一种高亮度积分球定标光源的热设计

针对目前光学口径不断增大的空间光学遥感器对实验室辐射定标的要求,设计了一种使用近距离小面源照明方式定标的高亮度积分球光源,并对该光源的光学参数和结构参数进行了详细设计。为了解决高亮度积分球使用时的散热问题,采用水冷的散热方式,设计了专门的散热管路。对该光源循环水流速0.1 m/s下利用有限元分析法热仿真分析,仿真结果表明,溴钨灯光源附近温度维持在125°C左右,积分球出光口温度维持在80°C左右。实验结果表明,溴钨灯光源附近温度维持在125°C左右,积分球出光口温度维持在100°C左右。通过对比分析了积分球出光口温度差异的原因,验证了仿真分析与理论计算的正确性。同时测试了该光源在400~900 nm波段范围内光谱辐亮度为6714 W/(m2·sr)。     

一种高亮度积分球定标光源的热设计EI北大核心CSCD

针对目前光学口径不断增大的空间光学遥感器对实验室辐射定标的要求,设计了一种使用近距离小面源照明方式定标的高亮度积分球光源,并对该光源的光学参数和结构参数进行了详细设计。为了解决高亮度积分球使用时的散热问题,采用水冷的散热方式,设计了专门的散热管路。对该光源循环水流速0.1 m/s下利用有限元分析法热仿真分析,仿真结果表明,溴钨灯光源附近温度维持在125°C左右,积分球出光口温度维持在80°C左右。实验结果表明,溴钨灯光源附近温度维持在125°C左右,积分球出光口温度维持在100°C左右。通过对比分析了积分球出光口温度差异的原因,验证了仿真分析与理论计算的正确性。同时测试了该光源在400~900 nm波段范围内光谱辐亮度为6714 W/（m2·sr）。     

4m直径均匀扩展定标光源

针对目前光学口径不断增大的空间光学遥感器实验室辐射定标的需求,基于近距离扩展源照明方法设计了400～900 nm谱段内最大积分辐射亮度为200 W/(m²·sr)的4 m直径均匀扩展定标光源。该定标光源内径为4 000 mm,出光面直径为1 600 mm。对该定标光源光机结构进行了详细设计,利用光纤光谱仪监视输出的相对光谱分布,CPLD结合单片机实现输出光谱辐亮度值无人值守智能化远程自动控制。使用PR 735光谱辐射计测量该光源400～900 nm谱段内最大积分辐射亮度为222.62 W/(m²·sr),通过对定标光源的稳定性、面均匀性及角度均匀性测试,分析了定标光源的测量不确定度为3.57%。实验结果表明:该定标光源可以满足口径1 600 mm以下可见/近红外空间光学载荷的实验室辐射定标需要,并可实现智能程控化控制,提高了定标测试精度。     

近紫外到近红外光谱辐射计及定标方法研究

为实现目标光谱辐射亮度的高精度测量，研制了一种小视场近紫外到近红外光谱辐射计，光谱范围为300 nm~2 000 nm，光谱辐射亮度测量范围为50μW/cm2·nm·sr~1 000μW/cm2·nm·sr。阐述了近紫外到近红外光谱辐射计设计原理及关键部件，使用基于钨带灯的直接定标法实现了光谱辐射计光谱辐射亮度绝对定标，测量了标准积分球光源的光谱辐射亮度，测量值与积分球光源标准值偏差优于0.5%。     

紫外波段大口径积分球辐射源研制

为了满足航天载荷对大口径、高亮度紫外积分球辐射源的定标需求,采用全新工艺研制了内径为2200 mm、出光口径为800 mm且采用全压制聚四氟乙烯(PTFE)涂层的大型积分球辐射源,聚四氟乙烯涂层厚度为25 mm.积分球内置10 kW卤钨灯光源并外置两台带有电动光阑的总功率为14 kW的氙灯光源,可实现4个量级的大动态范围调节.经测试,该积分球在250 nm处的辐亮度为0.54 μW· cm-2·nm-1·sr-1,在279～400 nm紫外波段处的辐亮度大于1个太阳常数,辐亮度定标扩展不确定度为5.28％.对紫外积分球辐射源的各项性能进行了测试,结果表明,紫外辐射源的面非均匀性在380 nm处为0.65％;在扫描夹角为-20°≤θ≤+20°时,水平和垂直方向上的角非均匀性优于0.49％,±45°方向上的角非均匀性优于0.69％.对光谱反射率对面均匀性及角均匀性的影响开展了研究,研究结果表明,随着光谱反射率的提高,面非均匀性下降0.17个百分点,角非均匀性下降0.15个百分点.对辐射源稳定性、荧光效应及系统热平衡展开了测试研究,所研制的紫外积分球辐射源具有紫外波段(250～400 nm)亮度高、口径大、均匀性好及可靠性高等特点,是理想的大面积郎伯面源,可满足紫外波段航天载荷辐射定标需求.     

