光机械式红外探测器中镜面弯曲对探测灵敏度的影响

光学读出式红外成像技术是近年来研究的热点，本文讨论了镜面弯曲对光学检测灵敏度的影响。由双材料微悬臂梁组成的非致冷焦平面阵列通过体刻蚀工艺加工而成，由于残余应力的影响，制成的焦平面阵列将会发生弯曲，应力导致的镜面弯曲将会降低光学探测灵敏度。本文通过傅立叶光学模拟了镜面弯曲对光学探测灵敏度的影响，并通过实验验证了该模型。实验和模拟结果表明，在镜面曲率为0．1mm-1时，光学探测灵敏度将会降低到理想情况的40％。最后我们用这个模型评价了通过表面修饰来提高光学性能的效果。     

光机械式红外探测器中镜面弯曲对探测灵敏度的影响

光学读出式红外成像技术是近年来研究的热点,本文讨论了镜面弯曲对光学检测灵敏度的影响.由双材料微悬臂梁组成的非致冷焦平面阵列通过体刻蚀工艺加工而成,由于残余应力的影响,制成的焦平面阵列将会发生弯曲,应力导致的镜面弯曲将会降低光学探测灵敏度.本文通过傅立叶光学模拟了镜面弯曲对光学探测灵敏度的影响,并通过实验验证了该模型.实验和模拟结果表明,在镜面曲率为0.1mm-1时,光学探测灵敏度将会降低到理想情况的40%.最后我们用这个模型评价了通过表面修饰来提高光学性能的效果.     

光学读出微梁阵列红外成像性能分析与优化

系统响应率是光学读出微梁焦平面阵列(Focal Plane Array,FPA)红外成像的关键性能参数。在刀口滤波光学读出技术中,系统响应率的主要组成部分——光学读出灵敏度与微梁反光板的长度密切相关,并受到反光板弯曲变形的严重影响。由于残余应力在制作过程中不可避免地存在,微梁反光板都有弯曲变形,膜厚相同的反光板具有相同的变形曲率半径。本文利用傅里叶光学分析了反光板长度和弯曲变形对光学读出灵敏度的影响,构建并实验验证光学读出灵敏度理论模型。根据该模型,分析了系统响应率与反光板长度之间关系,理论分析与实验结果相符。结果表明,通过减薄SiNx厚度并使反光板处于该厚度下的最优长度,不仅能提高红外成像的系统响应率,而且能同时提高红外成像的空间分辨率。     

双材料微梁阵列非制冷红外成像技术--微梁阵列热变形的光学读出

针对双材料微梁阵列非制冷红外成像技术的光学读出系统,提出了在谱平面上进行刀口滤波将阵列转角转化为像平面上光强变化的高灵敏度测量技术,并对光学探测灵敏度进行了理论分析.利用该光学读出系统在实验中得到了120℃红外物体的热图像.通过对实验结果的分析和图像处理消除噪声技术,得到该系统在成像温度范围的噪声等效温度差(NETD)约为5K,并对系统噪声进行了讨论.     

基于无基底焦平面阵列的红外图像复原算法

与传统有基底焦平面阵列不同,无基底焦平面阵列的感热单元吸收的红外辐射以点扩散函数的形式向相邻单元进行热传导,该热力学特性虽然能够大幅提高红外探测性能,使红外目标在背景中更加凸显,但同时降低了系统对红外目标细节的分辨能力,使图像模糊。通过分析这种热扩散叠加效应对红外成像质量的影响,利用数字图像处理方法,提出了针对性的红外图像复原算法。仿真和实验均表明该算法能够有效增强红外图像细节轮廓,提升图像质量。     

基于MEMS的光力学红外成像

非制冷红外成像仪以其优良的性价比和高可靠性而倍受关注。近期 ,非制冷的热机械型红外成像仪有望发展成为新的低价格高性能的红外成像设备。本文提出了一种新型光学读出的红外探测仪。此红外探测仪的核心器件焦平面阵列 (FPA)由无硅基底结构的微悬臂梁阵列构成。每个微悬臂梁独立地把入射的红外热辐射转化为被光学系统探测的热变形。它不需要读出电路、真空腔和制冷装置 ,其理论上的噪声等效温度差接近致冷型红外成像系统 ,而制作成本和难度将大幅降低。制作的无硅基底单层膜结构的FPA ,其单元尺寸为 2 0 0 μm× 1 0 0 μm ,阵列大小为 1 5 0× 1 0 0像素数。实验制作的系统探测到温度为 5 0 0K左右的热物体像 ,热像采样频率为 1 2幅 /秒。     

