Li Jiarui, Wei Haoyun, Li Yan
Appl Opt. 2019 Sep 20;58(27):7636-7642. doi: 10.1364/AO.58.007636.
One of the greatest challenges of long distance measurement is the beam drift caused by the air refractive index gradient. It has been established in many researches that optical phase conjugation (OPC) can be used to compensate for the beam bending. However, this method is limited to responding speed, phase conjugate reflectivity, flexibility, and specific source and medium. To reduce beam drift, instead of OPC, this study applies a digital OPC (DOPC) method, which is also creatively applied to collimation and flatness measurements. The main devices in the wavefront correction unit are the spatial light modulator and the Shack-Hartmann wavefront sensor. For the straightness measurement unit, the collimation and flatness of the optical rail are measured through the prism system and a position-sensing detector. After wavefront compensation, the root mean square is decreased from 0.0029λ to 0.0005λ. The beam drift is decreased from 1.22 mm to 0.70 mm in the x direction and from 2.49 mm to 1.55 mm in the y direction. The experimental data indicate that the straightness measurement system based on DOPC can effectively decrease the beam drift.
长距离测量面临的最大挑战之一是由空气折射率梯度引起的光束漂移。许多研究已经证实，光学相位共轭（OPC）可用于补偿光束弯曲。然而，该方法在响应速度、相位共轭反射率、灵活性以及特定光源和介质方面存在局限性。为了减少光束漂移，本研究采用了数字光学相位共轭（DOPC）方法，而非光学相位共轭方法，并且该方法还创造性地应用于准直度和平整度测量。波前校正单元中的主要器件是空间光调制器和夏克-哈特曼波前传感器。对于直线度测量单元，通过棱镜系统和位置敏感探测器来测量光轨的准直度和平整度。经过波前补偿后，均方根从0.0029λ降至0.0005λ。在x方向上，光束漂移从1.22毫米降至0.70毫米；在y方向上，从2.49毫米降至1.55毫米。实验数据表明，基于数字光学相位共轭的直线度测量系统能够有效降低光束漂移。
