Generation of control signals for adaptive systems using laser atmospheric backscatter

A method for controlling an adaptive optical system by using the intensity of laser atmospheric backscatter is studied. Mathematical modeling is used to study the generation of a control signal in a monostatic loop and, as a consequence, the range of beam focus with the closed loop. It is shown that this method of generation does not lead to beam collimation even for beams of diffraction quality.     

自适应光学技术在通信波段对大气湍流的校正

针对大气湍流引起的激光光强、相位和传输方向的随机变化对大气激光通信质量的影响,开展了用自适应光学(AO)技术校正大气湍流影响的研究。定量分析了自适应光学技术在通信波段校正大气湍流的效果。利用中国科学院光电技术研究所研制的安装在云南丽江高美谷观测站的1.8m望远镜和127单元AO系统,在1 550nm通信波段对不同高度角的恒星进行了大气湍流校正实验。通过采集校正后的恒星图像,分析了校正后的斯特勒尔比,同时记录下当时的大气相干长度,由此得到了在不同大气湍流条件下的校正效果。实验表明,当大气湍流强度D/r0(1 550nm)小于6.5时,校正后的波面RMS值可以小于1rad,即在中弱大气湍流条件下,该AO系统可以有效地对大气湍流进行校正。     

冻结大气湍流下自适应光学系统的预测校正性能

针对自适应光学系统的校正滞后问题,提出预测校正方法,并对预测校正的鲁棒性进行了分析。冻结湍流假设下,Shack-Hartmann波前传感器的探测斜率一定程度保留了湍流的时域演变模式。利用横向风信息对斜率进行傅里叶平移,能实现斜率的预测。采用直接斜率法计算变形镜面形,能实现预测校正。仿真结果表明,提出的波前预测方法在横向风已知时,几乎能完全克服延迟导致的性能损失;当横向风需要估计时,该方法在风向估计准确的条件下能容忍1倍于自身的风速估计误差,或者在风速估计准确的条件下60°的风向估计误差,均能实现校正性能的提升;在风速和风向误差同时存在时,在较大的误差范围内依然能够提升系统的校正能力。     

微结构光学零件的大气等离子体数控加工

为了实现对微结构光学零件无表面损伤和亚表面损伤的高效加工,建立了大气等离子体数控加工系统.研究了该系统的平台设计、大气等离子体加工工艺特性及其数控加工过程.首先,根据大气等离子体加工的原理及要求介绍了该数控加工系统的组成.然后,以He/SF6/O2加工熔融石英为例,采用针状电极等离子体矩对系统加工工艺的可控性以及多参数工艺特性进行了探索,并根据工艺实验结果拟合出该加工条件下的去除函数.最后,介绍了整个大气等离子体数控加工的实现过程.实验结果表明:利用该系统可以在平面融石英材料上加工出幅值为150 nm、波长为6 mm的正弦网格结构,由此验证了该数控加工系统的可行性,实现了对复杂面型光学零件表面的确定性加工.     

Time-dependent FEM simulation of dilution control of laser cladding by adaptive mesh method

Dilution is an important factor which influences the properties of clad layer. In this paper the change of dilution during laser cladding and the control of dilution are simulated by a finite element method. The adaptive mesh method is adopted for the time-dependent finite element method computation so that the shape of melt pool can be well represented. The situation of the width control of melt pool is also simulated, which indicates that the dilution can be controlled if the width of melt pool is controlled. Computational results indicate that if a line energy (input energy per unit distance) remains constant the dilution will increase with time, especially at the beginning. Simulation results show that it is possible to control dilution in a certain range if the line energy decreases with time. Experiment of Nd: YAG laser cladding with wire feeding is performed. Experiment results coincide well with the FEM results.     