无基底焦平面阵列结构优化设计及性能分析

基于光学读出非制冷红外成像技术,本文作者提出并成功设计制作了无基底焦平面阵列结构(Focal Plane Array,FPA),不仅简化了制作工艺,而且大幅提升了成像性能。但由于其为单层膜结构,固有频率值低,可能会引起热机械振动噪声(NETDTM),导致噪声等效温度差(NETD)上升。为解决这一问题,本文提出两种改进的加强梁结构,借助有限元简化模型和激光位移传感器,通过数值模拟和实验验证,证实这两种结构可以大幅度提高FPA固有频率值(分别从74Hz提升至835Hz和404Hz),NETDTM降低约两个数量级,从而实现了对FPA的优化设计。     

大展弦比机翼中液压管路的抗大变形设计与优化方法

提出了一种大展弦比机翼管路的抗大变形设计与优化方法。首先建立了大展弦比机翼平板-不同布局管路的装配简化模型;然后分析了在机翼大变形下,管道的弯曲位置、弯曲半径、横向距离、弯曲角度等几种不同布局参数,对管路根部应力、最大应力和卡箍处变形的影响关系。结果表明:弯曲位置与横向距离对应力有较大影响,弯曲位置靠近机翼根部可以降低管道根部应力,但是最大应力显著增加,横向距离的增加可以降低管路根部应力以及最大应力;弯曲位置和弯曲半径对卡箍处变形有较大影响,随着弯曲位置从机翼板根部向变形处移动,卡箍处变形量均先减小后增加,弯曲半径的增加会降低卡箍处变形量。采用遗传算法得到在机翼大变形下最优的管形布局,结果表明,卡箍附近最大应力比直管降低了51%。     

一种动光弹模型材料的制作方法及其应用

基于#618环氧树脂、甲基六氢苯酐、促进剂DMP-30、环氧树脂消泡剂四种原料,提出制作光弹性模型的新配方和新方法,并利用单轴压缩实验、电测法和动态光弹法分别测定了制作的光弹模型的动态力学参数。新方法工艺简单,制作周期短,对人体无害。制作的光弹模型初始应力小,表面光洁,质地均匀,透光性好,光学灵敏度高,具有良好的机械加工和切削性能。通过三点弯曲梁冲击实验,得到了清晰的光弹等差条纹图像,验证了该配方和方法制作的模型可以应用于动态光弹性实验。     

轴向冲击载荷作用下锥壳中弹性应力波传播的计算和实验研究

本文利用有限元分析和模型实验研究了在轴向冲击载荷作用下,锥壳中弹性应力波的传播、计算和实验结果表明,结构中存在着弹性纵波和弹性弯曲波的传播,它们传播的速度各不相同,使壳面承受不同的应力状态;讨论了纵波和弯曲波随壳面的衰减;实验指出,由于边界的影响,即使纵波的反射也会产生新的反射弯曲波沿锥面传播。     

基于MEMS和光学读出的非制冷红外成像技术

由于军事和商业应用的巨大潜力,红外成像技术至今仍是研究热点之一。针对本课题组提出的基于MEMS和光学读出的新型非制冷红外成像技术,本文一方面通过有限元仿真分析,详细讨论了新型无基底双材料微梁阵列FPA的热转换效率和热变形效率,另一方面通过光学理论分析,详细讨论了光学读出系统在极限操作下的光学测量灵敏度。理论和仿真分析显示,课题组提出的非制冷红外成像技术的NETD的理论极限与当前制冷型红外成像技术的典型指标相当,约为4mK。同时,本文对设计制作的FPA,在构建的系统上进行了红外实时成像实验和理论仿真分析,显示其系统级NETD已达到110mK。     

锗-硼硅玻璃局部加热低温封接温度场研究

在光学读出非制冷红外热像仪焦平面阵列(FPA,Focal Plane Array)真空封装结构中,硼硅玻璃和双面镀增透膜的锗片分别作为透可见光和透红外光的窗口材料.由于锗窗上增透膜不能承受高温(<250℃),同时FPA也不能承受高温(<100℃),因此封装过程须在低温下进行,并对锗窗上的增透膜及FPA进行保护.本文提出了一种用于锗-硼硅玻璃低温扩散焊接的局部加热方法.该方法从导热系数较大的锗窗外表面加热(200℃),而导热系数较小的硼硅玻璃窗口外表面维持低温(60℃).有限元模拟计算结果表明,该加热过程稳态情况下待焊接区域温度约200℃,满足低温焊接的温度要求.锗窗上温度(200℃)低于250℃,且FPA区域的温升在75℃以下.用实验方法对模拟结果进行了验证,实验结果同模拟结果一致,证明该方法能够有效地保护FPA及锗窗上的增透膜.     

