Research On Dynamic Object 3D Measurement Based On Fringe Projection

3D mearsurement is an important direction of research in instrument science.With repid advancements on imaging techniques and computing devices,scientists and engi-neers in fields such as industrial inspection and medical imaging are seeking constantly in high speed and high accuracy 3D measurement for dynamic object.In fields such as entertainment and human-computer interaction,dynamic 3D imaging techniques has come to life of ordinary people and achieve large commercial success which promotes the repid advancements in relevant fields further.Among different dynamic 3D mea-surement techniques,phase-shifting profilometry is broadly applied because of its high spatial resolutions,and robustness to noise or surface reflectivity variations.Phase-shiffting profilometry requires phase unwrapping algrithm due to the phase period ambiguity in the inverse tangent calculation.In measurement of dynamic objects,traditional temporal phase unwrapping methods require auxiliary projection sequences which slow down the measurement speed and introduce the motion artifacts.In recent research,spatical reference is introduced to reduce the fringe patterns,but suffers from the lack of the flexibility in the in-situ measurement.To sovle the problem that the current absolute phase unwrapping methods require extra reference information,our paper inspects the projected illumination model in the structured light system and the reflection model on the surface of the object.Moreover,our paper proposes a shading based absolute phase unwrapping method,and establish a 3D measurement system to achieve 3D measurement for dynamic objects.First,we inspect the imaging model of the structured light system and its calibra-tion method.We also review and analyse the fringe projection and phase unwrapping algorithms.Then,we inspect the illumination model of the projection in the structured light system and the reflection model of the object.This paper propose a method to esti-mate the shading of the object surface in the structured light system with above model,which estimate the shading of the object surface effectively with the 3D coordinates of the surface and the calibration parameters of the structured light system.Due to the specular reflection model too complicate to estimate,we propose to split the spec-ular reflection region based on the surface normal and the illumination,and estimate the diffuse reflection only.Finlly,combined with the surface shading estimation in the structured light system,we propose a novel phase unwrapping method.Our method can obtain the absolute phase with only three fringe pattern and without spatial reference.We propose the phase histogram check method to obtain a continuous phase map.By calculating the histogram of the phase point distribution,the invalid relative phase map can be identified and converted to a valid relative phase map.Then,we propose the shading matching check method to determine the correct absolute phase map candidate without additional patterns or spatial references.The absolute phase map candidates are derived with different fringe orders from the relative phase map.By calculating the shading distribution similarity between the estimated shadings and the shading ex-tracted from the captured images,the correct candidate can be determined.We establish the structured light fringe projection 3D measurement system.The experimental results demonstrate the validity of the proposed phase upwrapping method.