Collaborative Research: Improved Freeform Measurement through Fiber-based Metrology

计量学是测量的艺术和科学，是先进制造业的核心。在自由曲面的微纳尺度超精密制造中，迫切需要改进计量科学。这项研究的目的是提高这种超精密光学表面的测量能力。这种表面测量不仅在光学器件生产之后很重要，而且在制造过程中也很重要，以评估工艺性能。现有的测量方法存在基本误差，这些误差限制了可实现的精度。此外，传统技术经常会中断制造过程，限制生产率。在这项研究中，使用一种新的测量策略的在机计量将被用于提高具有挑战性的光学元件的制造能力。这项工作的结果将用于提高自由形状测量能力，因此将促进光学、照明、能源、航空航天和生物医学领域的科学进步。其他更广泛的影响包括田纳西理工大学为期两周的“面向精密工程的多学科实习计划”、田纳西州库克维尔库克维尔儿童博物馆展示以精密工程为基础的历史设备的永久画廊，以及面向夏洛特-梅克伦堡市区学校系统中学女生的“为我工程项目(E4Me)”。这些教育努力将使K-12学生接触STEM研究和职业，重点是精密工程。研究目的是通过将一种新型的光纤传感器集成到在机测量配置中来消除自由曲面测量中的余弦误差。表面轮廓测量中的余弦误差是由于测量轴和运动轴之间的角度不对准而引起的，限制了测量精度。例如，在测量菲涅尔透镜、光栅、球面/非球面和高次多项式表面时尤其如此。在当前的自由曲面测量策略中，余弦误差无法消除，因为测量工具不沿垂直于测量平面的方向进行测量。通过将光纤技术(自动聚焦、Fizeau干涉测量)集成到机器配置中，计划了一种用于自由曲面的新方法。该项目的方法还避免了机床的误差运动，因为测量路径与加工路径重合。通过回答与该方法的性能限制有关的基本问题，预计这项研究将在高精度、在机仪器方面产生新的知识。

Metrology is the art and science of measurement, and is central to advanced manufacturing. There is a critical need for improved metrology science in micro- and nano-scale ultra-precision manufacturing of freeform surfaces. The objective of this research is to improve measurement capabilities for such ultra-precision optical surfaces. This surface measurement is important not only after an optic device has been produced, but also during manufacturing to assess the process performance. Existing measurement methods suffer from fundamental errors that limit the achievable accuracy. Additionally, traditional techniques often interrupt the manufacturing process and limit productivity. In this research, on-machine metrology using a novel measurement strategy will be used to improve manufacturing capabilities for challenging optical components. The results of this work will be used to improve freeform measurement capabilities and will therefore lead to scientific advances in the optical, illumination, energy, aerospace, and biomedical fields. Other broader impacts include the two-week "Precision Engineering-Oriented Multidisciplinary Internship Program" at Tennessee Technological University, a permanent gallery that highlights precision engineering-based historic devices at the Cookeville Children's Museum, Cookeville, Tennessee, and "Project Engineering for Me (E4Me)" that targets middle school girls in the urban Charlotte-Mecklenburg school system. These educational efforts will expose K-12 students to STEM research and careers with a focus on precision engineering. The research objective is to eliminate cosine error in freeform surface measurement by integrating a novel fiber-optic sensor in an on-machine measurement configuration. Cosine error in surface profile measurement results from an angular misalignment between the measurement axis and the axis of motion and limits the measurement accuracy. This is especially true in measurements of Fresnel lenses, gratings, spherical/aspherical surfaces, and high-order polynomial surfaces, for example. Cosine error cannot be eliminated in current freeform surface measurement strategies because the measuring tools do not measure along the direction normal to the measurement plane. A novel methodology for freeform surfaces by integrating fiber optic techniques (autofocusing, Fizeau interferometry) in an on-machine configuration is planned. The project's approach also avoids machine tool error motions because the measurement path coincides with the machining path. By answering fundamental questions regarding the performance limits of the approach, it is expected that this research will produce new knowledge in high-precision, on-machine instrumentation.