Rotate Scanning Projection Moiré Technique And Its Application To Three-dimensional Surface Reconstruction

Optical surface profilometry and surface metrology are widely applied in many fields,from electron scanning microscope in micro,to antenna shape detection and terrain mapping in macro.The technique of three-dimensional surface reconstruction gets rapid development.Nevertheless,different reconstruction techniques have their own advantages and disadvantages.Increasing measurement area and maintaining high sensitivity contradicts with each other.This work is going to introduce scanning projection moiré profilometry based on deep research on projection moiré method,the idea of “scanning” will make the 3D surface metrology able to measure a large area with high accuracy and sensitivity.In the first place,a novel projection moiré model and its calibration method are proposed.The new model no longer put stricts restrictions on the optical setup configurations.As a universal model,it is much more flexible,allowing projection moiré method applicable to more situations.According to this model,a formula expressing the relation between phase value and three-dimensional coordinates is derived,an iterative method is put forward to calculate three-dimensional coordinates based on moiré phase.The receiving system can be directly calibrated using Zhang's method.The projection system can be seen as an inverse camera.The key to calibrate projection system is to establish the correspondence between camera pixels and projector pixels.It can be achieved by projecting horizontal and vertical fringe pictures successively.Then the projection system could be calibrated like a camera.Secondly,in order to expand measurement area and maintain high measurement resolution,a rotate scanning projection moiré profilometry technique is developed,as well as its calibration method.Considering the structure characteristics of measurement system,the scanning projection moiré system can be classified into two types,singleaxis mode and dual-axis mode.Changes of the system parameters after the projection system and the receiving system being rotated with different angles will be discussed.There will be extra parameters of the rotation axes to be calibrated besides projection system calibration and receiving system calibration.The last two can be calibrated using the same method in Section Two,the rotation axes could be calibrated by design an object function to fit every grid point's arc locus of the calibration board in different positions.Absolute phase extraction plays an important role in moiré method.A multi-frequency phase compensation method to solve this 2?-ambiguity problem in projection moiré is proposed.On the one hand,it makes projection moiré method able to measure objects with large discontinuities in surface,on the other hand,it helps in recognition of the absolute moiré fringe order,which means we need not to find a reference point or using other physical techniques to mark the zero-order moiré fringe any more.