基于多步相位恢复的激光远场焦斑测量方法  

Laser Far-Field Focal Spot Measurement Method Based on Multistep Phase Retrieval

作　　者：陈晓义 段亚轩[1] 王拯洲[1] 袁索超 达争尚[1] Chen Xiaoyi;Duan Yaxuan;Wang Zhengzhou;Yuan Suochao;Da Zhengshang(Advanced Optical Instrument Research Department,Xi'an Institute of Opticsand Precision Mechanics,Chinese Academy of Sciences,Xi'an,Shaanxi 710119,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院西安光学精密机械研究所先进光学仪器研究室,陕西西安710119 [2]中国科学院大学,北京100049

出　　处：《中国激光》2022年第7期43-53,共11页Chinese Journal of Lasers

基　　金：国家自然科学基金(61705254);陕西省重点研发计划项目(2020GY-114)。

摘　　要：为了实现激光远场焦斑的高精度测量,提出一种基于多步相位恢复的激光远场焦斑测量方法。理论推导了基于多步相位恢复的激光远场焦斑重构模型,其中为了解决焦斑计算中出现的欠采样问题,引入了线性调频z变换(CZT)技术,相较于传统的快速傅里叶变换(FFT)补零计算,此方法避免了计算冗余。同时,提出一种基于多步相位恢复的激光远场焦斑重构算法,并仿真分析了扫描步长和探测位置数对所提方法收敛性的影响,确定了最佳扫描步长和探测位置数。为了验证所提方法的有效性,搭建了基于纯相位型液晶空间光调制器(SLM)的实验验证装置,实验结果和理论值的相关系数为0.9976。同时,所提方法与传统长焦距透镜成像法相比,测量精度更高,可为激光远场焦斑高精度测量提供一种技术手段。Objective The intensity distribution of the laser far-field focal spot is an essential index for measuring the quality oflaser beams.It is also the main parameter that reflects the laser beam’s ability to enter the hole in the inertialconfinement fusion system.How to measure the intensity distribution of the laser far-field focal spot with highprecision determines the evaluation result of the overall performance of the laser system.It is of great guidingsignificance in the theoretical design stage,development stage,or final stage of practical operation of the laserdevice.Direct measurement methods of far-field focal spots include the long-focal-length imaging,array camera,andschlieren methods.The long-focal-length lens imaging method is limited by the linear response range of the detector.The array camera method uses a wedge,which introduces additional optical path difference and wave aberration.Theschlieren method measures the main lobe and side lobe of the focal spot separately,which is easily affected by themeasured environment and noise.The Shack-Hartmann wavefront measurement is an indirect measurement methodand causes the loss of middle and high frequency information due to its frequency response characteristics.Toachieve a high-precision measurement of far-field focal spot,this paper proposes a method based on multistep phaseretrieval for measuring far-field focal spots.Theoretically,a focal spot reconstruction model based on multistepphase retrieval is derived.Then,the chirp-z transform(CZT)is introduced to solve the problem of under-samplingin calculating focal spots.Compared with the traditional fast Fourier transform(FFT)with zero-padding,using CZTto calculate the focal spot avoids calculation redundancy.The proposed method has a higher measurement accuracy ofa focal spot than the traditional long-focal-length lens imaging method.Methods The proposed laser far-field focal spot measurement method based on multistep phase retrieval can be divided into two parts.First,the multistep phase retrieval metho

关 键 词：测量 激光 远场焦斑 相位恢复 线性调频Z变换 

分 类 号：O436[机械工程—光学工程]