Hypercentric Imaging in Coherent Optical Metrology (HyperCOMet)

相干光学计量中的超中心成像 (HyperCOMet)

• 批准号: 430572965
• 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: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/430572965?language=en
• 关键词: Hypercentric; Imaging; Coherent; Optical; Metrology

During production, technical parts are subject to unwanted geometrical distortions and surface defects such as fractures, scratches and dents. Therefore, shape inspection is a mandatory perquisite for industrial quality assurance. If high precision is required, interferometric methods are well established, because they work contactless and provide a measurement uncertainty down to a fraction of the illumination’s wavelength.Advancements in micro cold forming and micro systems engineering allow for the production of increasingly complex shaped micro parts, which leads to new challenges in optical metrology. Thus, in addition to the high precision, future interferometric measurement systems have to meet these requirements by offering the ability to measure highly complex shaped objects in a reasonable time frame. Currently available systems based on standard imaging systems cannot accomplish this task, because they have a limited viewing angle, and measuring the full 3D form of a complex geometry often requires a number of individual measurements from different observation directions. This requires extensive hardware and involves time-consuming calibration and stitching procedures to reconstruct the object’s form.A solution to this problem could be hypercentric (or pericentric) imaging, which has recently been introduced to the field of machine vision. It enables circumferential visibility (simultaneous imaging of the front and the side surfaces) of convex objects. Currently the technique is mainly used in combination with image processing, e.g. to rapidly detect irregularities of an object's surface texture. Even though interferometric shape measurement techniques could largely benefit from this imaging modality, an application of hypercentric imaging to the field of coherent optical metrology has, to the best of our knowledge, not been reported.The aim of the proposed project is to introduce hypercentric imaging to the field of interferometric shape measurement. It is expected that this concept provides fast and precise form determination in industrial quality inspection of complex shaped objects for all cases in which the objects have convex shape. Exemplarily, the two coherent optical shape measurement methods of multi wavelengths phase shifting interferometry (MW-PSI) and frequency domain white light interferometry (FD-WLI) will be adapted. This requires understanding of the hypercentric imaging process on a wave optics level with a focus on speckle statistics and coherence properties of the light in the image plane. Furthermore, a specific geometry model has to be developed, that links the observed path differences to the actual shape of the object, while taking the reversed magnification of hypercentric lenses into account. The results of the project could lead to a new generation of compact, flexible and precise interferometric sensors offering circumferential shape data with a measurement uncertainty down to the sub micrometer range.

在生产过程中，技术零件会遭受不必要的几何变形和表面缺陷，例如碎片，划痕和凹痕。因此，形状检查是工业质量保证的必要条件。如果需要高精度，则可以很好地确定干涉方法，因为它们无接触式工作，并提供了微照明波长的一部分的测量不确定性。微冷形成和微型系统工程的预测允许产生日益复杂的形状零件，从而导致光学学分的新挑战。除了高精度外，未来的干涉测量系统还必须通过在合理的时间范围内测量高度复杂形状的对象来满足这些要求。当前基于标准成像系统的系统无法完成此任务，因为它们的视角有限，并且测量复杂几何形状的完整3D形式通常需要从不同的观察方向进行许多单独的测量。这需要大量的硬件，并涉及耗时的校准和缝合程序，以重建对象的形式。解决此问题的解决方案可能是超中心（或周围的）成像，最近已将其引入机器视野。它可以实现凸对象的圆周可见性（同时对正面和侧面表面的成像）。目前，该技术主要与图像处理结合使用，例如快速检测物体表面纹理的不规则性。即使干涉形状测量技术可以在很大程度上受益于这种成像方式，但据我们所知，超中心成像在相干的光学计量学领域的应用都没有得到报道。该项目的目的是将超中心成像引入干扰素测量的领域。预计该概念在对物体具有凸形形状的所有情况的复杂形状对象的工业质量检查中提供了快速，精确的确定。示例性的，多波长相位转移干扰（MW-PSI）和频域白光干扰（FD-WLI）的两个相干光学测量方法将得到调整。这需要在波光学级别上了解超中心成像过程，重点关注图像平面中光的斑点统计和相干性能。此外，必须开发一个特定的几何模型，该模型将观察到的路径差异与对象的实际形状联系起来，同时考虑到了超中心镜头的反向放大倍率。该项目的结果可能导致新一代的紧凑，柔性和精确的干涉量传感器，可提供圆周形状数据，并通过测量不确定性降低到子千分尺范围。