多轴激光加工机器人光路几何误差建模方法研究

本文提出了一种激光光路几何精度建模的方法,用于多轴激光加工机器人光路几何误差的建模。在每个反射镜上定义一个与其固连的笛卡尔坐标系,用齐次列阵表示激光光路特征点(光源、入射点和激光光线末端点)和光线矢量在坐标系中的位置坐标和姿态方位,将激光光束在理想条件下和实际条件下的传输过程用4×4阶齐次方阵运算来实现,在此基础上提出光线几何误差反射传递函数,清楚地反映了各误差源对末端误差的影响情况,从而完整的描述了光束在传输过程中的实际误差。本文以五轴数控激光加工机器人为例,建立其光路传输路径和几何误差模型,试验结果表明了该方法的有效性。     

Performance evaluation of a sensorless adaptive optics multiphoton microscope

A wavefront sensorless adaptive optics technique was combined with a custom‐made multiphoton microscope to correct for specimen‐induced aberrations. A liquid‐crystal‐on‐silicon (LCoS) modulator was used to systematically generate Zernike modes during image recording. The performance of the instrument was evaluated in samples providing different nonlinear signals and the benefit of correcting higher order aberrations was always noticeable (in both contrast and resolution). The optimum aberration pattern was stable in time for the samples here involved. For a particular depth location within the sample, the wavefront to be precompensated was independent on the size of the imaged area (up to ～360 × 360 μm²). The mode combination optimizing the recorded image depended on the Zernike correction control sequence; however, the final images hardly differed. At deeper locations, a noticeable dominance of spherical aberration was found. The influence of other aberration terms was also compared to the effect of the spherical aberration.     

微光学自适应技术中基于PZT薄膜的微反射镜工艺研究

介绍了微光学自适应技术中基于PZT(PbZrxT i1-xO3)薄膜的微反射镜单元及其制作工艺。该制作过程中用重掺杂硅片作为基底和下电极,采用了钛酸丁脂[(C4H9O)4T i]、乙酸铅[Pb(CH3COO2).3H2O]以及异丙醇锆[Zr(OCH(CH3)2 4.(CH3)2CHOH]为原料,通过溶胶-凝胶法(so l-gel)制作薄膜,薄膜厚度为纳米级。制成的PZT薄膜通过逆压电效应产生形变,对反射镜面局部进行微调,实现波前位相控制。     

Wavefront sensors for adaptive optical systems

Possibilities of constructing a wavefront sensor for the adaptive system in the Big Solar Vacuum Telescope are considered. A modified correlation tracker (MCT) is proposed. The sensor is tested by measuring the displacement of the image of the solar granulation pattern in the first and second foci of the telescope under clear vision conditions. The change in the quality of the image being transferred to the second focus and the measured displacement of the image of solar granulation in the second focus with extremely good vision conditions and a certain granulation structure are analyzed. The effect of reduction of the input aperture to 170 mmon the image quality and, hence, on MCT operation is analyzed.     

适合于大气激光通信的双空间调制

相对于传统的光空间调制,光广义空间调制在传输速率和频谱效率上虽然有了较大的提升,但其误码性能不够理想。本文利用脉冲位置调制(PPM)和脉冲幅度调制(PAM),通过每次同时激活两个激光器而提出了一种双空间调制(DSM)。采用联合界技术推导出了DSM的误码率理论上界,分析了其频谱效率、传输速率和复杂度的影响因素,并与已有光空间调制的性能进行了对比。仿真结果表明:DSM不仅提升了系统的频谱效率和传输速率,而且有效地改善了系统的误码性能。在相同的传输速率下,当误码率为1×10-3时,相对于(4,4)-8PPM SPPM和(3,4)-4PPM GSPPM方案,(3,4)-8PPM-2PAM DSM的信噪比分别改善了约2.5 dB和6 dB,频谱效率分别提高了2.335 bits/(s·Hz)和0.375 bits/(s·Hz)。DSM方案为未来大气激光通信传输速率的提高提供了一种有效手段。     

CUDA架构下的液晶自适应波面数值解析

在GPU通用计算架构下,首次提出了CUDA架构下的液晶自适应光学波面数值解析方法。针对高分辨率液晶自适应光学系统,介绍了液晶自适应光学的波面数值解析算法,论述了CUDA的通用架构;然后,建立了CUDA实现波面数值解析的编程模型,在此模型中引入了并行线程的有效利用,全局存储器的高效访问和数据直接回写3种优化方案;最后,给出了GPU与CPU的实验对比结果。结果表明:CUDA计算分辨率为512×512,对35项Zernike多项式的波面数值解析需时不到1ms,计算速度是传统CPU波面数值解析的几十倍。提出的方法减小了系统延时,提高了校正速度,建立波面数值解析CUDA编程模型采用的优化手段可为其它数学计算模型提供参考。     

