大气气溶胶消光系数检测系统设计

利用半导体激光器照射大气气溶胶试样后光强衰减得到大气气溶胶消光系数。光束经过气溶胶后检测透射方向的光强值,经光电转换、信号调理、AD采样后根据朗伯比尔定理计算气溶胶消光系数。采用双通道测量气溶胶消光系数的方法,减小了由于半导体激光器光强不稳定和大气分子对测量结果的影响。对设计的系统以不同浓度的气溶胶进行了检测,其线性度良好,相对误差小于4%。所设计的大气气溶胶检测装置体积小、操作简单、探测速度快,对监测大气污染和能见度等有一定的应用价值。     

野战激光通信中多口径发射与大口径接收试验研究

针对野战无线激光通信中大气衰减和光强起伏问题,分析了大气对激光通信的影响,探讨了多口径发射与大口径接收对大气影响抑制机理,在此基础上,构建了多口径发射和大口径接收试验装置,发射端发射孔径数目可调,接收端光学天线采用卡塞格伦结构,通过在光学天线前面增加不同口径光阑方式,改变天线口径。发射孔径数目增加到4束时,光强起伏方差约为单光束时的1/2,接收口径直径相差1.5倍时,闪烁方差之间相差1.6倍,验证了对大气湍流的抑制效果。根据理论分析与试验结果,对野战激光通信光端机的部分参数进行了优化设计。     

Fiber-coupled position sensors for aerospace applications

Fiber-coupled position sensors promise advantages over their electrical counterparts for aerospace applications such as weight savings, immunity to radiated electrical interference, and improved performance, but so far, no sensor has gained widespread acceptance. This paper describes three fiber-coupled sensors presently under development at the Boeing High Technology Center including a single track analog sensor, a sensor based on weighted number system encoding, and a sensor based on FMCW laser radar techniques. Technical difficulties encountered, customer requirements, and a summary of a standardized WDM sensor interface including a broadband LED source and a compact spectograph are also discussed.     

连续变焦大气相干长度测量系统设计

望远镜在大气光学参数测量中起到至关重要的作用,测量方法是通过跟踪恒星或者信标实时测量数据。基于不同速度信标的移动特点,需要设计3 m~6 m变焦大气相干长度测量系统用于大气相干长度的测量,设计波段为可见光486 nm~656 nm,探测元全视场11 mm,入瞳直径300 mm。利用光学设计软件设计出一款折返式变焦望远系统,光学结构由卡式望远系统和三组元机械补偿式连续变焦系统组成,系统结构简单,成本低,凸轮曲线平滑,压力升角均小于45。系统可对变焦焦距数据实时输出,适合于快速和慢速不同场合下实时进行大气参数测量。     

便携式激光辐照度测量系统

激光驾束制导中,制导激光的辐照度是一个重要的性能参数。为了实现制导激光辐照度的野外快速、准确测量,研制了小型、便携式激光辐照度测量系统。系统利用微处理器进行控制和数据采集处理,实现了测试数据的自动修正,提高了测量结果的准确性。同时可选择测量0.92μm、0.98μm和1.06μm三种波长的激光辐照度。经实验验证,该系统测量准确、结构简单、使用方便,适合室内以及野外测试。     

A steerable laser radar system for atmospheric studies

A steerable laser radar suitable for a wide range of atmospheric studies is described. The system incorporates a flashlamp-pumped dye laser and a receiving telescope with a 0.3 m mirror. The steering capability is provided by the use of a 0.61 m by 0.46 m plane mirror for both transmission and reception. Manual and automatic control of the mirror drive is provided, with its angular position being recorded. Digital counting is used in the recording electronics. The performance of the system in measurements over a large range of heights in the atmosphere is illustrated.     

Development of portable laser machining system for laser writing applications

This study presents a portable laser machining system that consists of a fiber-optic diode laser source with a wavelength of 808 nm, optic/opto-mechanical components, a laser scanning module, and a laser energy control module. The laser beam quality was measured at different operation frequencies during system evaluation. The experimental results of beam profile evaluation indicate that the enlarged collimated beam was the TEM₀₀ mode with a roundness of approximately of 96%. The output laser power level increased as the pulse frequency increased during laser power evaluation. To control the rotating angle of the galvanometric scanning system, the deflective angle was adjusted using a 0.192 voltage to obtain a deflective value of 1mm and the maximum scan field of 100 × 100mm². The laser source operated at different frequencies, with pulse widths ranging from 530 to 48 μs. Finally, the proposed machine can also be used for black thick paper laser writing applications.     

