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摘要: 在确保固态面阵激光雷达安全性的前提下,为了提高光学系统的像面能量均匀度以及增加光学系统所接收到的能量,保证在探测过程中的低信噪比以及对目标的可探测性,本文通过对发射激光能量和接收能量进行建模,给出了光学参数,研究了影响接收光学系统像面照度的因素。指出大视场大相对孔径高照度均匀性光学系统的设计要素,并通过ZEMAX优化分析给出了具体的实施过程。最终设计了λ=905(±5)nm,焦距为15 mm,相对孔径为1/1.4,视场角为2ω=76°的激光雷达接收镜头,系统总长小于77 mm,在空间频率为20 lp/mm处MTF值大于0.5,在0.85视场内的相对畸变小于8%,像面照度不均匀性小于7.2%。满足激光雷达的探测要求。Abstract: With regards to the safety of solid-state area array lidars, in order to improve the energy uniformity of imaging plane and increase the energy received by the optical system, this paper works to ensure a low signal-to-noise ratio and the detectability of a target. The optical parameters are given by modeling the emitted and received laser energy. The factors affecting the image plane's illumination in the optical receiver are studied and the design elements of optical systems with large fields of view, large relative aperture, and high illumination uniformity are described. Through ZEMAX optimization analysis, a detailed implementation process is then provided. A lidar receiving lens with λ = 905 (±5) nm, a focal length of 15 mm, a relative aperture of 1/1.4, and a field of view 2ω = 76° was designed. The total system length was less than 77 mm, and the MTF value at the spatial frequency of 20 lp/mm was greater than 0.5. The relative distortion at the 0.85 field of view was less than 8% and the unevenness of the image plane illumination was less than 7.2%.This design meets the requirements for lidar detection.
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表 1 概率密度函数参数
Table 1. Parameters of probability density function
参数 ax bx cx ay1 ay2 数值 5.58 0.820 7 16.91 9.508 −0.562 参数 ay3 ay4 by1 by2 cy 数值 0.144 5 0.237 8 −0.181 6 −2.311 3.626 表 2 积分时间为1.2×10−6 s单像元接收光能量的光电转换值
Table 2. Photoelectric conversion value of single pixel receiving light energy when integration time is 1.2×10−6 s
项目 光子数 电子数 电压 / V 中心 3.024×103 604.796 8 6.451×10−4 快轴边缘 26.157 0 5.231 4 5.580×10−6 慢轴边缘 26.157 0 4.761 1 5.078×10−6 表 3 积分时间为2×10−2 s单像元接收光能量的光电转换值
Table 3. Photoelectric conversion value of single pixel receiving light energy when integration time is 2×10−2 s
项目 光子数 电子数 电压 / V 中心 5.040×107 1.008×107 2×10−2 快轴边缘 4.359 5×105 8.719 0×104 10.751 9 慢轴边缘 3.967 6×105 7.935 2×104 0.093 0 表 4 光学参数表
Table 4. Optical parameter table
Items Requirement Field of view(FOV)/(°) 76 Relative aperture 1/1.4 Focal length/mm 15 Spectral range/μm 0.895~0.910 Relative distortion @ 0.8 FOV <10% Llumination uniformity <10% Dispersion spot radius/μm 20 MTF@20 lp/mm >0.5 表 5 光学结构参数
Table 5. Parameters of optical structure
Surface Radius/mm Thickness/mm Glass Conic 1OBJECT 37.384 2 H-ZLAF53B 0 2 15.434 8 0 3 36.146 3 EP8000 −3.241 4 17.647 15 −0.111 5 32.146 6 H-QF3 0 6 −45.553 1 0 7STOP Infinity 8.394 0 8 −58.153 3 H-ZLAF92 0 9 −124.417 0.957 0 10 95.702 4.927 H-ZLAF90 0 11 −53.595 0.723 0 12 2 848.534 4 EP8000 39.972 13 −67.378 28.409 9.173 14IMACE Infinity 表 6 非球面高次项数据表
Table 6. High-order data of aspheric mirror
Surface 2nd 4th 6th 8th 12 0 −1.573×10−5 2.001×10−8 −9.333×10−10 13 0 1.065×10−5 −7.026×10−8 3.473×10−10 Surface 10th 12th 14th 16th 12 4.642×10−12 −1.225×10−14 −1.047×10−17 9.050×10−20 13 −2.131×10−12 −1.311×10−14 3.658×10−17 −6.123×10−20 表 7 公差参数表
Table 7. Tolerance parameters
Items Value Fringe power/λ 3~5 Surface irregular/λ 0.2~0.3 Thickness/mm 0.05~0.08 Airspace/mm 0.01~0.02 Tilt/(') 0.5~0.9 Decenter&Roll/mm 0.05~0.07 Refractive index 0.000 5~0.000 7 Abbe number 0.005~0.007 -
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