decoding is studied.(3)For the traditional binary Gray code combined with the sinusoidal phase shift coding method,there are many projection patterns and high decoding complexity.In this paper,a multi-gray level Gray code combined with gray-scale trapezoidal phase shift coding method is proposed.This method reduces the code pattern projected by the gray code to half,and the decoding method is simpler,greatly speeding up the measurement speed.In thispaper,3D measurement is firstly performed using four-gray-level Gray code and three-step trapezoid phase-shifting symmetric combination coding method,and the periodic dislocation phenomenon in decoding is corrected,and the principle error is analyzed.On this basis,an asymmetric combination coding method for four-gray-level Gray code and three-step trapezoidal phase shift is further proposed,which eliminates the periodic dislocation phenomenon in principle,and reduces the inherent one-bit decoding error of Gray code to an intensity ratio error,which improves measurement accuracy.And coding pattern of the projected trapezoid intensity ratio is corrected by the gray level,which reduces the influence of environmental noise.Through practical measurement experiments,the feasibility of the coding method in this paper is verified,and it is proved that the proposed coding method has the advantages of less projection pattern,high measurement accuracy,strong anti-interference ability and fast measurement speed.