Light extinction method for solubility measurement

A novel measurement method for chemical solubility determination is brought forward, in which the advantages of two kinds of traditional methods are united. The results show that the concentration of unsolved particles suspending in the solution can be determined by measuring I/I0 (ratio of the transmission intensity to the incident intensity) of the laser beam permeating through the solution according to Lamben-Beer law. The biggest relative deviation for the solubility data determined is less than 1.5% for the sparingly soluble substances and 0.3% for the opulently soluble substances. By comparison of the experimental solubility data with previous data, the light extinction method is demonstrated to be stable and reliable.     

探测大气气溶胶消光系数的便携式米散射激光雷达

 介绍了一种新型的便携式米散射激光雷达的总体结构及其各部分的功能，分析讨论了该激光雷达在夜晚与白天探测大气气溶胶消光系数垂直廓线的性能。其夜晚的探测高度达到15km左右，白天的探测高度达到10km左右。还可对卷云进行探测，获得卷云的厚度及其峰值消光系数。该激光雷达具有结构紧凑、体积小、重量轻、自动化程度高、探测速度快等优点。     

Reducing measurement time for a laser Doppler vibrometer using regressive techniques

In the last decade the laser Doppler vibrometer (LDV) has become a widely spread instrument for measuring vibrations. It often offers accurate measurements with a high spatial resolution. However, the measurement time of the LDV and especially for the scanning LDV is long. Therefore, reducing the measurement time is an attractive objective. A way to achieve this is to use a single sine excitation (on a resonance frequency). However, this technique has two major drawbacks: the inability to provide information on the damping and a operational deflection shape that can differ from the true mode shape. In this article two methods will be introduced to reduce measurement time without these defaults. In the first method introduced in this article a narrow band multisine is used as excitation signal and the measured vibration signal in the time domain is represented by a model using sines and cosines with these fixed narrow band frequencies. The coefficients of those sines and cosines are then estimated on a global scale by means of a least-squares estimator. An important advantage of this particular technique is that one does not have to measure a full period of the signal, reducing time. The second method accelerates the measurement time for scanning LDV measurements. Using the time domain sequence from each previous scan point and a limited number of time samples from the current scan point, the full time domain sequence of the current scan point can be estimated. Both these methods are a key benefit for in-line quality control, which can have upwards of 1000 spatial measurement locations. The proposed techniques will be validated on both simulations and experiments of varying complexity.     

星载激光测高系统大气折射延迟的影响分析

星载激光测高系统发出的测距光束经过大气层时会发生折射,由此产生的与大气延迟相关的测距误差在数米量级。讨论了激光测高系统大气延迟修正理论及实现算法,通过使用沿天顶方向的大气传输延迟值与非天顶方向相应映射函数乘积的方法来计算大气延迟,并对影响大气延迟主要气象参数地表气压进行修正。结合全球首个对地观测星载激光测高系统GLAS测量数据和美国国家环境预报中心NCEP气象数据进行大气延迟修正,并与GLAS系统公布延迟数据对比。结果表明:大气干项延迟偏差小于2 cm,湿项延迟偏差小于1 mm。     

Novel photonic applications of nonlinear semiconductor laser dynamics

With a proper perturbation, even a single-mode semiconductor laser can exhibit highly complex dynamical characteristics ranging from stable, narrow-linewidth oscillation to broadband chaos. In recent years, three approaches to invoke complex nonlinear dynamical states in a single-mode semiconductor laser have been thoroughly studied: optical injection, optical feedback, and optoelectronic feedback. In each case, the nonlinear dynamics of the semiconductor laser depends on five intrinsic laser parameters and three operational parameters. The dynamical state of a given laser can be precisely controlled by properly adjusting the three operational parameters. This ability to control the dynamical behavior of a laser, combined with the understanding of its characteristics, opens up the opportunity for a wide range of novel applications. This paper illustrates the utilization of the rich nonlinear dynamics of single-mode semiconductor lasers by focusing on the period-one oscillation for its applications in tunable photonic microwave generation, AM-to-FM conversion, and dual-frequency precision Doppler lidar.     

