Flood-fill Phase Unwrapping By Using Random Starting Points In 3-D Profile Measurement

In order to solve the problem of the cumulative error caused by the path dependence of the phase unwrapping algorithm in the grating fringe projection phase shift measurement technique,the flood-fill phase unwrapping algorithm is used to carry out the phase expansion,while plenty of initial values of the flood-fill phase unwrapping algorithm are randomly selected in the wrapped phase diagram,and the average of multiple computation output is obtained.This method can effectively reduce the error of path dependencies and improve the accuracy of 3-D profile measurement,so as to provide an effective solution for 3-D profile measurement technology cumulative error problem.This paper is organized as follows:(1)The grating projection phase-shifting measurement experiment system is built.The grating projection method is applied.The sinusoidal grating is projected on the surface.The grating fringe image which is distorted due to the high degree of modulation are obtained through the CCD camera.The four-step phase-shifting method is used to get the fringe images with phase(?).(2)The four-step phase-shifting unwrapping calculation program is written.Flood-fill phase unwrapping algorithm is used to get the distribution of phase value associated with the object surface shape in closed area by the poly line.(3)A number of initial values are selected randomly with uniform distribution in the closed area.The unwrapping phase is conducted multiple times and the average is calculated,the method reduces the error produced by the path dependence effectively to improve the accuracy of the experiment system successfully.(4)The measurements of actual objects are carried out by using the three-dimensional surface measuring system in this paper.The experimental results are analyzed and compared with the actual objects..