Holistic multi-camera deflectometry (MultiDeflect)

整体多相机偏转测量（MultiDeflect）

• 批准号: 411170139
• 负责人: Professor Dr. Ralf Bernhard Bergmann
• 金额: --
• 依托单位: BIAS - Bremer Institut für Angewandte Strahltechnik GmbH
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/411170139?language=en
• 关键词: Holistic; multi; camera; deflectometry; MultiDeflect

Geometric-optical metrology enables fast, robust, non-contact and accurate 3D shape measurement. Hence, its application is preferential in quality control of many manufacturing applications. Deflectometry is particularly suited as a measurement technique for specular surfaces such as varnished car bodies and optical components. Deflectometry uses specific patterns on a display area which are reflected on the object surface and observed by an imaging system as such as a CCD-camera. Phase Measuring Deflectometry (PMD) uses sinusoidal fringe patterns to yield a unique coding by applying phase shifting. The geometry of the surface under test is assessed by identifying surface positions and local slopes using ray tracing. From this approach some fundamental properties of deflectometry arise: i) Position and local slope are ambiguous. Uniqueness is achieved by introducing prior knowledge or additional sensors. ii) The sensitivity with respect to the local slope is significantly higher compared to the position. Shape acquisition is gained by integrating over the slopes. This leads to particularly high demands on the system calibration since calibration errors will propagate through this process. The project aims at making best use of the huge amount of sensor information and prior knowledge as well as various methods to solve ambiguities in order to improve the system calibration and to lower the measurement uncertainty. This is approached by holistic treatment of all system parameters analogous to the Bundle Adjustment used for auto-calibration of cameras. In the literature, only rudimentary studies on investigating the improvement of the accuracy during calibration and measurement by introducing additional independent information in a holistic approach have been presented yet. Cameras were mainly treated in the photogrammetric model although the model-free Vision Ray Calibration is capable of providing additional information to the holistic approach. The proposed project therefore envisages the assembly of a PMD setup with access to 4 cameras and a distance sensor for the determination of a reference point. The following sub goals must be archived: i) Development and qualification of holistic optimization procedures considering 1 to 4 cameras; ii) solving the ambiguity by combining the multi camera technique and the knowledge of a reference point; iii) improved optimization by additional application of the vision ray model to the cameras. The procedures to be developed here are applicable to existing PMD systems to reduce their measurement uncertainty and the time required for measurement and calibration due to a more effective usage of available sensor information. Furthermore, confinements and possibilities for improving the accuracy by additional sensors are demonstrated.

几何光学计量可实现快速、稳健、非接触式且准确的 3D 形状测量。因此，它的应用在许多制造应用的质量控制中是优先的。偏转测量特别适合作为镜面表面（例如清漆车身和光学部件）的测量技术。偏转测量使用显示区域上的特定图案，这些图案反射在物体表面上并由成像系统（例如 CCD 相机）观察。相位测量偏转 (PMD) 使用正弦条纹图案通过应用相移来产生独特的编码。通过使用光线追踪识别表面位置和局部坡度来评估被测表面的几何形状。通过这种方法，产生了偏转测量的一些基本属性： i) 位置和局部斜率不明确。独特性是通过引入先验知识或附加传感器来实现的。 ii) 与位置相比，对局部坡度的敏感性明显更高。形状获取是通过在斜坡上积分来获得的。这导致对系统校准的要求特别高，因为校准误差将通过该过程传播。该项目旨在充分利用大量的传感器信息和先验知识以及解决模糊性的各种方法，以改进系统校准并降低测量不确定度。这是通过对所有系统参数进行整体处理来实现的，类似于用于相机自动校准的捆绑调整。在文献中，仅提出了通过在整体方法中引入额外的独立信息来调查校准和测量期间精度的提高的初步研究。尽管无模型视觉射线校准能够为整体方法提供附加信息，但相机主要在摄影测量模型中进行处理。因此，拟议项目设想组装一个 PMD 设置，可使用 4 个摄像头和一个距离传感器来确定参考点。必须归档以下子目标： i) 考虑 1 至 4 个摄像机的整体优化程序的开发和鉴定； ii）通过结合多相机技术和参考点的知识来解决模糊度； iii) 通过将视觉光线模型额外应用到相机来改进优化。这里要开发的程序适用于现有的 PMD 系统，以减少其测量不确定性以及由于更有效地利用可用传感器信息而减少测量和校准所需的时间。此外，还证明了通过附加传感器提高精度的限制和可能性。