In turbid water, target reflected lidar signal is easily buried in “clutter” due to scattering. We proposed an underwater laser ranging model applying an optical vortex in the receiver to separate the scattering clutter from the target reflected signal. A spiral phase plate (SPP) was placed in front of the detector to convert the target reflected Gaussian beam to an optical vortex. While the scattering clutters were not able to be converted due to the loss of spatial coherence. Therefore, the target reflected signal and scattering clutters were spatially separated by the SPP. An underwater laser detection simulation using Zemax software was carried out. The numerical simulation showed that when the SPP was placed in front of the receiver, the contrast of signal to clutter of the detection was improved by blocking the scattering clutters which had a Gaussian distribution at the center on the detection plane. The effects of beam divergence and orbital angular momentum (OAM) order to the lidar performance were also analyzed.

中文翻译：

---

使用螺旋相位板作为空间滤波器提高水下激光雷达性能的数值模拟

在混浊的水中，目标反射的激光雷达信号很容易由于散射而被掩埋在“杂波”中。我们提出了一种水下激光测距模型，在接收器中应用光学涡流将散射杂波与目标反射信号分开。一个螺旋相位板（SPP）被放置在探测器的前面，以将目标反射的高斯光束转换为光学涡流。而散射杂波由于空间相干性的损失而无法转换。因此，目标反射信号和散射杂波被 SPP 在空间上分开。使用 Zemax 软件进行水下激光探测模拟。数值模拟表明，当 SPP 置于接收机前方时，通过遮挡检测平面中心呈高斯分布的散射杂波，提高了检测信号与杂波的对比度。还分析了光束发散角和轨道角动量 (OAM) 阶数对激光雷达性能的影响。