基于表面等离子体效应的MEMS红外辐射源特性研究

研究了一种新型的基于二维光子晶体结构的表面等离子体共振SPR(Surface plasmon resonance)效应的红外辐射源,该辐射源基本结构为Si-SiO2(650nm)-Cr(100nm)-Au(800nm),并在Au表面刻蚀5μm的周期性排列的圆孔。设计加工了几种不同的结构,包括三种不同的圆孔间距即晶格常数:6μm,7μm,和8μm;四种占空比(圆孔直径与晶格常数之比):3/8,4/8,9/16和11/16;以及三种圆孔排列方式:正方形排列,六边型排列,和带规则缺陷六边型排列。本文采用红外傅立叶测量设备对辐射源进行测试分析,通过该辐射源的红外反射谱表征其辐射性能,并利用FDTD软件进行模拟,和实验数据作了比较。研究结果得出了红外辐射源反射谱波谷位置即SPR共振峰位置,波谷强度即SPR共振峰强度与不同结构参数之间的关系。研究发现该辐射源SPR共振峰位置基本与圆孔间距即晶格常数成正比,正方型排列基本接近于1:1,而六边型排列基本接近于3/2;常规六边型排列比带缺陷六边型排列和正方型排列具有更窄的半波宽和更大的SPR共振强度;随着占空比变大,该辐射源的SPR共振峰强度变大。     

Plasmonic holographic nanostructures

Surface plasmon resonance (SPR) in planar nanostructures is considered. SPR-based methods of measuring optical characteristics and thicknesses of nanolayers are given. Use of diffraction and holographic gratings comprised of small sub-gratings displaced perpendicular to the grooves is considered to achieve the fine structure of plasmonic resonance and more accurate measurements.     

Device‐dependent angular luminance enhancement and optical responses of organic light‐emitting devices with a microlens‐array film

Abstract— By taking the organic emitter apodization calculated from electromagnetic theory as input, the angular luminance enhancement of organic light‐emitting devices (OLEDs) with a microlens‐array film (MAF) can be further evaluated by the ray‐tracing approach. First, the OLEDs of different Alq³ thickness are fabricated and their angular luminance measurements are compared to simulation results. Second, mode analyses for different layers are performed to estimate the enhancement potential of the MAF‐attached devices. Finally, by decreasing the Alq³ thickness, increasing the viewing angle, and attaching the MAF, the EL spectral peak shifts of the OLEDs seem irregular, but the spectral blue shifts induced by the optical structures are all explained by the optical responses (EL spectra divided by the intrinsic PL spectrum). In conclusion, the organic emitters with higher off‐axis‐angle luminous intensity cause lower out‐coupling efficiency but gain higher enhancement after the MAF is attached. With the choices of apodizations and microstructures, the tailored or customized angular radiation patterns can be also made possible.     

Modeling an Inhomogeneous Coating of an Elastic Sphere with the Required Sound Reflecting Properties

We consider the inverse problem of determining the covering inhomogeneity of an elastic sphere characterized by the minimal reflection of a plane sound wave in a preset angular sector and frequency range. Based on an analytic solution to the direct problem, a functional expressing the reflection’s intensity is constructed and an algorithm for its minimization is proposed. The analytic expressions describing the mechanical parameters of an inhomogeneous coating are obtained.     

基于LabVIEW的太赫兹时域光谱分析软件

针对目前太赫兹光谱仪的数据采集和数据处理软件不能兼容的情况,设计了一个基于LabVIEW软件平台的THz时域光谱分析软件。主要研究了THz时域光谱系统的反射式以及透射式样品光学信息提取算法、支持向量机分类算法、以及偏最小二乘等分析算法以及它们的LabVIEW实现。该软件采用全LabVIEW代码实现,能够实现样品光学信息提取,物质分类识别以及多组分样品浓度分析,并且具有很高的移植性,可扩展性,与数据采集软件具有很好的兼容性。利用该光谱分析软件,分析了三种塑化剂的THz时域光谱信号,得到了它们在THz波段的折射率和吸收系数, 结果表明三种塑化剂可以用THz时域光谱完全区分,软件运行稳定可靠。     

Robust Photometric Invariant Region Detection in Multispectral Images

Our aim is to detect photometric invariant regions in multispectral images robust against sensor noise. Therefore, different polar angle representations of a spectrum are examined for invariance using the dichromatic reflection model. These invariant representations take advantage of white balancing. Based on the camera sensitivity, a theoretical expression is obtained of the certainty associated with the polar angular representations under the influence of noise. The expression is employed by the segmentation technique to ensure robustness against sensor noise.     

Extraordinary spin momenta in birefringent structures

Mechanical action caused by the optical forces connected with the canonical momentum density associated with the local wave vector or classical spin angular momentum, the helicity dependent and the helicity independent forces determined by spin momenta of different nature open attractive prospects to use optical structures for manipulating with nanoobjects of different nature. The main finding of our study consists in demonstration of mechanical action of extraordinary transverse component of the spin angular momentum arising in an evanescent light wave due to the total internal reflection of linearly polarized probing beam with azimuth 45° at the interface ‘birefringent plate–air’.     