Determination of the yield properties of thin films using enhanced coherent gradient sensing

This paper describes coherent gradient sensing (CGS) as an optical, full-field, real-time, nonintrusive, noncontact technique for measurement of curvature and curvature changes in single-layered and multilayered thin films deposited on substrates. The sensitivity of the basic CGS technique is enhanced using optical fringe multiplication to map curvature in very flat specimens (k0.001 m^–1). Subsequently, this curvature measurement technique is applied to the determination of the yield properties of thin films subjected to cyclic thermomechanical loading.     

Sensitivity analysis of thermal design parameters for focal plane assembly in a space spectral imaging instrument

There are deviations between real parameters and thermal design parameters on thermophysical attribute of focal plane assembly (FPA). The parameters are difficult to be determined accurately and the thermal design scheme will be affected with the values of the parameters. The thermal design problem of FPA is described by means of system sensitivity theory. The in-orbit heat balance equations are established, and the thermal design parameters, which might affect the temperature distribution of the FPA, are given. As an example, the sensitivity of thermal design parameters is analyzed for a FPA in a space spectral imaging instrument. A basis to determine the structural and thermophysical parameters for FPA is gotten, furthermore, an analytical method is provided for reliability validation of thermal design and operating reliability on orbit. It is shown that contact heat-transfer coefficient between mounted surfaces and surface emissivity are the main parameters affecting mean temperature of Charge converse device (CCD). The power of the inner heat source, thermal conductivity and inner contact heat-transfer coefficient are the primary parameters affecting temperature difference between CCD and the heat-transfer block. The thermal test is set up, and it is illuminated that the sensitivity analysis strategy based on the thermal design scheme is effective and feasible.     

Influence of curvature on drag reduction by opposition control in turbulent flow along a thin cylinder

Opposition controlled fully developed turbulent flow along a thin cylinder is analyzed by means of direct numerical simulations. The influence of cylinder curvature on the skin-friction drag reduction effect by the classical opposition control (i.e., the radial velocity control) is investigated. The curvature of the cylinder affects the uncontrolled flow statistics; for instance, skin-friction coefficient increases while Reynolds shear stress (RSS) and turbulent intensity decrease. However, the control effect in the case of a small curvature is similar to that in channel flow. When the curvature is large, the maximum drag reduction rate decreased. However, the optimal location of the detection plane is the same as that in a flat plate. Further, the drag reduction effect is achieved even on a high detection plane where the drag increases in the flat plate. Although a difference in the drag reduction effect can be observed with a change in the curvature, its mechanism considered in this analysis based on the transport of the Reynolds stress is similar to that of the flat plate.     

微悬臂梁生化传感系统的性能分析

在基于光杠杆原理检测微悬臂梁变形的生化传感实验系统中,液体折射率的变化会导致PSD上光斑的位移,从而影响系统的检测信号。本文从理论上分析了在不同检测光束的入射角度、微梁的放置角度等参数条件下,液体折射率的变化对系统检测信号的影响。结果表明：在传统的光路下,液体折射率改变10-3引起的光斑位移与一般的生化反应引起的位移相当,即液体折射率的改变严重影响系统的检测信号。通过理论分析还发现在适合的参数配置下,可以忽略折射率变化对系统检测信号的影响。同时,参数的改变不影响系统的检测灵敏度。理论分析的结果得到了实验验证。     

Optical Detection of Impact Contact Times with a Beam Deflection Probe

We present an optical detection technique, called the beam deflection probe, to accurately measure contact times of normal-incidence impacts of steel and sapphire spheres with a transparent glass block. It exploits the deformation of the area that is in a mechanical touch during the rebound. The deformation of the surface acts as a dynamic contact mirror. When illuminated by a laser beam, total internal reflection takes place at the contact mirror, the beam is deflected from it, and its angular deflection history is monitored by a quadrant photodiode. A simple threshold-level data processing of the photodiode signals is used to determine the impact duration. It is shown that the shape of the signal is highly dependent on the location of the impact relative to the center of the laser-beam illuminated area while the determination of the contact time does not depend on the impact position. Using an automated ball release mechanism, the contact time of low-velocity impacts was measured for various ball diameters and approach velocities conforming to the Hertz contact theory. The proposed optical detection of contact times supplements the existing measurement techniques and represents the only alternative to the piezoelectric detection when contact times are to be measured on the microsecond scale.