Near-field optical imaging using force detection with new tip-electrode geometry

We propose a new tip-electrode geometry to detect an (optical) evanescent field using noncontact atomic force microscopy. Using a semi-transparent metal electrode on the prism surface, the force sensitivity due to evanescent field in new tip-electrode geometry was enhanced by a factor of about 1000, comparing with that in old tip-electrode geometry where electrode was located behind the prism. Furthermore, this tip-electrode geometry avoids the electrostatic field caused by the residual charges and contact-electrified charges near the prism surface, which affects the force sensitivity due to evanescent field. We demonstrated the high resolution imaging of the evanescent field on the Au film with 15-nm (λ/33) lateral resolution.     

Near-field spatial imaging of the Ni-like palladium soft-X-ray laser

We report on a series of near-field imaging experiments for the nickel-like 14.7-nm Pd X-ray laser that were conducted with the aim to characterize the two-dimensional source intensity distribution and its position relative to the target surface. The effect of different prepulse amplitudes at variable main pulse-to-prepulse delays is investigated. For larger prepulses (2.8% and 8%) the peak emission is moved farther away from target surface with increasing delay whereas for the weak prepulse (0.5%) the position of peak emission remains rather stable over a delay range of several nanoseconds. A great deal of structure was observed in the near-field image. The size of the smallest structures detected is consistent with the coherence length-obtained from the corresponding far-field data – at the output aperture. The measurements are compared to the simulations performed with the LASNEX and CRETIN codes. The LASNEX code is used to calculate the hydrodynamic evolution of the plasma and provide the temperatures and densities to the CRETIN code, which then does the kinetics calculations to determine the gain.     

Near-field imaging of pyramid-like nanoparticles at a surface

An exact analytical solution of the self-consistent equation for the local field is used to calculate the near-field optical images of pyramid-like nano-objects placed at a surface of a solid. The diagram method developed previously for near-field image formation is generalized in order to describe layered objects, which are treated as many-body systems. The near-field optical images of triangular and square pyramids are calculated for the illumination configuration as well as those of triangular and square prisms. It is found that the near-field images of nanoparticles having the dielectric constant close to that of the substrate change rapidly and in a complicated manner with the probe–sample distance.     

红外热成像法研究电路板热分布特性

介绍了一种红外热成像处理技术,以及利用这种红外热成像处理系统研究通电电路板的热平衡分布特性。     

扫描型亚像元成像处理对热成像系统性能改善的模拟分析

基于光学微扫描的亚像元成像技术是当前国内外迅速发展的一种高性能成像技术,它对探测器单元数较少且探测器单元尺寸较大的热成像系统更为有效。以扫描型焦平面探测器热成像系统FC和GP为研究对象,采用热成像系统性能模拟软件包CFLIR4.0,分析了光学系统的相对孔径、过采样和亚像元成像等对热成像系统性能的影响,包括传递函数MTF、噪声等效温差NETD、最小可分辨温差MRTD以及系统的探测和识别距离。模拟分析表明:过采样成像可提高热成像系统的性能,亚像元成像处理可进一步提高热成像系统的性能,可明显地提高系统的作用距离。研究结果对亚像元热成像技术的发展具有参考意义。     

Near-field optical characterization of GaN and InxGa1−xN/GaN heterostructures grown on freestanding GaN substrates

Using near-field scanning optical microscopy (NSOM), we report the spatial distribution of photoluminescence (PL) intensity in III-nitride-based semiconductor layers grown on GaN substrates. Undoped GaN, In_0.11Ga_0.89N, and In_0.13Ga_0.87N/GaN multi-quantum wells (MQWs) were grown by metal organic chemical vapor deposition (MOCVD) on freestanding GaN substrates. Micro-Raman spectroscopy has been used to evaluate the crystalline properties of the GaN homoepitaxial layers. The variation of the PL intensity from the NSOM imaging indicates that the external PL efficiency fluctuates from 20% to 40% in the 200 nm InGaN single layer on freestanding GaN, whereas it fluctuates from 20% to 60% in InGaN/GaN MQWs. In the NSOM-PL images, bright island-like features are observed. After deconvolution with the spatial resolution of the NSOM, the size of these features is estimated to be in the range of 150–250 nm.     

