纳米分辨率外差干涉信号处理电路相位畸变的实验研究

外差干涉是实现纳米精度长度测量的重要手段。采用电子倍频、混频、高频计数的方法可处理外差信号实现亚纳米分辨率，具有电路简单、能计大数的优点，但会引入电子信号的相位畸变，引入测量的动态误差。本文通过理论和实验分析了这一误差，表明在电子倍频中锁相环引起的相位畸变仅在亚纳米量级，但在混频环节中带通滤波器引入的相位畸变则可达几纳米，引入较严重的误差。本文通过采用低频差横向塞曼激光器产生３２０ｋＨｚ的外差信号，并采用ＦＰＧＡ技术实现倍频后的高频率信号直接计数，省略混频环节，从而实现了高测量分辨率并避免了这一误差。

Study on phase error of the heterodyne signal process system for nanometrology

Heterodyne interferometer is a important method for nanometrology. In order to realize subnanometric resolution, a signal process system based on frequency multiple, frequency mixing and FPGA for high frequency counting is established. However, the nonlinear unit such as Phase Lock Loop(PLL) and Band Pass Filter(BPF) will arise dynamic phase error. Experimental result indicated that the phase error of PLL is less than 1nm and can be ignored while the phase error of BPF is in the order of nanometer. The transverse Zeeman laser whose beat frequency is only 320kHz is introduced, its electronic signal can be directly multiple to 25MHz and realize resolution of 4nm without frequency mixing unit. As a result, this kind of phase error is avoided.