一种具有自适应非均匀校正功能的非制冷焦平面探测器组件

基于场景的非均匀校正算法(scene based nonuniformity correction,SBNUC)是非均匀校正技术今后的重点发展方向,介绍了近年来基于恒定统计约束的SBNUC、神经网络的SBNUC和运动估计的SBNUC算法的研究进展。研究了SBNUC算法在实际焦平面探测器组件上的实现方法,该方法仅依赖拍摄序列的信息对焦平面探测器的增益和偏置参数进行组间更新或帧间更新,可有效补偿温漂。研制了一种具有自适应非均匀校正功能的非制冷焦平面探测器组件,红外视频经该组件处理后,图像质量有所提高。该组件可明显提高热成像系统的成像性能,并能动态地保证热成像系统随场景变化的稳定性。     

Photonic time-stretch analog-to-digital converter employing envelope removing technique

The previously proposed differential time-stretch preprocessor can eliminate the distortions induced by the non-uniformity of optical pulse and the pulse-to-pulse variations of the optical source. However, the time-delay element in this method reduces the processing speed of the system. In this paper, we propose an envelope removing technique to mitigate these distortions and improve the time efficiency of time-stretch system simultaneously. To verify the feasibility of this technique, a comprehensive mathematical model for this technique is developed and numerical simulation is also presented. Simulation results show that this method can effectively eliminate non-uniformity and pulse-to-pulse variations in time-stretch system. This method has two times faster processing speed than the differential time-stretch preprocessor.     

基于棱镜二次聚光的高倍聚光模组聚光特性与三结电池光谱响应匹配与优化

目前Ⅲ-Ⅴ多结高倍聚光(HCPV)太阳电池实验室效率记录已高达46%,而相对应的模组效率与之相差仍较大,其中由于模组中聚光非理想性引起的损失就高达20%.本文通过建立光学模型和非均匀光照的三维电池电路网络模型,以Ⅲ-Ⅴ族三结电池为例,研究了菲涅耳透镜一次聚光、棱镜二次聚光的HCPV模组的聚光特性和光电特性.结果发现.由于光线非平行入射和-菲涅耳透镜的色散现象,使得沿光轴方向短、中、长波段聚光发散及聚光不均匀,从而造成了三结电池的上、中、下各子电池光谱响应失配损失,模组光电转换性能下降;进一步,通过采用棱镜二次聚光,能较好地改善聚光和温度均匀性;通过对光轴方向上短、中、长波段的聚光特性与三结电池光谱响应匹配优化,使得模组输出功率提高10%以上.模拟结果己得到实验验证.     

Fast,non-diffusive ignition of a gaseous reacting mixture subject to a point energy source

The ignition of a gaseous reactive mixture subject to a localized energy source is analysed using large activation energy asymptotics. The energy released by the source results in a thermal non-uniformity in a small region of the gas. We distinguish two different regimes, non-diffusive and diffusive, depending on the dominant cooling mechanism during the ignition stage: expansion effects or heat conduction. We focus on the non-diffusive ignition, considering the energy source as instantaneous. We show the existence of a critical value of a Damköhler number, defined as the ratio of the characteristic times of the expansion waves and chemical reaction, such that ignition only occurs for supercritical values at a well-defined ignition time, which is calculated numerically. The ignition process for a non-instantaneous energy source is also described in terms of an initial inert heating stage and a shorter reactive stage ending in thermal runaway for supercritical values of the Damköhler number.     

