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多波段激光发射方向直接监测与校正方法研究

Research on Direct Monitor and Correction Methods for Emitted Direction of Multi-wavelength Laser Beam

【作者】 周子云

【导师】 高云国;

【作者基本信息】 中国科学院研究生院(长春光学精密机械与物理研究所) , 机械制造及其自动化, 2014, 博士

【摘要】 目前国内外广泛应用的大型激光发射系统具有结构响应速度快,瞄准精确,抗干扰能力强等特点,且正朝着高能量、多波段的方向发展。由于外界环境和内部构造等诸多原因,激光发射系统所发出的光束与预定方向相比会有一定偏差,为了保证激光发射系统的准直精度,需要对激光光束方向进行监测,并对其产生的指向误差进行校正。在系统方案设计方面,运用齐次坐标变换,分析了光束从激光器出光口到进入监测系统前这一段传播光路中可能引入的误差,并建立了相应的数学模型和灵敏度矩阵,为进行光束方向的监测与校正提供了理论依据;对比以往对光束方向间接监测方法的不足,提出了新的直接监测方案。在光束方向监测方面,基于所提直接监测方案,提出了一种分时监测的研究方法,拟通过同一监测机构,实现对中、长波激光束发射方向的直接监测。针对四象限探测器对光斑的采集要求,设计了一组光学镜头,保证长波、中波两种波段的红外激光束经过透镜组后,均能以合适的尺寸和位置成像在探测器靶面上;提出了一种基于椭圆模型的光斑中心定位算法,并采用正交微动算法获得椭圆光斑的长短轴参数。在光束校正方面,设计了一种新型快速反射镜结构,应用于校正系统中。在现有结构的基础上,首次将柔性铰链应用于两轴系快速反射镜中,采用序列二次规划法对铰链的关键尺寸进行优化,并对系统的运动传递精度进行了理论计算及仿真分析。分别以长波监测校正光路和中波监测校正光路为研究对象,建立了四象限探测器接收光斑中心位置与快速反射镜旋转角度之间的对应关系,为光束监测校正系统的闭环调节提供了理论依据。通过监测系统的指向精度实验,验证了光束监测精度可达2″;快速反射镜性能实验验证了校正系统对发射光束方向的控制精度能达到0.95″,计算出了快速反射镜的闭环传递函数,通过实验验证了系统的一阶谐振频率在工作频率之外。以长波激光器光束方向监测与校正系统为例进行实验,实验结果表明了所设计的光束方向监测校正系统对激光光束方向漂移的监测与校正精度可达2″。综合各项实验结果,证明了所提出的将光束方向监测与快速反射镜相结合的监测校正系统,能够对激光发射方向实现快速检测和调整,设计方案可行,校正精度可靠。

【Abstract】 State-of-the-art laser transmitter systems at home and abroad arecharacterized by fast structural response, accurate pointing, and strong resistanceand so on, further presently developing in the direction of high-energy andmulti-band. Compared with the predictable directions, the lasers emitted from thelaser transmitter systems have some certain deviations due to many factors likeexternal environments and internal structures for example. For the sureness ofalignment accuracy of laser transmitter systems the directions of laser beams arenecessary to be monitored and then the generated pointing errors are necessary tobe corrected.In the design of system scheme, the errors of which laser beams travels fromthe light outlet of lasers through before the monitor system are to be analyzed byemploying the homogeneous coordinate transformations. Furthermore, themathematical model and sensitivity matrix both established provide theories forconducting the monitor and correction of beam directions. In comparison of theshortcomings in previously indirect monitor approaches, a novel scheme of directmonitor is proposed and the research plan is designed.In the monitor of laser beams, the time division monitor, a scheme of directmonitor, is designed to realize the direct monitor of emitted directions of long andmiddle laser beam waves by the same monitor system. A set of optical lenses is devised, according to the collection requirements the four quadrant detector putson light spots, to make sure to image on the target surface in suitable dimensionsand positions after two sorts of infrared laser beams travel from the lenses. Also,based on ellipse light spot model a spot center positing algorithm is proposed. Thelong and short axes parameters of ellipse spots are obtained through employingthe orthogonal tiny motion algorithm.In the correction of laser beams, a new kind of fast steering mirror isdesigned to apply into the correction system. Upon the present structures it is thefirst time to use flexible hinges in two-axis fast steering mirror. After adopting thesequence of two quadratic programming methods, critical dimensions of hingesare optimized. Then, theoretical calculations and simulation analyses are carriedout in the transmission accuracy of system motions.With researching respectively on the monitor and correction of long andmiddle wavelength paths, the relations established between the center positions ofspots received by the four quadrant detector and the rotating angles of fast steeringmirror provide theoretical guidance for the closed-loop control of monitor andcorrection systems of laser beams.Through the pointing accuracy experiment in monitor system, the accuracy ofmonitoring laser beams is testified as2’’. And then, the feature experiment of faststeering mirror verifies the accuracy in which the correction system controls thedirections of emitted laser beams as0.95’’. The research work also gives theclosed-loop transfer function of fast steering mirror, making sure that the firstnatural frequency of system is out of the working frequency by experiment. Takethe experiment of the monitor and correction system of long wavelength laserbeam directions as the example, the experimental results show that the designedsystem can monitor and correct the accuracy of direction shift of laser beams to2’’.The synthesis of every experimental result validates the monitor and correctionsystems in which it combines the monitor of laser beam directions and the faststeering mirror is capable of achieving fast detections and adjustments of laser beam directions in the multi-band laser transmitter system. Finally the designedscheme is feasible and the correction accuracy is reliable.

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