干涉条纹的相位变化与干涉条纹中某一固定点的光强密切相关, 基于这一原理, 通过对干涉场光强分析, 提出并设计了一种用于干涉条纹相位锁定的控制系统.光电探测器检测干涉条纹中固定目标点的光强, 并以该光强电压作为反馈控制信号, 利用声光调制器对干涉系统中两束高斯光束中的一束进行实时频率调制, 将光强电压控制在一个固定值, 实现干涉条纹的相位锁定.构建了条纹锁定控制系统控制对象的理论模型, 通过实验进行了验证, 并基于该模型的特点设计了条纹锁定控制器.实验结果表明: 在400 Hz的控制频率下, 干涉条纹相位漂移不超过±0.04个条纹周期, 满足干涉光刻的曝光需求.

The intensity of a fixed point in the interference fringes is closely related to the phase change of interference fringes. According to this principle, a real-time phase locking system was established by the analysis of the intensity field. The intensity voltage of a fixed point in the interference fringes was detected as a feedback signal by a photodetector, and an acoustic optical modulator was used to shift the frenquency of the Gaussian beam in real time. By setting intensity voltage to a fixed value, phase locking function was realized. Theoretical model of fringe phase locking system was derivated and verified by experiment. A phase locking controller was also designed based on the model. The experiment results illustrate that, the phase drift is within ±0.04 period under the 400 Hz control frequency, which satisfies the exposure requirements of interference lithography.