Etch slope compensation for planar silica waveguide lens pair

A silica lens pair has been designed to facilitate the free-space optical propagation between opposing planar waveguides. Each lens consists of a graded refractive index slab with a convexly shaped front face. A technique for compensating for the non-vertical etch of the front face curvature is described and shown to result in a significant reduction of optical loss.     

Theoretical analysis of integrated collimating waveguide lens

An integrated collimating waveguide lens is analyzed for applications which require the focusing of an optical beam onto the waveguide of a planar lightwave circuit. The lens has a refractive index profile which is parabolically graded as a function of height to focus light in the vertical plane, and has a convex front face to focus light in the horizontal plane. Analysis based on the propagation of a Gaussian field is used to design a lens pair which minimizes the optical loss for a given propagation length. The beam propagation method is used to identify fabrication tolerances which may have impact on the performance of the lens pair. The lens pair has application in micro-optoelectromechanical (MOEM) switches based on planar optical waveguide circuits.     

Wide-angle microwave lens for line source applications

A new "time-delay" scanner consists of a constrained wide-angle two-dimensional microwave lens with a straight front face in which lens elements connect arbitrary points on the inner and outer contours. The lens can operate at very short pulse lengths and can scan more beamwidths than any previously known device of its type. A phase analysis shows that this design has very small coma aberrations and that the lens can generate fractional degree beams. Criteria developed for selecting optimum lens parameters are given. The radiation patterns of an experimental model in which the lens elements consist of coaxial cables show the expected wide-angle characteristics. In further tests incremental scanning was obtained through the use of phase shifters in the coaxial lens elements. The design of symmetrical three-dimensional lenses is briefly discussed. A table of lens contour parameters is given for an optimum lens design with scan anglealphaof30deg.     

半导体激光器阵列耦合系统透镜导管的效率研究

为了将透镜导管应用于激光二极管阵列耦合系统,利用镜像法得到了耦合效率与透镜导管参量之间的关系,即透镜导管长度、曲率半径、输出面边长和快轴发散角均影响透镜导管耦合效率;分析了不同尺寸的半导体激光器面阵耦合到不同尺寸的激光棒中的耦合效率.结果表明,半导体激光器阵列及激光棒的尺寸对耦合效率有一定影响.所得结论为透镜导管的设计...     

A dual-band TEM lens for a multiple beam antenna system

A three-dimensional electromagnetic (TEM) lens is made of many printed circuit cards for future satellite multiple beam antenna applications. To obtain a low scan aberration lens combined with cross-polarization suppression, the lens array faces have a nonuniform distribution of element rotational orientations, making the array faces electrically nonuniform as to mutual coupling. An experimental procedure is presented for developing dual-band active impedance matched lens elements. Using such elements, a lens is built and tested to verify the adequacy of the design procedure.     

大口径线视场菲涅尔准直透镜设计

针对某一特殊应用设计了一款菲涅尔准直透镜,利用菲涅尔透镜的基面弯曲和单向点列半径的像差控制,实现了一维方向的高精度准直.分析比较了平面菲涅尔透镜与球基面菲涅尔透镜的像差状况,得出了两种结构透镜在本项目应用中校正像差的差异,提出了在类似菲涅尔透镜的应用中像差校正的方案及面型选择的思路.     

白光全息光学元件——视觉显示反射全息透镜的研究

用重铬酸盐明胶介质记录了用于飞机平视显示器的平面离轴反射全息目视显示元件。分析了该显示元件诸如衍射效率、象差、色散、畸变和光学传递函数等显示和成象特性,推荐制备和处理重铬酸盐明胶薄膜的某些重要技术。     

An equal group delay waveguide lens

Analytical and experimental results are presented on a circularly polarized waveguide lens that has much greater bandwidth than conventional waveguide lenses. This is achieved by designing the lens to have equal group delay for all rays from the focal point of the lens to the aperture plane. Haft-wave-plate phase shifters in each waveguide element are then oriented to produce a planar phase front. This results in a lens whose aperture phase distribution remains essentially constant over a much wider frequency range than in conventional waveguide lenses. A comparison with a minimum thickness conventional lens and with a phase compensated (Coulbourn) lens is made. A 46-in X band lens was built and tested over a frequency range from 7-9 GHz to confirm the bandwidth performance.     

