建立了移频式全息光栅曝光干涉条纹锁定系统以提高全息光栅槽型对比度并降低由外部环境造成的曝光干涉条纹相位移动。根据系统的组成原理, 分析了相位测量系统中莫尔条纹的产生条件及其与干涉条纹相位变化的关系, 给出了探测器的选择方法。根据系统精度要求计算了A/D转换位数, 自行设计了数字控制系统。提出采用光束移频方法来调整条纹相位, 应用声光调制器对干涉条纹移动进行实时校正。实验结果表明, 该系统采样频率可以达到5 kHz, 对干涉条纹漂移和10 Hz以下的低频振动都有较好的抑制作用, 相位变化3σ值小于0.12 rad, 即相位变化小于±0.02个干涉条纹周期。该系统可以实时有效地锁定曝光干涉条纹, 较好地满足全息曝光的要求。

A frequency-shift interference fringe locking system was established to enhance the contrast of holographic grating profile and to decrease the phase shift of exposure interference fringe caused by the external environment. According to the composition and the working principle of the system, the moiré pattern occurrence condition in the measuring system and its dependence on the phase change of interference fringe were analyzed and the selection method for photodetectors was given. On the basis of the system accuracy, the digital control system was self-designed including A/D conversion digit. A optical frequency shifting method was used to regulate the fringe phase, and an acousto-optic modulator was taken to correct the frequency shifter of the interference fringe movement in real time. The experimental results illustrate that the system can offer a sampling frequency of 5 kHz and can restrain the interference fringe drift and low-frequency moving below 10 Hz. The 3σ value of the phase shift is below 0.12 rad, which means its phase is within ±0.02 interference fringe period. The system can lock the phase of the exposure interference fringe effectively in real time, and can satisfy the requirements of the holographic grating lithography better.