High-precision beam array scanning system based on Liquid Crystal Optical Phased Array and its zero-order leakage elimination
High-precision beam array scanning system based on Liquid Crystal Optical Phased Array and its zero-order leakage elimination
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DOI：
10.1016/j.optcom.2021.127610
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发表时间：
2021-11
影响因子：
2.4
通讯作者：
Chengmiao Wang;Qi-dong Wang;Q. Mu;Zeng-hui Peng
中科院分区：
文献类型：
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作者：
Chengmiao Wang;Qi-dong Wang;Q. Mu;Zeng-hui Peng
为了提高激光雷达的扫描效率，建立了一套40× 40子光束的高精度扫描系统，利用液晶光学相控阵加载Gerchberg-Saxton（GS）算法计算的相位，对入射平面波进行分裂。从技术上讲，GS算法的不完善往往会导致旁瓣和输出光斑强度不均匀等问题，最终导致子光束指向精度差，激光雷达扫描分辨率低。为了解决这些问题，本文提出了一种光学方法，而不是经典的算法优化方法，该方法将预设的子光束限制在衍射极限内，以统一实际的子光斑形态，并确保高的指向精度。这样，指向误差的标准偏差最终从42 μ rad减小到16 μ rad。在消除零级泄漏方面，在产生的光束阵列的空间光谱跨度超过截止频率的情况下，传统的倾斜方法无法分离零级光泄漏。针对这一问题，提出了一种新的零级泄漏消除方法，通过在截止频率两侧拼接两个相邻衍射级的半光束阵列来消除零级泄漏。同时，在不破坏光束阵列光强均匀性的前提下，对光束进行强度校正，以避免泄漏。
In order to improve the scanning efficiency of lidar, a set of high precision scanning system with 40× 40 sub-beams is established, in which a liquid crystal optical phased array is used to load the phase calculated by Gerchberg–Saxton (GS) algorithm to split the incident plane wave. Technically, the imperfections of GS algorithm often lead to problems such as sidelobes and uneven intensity of output spots, which eventually result in poor pointing accuracy of sub-beams and low scanning resolution of lidar. To solve those problems, we propose an optical method rather than the classical algorithm optimization methods, which restricts the preset sub-beams to the diffraction limit to unify the actual sub-spot morphology and ensure high pointing accuracy. In this way, the standard deviation of pointing error eventually decreases from 42 μ rad to 16 μ rad. In the aspect of eliminating zero-order leakage, the zero-order light leakage cannot be separated by the conventional tilt method in the case that the spatial spectrum span of the generated beam array exceeds the cut-off frequency. Concerning this issue, a novel zero-order leakage elimination method is proposed to avoid zero-order leakage by splicing two half beam array of adjacent diffraction orders on both sides of the cut-off frequency. Meanwhile, the intensity correction is carried out to achieve leakage avoidance without damaging the intensity uniformity of the beam array.