Simultaneous measurement of optical constants of dispersive material at visible and infrared wavelengths

A systematic method has been proposed to evaluate the complex refractive indices and thicknesses of dispersive polymer thin films in both visible and infrared regions. The curve-fitting method has been applied to the measurement of the film thicknesses and complex refractive indices in the visible and near-infrared regions. The accuracy of the evaluated film thickness is of the order of +/-0.5%. The presented method is useful for characterizing the optical properties of polymers whose refractive indices are near to those of substrates.     

Determining the roughness parameters of the surface of transparent objects from the indicatrix of diffusion of transmitted light

An analytical solution for the indicatrix of diffusion of the one-dimensional statistically rough surface is considered. Translated from Izmeritel'naya Tekhnika, No. 6, pp. 23–28, June, 2000.     

Fusion of visible and infrared images based on multiple differential gradients

ABSTRACT

The ideal fusion of infrared and visible images is to preserve the details of the visible image as much as possible and superimpose important highlights of the infrared image on the visible image. Therefore, this paper proposes a multiple differential gradient method (MDG) that fuses the infrared image with the difference image of the visible light image and the gradient image of the infrared image. First, an image with comprehensive information is obtained through the difference between the infrared image and the visible image, and it is fused with the suppressed visible image. The new image obtained is then fused with the divergent image of the infrared gradient. Finally, the gray value of the visible image is compared with the new image, and the point with the larger gray value is selected to be fused into the new image. The result is better than most classical algorithms.     

Fusion of infrared and visible images based on focus measure operators in the curvelet domain

Aiming at the differences of physical characteristics between infrared sensors and visible ones, we introduce the focus measure operators into the curvelet domain in order to propose a novel image fusion method. First, the fast discrete curvelet transform is performed on the original images to obtain the coefficient subbands in different scales and various directions, and the focus measure values are calculated in each coefficient subband. Then, the local variance weighted strategy is employed to the low-frequency coefficient subbands for the purpose of maintaining the low-frequency information of the infrared image and adding the low-frequency features of the visible image to the fused image; meanwhile, the fourth-order correlation coefficient match strategy is performed to the high-frequency coefficient subbands to select the suitable high-frequency information. Finally, the fused image can be obtained through the inverse curvelet transform. The practical experiments indicate that the presented method can integrate more useful information from the original images, and the fusion performance is proved to be much better than the traditional methods based on the wavelet, curvelet, and pyramids.     

Variability in surface infrared reflectance of thirteen nitrile rubber gloves at key wavelengths for analysis of captan

The aim of this study was to investigate the surface variability of 13 powder-free, unlined, and unsupported nitrile rubber gloves using attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectrophotometry at key wavelengths for analysis of captan contamination. The within-glove, within-lot, and between-lot variability was measured at 740, 1124, 1252, and 1735 cm(-1), the characteristic captan reflectance minima wavelengths. Three glove brands were assessed after conditioning overnight at relative humidity (RH) values ranging from 2 +/- 1 to 87 +/- 4% and temperatures ranging from -8.6 +/- 0.7 to 59.2 +/- 0.9 degrees C. For all gloves, 1735 cm(-1) provided the lowest background absorbance and greatest potential sensitivity for captan analysis on the outer glove surface: absorbances ranged from 0.0074 +/- 0.0005 (Microflex) to 0.0195 +/- 0.0024 (SafeSkin); average within-glove coefficients of variation (CV) ranged from 2.7% (Best, range 0.9-5.3%) to 10% (SafeSkin, 1.2-17%); within-glove CVs greater than 10% were for one brand (SafeSkin); within-lot CVs ranged from 2.8% (Best N-Dex) to 28% (SafeSkin Blue); and between-lot variation was statistically significant (p < or = 0.05) for all but two SafeSkin lots. The RH had variable effects dependent on wavelength, being minimal at 1735, 1252, and 1124 cm(-1) and highest at 3430 cm(-1) (O-H stretch region). There was no significant effect of temperature conditioning. Substantial within-glove, within-lot, and between-lot variability was observed. Thus, surface analysis using ATR-FT-IR must treat glove brands and lots as different. ATR-FT-IR proved to be a useful real-time analytical tool for measuring glove variability, detecting surface humidity effects, and choosing selective and sensitive wavelengths for analysis of nonvolatile surface contaminants.     

