随着社会对三维测量的需求日益渐高，提升测量精度是至关重要的问题。相比于其他三维检测方法，结构光技术具有高精度、高效率、非接触等优点，适合对工业场景中大型部件进行质量检测。但由于产品尺寸庞大，设置恒温车间成本代价较高，而非恒温车间中的环境温度变化又会使结构光系统三维测量精度大幅降低。针对此问题本文意在研究结构光温漂标定及补偿算法，对温漂问题进行参数与热误差补偿，实现高稳定高精度的结构光三维检测; 同时考虑对于实际应用场景中存在的非稳态传热情况，为了保证补偿参数有效性，本文拟通过基于条纹辅助的图像质量评价估计系统温漂程度，对应补偿系统参数，提高鲁棒性。首先，为了满足三维测量的高精度要求，本文剖析了影响结构光精度的要素,分别为系统标定、图像编码与硬件选型，因此本文采用离线标定、相移编码法以确定坐标匹配与相位解码精度。最终本文搭建了一套可控温的高精度三维结构光测量系统，为后续结构光温漂研究做为铺垫。其次，为了深入研究结构光温漂导致的热误差问题，本文分析了温漂对结构光三维重建的影响，并以此建立三维误差模型。由于温漂造成结构光热误差影响耦合并且分别建模繁琐复杂，因此本文提出基于虚拟点的结构光温漂标定补偿方法，利用添加虚拟估计点至三维空间域中的方法优化标定算法，补偿热误差并获得参数与温度的关联性。实验显示了温漂三维误差模型的合理性，并且证明了基于虚拟点的结构光温漂标定补偿方法能有效补偿热误差。最后，针对真实应用场景存在的非稳态传热造成参数与温度不匹配问题，本文首先阐述温漂与图像质量评价的关联性，并对图像质量评价方法进行研究，提出基于结构光条纹辅助的图像质量评估方法。相较于传统方法，本方法利用结构光主动视觉投影，增强图像数据的特征信息，克服实用性差的问题，实现对结构光当前温漂程度的估计。实验证明了本文提出的基于结构光条纹辅助的图像质量评价方法能精确的估计出当前失真值，利于建立参数、温度、失真程度的关联，提高温漂参数补偿算法鲁棒性。
As the increasing demand for three dimensional(3D) measurement, improving measurement accuracy is a crucial issue. Compared with other 3D reconstruction methods,structured light technology has the advantages of high precision, high efficiency, high point cloud density and non-contact, which is suitable for quality inspection of large parts in industrial manufacturing. However, there are also disadvantages: large size of products, higher costs in setting constant temperature, and decreasing measurement accuracy of structured light system temperature caused by variation in non-constant temperature workshop. And thus this paper aims at studying on temperature drift calibration of structured temperature and compensation algorithm as well as parameters and thermal error compensation of temperature drift for realizing high stability and accuracy of structured light 3D measurement; At the same time, unsteady heat transfer in practical application will be considered. Based on fringe assisted Image Quality Assessment (IQA), this paper planed to estimate system temperature drift degree, compensate corresponding system parameters and improve robustness.Firstly, in order to meet the high accuracy of 3D measurement, this paper analyzes the factors that affect the accuracy of structured light, including system calibration, image coding and hardware.And off-line calibration and phase shift coding used to determine coordinate matching and phase decoding accuracy are employed in this paper; Then, this paper constructed a set of high precision 3D structured light measurement system with controllable temperature, which paves ways for the later temperature drift study.Secondly, the influence of temperature drift on 3D reconstruction of structured light is analyzed in this paper for deeply studying the thermal error caused by temperature drift of structured light, and thus 3D thermal error model has been established accordingly. Due to the coupling effect of structured light errors caused by temperature drift and the complexity of individual modeling, a temperature drift calibration and compensation method of structured light based on virtual-points is proposed in this paper. Virtual points wereadded to the three-dimensional space domain to optimize the calibration algorithm for compensating the thermal errors and obtain the correlation between parameters and temperature. The experiments show that the 3D error model of temperature drift is reasonable and the temperature drift calibration and compensation method of structured light based on virtual point can effectively reduce the thermal error.Finally, in view of the mismatch between parameters and temperature caused by unsteady heat transfer in real application scenarios, the relationship between temperature drift and image quality evaluation is firstly described, and the IQA methods are studied. An IQA method assisted by structured light stripe is proposed. Compared with the traditional method, this method utilizes the active vision projection of structured light to enhance the feature information of image data, overcome the problem of poor practicability, and realize the estimation of the current temperature drift degree of structured light. The experimental results show that the IQA method is based on structured light fringe and can accurately estimate the current distortion value, which is conducive to establishing the correlation between parameters, temperature and distortion degree, and improving the robustness of temperature drift parameter compensation algorithm.