用于多波段激光大气透过率测量的太阳辐射计

为了实时测量多个波段激光大气透过率,研制了ISP02型近红外太阳辐射计。详细阐述了该仪器的硬件组成、光学系统设计以及工作流程,并对仪器进行了定标,给出仪器能达到的性能指标。依据建立的基于太阳宽谱直接辐射测量获取激光波段大气透过率的方法,实测得到1.064,1.315,1.54μm大气透过率,将结果与POM02型太阳辐射计采用外推法获取的激光大气透过率进行对比,误差均小于6%,测量的水汽总量与POM02对比,误差均小于7%;然后,将两者外推的3.78μm透过率进行对比,误差均小于5%。秋冬季实测的1.315μm透过率与激光大气传输评估软件对比,误差小于2%。该仪器测量结果可靠、性能稳定,可为同时获取多个波段激光大气透过率提供有效测量手段。     

Computer simulation of wear

A digital record of the profile of a machined surface is processed by a computer to yield a number of wear-sensitive parameters such as mean slope and peak curvature. Numerical techniques are used to simulate removal of successive layers of the surface. Wear sensitive parameters are recomputed at each such removal. The results agree with experimental values obtained by a computer analysis of records, obtained by relocation profilometry, of a real wear experiment performed on the same surface. It is found that the variation with depth of wear of several surface parameters can be represented by the normal probability integral.     

Modelling the application of adaptive optics to wide-field microscope live imaging

Wide‐field fluorescence microscopy is an essential tool in modern cell biology. Unfortunately the image quality of fluorescence microscopes is often significantly degraded due to aberrations that occur under normal imaging conditions. In this article, we examine the use of adaptive optics technology to dynamically correct these problems to achieve close to ideal diffraction limited performance. Simultaneously, this technology also allows ultra‐rapid focusing without having to move either the stage or the objective lens. We perform optical simulations to demonstrate the degree of correction that can be achieved.     

Biomimetic control for adaptive camera stabilization in driver-assistance systems

Throughout the last decade, a large number of electronic driver-assistance systems have been developed in order to improve vehicles’ comfort and safety. Up to now, they more or less all rely on odometric data. However in the future, a new form of information is likely to be used: visual sensors, e.g. cameras, can provide additional knowledge on traffic and the vicinity. This paper presents an inertially stabilized camera platform for high precision tracking of points of interest, that has been developed within the project FORBIAS (Research cooperation for biomimetic assistance systems). The inertial stabilization is based on a specially designed sensor system that uses MEMS components in connection with a biologically inspired control algorithm for adaptive enhancement and online calibration of the gaze stabilization system.     

A device for atmospheric laser deposition of noble metal nanostructures

An experimental device has been developed for atmospheric laser deposition of nanostructures of noble metals (Ag, Au, Pt, and Pd) on the surfaces of functional materials. This device is composed of functional units with a simple engineering design. A number of experimental samples have been obtained on the device in different laser-deposition modes; these were investigated using the scanning electron microscopy and atomic-force microscopy methods.     

一种自适应激光电源的设计

本文介绍了一种自适应激光电源的设计。该电源基于电压源加大功率场效应管结构,采用小注入电流下检测负载电压的方法调整电压源电压,可最大限度提高电源效率,并降低系统散热量。该电源输出电压可在大范围内自适应,可通用于半导体单管激光器及其阵列。     

高亮度LED大屏幕的仿真

高亮度 LED屏幕越来越多地被广泛使用 ,但是从计算机上编辑画面后输出到大屏幕的过程比较复杂。可以用计算机模拟仿真高亮度 LED大屏幕来实现预览功能 ,并且通过计算机辅助分析帮助铺设二极管阵列     

Novel adaptive laser scanning sensor for reverse engineering measurement

In this paper, a series of new techniques are used to optimize typical laser scanning sensor. The integrated prototype is compared with traditional approach to demonstrate the much improved performance. In the research and development, camera calibration is achieved by extracting characteristic points of the laser plane, so that the calibration efficiency is improved significantly. With feedback control of its intensity, the laser is automatically adjusted for different material. A modified algorithm is presented to improve the accuracy of laser stripe extraction. The fusion of data extracted from left and right camera is completed with re-sampling technique. The scanner is integrated with a robot arm and some other machinery for on-line measurement and inspection, which provides a flexible measurement tool for reverse engineering.