基于MOS电阻阵列的红外目标模拟器非均匀性校正技术研究

红外成像目标模拟器是红外成像半实物仿真系统中的关键组成部分,基于微机械技术发展起来的MOS电阻阵列是红外图像生成器的重要发展方向。其中红外图像生成的质量是设计和研制红外成像目标模拟系统需重点考虑的问题。多种原因导致电阻阵列具有一定的非均匀性,因此在使用之前必须对其进行非均匀性校正。结合实际应用,阐述了基于MOS电阻阵列的红外成像目标模拟器的非均匀性产生机理,建立红外目标模拟器的非均匀性修正数据库对红外目标模拟器的图像数据源进行校正和补偿,产生校正后的图像数据,完成对红外目标模拟器存在非均匀性的离线修正。     

Current distribution in multistrand superconducting cables — experimental methods and results

It is widely acknowledged that current non-uniformity is a major source of reduction of quench currents in superconducting multistrand cables at non-steady state conditions. Recently we performed several experimental studies on the current non-uniformity in CICC and AC cables. In this paper we present the summary of the experimental methods used. Indirect methods with use of local magnetic field sensors can provide general information about non-uniformity inside CICCs and other large size cables. Indirect methods may be used in real superconducting devices. Direct measurements of the current in each strand provide exact information about the current distribution, but they need special sample preparations. Because no method is perfect, the best idea is to use them as complementary to each other in the study of a certain type of a cable. The results obtained from the measurements of the current non-uniformity in CICC and AC cables by both methods are briefly discussed.     

基于欠采样技术的束流相位测量电子学系统设计北大核心CSCD

采用欠采样技术为中国散裂中子源(CSNS)直线加速器研制了全数字化束流相位测量电子学系统。介绍了该系统的测量原理、整体设计情况,并进行了实验测试。测试采用324 MHz,100 mVpp的正弦信号,测试结果显示相位分辨率优于0.1°,通道间相位不一致性可控制在±0.2°以内,满足设计指标要求。     

光电成像检测系统像面照度均匀性分析

非均匀发光光源、大视场角等因素会造成光学成像检测系统像面照度分布不均匀,进而导致检测效率下降。研究非均匀发光光源和大视场角对像面照度均匀性的影响程度,首先建立光源间距与受光面接收照度间的关系模型,仿真分析不同LED间距对像面照度均匀性的影响,然后建立光学耦合系统的物面张角和像面照度间的关系模型,仿真分析物面张角对像面照度均匀性的影响。实验结果表明:在非均匀发光光源和大视场角的作用下,检测系统会造成像面照度严重不均匀现象。研究结果为后续像面照度校正算法设计提供了理论依据。     

A study of the impact on telecentricity to the illumination system based on CCD imaging

One of the important properties of the illumination system is of determining telecentricity for the realization of the place of wafer in the optical lithography. In this paper, we present numerical simulations of the optical imaging using four different illumination models and based on CCD imaging. We simulate the imaging of light source for different illumination pupil distributions and determine the energy centroid through the imaging of the conventional illumination which exist telecentricity of 11 mrad. Furthermore, we discuss the influencing factors of two aspects on telecentricity. One is the non-uniformity of light intensity distribution, and the other is pinhole defocus in the wafer. The range between the non-uniformity of light intensity distribution and pinhole defocus are quantified by computing the allowed telecentricity error in the illumination system. Finally, experiments have verified telecentricity measurement feasibility and validity. The presented scheme that with CCD imaging instead the actual wafer which saves cost and improves the accuracy in the optical lithography. In comparison with the measurement methods of convention the CCD imaging has a series of advantages such as fast response, high sensibility, high precision and the measurement is carried out on-line.     

Modelling of processes occurring in deep geological repository - Development of new modules in the GoldSim environment

Three new modules modelling the processes that occur in a deep geological repository have been prepared in the GoldSim computer code environment (using its Transport Module). These modules help to understand the role of selected parameters in the near-field region of the final repository and to prepare an own complex model of the repository behaviour. The source term module includes radioactive decay and ingrowth in the canister, first order degradation of fuel matrix, solubility limitation of the concentration of the studied nuclides, and diffusive migration through the surrounding bentonite layer controlled by the output boundary condition formulated with respect to the rate of water flow in the rock. The corrosion module describes corrosion of canisters made of carbon steel and transport of corrosion products in the near-field region. This module computes balance equations between dissolving species and species transported by diffusion and/or advection from the surface of a solid material. The diffusion module that includes also non-linear form of the interaction isotherm can be used for an evaluation of small-scale diffusion experiments.     

