近红外车载激光雷达高耐磨双层减反膜

High wear resistant double-layer antireflection coatings for near-infrared vehicular lidar

  • 摘要: 工作波长为905 nm的激光雷达在汽车自动驾驶领域具有强大的应用前景,但工业常用的磁控溅射减反膜,作为其光学窗口表面涂层之一,存在耐磨性不足问题,难以适应恶劣户外环境。采用溶胶凝胶法结合高温固化工艺,为工作波长为905 nm的车载激光雷达减反膜提供高耐磨、低成本的解决方案,并研究了固化温度、盐酸浓度、络合剂存在且低酸浓度下的含水量对TiO2折射率的影响。从反射率、粗糙度、硬度、耐磨性等方面对采用不同底层固化方式的双层减反膜的光学性能和机械性能进行评估,结果表明:当入射光波长为905 nm时,薄膜表现出优良的减反性能,入射角为15°时反射率小于1%,入射角为60°时反射率小于5%,粗糙度最低为0.005 μm,基本满足水平视角120°的激光雷达的光学需求。薄膜铅笔硬度达8H,最多能够承受8000次往复摩擦且无明显损伤,具有优良的适应恶劣环境的能力。

     

    Abstract: The lidar operates at 905 nm is considered to have essential application values in automotive autonomous driving. The antireflection coatings made by magnetron sputtering commonly used in industry have the problem of insufficient wear resistance, which is difficult to adapt to the harsh outdoor environment. The sol-gel method combined with high-temperature curing process was used to provide a solution of high wear resistance and low cost for antireflection coatings applied to vehicular lidar which operated at 905 nm, and the influences of curing temperature, concentration of hydrochloric acid (HCl), water content in weak acid environment on refractive index of TiO2 were studied. The optical and mechanical properties of the coatings with different underlying curing methods were evaluated from the reflectivity, roughness, hardness and wear resistance. The results show that the coatings have excellent anti-reflection performance at the wavelength of 905 nm, the reflectivity is less than 1% when the incident angle is 15° and less than 5% when the incident angle is 60°, and the minimum roughness is 0.005 μm, which generally meets the optical requirements of the lidar with a horizontal angle of 120°. The coatings show the excellent capability of enduring harsh environments, with pencil hardness of 8H and withstanding 8 000 times of reciprocating friction without perceptible damages.

     

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