激光无线能量传输发射光学系统研制

Development of emission optical system for laser wireless power transmission

为了提升激光无线能量传输系统光能传输效率,避免使用准直镜头导致在数百米距离处接收端光斑边界模糊和照度均匀性差现象的发生,开展了基于共轭成像原理的可调焦发射光学系统研制。首先理论分析了准直法和共轭成像法的设计原理,然后针对光纤输出的808 nm半导体激光光源,采用共轭成像法设计了焦距550 mm、口径260 mm的发射光学系统,通过光纤端面的移动实现调焦设计,分析了不同调焦距离下光纤端面的移动量,并与准直法设计结果调焦后对比,在200 m~1 km处的波像差明显较小。利用Lighttools软件模拟对比了调焦前后的照射光斑,验证了调焦的作用。模拟结果显示,通过对基于共轭成像原理设计的发射光学系统增加调焦机构,可在不同距离处得到清晰的光斑边界。最后对激光发射光学系统进行了加工,经测试,波像差RMS为0.092λ(λ=632.8 nm)。结果表明:激光无线能量传输系统使用基于共轭成像原理设计的可调焦发射光学系统可获得边界清晰、更加均匀的照明光斑。

Objective The emission lens of the laser wireless power transmission system is mostly a collimated lens,which is designed using the optical fiber collimation principle and the non-focus mode of the optical design software.The end face of the optical fiber is placed at the focal plane of the lens,and the beam on and off the axis is emitted externally in the form of parallel beam.Because the end face of the optical fiber has a object height,there is a geometric divergence angle between the on-axis beam and the off-axis beam.For the collimated lens with the image plane at infinity,the off-axis beam and the on-axis beam present a staggered superposition state on the illuminated surface at a relatively close distance.Even if the illuminance distribution of the rectangular fiber core is uniform,the light spot on the receiving surface of the power transmission still presents a Gaussian distribution that gradually weakens from the center to the periphery,and the light spot boundary is not clear,which reduces the power transmission efficiency of the laser wireless power transmission system.In order to improve the optical power transmission efficiency of the laser wireless power transmission system and avoid the blurring of the light spot boundary and the poor illumination uniformity at the receiving surface at a distance of hundreds of meters caused by the use of a collimated lens,the development of a focusing transmission optical system based on the conjugate imaging principle was carried out.Methods Firstly,the design principles of collimation method and conjugate imaging method are analyzed theoretically.Then,aiming at the 808 nm semiconductor laser light source output by optical fiber,a transmitting optical system with a focal length of 550 mm and an aperture of 260 mm is designed using conjugate imaging method(Fig.2).Focusing design is realized through the movement of optical fiber end face.The movement of optical fiber end face under different focusing distances is analyzed(Fig.4).Compared with the design results of collimation method after focusing,the wave aberration at 200 m-1 km is smaller(Fig.5).Lighttools software is used to simulate and compare the illumination spot before and after focusing.Results and Discussions The simulation results show that by adding a focusing mechanism to the transmission optical system designed based on the conjugate imaging principle,clear light spot boundaries can be obtained at different distances(Fig.6).The structure of the laser emission optical system is designed.The focusing structure rotates 360°and the end face of the optical fiber moves 2 mm,which meets the requirement of 1.19 mm of total end face movement of the optical fiber in the range of 200 m-1 km.The laser emission optical system is processed.The test optical path is built with ZYGO interferometer,standard lens and plane reflector.The wave aberration RMS of the laser emission optical system when focusing to infinity is 0.092λ(λ=632.8 nm)(Fig.9).The results show that the laser wireless power transmission system can obtain a clearer and more uniform illumination spot by using the focusing emission optical system designed based on the conjugate imaging principle.Conclusions A focusing laser emission optical system is developed,which can be used for laser wireless power transmission at different distances.Through theoretical analysis of the collimation method and the conjugate imaging principle,the design method of the laser emission lens is determined in the case of non-infinite distance.The optical system design is carried out.The relationship between the focusing movement and the energy transfer distance is analyzed.The changes of the light spot before and after focusing at different distances are simulated and compared.Finally,the equipment development is completed,and the optical performance test is carried out to meet the design requirements.