Novel optical techniques for measurements of light extinction,scattering and absorption by single aerosol particles

Aerosol particles play important roles in a broad range of scientific disciplines, from atmospheric chemistry and physics, to the delivery of fuels for combustion and drugs to the lungs, and extending to industrial processes such as spray drying. Measurements of the light extinction, scattering and absorption by ensembles of aerosol particles can be used to non‐intrusively characterise aerosol particle samples. However, such measurements often lead to ambiguity in interpreting the properties and processes occurring on individual particles. In this review, recent developments in the use of laser based techniques to isolate and manipulate single particles and to characterise them will be highlighted. In particular, the use of cavity ring down spectroscopy, Bessel beams and optical tweezers for investigating light extinction, scattering and absorption, respectively, will be considered. The prospects for using optical techniques to interrogate the fundamental processes occurring in aerosol at the single particle level are discussed.     

高速空间激光通信系统在空天信息网中的应用

 针对高速空间激光通信系统应用时面临的主要问题：节点高速运动的跟踪瞄准和与组网载荷协同工作,提出将高速空间激光通信系统作为节点主要通信载荷的双通信载荷结构,并设计了高速空间激光通信系统与组网载荷协同工作机制和协议模型,依据协议模型进行了原理样机开发与试验。试验结果表明,提出的协同工作机制与协议模型能很好地适用于高速空间激光系统,支持超高速率数据传输,最高MAC层协议数据速率可达1.772 Gb/s,平均处理时延20 μs。     

脉冲激光测距机消光比测试系统精度分析

介绍了脉冲激光测距机最大测程———消光比测试方法中的消光比测量原理公式。并以原理公式为依据 ,对影响系统测量精度的诸因素逐一进行了分析和估算 ,根据测量消光比值的合成标准的不确定度进行精度分配。     

自由电子激光摇摆器磁测系统

根据理论分析及实际加工水平,设计了一套摇摆器磁场测量系统,同时对影响磁测系统整体性能的主要参数进行了详尽分析。摇摆器磁测装置主要由气浮运动平台、测磁设备及控制系统组成,其主要功能是对霍尔探头的位置与磁场数据进行高精度测量及同步采集。主要参数如下: z向定位精度小于5 m,重复定位精度小于2 m;霍尔探头的测量精度为0.05%,重复测量精度为0.01%,响应频率为1 kHz;数据采集卡的采样率不小于1000。     

Design and analysis of a laser micrometer for undulator gap measurement applications

In this paper we report the design of a laser micrometer for undulator gap measurement studies. In this scheme, the parallel light emerging from the rotating polygon mirror passes through an F-theta lens makes a vertical line on the image plane. When an object intercepts the line, the interrupted and the uninterrupted light is detected in a DSO through a detector. The beam spot size and the linear velocity of the beam spot on the scan line are the two important parameters of the laser micrometer. The beam spot size measurements show that it is constant along the scan line for a number of RPMs. It measures a constant value at ±3 mm to the effective focal length of the F-theta lens. The measurements are verified for two types of objects i.e. solid object and a circular hole and also for an electromagnet undulator. The electromagnet undulator is measured with an accuracy of 3–5 µm.     

自由电子激光摇摆器磁测系统

根据理论分析及实际加工水平,设计了一套摇摆器磁场测量系统,同时对影响磁测系统整体性能的主要参数进行了详尽分析。摇摆器磁测装置主要由气浮运动平台、测磁设备及控制系统组成,其主要功能是对霍尔探头的位置与磁场数据进行高精度测量及同步采集。主要参数如下:z向定位精度小于5μm,重复定位精度小于2μm;霍尔探头的测量精度为0.05%,重复测量精度为0.01%,响应频率为1kHz;数据采集卡的采样率不小于1000。     

Ratio of aerosol backscatter to extinction coefficients as determined from angular scattering measurements for use in atmospheric lidar applications

Wavelength dependence as well as relative humidity dependence of aerosol extinction to backscatter ratio was examined. The extinction to backscatter ratio is essential in solving lidar signal and was estimated from aerosol size distribution and refractive index (which were derived from angular light scattering measurements) using the Mie scattering theory. The extinction to backscatter ratios were calculated for wavelengths of 355 nm, 532 nm, 694 nm and 1064 nm, the major laser wavelengths used for lidars, where the refractive indices were assumed to be constant with wavelength. p ]When relating the aerosol extinction ₁ to the backscatter ₁ with a functional form of _{1 1} k ₁, the exponentk ₁ was evaluated by the least square method and tabulated for the four wavelengths. The extinction to backscatter ratio defined asS ₁= ₁/ ₁ was calculated and their dependence on the wavelength and relative humidity was examined. Their dependence on the relative humidity is small whileS ₁ in the average takes the value of 66 (±17), 60 (±13), 52 (±13) and 42 (±11) for the wavelengths 355 nm, 532 nm, 694 nm and 1064 nm, respectively