双层植被结构冠层光谱特性的理论模拟

利用双层冠层反射率模型ACRM，模拟不同叶面积指数LAI、含水量Cw和结构参数N下，波长是820nm和1600nm冠层反射率的角度分布。结果说明，该模型能准确模拟出“热点”效应 |冠层反射率角度分布对LAI的敏感性小于LAI和Cw以及LAI和N的共同作用。其中LAI和Cw共同作用对波长1 600 nm反射率角度分布的影响非常显著，而LAI和N的共同作用在820 nm略微大于1 600 nm。另外，提取冠层含水量的土壤可调节水分指数SAWI受冠层结构的影响也较大。今后在模型选取中应该更好的考虑冠层结构影响。     

Contactless functional testing of grating-coupled evanescent wave (bio)chemical sensors

The contactless measurement of the sole modulus of the reflection coefficient of a grating-coupled slab waveguide sensor at three definite points of the reflection spectrum gives all necessary information for the determination of the complete set of phenomenological parameters of a waveguide grating (bio)chemical sensor thanks to a physically meaningful representation of the resonant reflection of a free space wave in the form of a circle in the complex plane. This property leads to a simple, non-destructive, wafer-scale functional testing methodology for grating-coupled (bio)chemical sensor chips.     

An Inexpensive BRDF Model for Physically-based Rendering

A new BRDF model is presented which can be viewed as an kind of intermediary model between empirism and theory. Main results of physics are observed (energy conservation, reciprocity rule, microfacet theory) and numerous phenomena involved in light reflection are accounted for, in a physically plausible way (incoherent and coherent reflection, spectrum modifications, anisotropy, self-shadowing, multiple surface and subsurface reflection, differences between homogeneous and heterogeneous materials). The model has been especially intended for computer graphics applications and therefore includes two main features: simplicity (a small number of intuitively understandable parameters controls the model) and efficiency (the formulation provides adequation to Monte-Carlo rendering techniques and/or hardware implementations).     

室内漫射光无线接入的准确信道表征

室内光无线链路的表现主要受制于多径传输所导致的时延扩展效应。目前仍然缺少建模方案能够在考虑复杂反射存在的前提下高效地完成此类信道的准确表征。针对这一问题,提出了一种称为独立反射交互表征的新颖建模方案。这一新方案的核心思想是将接收器参数、发送器参数以及室内环境的相关性分离。在链路参数改变的情况下只需对相应部分进行重新计算即可完成新的建模,在很大限度上避免了重复运算。借助这一新的建模方案可以高效地获取接收信号功率以及时延扩展在整个房间的准确分布情况。     

基于LabVIEW的光纤光栅传感的动态解调

设计了一种基于LabVIEW和可调谐光滤波器的光纤光栅传感动态解调系统。用LabVIEW编写虚拟仪器(VI)程序,通过硬件接口由计算机控制可调谐光滤波器,使其在固定波长范围内扫描;采集电路对光电转换后的信号进行采集并送到计算机中分析处理,得到传感信号的反射波长以获得应变量。最后把传感解调系统的测试结果和光谱仪的测试结果进行比较,两者基本一致,说明了解调系统的设计是正确的。     

一种新型颜色传感器设计

本文介绍一种采用脉冲光源照明、双光纤束导光的新型颜色传感器，光电探测器由光电二极管和覆盖其上方的滤色片组成。用光电积分法进行测量，在整个可见光谱区间内，对反射光谱功率进行积分，得到被测物体的颜色三刺激值X、Y、Z。同步控制脉冲光源发光与电路测量，由双光路捡测系统测量颜色三刺激值X、Y、Z和脉冲光源的微小变化，并根据后者对测试结果实时修正。该颜色传感器适合于本身不发光物体的表面颜色测量。     

Holographic backlight unit for mobile LCD devices

Abstract— The commercial backlight unit for a portable liquid‐crystal display (LCD) device typically consists of several light‐emitting diodes (LEDs) as the light source, a couple of prismatic sheets and diffusers, and a guide plate for backlight optics. A simplified backlight unit for portable LCDs, merely consisting of a hologram‐imprinted light‐guide plate (H‐LGP) and one diffuser, is proposed in this paper. By employing H‐LGP, it is expected that several optical films essential to the conventional backlight unit can be eliminated. This paper aims to improve the optical efficiency of LGPs by deriving the design parameters of the H‐LGP and performing the related computations. The angular luminance distribution of the emanating light from H‐LGP has been measured and compared with the results obtained by simulation. A proper collimation is necessary in order to increase the luminance. The backlight developed through this work has high optical performance combined with low cost.     

