衍射光栅刻划机精密工作台定位特征识别试验研究

针对机械式衍射光栅刻划机精密定位工作台定位过程中产生的振动信号特性与光学性能指标（杂散光强度和波前质量）之间的关系，提出利用改进的Hilbert-Huang变换(HHT)获得的时频谱和边际谱对超精密工作台精定位特性进行研究。首先，给出了基于固有模态函数（IMF）筛选和瞬时频率差分求解的HHT信号处理算法。然后，设计了光学测量实验获得工作台50nm定位信号。最后，完成精密定位信号的特征提取和振动测试验证。结果表明:利用改进的HHT可以精确地完成精密定位信号的特征提取，从而为在衍射光栅的制造工艺中从根源上降低衍射光栅的杂散光强度和提高波前质量提供依据。

Positioning feature recognition for precision worktable of a diffraction grating ruling engine

An improved Hilbert-Huang transform (HHT) is put forward to reveal the positioning signal characteristic of ultra-precision worktable by considering the relations between optical performance index of diffraction grating(stray light intensity and wavefront quality) and the vibration signal generated in the precision positioning process of the worktable of mechanical diffraction grating ruling engine. Firstly, the HHT based on intrinsic mode functions’ selecting criteria and instantaneous frequency’s differential solution is introduced. Then, an optical measurement experiment is designed to obtain 50nm positioning response data of worktable. Finally, the characteristics of measured signal are extracted and validated by vibration testing. The results indicate that the characteristics of precision positioning signal can be extracted accurately by means of improved HHT, which provides a theoretical reference for reducing the stray light and improving the wavefront quality in the process of fabricating gratings essentially．