Optical 3D geometry reconstruction, or more specific, fringe projection profilometry, is a state-of-the-art technique for the measurement of the shape of objects in confined spaces or under rough environmental conditions, e.g., while inspecting a wrought-hot specimen after a forging operation. While the contact-less method enables the measurement of such an object, the results are influenced by the light deflection effect occurring due to the inhomogeneous refractive index field induced by the hot air around the measurand. However, the developed active compensation methods to fight this issue exhibits a major drawback, namely an additional cooling of the object and a subsequent transient illumination component. In this paper, we investigate the cooling and its effect on temporal phase reconstruction algorithms and take a theoretical approach to its compensation. The simulated compensation measures are transferred to a fringe projection profilometry setup and are evaluated using established and newly developed methods. The results show a significant improvement when measuring specimens under a transient illumination and are easily transferable to any kind of multi-frequency phase-shift measurement.

中文翻译：

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改变照明条件的适应条纹投影序列，以测量受强制冷却影响的锻热物体为例

光学3D几何重建，或更具体地说，是条纹投影轮廓测量法，是一种用于在狭窄空间或恶劣环境条件下测量物体形状的最新技术，例如，在之后检查变形的热试样时锻造作业。尽管非接触式方法可以测量这样的物体，但是由于受测者周围的热空气引起的折射率场不均匀而产生的光偏转效应会影响结果。然而，针对该问题而开发的主动补偿方法表现出主要缺点，即，物体的额外冷却和随后的瞬态照明分量。在本文中，我们研究冷却及其对时间相位重建算法的影响，并采取理论方法对其进行补偿。模拟的补偿量度将转移到条纹投影轮廓测定仪中，并使用已建立和新开发的方法进行评估。结果表明，在瞬态照明下测量样品时，显着改善，并且可以轻松转移到任何一种多频相移测量中。