星载微光遥感器外场辐射定标光源的研制和检测

LED外场辐射定标积分球光源基于辐射通量等效理论,用于星载微光遥感器的在轨辐射定标。该定标光源采用12组峰值波长670 nm的LED密集阵列发光单元,每组最大电功率300 W,辐亮度输出达到5.2×10?2 W·cm?2·sr?1,通过等效辐射通量面积校正后,能够适用于10?9 W·cm?2·sr?1量级的微光通道在轨定标。光源的参数检测结果表明:定标光源角度均匀性在±30°以内优于99.6%,平面均匀性优于99.7%,1 h内稳定性优于99.9%,具有优良的辐射特性。在敦煌中国遥感卫星辐射校正场对VIIRS微光通道进行了在轨实测试验,在轨响应结果为8.27×10?9 W·cm?2·sr?1（含月光贡献和大气影响）,证明了该外场微光定标光源辐射量值设计的合理性。     

可调对比度光学无穷远目标源设计

在光电跟踪测量设备对低对比度目标捕获能力检验中,提出一种利用可调对比度光学无穷远目标源检验的新方法。采用这种方法需建立可调对比度光学无穷远目标源装置,介绍这种装置的设计依据和设计过程。该装置可以模拟天空背景的辐亮度及这个背景下的一个低对比度目标,它利用大、小两个积分球分别模拟背景与目标的辐亮度,利用安装在大积分球上的准直物镜使目标及背景成为无穷远的目标源,在积分球上分别安装内置和外置照明光源,外置照明光源中装有光束准直系统,使卤素灯发出的光束成为平行光后射入积分球内,利用可调光栏控制通光口径的大小,从而控制了进入积分球的光通量,使得背景与目标的辐亮度在色温不变的条件下连续可调,实现目标对比度连续变化,变化范围0~90%,对比度稳定精度优于1%,光谱范围400 nm~800 nm内最大背景辐亮度优于60 W/m2sr。     

积分球光源分布温度对宽波段光学遥感器绝对辐射定标的影响及其校正

实测了积分球输出光谱辐亮度分布曲线,并得到积分球光源的分布温度。从理论上分析了积分球光源分布温度影响宽波段光学遥感器绝对辐射定标精度的原因和机理,并仿真计算了包括积分球和太阳在内的几种不同分布温度光源定标某宽波段光学遥感器时得到的定标系数。仿真结果表明,不同分布温度间的定标系数最大差别大于2%。在此基础上提出了积分球光源分布温度影响绝对辐射定标系数的校正方法,为提高宽波段遥感器的辐射定标精度和遥感图像辐射校正提供了思路和依据。     

高光谱遥感器现场光谱定标精度验证方法研究

鉴于精确的光谱辐射定标精度验证对于高光谱遥感器的现场定标和数据应用非常必要,以SVC光谱辐亮度计为例,利用多波段辐亮度标准传递探测器和新型的光谱可调积分球参考光源,设计了一种高光谱遥感器光谱定标精度的验证方法。该方法利用新型光谱可调积分球参考光源在待测波段内分别输出光谱形状单调上升和单调下降的光谱辐亮度状态,通过光谱匹配技术,即平移改变SVC光谱辐亮度计的波长,分析比对MRSTD和SVC光谱辐亮度计测量辐亮度的相对偏差。比对结果为光谱定标验证精度优于±0.2 nm,辐射定标验证精度小于5%。     

一种新型的红外辐亮度绝对定标方法研究

介绍了一种新型的辐亮度绝对定标的方法原理和实验装置。采用355 nm激光抽运偏硼酸钡(BBO)晶体,产生两个下转换光子波长分别为532.75 nm和1064 nm。利用这对可见-红外下转换相关光子对在时间、空间上的高度相关性,在红外下转换光子方向注入1064 nm待测激光光源,通过测量532.75 nm的下转换光子信号的光子计数,实现1064 nm激光光源辐亮度的绝对定标,并将红外波段的测量转移到了可见光谱区域内。改变待测激光光源的功率,实验结果显示具有较好的线性。实验过程中设置输入光功率为3.39 mW,在对系统的各项损耗和效率进行评估的基础上,测量得到相应的辐亮度大小为4.09×1017W/(m2.sr),相对不确定度为4.78%。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.