Study Of Measuring 3D Shape Of Mirror With Discontinuous Surface Based On Fringe Pattern Reflection Technique

With the development of three dimensional optical shape measurement technology,it is widely applied in the fields of reverse engineering,biological recognition and digitalization of cultural relics,etc.However,all of the existing techniques are applied to measure objects with diffused surface.There are a large number of transparent,black,and reflective objects in industrial applications.The research of shape measurement for these objects is still in the early stages.At present the main methods in industry are using three coordinate measuring machine or changing the surface characteristics by spraying paint.Optical shape measurement has many advantages such as high speed,non-contact,and high measurement precision.Therefore a direct optical shape measurement method for the above-mentioned objects is needed.This thesis presents a new method of 3D shape measurement of specular reflective surface based on fringe reflection method.A new mathematical relationship between phase and depth is established,instead of calculating gradient which is unable to measure discontinuous surface.Based on the mathematical model,a system is setting up,which consists of a beam splitter to change the optical path,and two LCD screens with monoscopic fringe reflectometric method.All the components are static.By using model-based and machine vision method,system calibration is accomplished to provide the required parameters and conditions for measurement.The verification tests are given to evaluate the accuracy of the system,to analyze the error source.The 3D shape of a specular step and a reflective mirror has been measured.Experimental results show that the proposed measurement method can obtain 3D shape of specular objects effectively.