移栅型全息光栅曝光干涉条纹锁定

Interference Fringe Locking by Grating-Shifting Holographic Grating Exposure

为了提高全息光栅曝光系统的曝光对比度,抑制外部环境变化引起的曝光干涉条纹漂移,提出了一种移栅型干涉条纹锁定方法。采用分束光栅实现光源激光的分光及干涉条纹的相位调整。通过叠栅条纹间接测量干涉条纹相位变化,给出了双光电探测器的最佳探测位置。结合分光及相位调整功能,给出了分束光栅参数的设计方法。针对光栅曝光特点设计了控制器。从理论上对比了分束光栅与压电反射镜的相位调整性能。实验结果表明,采样频率为500Hz时,干涉条纹的低频漂移得到有效抑制,相位锁定精度达到0.13rad(3σ),即条纹漂移量低于±0.021个周期。该方法可以实时有效地锁定曝光干涉条纹,提高曝光对比度。且分束光栅偏转对条纹周期影响小,相位调整性能仅与分束光栅参数相关,便于光路设计。

In order to increase the exposure contrast of the holographic grating exposure system, and depress the exposure interference fringe drifts caused by the environmental changes, a method of interference fringe locking by grating-shifting is proposed. The beam splitter grating is used to split the beam from laser source and adjust the phase of the interference fringe. The phase changes of the interference fringe are measured indirectly by Moire fringe. The best detection locations of the two photoelectric detectors are given. The parameters design method of the beam splitter grating is presented by combining the function of splitting beam and regulating phase. The controller is designed aiming at the characteristic of the grating exposure. The phase-regulating performances of the beam splitter grating and the piezomirror are contrasted theoretically. The experiment results illustrate that the low-frequency drifts of the interference fringe are depressed at a sample frequency of 500 Hz. The value of the phase locking is below 0.13 rad （3σ）, namely the fringe drift is below ±0.021 period. The exposure interference fringe can be timely and effectively locked by this method, and the exposure contrast is improved. The tilt of the beam splitter grating has little effect on fringe＇s period. Besides, the phase regulating performance is only relevant to the parameters of the beam splitter grating, which is convenient to the design of the optical layout.