Nature of light scattering in dental enamel and dentin at visible and near-infrared wavelengths

The light-scattering properties of dental enamel and dentin were measured at 543, 632, and 1053 nm. Angularly resolved scattering distributions for these materials were measured from 0° to 180° using a rotating goniometer. Surface scattering was minimized by immersing the samples in an index-matching bath. The scattering and absorption coefficients and the scattering phase function were deduced by comparing the measured scattering data with angularly resolved Monte Carlo light-scattering simulations. Enamel and dentin were best represented by a linear combination of a highly forward-peaked Henyey-Greenstein (HG) phase function and an isotropic phase function. Enamel weakly scatters light between 543 nm and 1.06 μm, with the scattering coefficient (μ(s)) ranging from μ(s) = 15 to 105 cm(-1). The phase function is a combination of a HG function with g = 0.96 and a 30-60% isotropic phase function. For enamel, absorption is negligible. Dentin scatters strongly in the visible and near IR (μ(s)?260 cm(-1)) and absorbs weakly (μ(a) ? 4 cm(-1)). The scattering phase function for dentin is described by a HG function with g = 0.93 and a very weak isotropic scattering component (? 2%).     

红外热像仪与表面热电偶测量发射率的匹配法

使用红外热像仪测量物体温度时,需要知道被测物体的发射率。为测量物体的发射率,提出红外热像仪和表面热电偶组合的匹配法。建立匹配法测量发射率的实验装置,使用该实验装置,利用恒温源对测试样品进行加热,在近环境温度范围内对两种测试样品3M Scotch Super 88型绝缘胶带和3M 1721型绝缘胶带的发射率进行测量。实验结果表明,测量值与文献值一致。该文给出两种样品在不同温度区间的具体发射率值,该发射率值可用做红外热像仪工程测温中的参考值。     

Concentration detection of quantum dots in the visible and near-infrared range based on surface plasmon resonance sensor

We employ an optical sensor based on surface plasmon resonance (SPR) operating in the near-infrared and in the visible range to determine the concentration of CdSe/ZnS core-shell quantum dots (QDs) which are embedded in the SU8 organic films. Attenuated total reflection (ATR) measurements show that the amplitude of the shift of the resonance dip is closely related to the concentration variation of QDs in the organic films and the incident laser. The sensitivity is enhanced by 1.5-time and the detect limitation is expanded to 10⁻⁵ μmol/L in the visible range as compared to that in the near-infrared. The sensitivity enhancement and the expansion of detect limitation of the visible SPR sensor may originate from the coupling of surface plasmons to luminescence from QDs.     

Characterization of the influence of polarization orientation on bulk damage in KDP crystals at different wavelengths

The investigation of polarization orientation on damage performance of type I doubler KDP crystals under different wavelengths pulses irradiation is presented in this work. Pinpoints densities (PPD) and the size distribution of pinpoints are extracted through light scattering pictures captured by microscope. The obtained results indicate that the measured PPD as a function of the fluence is both wavelength and polarization dependent, although neither fluence nor polarization have impact on the size distribution of pinpoints. We also find that the damage performances can separate into three groups depending on the wavelength, which suggests the existence of different categories of precursors and different mechanisms responsible for bulk damage initiation in SHG KDP crystals.     

Fluorescence efficiency and visible re-emission spectrum of tetraphenyl butadiene films at extreme ultraviolet wavelengths

A large number of current and future experiments in neutrino and dark matter detection use the scintillation light from noble elements as a mechanism for measuring energy deposition. The scintillation light from these elements is produced in the extreme ultraviolet (EUV) range, from 60 to 200 nm. Currently, the most practical technique for observing light at these wavelengths is to surround the scintillation volume with a thin film of tetraphenyl butadiene (TPB) to act as a fluor. The TPB film absorbs EUV photons and re-emits visible photons, detectable with a variety of commercial photosensors. Here we present a measurement of the re-emission spectrum of TPB films when illuminated with 128, 160, 175, and 250 nm light. We also measure the fluorescence efficiency as a function of incident wavelength from 120 to 250 nm.     