基于多角度微波辐射亮温数据反演冬小麦光学厚度

基于高级积分方程模型(Advanced Integrated Emission Model,AIEM),构建了包含宽范围土壤参数的C波段(6.925GHz)多角度裸露土壤发射率模拟数据库,利用该模拟数据分析了不同观测角度的裸露土壤发射率极化差之间的关系。在此基础上,结合ω-τ零阶辐射传输模型发展了C波段低矮植被光学厚度反演算法,并利用地基微波辐射计观测数据开展了冬小麦的光学厚度反演。结果显示,冬小麦光学厚度反演结果与实测冬小麦LAI在变化趋势上具有较好的一致性,反演算法具有一定的可行性。     

Geometrical considerations on the directivity of reflected light from a paraboloidal mirror

A divergence angle of the light emanated from an optical source composed of a source of light with finite size and a paraboloidal reflector is analyzed on the basis of geometrical considerations. The divergence angle distributions of the reflected light rays from each reflection point on the paraboloidal mirror are numerically calculated as parameters of the shapes of a lamp arc body and a paraboloidal reflector. It has been found from the analyses that the divergence angle can be reduced by prolongation of the optical path length PO to the reflection point P on the paraboloidal mirror from the focal point O of it, at which the center of the extent of the arc is located. A new approach different from conventional one to reduce the divergence angle of the light rays emanated from the optical source is proposed. The new configurations of the optical source composed of a source of light with finite size and a paraboloidal reflector or a spheroidal converging reflector are shown and discussed.     

Reference panel anisotropy and diffuse radiation - some implications for field spectroscopy

Field goniometer measurements were obtained to examine the angular variation in the reflectance of direct beam, diffuse and global radiation from two types of Spectralon^TM panel. The results indicate that optical grade (99% reflective) and grey (20% reflective) SpectralonTM exhibit different non-Lambertian properties with respect to direct beam irradiance. The angular variation in the reflectance of diffuse radiation by the panel appears independent of the panel type but varies with the diffuse to global (D : G) irradiance ratio, especially at large solar zenith angles. The combined effect of the angular response to direct beam and diffuse radiation is that panel reflectance of the global flux shows only slight variation with angle for solar zenith angles up to 55 for optical grade Spectralon^TM. For larger solar zenith angles panel reflectance increases markedly with angle.     

The accuracy of the computation of optical flow and of the recoveryof motion parameters

The accuracy and the dependence on parameters of a general scheme for the analysis of time-varying image sequences are discussed. The approach is able to produce vector fields from which it is possible to recover 3-D motion parameters such as time-to-collision and angular velocity. The numerical stability of the computed optical flow and the dependence of the recovery of 3-D motion parameters on spatial and temporal filtering is investigated. By considering optical flows computed on subsampled images or along single scanlines, it is also possible to recover 3-D motion parameters from reduced optical flows. An adequate estimate of time-to-collision can be obtained from sequences of images with spatial resolution reduced to 128×128 pixels or from sequences of single scanlines passing near the focus of expansion. The use of Kalman filtering increases the accuracy and the robustness of the estimation of motion parameters. The proposed approach seems to be able to provide not only a theoretical background but also practical tools that are adequate for the analysis of time-varying image sequences     

Design of multi‐beam antenna based on Rotman lens

A planar Rotman lens antenna that generates multiple beams is presented over a wide angular range. The proposed multi‐beam antenna consists of a Rotman lens and a ten‐element printed Yagi antenna array. By properly comparing optical aberrations, expressing as the normalized path length errors Δl, the suitable ratio of on‐axis to off‐axis focal length (g = G/F) is acquired so as to minimize phase errors for the array elements. Ten dummy ports are employed to reduce the performance deterioration caused by energy reflection. A prototype with seven input ports was fabricated and measured, covering a wide scanning angle of 60° (–30°, 30°). The measured beam patterns show that the seven beam gains are distributed from 11.9 to 13.6 dBi under operating of 8.15 GHz. Both the simulated and measured results are used to verify the design approach.     

Optimizing angular placements of the LEDs in a LCD backlight module for maximizing optical efficiency

This study aims to optimize angular placements of the LEDs with novel cone-shaped caps for achieving high optical efficiency in an ultra-thin, directly-lit RGB LED backlight unit (BLU) for large-sized LCD-TVs. This novel lens cap is used as a diffuser with the purpose to gain higher efficiency and provide satisfactory uniformity over a display panel. To this aim, the outer surface of the novel lens is coated with aluminum for mirroring effects to reflect most of the LED emitted light horizontally and then reflect the light at the BLU boundaries, finally to the output plane. Since the emitted white light from LEDs result from color-mixing of three individual RGB chips in a LED package, the addition of the LED cap however deteriorates the aforementioned expected color mixing. The optimal design on angular placements of LEDs presented in this study for satisfactory color-mixing and emission uniformity is achieved by necessary optics simulations via TracePro, followed by utilizing an intelligent numerical optimization technique, genetic algorithm (GA). The design parameters for GA optimization are different combinations of LED placement angles in a backlight module. Favorable color balance is shown achievable in terms of high low color difference resulted. Finally, experiments are conducted, which successfully validate the expected performance of color balance and emission uniformity for a novel cone-shaped LED lens with optimized angular placements in a large-area backlight module.