Non-uniformity correction of infrared focal plane array in point target surveillance systems

We discuss the influence of non-uniformity and non-uniformity correction on point target detection in infrared surveillance system, and propose a non-uniformity correction approach which is based on signal intensity and sensor characteristics. Theoretical models are used to derive the combined effect of background clutter, sensor random noise, target, non-uniformity and correction error on the signal-to-noise-and-clutter ratio. From our analysis, it can be noted that background clutter intensity is successively modulated by sensor non-uniformity and non-uniformity correction, while sensor random noise is modulated by the non-uniformity correction process only. Furthermore, background clutter and sensor random noise are the key factors that affect the performance of a surveillance system, when it is used to detect point targets. The method presented in this paper takes all of the above into account, moreover, it considers the difference between scanning and staring focal plane array. The experimental results demonstrate the effectiveness of the proposed method.     

Efficient and compact reflective-type encapsulation module for high-power light-emitting diode

This paper presents a practical and effective reflective-type encapsulation module employing a high-power LED chip and a light concentrator with the advantages of high-performance and ultra-compactness. Linear-segment and cubic-spline (LSCS) synthesis method is proposed for the light concentrator design, the detailed of which is thoroughly investigated. Design results show that the reflective encapsulation module could not only reduce the irradiance non-uniformity from 28.72% down to 8.34% within the prescribed illumination region, but also minimize the optical dimension by 9.6%, which demonstrate both the effectiveness and robustness of the LSCS method. It is believed that there would be a huge market potential to commercialize this design.     

A novel non-uniformity compensating method for microbolometric focal plane array

This paper describes a non-uniformity compensating method for microbolometric focal plane array. Through the analysis of the basic principle of conventional non-uniformity compensating methods for microbolometric focal plane array, we have pointed out their common fatal limitation unable to compensate the nonlinear non-uniformity of microbolometer array. Based on our previous constant power optimized bias, a novel and simple nonlinear non-uniformity compensating method for microbolometric focal plane array is proposed in this paper. The proposed compensating method is simply configured and can easily and effectively be utilized to compensate the nonlinear non-uniformity of microbolometer array.     

用于高能激光系统的共孔径光学装置设计

高能激光系统的主要工作方式是利用其精跟踪模块将发射激光传输聚焦至闭环跟踪条件下的目标上,使之受到毁伤或失效。为实现该工作方式,本文研究设计了一套共孔径光学收发装置。该装置的发射系统主要由离轴两反式主望远镜模块、伽利略透射式调焦望远镜模块和光束馈送模块共同组成二级扩束系统,接收系统主要由离轴两反式主望远镜模块、精跟踪成像模块和光束馈送模块共同组成长焦距光学系统,其中光束馈送模块由二向色镜、快速反射镜等光学元件组成。以非相干空间合束的基模高斯光作为激光光源,利用光学设计软件对该装置进行了优化设计。对于发射系统,获得了激光经过调焦望远镜模块不同的调焦量调制后,传输至0.5~5 km处的光斑分布情况,且激光波前像差RMS值均优于λ/20;对于接收系统,由各模块一同构成的成像光学系统的性能经优化后接近衍射极限,其中系统传递函数在70 lp/mm时大于0.6,最后通过样机实验也验证了设计的正确性。本文的设计和实验结果证实了该共孔径光学收发装置结构合理,性能可靠,满足高能激光系统的工程应用需求。     

热释电IRFPA非均匀性校正实验系统研究

采用虚拟仪器技术,设计了基于LabVIEW软件平台的热释电IRFPA（红外焦平面阵列）非均匀性校正系统。该系统可通过控制面板选择校正算法,选取3种不同的标准像元的标准校正曲线。可以对IRFPA待校正的像元输出进行采集,对非均匀性参数进行测试,还可以进行非均匀性校正。系统通过三维波形以及图像的显示来观察校正前后对比,并能计算出校正前后的NU（非均匀性）值大小。对像元数为120160的热释电IRFPA输出的视频信号进行了非均匀性校正实验,对非均匀性校正算法进行了统计对比,对仿真结果及数据进行了分析总结。经过校正实验验证了系统的可行性,结果证明基于平均值法的两点定标算法对热释电IRFPA非均匀性校正后的NU值是最小的。通过统计数据得出校正后的NU可平均下降30%。     

