Calibration And Improvement Of Fringe Projection Three-Dimensional Measurement System Based On The Light-Source-Stepping Method

Optical three-dimensional topography measurement technology is a non-contact three-dimensional measurement technology.It has the advantages of high speed,high precision,and high resolution,and is widely used in various industries,such as industrial inspection,cultural relics protection,reverse engineering,and the recent rapid development of 3D printing and augmented reality(AR).Currently,three-dimensional topography measurement methods based on fringe projection,such as phase measurement profiling and Fourier transform profiling,have been widely used and studied.Projectors using liquid crystals and digital micromirrors are commonly used fringe projection devices.Digital micromirror projection is fast,but digital micromirror projection is expensive.The price of LCD projectors is relatively low,but the projection speed is slow,which is not suitable for high-speed measurement.At the same time,these projectors occupy most of the volume of the measurement system,which is not conducive to the compactness of the measurement system.The light source stepping method phase shift fringe projection system using Luoqi grating and LED light source array has fast speed,small size and low price,and has good application prospects in three-dimensional structured light measurement.This paper analyzes the principle of the three-dimensional measurement system of the light source stepping method.The calibration method of the measurement system was improved,and the measurement depth range of the system was extended.The main contents of the thesis are as follows:(1)introduced the optical 3D topography measurement technology and its research status;(2)introduced the fringe projection 3D measurement technology and the principle of the light source steppingprojection system;(3)studied the measurement System calibration method.Aiming at the characteristics of the three-dimensional measurement system of light source stepping method,the mapping method of phase and three-dimensional coordinates is discussed,and a system calibration method using a planar target is proposed.(4)The relationship between phase measurement error and depth of the light source stepping method is analyzed.It is found that when the deviation from the set depth range,the phase shift amount deviates greatly from the standard value,the phase smoothness of the phase measured by the phase shift method becomes worse,and the phase-height mapping error becomes larger,resulting in a smaller system measurement range.Aiming at this problem,an improved Fourier transform method is proposed to improve the local smoothness of the phase and expand the measurement range of the system.(5)A light source stepping fringe projection three-dimensional measurement system was built,and calibration experiments were performed to analyze the calibration accuracy.The innovations of this thesis are as follows:(1)A system calibration method using a planar target is proposed to calibrate the source stepping fringe projection 3D measurement system,which simplifies the hardware requirements for system calibration.(2)The improved Fourier transform method is used to expand the measurement depth range of the system.