Real-time adjustment of optical transmitter by laser beam parameter measurement based on two linear array CCD scanning imaging

In this paper, we present a real-time measurement and adjustment method, based on scanning imaging, for optical transmitter which emits 90° × 2° linear laser beam. This novel optical arrangement consists of an area array CCD and two linear array CCDs. According to the relationship between the positions, angles of transmitter optical components and the beam parameters of emergent laser, the system can help us to decide the real-time adjustment of optical transmitter by measuring the related beam parameters. In order to improve the measurement speed, avoid occlusion and ensure simultaneous measurement, the two linear array CCDs are placed at near field, far field and separated by a definite angle to acquire the beam intensity distribution through suitable nonlinear correction during the process of scanning. After a complete scanning, the beam parameters and the spot image are acquired by continuous measurement. The proof-of-principle experiments showed that the measurement results were in agreement with the analysis. The presented method was applied to direct fast adjustment for higher quality on the assembly of the optical transmitter. The presented procedure is highly advantageous for diverse laser beam emitted from the optical transmitter, such as elliptic, linear and so on.     

一种大功率宽波段激光束散角的校准测试方法

在大功率激光系统的评价与分析中,激光器的光束品质是系统光束品质的决定性因素,也是激光器验收、鉴定的重要指标,其中束散角是判别激光光束质量的重要参数。本系统测试激光波长的范围比较宽,一般在0.532μm～10.6μm之间,没有合适的探测器能够覆盖整个波段,所以采用了一种新的方法来解决宽波段束散角的测量问题。选用CCD成像和扫描狭缝相结合的方法来实现宽波段激光光束束散角的测量,可见光和近红外波段（0.532μm～1.2μm）激光光束采用CCD法测量激光束散角,中红外波段（1.2μm～10.6μm）激光光束采用扫描狭缝法测量激光束散角。两种方法的结合可以较为精确地测量出不同波段的激光束散角。     

A novel laser straightness measurement method with beam bend compensation

In this paper, a novel method to measure straightness errors with beam bend compensation based on Finite Element thermal analysis is proposed. According to the Edlen formula, the main factor that causes beam bend is thermal gradation in the air. Finite Element thermal analysis is applied to the thermal field around the beam. It is evident from the experimental results that high precision straightness errors in horizontal and vertical directions can be obtained after compensation. Hence, the feasibility of straightness errors measuring system with compensation for beam bend measurement is proved.     

基于线阵CCD的光学测角嵌入式系统设计

CCD作为一种光电转换器件,具有成本低、结构简单、扫描速度快、频率响应高等优点,越来越广泛地运用到测量领域。提出采用单色线阵CCD,以非接触的光学方式对角度信息进行编码调试,通过采集该信号利用数据处理模块,完成对图像信号的解调,实现角度值的测量。系统选用TSL1401和LPC2138为核心构成嵌入式测量系统,利用TSL1401采集信号,通过A/D传输到LPC2138中进行数据处理,最终得到角度值。系统通过光学的方式对角度进行测量,实现了非接触式测量。     

用于微位移测量的笔束激光干涉仪

介绍了一种基于空间干涉原理的亚微米零差干涉位移测量方法。该方法是对笔束激光干涉仪在微位移测量领域的应用 ,干涉仪的测量精度不受光束波前畸变等光源噪声的影响。给出了干涉仪主要结构参数的选取原则 ;构建了用于微位移测量的笔束激光干涉仪实验系统。实验结果表明 ,该系统具有纳米测量分辨率。     

Differential confocal measurement method of linear scanning based on dual linear array camera北大核心CSCD

针对目前微观三维表面形貌测量技术中存在检测效率和测量范围较小的问题,提出一种基于双线阵相机的线扫描差动共聚焦三维形貌测量方法。采用线扫描光源,利用线扫描拼接算法,分别合成焦前和焦后图像;再利用差动算法获得样本位于测量区域的差动图像,结合预先刻度的轴向响应曲线,完成样本的三维形貌还原,实现大范围高效测量。实验结果证明:基于双线阵相机的线扫描差动共聚焦三维形貌测量方法在相同时间内测量范围和测量效率分别是白光干涉仪的16.48倍和6.59倍,并且该方法在测量过程中不需要停顿,只需实现一次对焦,就可以对样品进行连续不间断的扫描检测。研究成果为满足智能制造中在线在位、实时高效、大范围测量的检测需求提供依据。     

基于Isight的激光束散角快速计算法

在完成激光扩束设计后,为了保证投射全程的光斑尺寸要求,需要输出几百甚至上千组镜组位移-束散角的对应数据。基于Isight的实验设计模块,利用code V的命令语句进行快速计算,在不到2 h的时间里得出了想要的众多数据,较大地提高了效率,并且由于位移数据都是由软件进行修改,避免了人工操作可能产生的错误。     

基于LabVIEW的激光发散角测试软件开发

根据可变光阑法测量发散角的原理,利用具有强大数值计算与串口通信能力的LabVIEW语言搭建发散角测试软件平台.平台测试结果表明,测试软件具有较好的显示功能与可操作性,同时具有参数设置灵活、可二次开发等优点.在总程序设计的基础上,分别介绍了数据采集、数据处理及数据存储的三个程序模块,最后提出用LabVIEW的循环、嵌套等...     