A study of extended optimization of U-type rod for LED projectors

The paper proposes a new U-type integral rod for a miniature DLP projector's optical engine with a high-power LED source and L-type optics in order to minimize volumetric size of optical engine. In addition, Taguchi method is applied in this research in order to extendedly optimize the performance of optical engine after initial optimization by damped least square (DLS). A miniature optical engine with LED light source has the advantages of good power consumption, useable projected image, reasonable brightness and uniformity, compactness in volumetric size and decent performance specifically for high spatial frequencies. However, there are still rooms for development with regard to light efficiency and uniformity due to non-uniformity of LED light distribution. Two critical design methods are proposed in this research. Firstly, a “U-type integrator” working with high-power LED which not only causes rays to make a “U-turn” in order to minimize volumetric size of optical engine but also, after optimization, controls output uniformity well after extended optimization by Taguchi method. With regard to gain of optical efficiency, we also consider the factors of a U-type integrator: shape and length with a Taguchi optimizer. It is concluded that the newly developed design achieves good results for the performance and volumetric size of the module. Extended optimized parameter design is able to improve the luminous flux by 4.84%, the illumination uniformity 5.62% and the packing size by 12%.     

Brownian motion and diffusion: from stochastic processes to chaos and beyond

One century after Einstein's work, Brownian motion still remains both a fundamental open issue and a continuous source of inspiration for many areas of natural sciences. We first present a discussion about stochastic and deterministic approaches proposed in the literature to model the Brownian motion and more general diffusive behaviors. Then, we focus on the problems concerning the determination of the microscopic nature of diffusion by means of data analysis. Finally, we discuss the general conditions required for the onset of large scale diffusive motion.     

Optical characteristics of a turbid medium between two mirrors

Using the one-dimensional Boltzmann equation, we examine the optical scattering properties of a turbid medium that is located between two mirrors with controllable reflectivity. We examine how the mirrors can be used to enhance the total transmission of an intensity modulated laser beam through this system. The analytical results show that, for certain modulation frequencies, the total transmission can be increased if the laser source is placed between the mirrors. This finding could improve diffusive imaging for those highly scattering media that are so thick that the laser light would not penetrate sufficiently deep in the absence of any mirrors.     

An opto-electrical method for measuring the gap of LCD glass plates

We focus on the experimented system development for the measurement of the gap of LCD glass plates. The measurement system includes a laser light source, lens module, image capturing system and the algorithm for calculation of the position of light spots. We emphasize the structure of laser triangulation in an optical system. The software is focused on the algorithm for calculating the position of light point, including centroid calculation method (CCM) and Fourier phase shift (FPS).

Furthermore, to verify the feasibility of the algorithm, we use computer software to simulate experiments. We also discuss the contribution of the noise to the accuracy for the CCM and FPS. To complete the development of the opto-electrical measurement system and to verify the accuracy for the hardware architecture, we use a novel mechanism of multi-track and concentricity, laser light source, lens module, and image capturing system.     

A method for fringe normalization by Zernike polynomial

A new approach for fringe normalization by Zernike polynomial fitting to cancel background illumination in an interferogram is proposed. With this method, background illumination can be suppressed, high frequency noise is immunized and the contrast is improved by normalization. The main idea for this paper is to use the Zernike polynomial fitting interferogram to cancel background illumination; the high frequency noise is then filtered by a Wiener filter. Finally, the paper uses the method of local region contrast modulation to enhance fringe contrast. This method can overcome the problem of the non-uniformity illumination of fringe patterns resulting from the marginal reflection of optical components and a non-uniformity light source