基于FPGA的近红外实时透雾成像方法

针对雾天图像的退化现象,提出采用近红外波段成像和视频图像处理技术相结合的透雾成像方法。根据视频图像相邻两场直方图相似性特点,提出了改进的直方图均衡化算法处理雾天降质图像。改进算法简化系统结构,降低逻辑设计复杂度,节约了高速存储器部分硬件资源。算法经过MATLAB仿真验证,并在FPGA视频图像处理平台上硬件实现。实验证明改进算法增强雾天图像的同时满足标准视频图像处理25帧/秒的实时性要求,结合近红外波段透雾能力使雾天能见距离提高1.5倍以上。     

引信红外偏振成像探测机理及关键技术

目标处于复杂场景时会对目标探测带来负面影响的干扰,会给目标识别带来了很大的影响。红外偏振成像探测是利用人造目标与自然目标以及真实目标与伪装目标的红外辐射偏振特征的差异来提高目标识别效果的。在复杂背景下识别和攻击目标是引信智能化的重要体现,因此探讨如何将红外偏振探测技术应用于引信是十分必要的。在分析红外偏振成像探测机理的基础上,对该技术用于引信的关键技术问题进行了分析,为引信红外偏振成像探测的研究奠定了基础。     

Evaluation of infrared collimators for testing thermal imaging systems

Infrared reflective collimators are important components of expensive sophisticated test systems used for testing thermal imagers. Too low quality collimators can become a source of significant measurement errors and collimators of too high quality can unnecessarily increase cost of a test system. In such a situation it is important for test system users to know proper requirements on the collimator and to be able to verify its performance. A method for evaluation of infrared reflective collimators used in test systems for testing thermal imagers is presented in this paper. The method requires only easily available optical equipment and can be used not only by collimator manufactures but also by users of test equipment to verify performance of the collimators used for testing thermal imagers.     

利用QuickBird数据进行热红外遥感成像模拟的研究

针对基于机载热像仪图像或随机产生仿真场景的早期热红外成像模拟系统,提出了对高分辨率QuickBird图像进行星载热红外成像模拟的方法。基于高分辨率QuickBird图像,采用ISODATA法进行非监督分类,得到土地分类专题图,通过地物光谱数据库获得场景地物温度及发射率,从而可获得地面辐亮度图像;利用大气辐射传输软件MODTRAN对其进行大气修正,结合卫星遥感器辐射定标系数,最终可得到卫星遥感器输出图像。仿真结果表明,利用QuickBird进行热红外遥感成像模拟是一种全新而有益的尝试,对伪装效果检验等具有一定的参考价值。     

近红外光谱成像系统在液体安检中的应用

易燃易爆液体的实时、远程和动态探测对于保障公共安全具有重要意义,在公安、民航和海关等领域应用前景广阔。研制了基于液晶可调滤光片的近红外光谱成像系统,通过波长优选算法大幅降低了光谱通道数,有效提高了扫描成像速度和数据处理速度,可实现对低速运动的液体危险品的远程和实时检测。利用该系统开展了不同环境下对易燃易爆液体的检测实验,结果表明该系统对静态目标检测精度为100%,对速度小于0.2 m/s的运动目标检测精度高于95%。     

激光红外主被动复合导引系统

提出了采用激光主动三维成像技术配合被动红外成像技术共同工作的复合导引体制,用于提升地对地导弹的作战效能及对于隐身目标的识别能力。给出了各分系统的设计方案,并提出了合理的导引策略。该套系统能够兼顾红外大视场搜索及激光小视场三维成像,丰富的目标图像信息更加有利于对作战目标进行准确识别。整套复合光学导引系统结构简单、加工难度适中,在将整套导引系统口径控制在100 mm左右的情况下,同样能够实现4 km以上距离的导引。该项技术的提出对于我国复合导引技术的发展及我军导弹作战能力的提升有着重要意义。     

Strain imaging of a perpendicular recording head in a Hard Disk Drive

Imaging of magnetic-field-induced strains using scanning probe microscopy enables us to observe magnetic domain structures and magnetic force distributions. This method has an ability of observing magnetic structures in deep portions along with surface structures. We observed an air-bearing surface of a perpendicular recording head in a hard disk drive in large areas including the whole yokes, and investigated characteristics of the magnetic poles and layers subjected to magnetic fields produced by writing coil currents. Attractive forces independent of the field directions acted between the upper and lower yokes made by soft material, which generated surface displacements in the ABS. The signals were second-harmonic oscillations for alternating currents without a dc bias, and the amplitude images represented the field distribution. Meanwhile, fixed magnetic charges in both ends of the read sensor, which were produced by the hard-bias film, were subjected to the fields. The fixed charges, which hardly changed by the fields, lead to strains depending on the field directions, and generated specific contrasts of one pair of bright-dark spots in the strain images. In the absence of surface underlayer, the fields by the writing coil broke into the read sensor sandwiched by the shield layers.     