利用狭缝扫描法测量超声波扩散角

利用狭缝扫描获得超声波束横截面上强度积分分布曲线,利用此积分曲线对应的微分曲线的半峰全宽计算得到超声波扩散角。此方法克服了小孔测量扩散角方法中信号微弱的弊端,提高了超声波扩散角测量精度。     

基于双CCD的滚转角测量方法研究

提出了一种基于双CCD的滚转角测量方法。测量系统包括两部分:移动部分由通过连接杆连接的两个CCD组成,连接杆固接在被测物上;固定部分包括光源、光开关和两个光学准直器,可以得到两路分别以一定角度相交入射到两个CCD上的准直光束。被测物发生滚转变化时,两CCD也同步变化,通过投射在其上的两个光斑位置变化,可求解出滚转角变化。MATLAB仿真证明被测物的各平动变化对滚转角测量无影响,在200″范围内的俯仰和偏摆变化,引起的滚转角测量误差不超过1″。搭建了滚转角测量实验系统,并与HP5529A双频激光干涉仪测量结果进行比对。测量结果表明,在1000″的测量范围内,系统滚转角测量偏差最大不超过1.5″。     

基于激光光斑分时方法的弹目测角途径设计

提出了一种利用光电方法解决多发导弹测角的技术途径。示踪器向地面发射的脉冲光被跟踪目标的摄像机接收,解算出光斑和目标的偏角,形成制导修正依据;借助时序控制,使示踪器发光与相机曝光同步;设置各枚示踪器发光顺序,使摄像机每个曝光期内,只有目标或指定的导弹光斑进入,通过对像机视频图片的编组,可形成各枚导弹与目标的序列图片,实现各枚导弹独立制导。通过试验,在PM2.5指数为120的情况下,传输距离达到9 000 m,并实现100 Hz双光源切换,编码精度达到1 μs。该模式可满足探测距离和导弹区分。     

基于光斑二阶矩的阵列光束倾斜相差自适应控制方法

针对阵列光束相干合成中存在的倾斜相差大的问题,提出了基于合成光束远场光斑二阶矩的阵列光束倾斜相差自适应控制方法。以合成光束远场光斑二阶矩作为评价函数,理论上模拟了采用随机并行梯度下降算法实现7路光束的倾斜闭环控制过程。实验上搭建了7路光纤激光相干合成系统,利用自适应光纤准直器对倾斜相差进行校正。以合成光束远场光斑的二阶矩作为评价函数,采用随机并行梯度下降算法,实现了7路光束的倾斜的闭环控制,合成光束模拟远场光斑的桶中功率由0.05 V提升至1.95 V。实验中将倾斜扰动的增益系数变为与二阶矩相关的函数,实现了自适应变增益系数的倾斜闭环,在一定程度上提升了倾斜控制的带宽。从理论上和实验上验证了基于光斑二阶矩的倾斜相差自适应控制方法在光束合成及合成孔径探测领域应用的可行性。     

星地激光链路中光束发散角与跟瞄误差的最佳比值

 实际星地光通信系统的发射光束为高斯型的情况下,跟瞄误差和大气闪烁是星地激光链路中的主要信道噪声源。在结合两者对系统性能影响的前提下,对星地激光通信链路进行了理论分析和模型建立。基于该模型对星地激光链路中光束发散角与跟瞄误差之比的优化选择问题进行了研究。结果表明：对于上行链路,在不同误码率需求下都存在一个光束发散角与跟瞄误差的最佳比值,使得上行链路余量最大;对于下行链路,在不同误码率要求下均存在一个光束发散角与跟瞄误差的最佳比值,使得下行发射光功率的需求最小。利用最优化方法和最小二乘法拟合,得到星地激光链路中光束发散角与跟瞄误差的最佳比值和系统误码率的经验公式。     

星地激光链路中光束发散角与跟瞄误差的最佳比值

实际星地光通信系统的发射光束为高斯型的情况下,跟瞄误差和大气闪烁是星地激光链路中的主要信道噪声源。在结合两者对系统性能影响的前提下,对星地激光通信链路进行了理论分析和模型建立。基于该模型对星地激光链路中光束发散角与跟瞄误差之比的优化选择问题进行了研究。结果表明：对于上行链路,在不同误码率需求下都存在一个光束发散角与跟瞄误差的最佳比值,使得上行链路余量最大;对于下行链路,在不同误码率要求下均存在一个光束发散角与跟瞄误差的最佳比值,使得下行发射光功率的需求最小。利用最优化方法和最小二乘法拟合,得到星地激光链路中光束发散角与跟瞄误差的最佳比值和系统误码率的经验公式。     

