基于大口径、短焦距Fresnel透镜作为水下无线光传输(UWOT)系统中天线的应用需求,搭建了一套用于测量Fresnel透镜聚光性能的实验装置。采用450 nm和532 nm激光作为测试光源,获得了通光口径为75 mm、焦距为25 mm的Fresnel透镜聚光性能与透镜表面、激光波长、入射角之间的关系曲线,测量了激光入射角对450 nm和532 nm激光聚焦光斑的影响。实验结果表明:在相同的实验条件下,激光通过Fresnel透镜锯齿面的聚光效率要比平滑面高10%~15%;Fresnel透镜对532 nm激光的聚光效率要比450 nm激光高5.4%。随着激光入射角的增加,Fresnel透镜的聚光效率逐渐降低,入射角为0°时的聚光效率比±30°大25%以上。当激光入射角为5°时,450 nm激光聚焦光斑开始发生彗差畸变;当激光入射角增加至15°时,532 nm激光聚焦光斑开始发生彗差畸变。

Based on the application requirements of large aperture and short focal length Fresnel lens as an antenna in the underwater wireless optical transmission system, an experimental device was built to measure the focusing performance of Fresnel lens. The 450 nm and 532 nm lasers were adopted as the test light sources, and the relationship curves between the focusing performance of Fresnel lens with an aperture of 75 mm and a focal length of 25 mm and the lens surface, laser wavelength and incident angle were obtained. The influence of incident angle of laser on the focusing spots of the 450 nm and 532 nm lasers was measured. The experimental data results show that, under the same experimental conditions, the focusing efficiency for laser passing through the serrated surface of Fresnel lens is 10%~15% higher than that through the smooth surface. In addition, the focusing efficiency of Fresnel lens for 532 nm laser is about 5.4% higher than that of 450 nm laser. With the increase of incident angle, the focusing efficiency of Fresnel lens decreases gradually, and the focusing efficiency at a 0° incident angle is 25% higher than that at ±30°. Furthermore, when the incident angle of laser is 5°, the comet aberration occurs at the focusing spot of the 450 nm laser, and when the incident angle of laser increases to 15°, the comet aberration also occurs at the focusing spot of the 532 nm laser.