Study on probability of detection for fatigue cracks in sonic infrared imaging

Detection reliability of sonic infrared imaging is one of the increasingly important aspects for out of lab applications. And for the detection reliability evaluation, probability of detection (POD) for different defects under given test conditions has been successfully used as an accepted quantitative measurement. In this study, we test a set of C45 ferritic steel plates with artificial fatigue cracks. Experimental results show that the crack heating response increases with the increasing crack length, and the relationship between the logarithmic form of heat response signal and the crack length appears to be linear. Based on the above statistic characteristics, the linear regression analysis and the Wald method are adopted to estimate the POD function and its confidence interval. The study aims to provide a quantitative evaluation method for detection reliability in sonic infrared imaging.     

红外热成像技术在炮膛测温中的应用北大核心CSCD

火炮在连续射击过程中,炮膛内壁温度持续积累升高,当其温度超过全可燃药筒燃点时具有较高的安全隐患。介绍了一种基于红外热成像技术的炮膛测温方法与装置。叙述了该装置的组成以及测温基本原理与流程;分析了火炮连续射击换弹的过程,炮膛测温装置利用边缘检测、轮廓提取与识别判断等图像处理技术,自动分析有效测温时间段与目标区域;利用根据最小二乘法标定好的解算曲线,实时确定目标区域的最高温度值与平均温度值,并将温度数据及时上传至火炮控制系统,以判断是否换弹或击发,可有效提高火炮连续射击过程中的安全性。     

热像系统动态探测概率的研究

研究了热像系统动态探测概率。在对目前动态探测概率研究状况作简要讨论的基础上 ,建立了动态探测概率的一个微分方程。利用该方程可以研究探测器以速度 v(x)向目标运动过程中的动态探测概率。与传统的动态探测概率相比 ,所提出的方法考虑了目标的运动过程 ,而传统的动态探测概率虽然包含了时间 t,但它并不表征物体的运动过程     

Surface plasmon resonance (SPR) reflectance imaging: Far-field recognition of near-field phenomena

The surface plasmon resonance (SPR) reflectance imaging technique provides a label-free visualization tool to characterize the near-field fluidic transport properties within 100 nm from the solid surface. The key idea is that the SPR reflectance intensity varies with the near-field refractive index (RI) of the test fluid, which in turn depends on the micro- and nano-fluidic scalar properties such as concentrations, temperatures, and phase changes, occurring in the near-field. As essential knowledge to understand and implement the SPR reflectance imaging technique, this paper presents discussions on the basics of surface plasmon polaritons (SPPs), surface plasmon resonance (SPR), setup of the SPR reflectance imaging system, and the SPR reflectance imaging resolution. The second part of the paper elaborates the applications of the SPR imaging sensor technique in characterizing the near-field fingerprints of nanofluidic evaporative self-assembly.     

红外全景扫描跟踪成像系统设计与实现

针对红外搜索跟踪系统中全范围快速搜索和跟踪成像视场不同的问题,采用线列探测器配合高速转台和高均匀性扫描器,设计实现了一种360全方位搜索和跟踪的成像系统。实验结果表明,该系统成功实现了360全景扫描,在搜索到目标后可快速转入跟踪成像,由搜索转入跟踪成像状态的稳定时间小于1.94 s,系统性能指标达到实用要求。     

利用扫描近场红外显微镜对化学样品组分进行成像研究

介绍了用北京自由电子激光为光源的扫描近场红外显微镜对化学样品组分进行的成像研究，通过所得到的近场微区图像，可以对样品在微区范围内的成分组成，混合的均匀程度等作出比较清晰的判断. 关键词： 自由电子激光 近场光学 扫描近场红外显微镜