航空发动机是战斗机等尖端航空器的“心脏”，其高压涡轮叶片气膜孔的形状及位置精度是限制发动机性能的关键因素之一，而叶片面型的测量和定位精度不足是制约气膜孔形位精度的主要问题。针对该问题，本项目提出研究基于法向跟踪的自由曲面激光差动共焦测量方法与技术，其通过对物镜分割光瞳的伺服平移来控制物镜聚焦光束的照明角度实现对自由曲面法线方向的实时跟踪，以提高激光差动共焦技术的抗样品倾斜能力，从而在大倾角范围内保持纳米级的轴向分辨力。研究包括：（1）基于法向跟踪的激光差动共焦测量原理研究；（2）基于组合扫描振镜的四自由度光束扫描方法研究；（3）兼顾飞秒激光加工的差动共焦测量光束扫描头原理样机研制。预期主要技术指标：可测样品倾角范围：-30°~+30°，轴向测量分辨力<5nm，焦点横向位移分辨力<5nm，光束扫描频响>1kHz。本项目可为高性能航发涡轮叶片测量提供新方法与技术途径。

Aero-engine is the "heart" of fighter aircraft and other advanced aircraft. The shape and position accuracy of the air film holes in the high-pressure turbine blades is one of the key factors that limit the performance of the engine, and the lack of measurement and positioning accuracy of the blade profile is the main problem that restricts the air film hole shape and position accuracy. Aiming at this problem, the project is presented based on the research method to track the free surface of differential confocal laser measurement method and technology, the segmentation of through to the objective pupil servo translation to control objective focused beam of light angle to realize real-time tracking of the free surface normal direction, in order to improve the ability to resist sample tilt differential confocal laser technology, thus in the range of large dip angle of nanoscale axial resolution. The research includes: (1) research on the principle of laser differential confocal measurement based on normal direction tracking; (2) research on four-degree-of-freedom beam scanning method based on combined galvanometers; (3) development of the principle prototype of the scanning head for differential confocal measurement beam with femtosecond laser processing. Expected main technical indicators: measurable sample dip angle range: -30°~+30°, resolution of axial measurement <5nm, resolution of transverse displacement of focus <5nm, beam scan frequency response >1kHz. This project can provide a new method and technical approach for the measurement of high performance air-turbine blades.