Optical tomography of transparent objects with phase-shifting interferometry and stepwise-shifted Ronchi ruling

An experimental setup for tomographic inspection of phase objects is presented. The system uses a common-path interferometer consisting of two windows in the input plane and a translating grating as its pupil. In the output, interference of the fields associated with replicated windows is achieved by a proper choice of the windows' spacing with respect to the grating period. With a rotating object in one window and a plane wave in the second one, the phase distribution of each projection is encoded as a corresponding digital image row, which, in turn, constructs a composite interferogram over the plane of a traditional sinogram. Phase stepping of composite interferograms can be achieved by a proper translation of the grating in order to obtain the unwrapped phase distribution as the corresponding sinogram. This sinogram allows tomographic reconstruction of phase slices by standard procedures. Composite interferograms and reconstructions for some transparent samples are shown.     

偏振集成红外光电探测器研究进展与应用

偏振集成探测器具有体积小、重量轻、结构紧凑,并且无需图像配准对动态目标同时同地同源探测与识别的优势。本文主要介绍了偏振集成光电探测器单元器件、线列焦平面、面阵焦平面的研究进展,分析了光栅结构设计与仿真、亚微米偏振光栅制备、集成与测试、偏振图像数据重构等获得高消光比偏振集成探测器的关键技术,最后介绍了偏振成像针对无人机、伪装卡车、地雷、海面舰船、面部识别、无人驾驶道路识别、海面漏油检测及医疗检测等方面的典型应用。

     

陶瓷基透明防弹装甲研究进展

随着军用载具所受威胁的不断升级,对于驾驶舱的防护要求也在增加.传统以防弹玻璃为主的透明装甲已难以满足使用要求.更轻更薄的陶瓷基透明装甲正在逐渐成为主流选择.与其他防弹装甲相似,透明防弹装甲的主要研究方向包括:寻找性能更优的材料用于装甲组件;通过实验或计算机模拟对结构设计与弹道实验进行指导;更加深入地了解装甲材料所需的主要性能、系统整体性能以及整个系统各组件之间的相互影响.依据这一思路,本文首先简要综述了陶瓷透明防弹装甲研究较多的三种迎弹面陶瓷材料的优缺点、制备工艺以及各自的发展及应用水平,三种陶瓷中蓝宝石的静力学参数最优,而实际防弹效果则以多晶陶瓷更好,导致这一现象的原因主要是两类陶瓷碎裂模式的不同产生的弹丸-陶瓷相互作用效果的差异;然后对多晶陶瓷、单晶、玻璃三种类型材料高应变率下的裂纹扩展特性和防弹性能进行了讨论,高应变速率下材料裂纹扩展特性对冲击能量/速率是敏感的,多晶陶瓷是沿晶断裂和穿晶断裂的复合扩展方式,蓝宝石高能冲击下裂纹扩展特征类似多晶陶瓷,临界能量以下则以沿特定晶面的解理断裂为主;最后对透明防弹装甲各功能层的选材标准和结构设计原则进行了总结与展望,迎弹面优选高杨氏模量、高硬度的细晶粒多晶陶瓷材料,中间层选用具有良好的断裂韧度、高弯曲刚度以及将破碎控制在较小范围的能力的材料,背弹面要求材料具有一定的延展性和低密度的特点.各层之间需相互配合才能实现透明陶瓷装甲防弹效能的最大化.     

Efficient and monolithic polarization conversion system based on a polarization grating

We introduce a new polarization conversion system (PCS) based on a liquid-crystal polarization grating (PG) and louvered wave plate. A simple arrangement of these elements laminated between two microlens arrays results in a compact and monolithic element, with the ability to nearly completely convert unpolarized input into linearly polarized output across most of the visible bandwidth. In our first prototypes, this PG-PCS approach manifests nearly 90% conversion efficiency of unpolarized to polarized for ±11° input light divergence, leading to an energy efficient picoprojector that presents high efficacy (12 lm/W) with good color uniformity.