基于透镜阵列的三维姿态角度测量

三维姿态角的精确测量在航空、航天、国防等领域应用广泛,为方便准确地实现三维姿态角的测量,本文设计了一种基于透镜阵列的测量系统,并建立了微小三维姿态角测量分析模型。系统中,准直平行光束通过4个排列成金字塔形的阵列透镜,在CCD上形成规则分布的阵列光斑。通过分析CCD成像光斑间的距离、透镜阵列上相邻孔径之间的距离以及透镜阵列与CCD之间的倾斜角,可以得到光束相对于接收系统俯仰角和偏摆角,利用阵列光斑连线相对水平或垂直面的夹角,可同时得到绕Z轴的滚转角。通过与高精度自准直仪测量结果进行比较,证明所提方法的测量精度可以达到RMS≤0.1″,表明该方法能够实现三维姿态角的测量。     

A novel switchable single polarized Er-doped PMF linear cavity laser based on two PMF gratings

The switchable single polarized Er-doped polarization-maintaining-fiber (PMF) linear cavity laser based on two PMF gratings has been proposed. The gratings are fabricated in Er-doped PMFs, each grating has two single polarized wavelength and they function as the reflective mirror of the laser. So the laser can output switchable single wavelength polarized laser, with the switchable of the wavelength of grating the output of the laser can also be switched. Our experiment result shows that the laser has the OSNR of 48.5 dB, the degree of polarization (DOP) of 98.7%, and the laser linewidth with less than 9.2 pm.     

Dynamic measurement of beam divergence angle of different fields of view of scanning lidar

The laser beam divergence angle is one of the important parameters to evaluate the quality of the laser beam.It can not only accurately indicate the nature of the beam divergence when the laser beam is transmitted over a long distance,but also objectively evaluate the performance of the laser system.At present,lidar has received a lot of attention as a core component of environment awareness technology.Micro-electromechanical system(MEMS)micromirror has become the first choice for three-dimensional imaging lidar because of its small size and fast scanning speed.However,due to the small size of the MEMS micromirror,the lidar scanning system has a small field of view(FOV).In order to achieve a wide range of scanning imaging,collimating optical system and wide-angle optical system are generally added to the system.However,due to the inherent properties of the optical lens,it is impossible to perfect the imaging,so the effects of collimating and expanding the beam will be different at different angles.This article aims to propose a measurement system that dynamically measures the divergence angles of MEMS scanning lidar beams in different fields of view to objectively evaluate the performances of scanning lidar systems.     

Theoretical analysis of some problems in the measurement of beam divergence angle for EAST neutral beam injector

Beam angular divergence is one of the indicators to evaluate the beam quality. Operating parameters of the beam extraction system could be adjusted to gain better beam quality following the measurement results, which will be helpful not only to study the transmission characteristics of the beam and the power distribution on the heat load components, but also to understand the real-time working condition of the ion source and beam extraction system. This study includes: (1) the theoretical analysis of beam extraction pulse duration for measurement of beam angular divergence; (2) the theoretical analysis of beam intensity distribution during beam transmission for Experimental Advanced Superconducting Tokomak (EAST) neutral beam injector. Those theoretical analyses could point the way to the measurement of beam divergence angle for EAST neutral beam injector.

     

基于等离子体紫外辐射的强激光自动寻焦系统

精准定位激光束焦点位置是提高激光雕刻、切割、焊接等加工精度的重要基础,而传统测量方法不适用于自动寻找强激光焦点。基于激光烧蚀金属后等离子发光含大量紫外谱线的原理,以日盲的氮化镓肖特基光电二极管为传感器,设计了以304不锈钢靶材为耗材的红外强激光束自动寻焦方法及其装置。该方法与共聚焦显微镜检测平均烧蚀坑深的方法相比,当以脉冲宽度100 ns、重复工作频率20 kHz、平均功率10 W的1064 nm光纤激光雕刻机为实验对象时,二者定焦位置相差24 μm。     

太赫兹源发散角测量技术研究

发散角是太赫兹源光束特性的重要衡量指标,是太赫兹光学系统设计的重要参数。研究了太赫兹源发散角测量原理,设计了一种由精密弧形导轨、斩波器、狭缝组件、太赫兹高莱探测器、锁相放大器和计算机系统组成的测量装置,设计了一种由自准直仪、光学角规和CCD相机组成的发散角测量装置标定模块,对太赫兹肖特基倍频源和太赫兹雪崩固态源的发散角进行了测量。此外,对测量结果不确定度进行了评定,其不确定度水平达到U_(rel)=3.2%(k=2)。太赫兹源发散角的准确测量为深空探测、战术通信、反隐身、战场隐蔽目标识别等领域提供了有力的支撑。