Focus distance modulated fibre-coupled confocal sensor for surface metrology

复杂部件的小型化和微结构化以及相应的更紧密的制造公差对尺寸计量提出了新的挑战。利用特殊的微或纳米坐标测量系统，已经可以在几毫米的范围内实现传感器与测量物体之间高精度的三维相对运动，分辨率在纳米或亚纳米范围内。然而，仍然需要高精度的传感器来探测适合这些具有挑战性的测量任务的测量对象。本研究项目的目标包括研究基础、开发和评估一种鲁棒、精确、高频焦距调制共焦点传感器，并将该传感器集成到纳米坐标测量系统中并进行验证。为了实现这一目标，在保持共聚焦测量原理的已知优势的同时，采用了光纤耦合共聚焦照明和检测的创新组合，可调谐的声学驱动梯度折射率流体透镜（TAG透镜）用于调制聚焦距离，以及应用锁定放大器的新型信号处理，应使用用于纳米坐标测量系统的阶段扫描模式，可以显著提高精度，降低测量不确定度和测量时间。

Miniaturization and micro-structuring of complex components and accordingly even closer manufacturing tolerances put new challenges on dimensional metrology. Using special micro or nano coordinate measuring systems, it is already possible to realize highly accurate, three-dimensional relative motions between sensor and measuring object in range of a few millimetres and with resolutions in the nanometre or sub-nanometre range. However, there is still demand for high-precision sensors for probing of the measuring objects which are suitable for these challenging measuring tasks. The goal of this research project consists of investigations on the fundamentals, the development and evaluation of a robust, precise, high frequency focus distance modulated confocal point sensor and the integration and validation of this sensor into a nano coordinate measuring system. To achieve this, while maintaining the known advantages of the confocal measurement principle, an innovative combination of a fibre-coupled confocal illumination and detection, a tuneable, acoustically driven gradient-index fluid lens (TAG lens) for modulation of the focus distance and a novel signal processing, applying a lock-in amplifier, shall be used for the stage-scanning mode in a nano coordinate measuring system to significantly increase the accuracy and to reduce the measurement uncertainty and the measurement time.