Focus distance modulated fibre-coupled confocal sensor for surface metrology

复杂部件的小型化和微结构以及相应的更严格的制造公差给尺寸计量带来了新的挑战。使用特殊的微米或纳米坐标测量系统，已经可以实现传感器和测量对象之间几毫米范围内的高精度三维相对运动，分辨率达到纳米或亚纳米范围。然而，仍然需要高精度传感器来探测测量对象，以适应这些具有挑战性的测量任务。该研究项目的目标包括基础研究、鲁棒、精确、高频焦距调制共焦点传感器的开发和评估，以及将该传感器集成和验证到纳米坐标测量系统中。为了实现这一目标，在保持共焦测量原理的已知优势的同时，纳米坐标测量系统中的平台扫描模式应采用光纤耦合共焦照明和检测、用于调节焦距的可调谐声学驱动梯度折射率流体透镜（TAG透镜）和新颖的信号处理（应用锁定放大器）的创新组合，以显着提高精度并减少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.