Flat lens antenna concept using aperture coupled microstrip patches

A planar lens antenna based on aperture coupled microstrip patch elements with stripline delay lines is described. Features of this design are discussed, and results for transmission coefficient magnitude against frequency are presented. The background for the development of this lens configuration is discussed in terms of a natural progression from frequency selective surfaces, and the inadequacies of simpler geometries are explained     

具有成像功能的多重体全息光栅光谱色散器件

根据体全息光栅的透镜作用,使用平行光和会聚光记录多重光栅,光谱无需会聚透镜即可成像。在器件的设计中,分析了LiNbO3晶体材料色散的影响,并实验中对曝光时序实时监控,制作了8重光栅的光谱成像色散器件,整个输出谱面的宽度尺寸为8mm。     

3DFP-FCGAN: Face completion generative adversarial network with 3D facial prior

Face completion is a domain-specific image inpainting problem. Most existing face completion methods fail to synthesize fine-grained facial structures due to the undifferentiated treatment of face images and other scene images. To handle this problem, we propose an end-to-end deep generative model based approach which makes full use of the facial prior knowledge, including 2D facial geometry priors from facial parsing maps and landmarks, as well as the 3D depth prior. We adopt a coarse-to-fine inpainting framework where the 2D facial geometry priors based on coarse faces are extracted to guide the refinement network for better planar facial textures and structures. Moreover, a novel 3D regularized reconstruction loss is proposed for the enhancement of the stereo perception of generated faces. Experimental results on two large-scale benchmarks CelebA and CelebA-HQ show that our method significantly outperforms the state-of-the-arts in generating more visually realistic and pleasing faces. Code is available at .     

The performance of an iris-loaded planar phased-array antenna of rectangular waveguides with an external dielectric sheet

A new method for calculating the performance of an iris-loaded planar phased-array antenna of rectangular waveguides is presented. The method is based upon the expansion of the tangential electric aperture field in terms of judiciously chosen functions. Also, the influence of a dielectric sheet in front of an antenna the apertures of which are loaded with inductive irises is investigated. In the experiments, a sheet with a low relative permittivity (epsilon_{r} = 2.3orepsilon_{r} = 3.5) is spaced in front of a space-fed planar antenna of some 850 radiating elements, and the total transmitted power of the antenna is measured as a function of frequency and scan angle. The results indicate, that both in theory and in practice, an excellent match can be achieved with a polythene sheet (epsilon_{r} = 2.3) or a Perspex sheet (epsilon_{r} = 3.5).     

The dielectric-filled parabola: a new millimeter/submillimeterwavelength receiver/transmitter front end

A design is presented for a semi-integrated millimeter/submillimeter wavelength receiver/transmitter front end incorporating a planar antenna and a solid-state device in an efficient feed structure which can be matched directly to high f-number optical systems. The feed system combines the simplicity and robustness of a dielectric substrate lens with the high gain of a parabolic reflector in a single structure that is termed a dielectric-filled parabola. The same fundamental unit can be configured as either a heterodyne or direct detection mode receiver, a power transmitter or a frequency multiplier by changing out the solid-state device and/or the integrated antenna. The structure can also be used with a small integrated antenna array in a multibeam or imaging arrangement. Design and fabrication details for the feed system are given. These are followed by beam pattern and impedance measurements taken on a microwave model when dipole, bow-tie, log-periodic, and log-spiral antennas are used as the integrated feed elements     

共焦自聚焦光纤传感器回波干扰抑制方法分析

基于共焦原理的自聚焦光纤传感器将共焦光路、自聚焦透镜和光纤集于一体，实现了微型化和轴向高分辨率的统一，可用于内外曲面的微观形貌、坐标尺寸和曲面轮廓等的高精度检测。运用高斯光束传输原理和矩阵光学理论对影响传感器信号强度的端面回波问题进行了理论分析，提出了解决回波问题的技术途径。实验结果说明，通过对不同端面采用不同的抑制方法，回波问题被较好地解决。     

增大Bessel光束无衍射距离的凹透镜系统

根据传统轴棱锥法产生Bessel光束的原理和凹透镜的几何光学效应,设计并模拟了一套提高Bessel光无衍射距离的光学系统。利用凹透镜的发散特性,将其分别放置在轴棱锥的前方与后方,使用Math CAD软件进行模拟并与传统轴棱锥法进行比较,得出结论:在轴棱锥前方放置凹透镜使Bessel光的无衍射距离从244 mm增大至638 mm,同时增大中心光斑半径。在轴棱锥后方放置凹透镜使Bessel光的无衍射距离从244 mm增大至406 mm。使用He-Ne激光作为光源进行实验验证,实验结果与理论分析及仿真模拟基本一致。可根据实际要求选择凹透镜的曲率半径和位置,得到无衍射距离较大、质量较高的Bessel光束。     

Application of robust face recognition in video surveillance systems

In this paper, we propose a video searching system that utilizes face recognition as searching indexing feature. As the applications of video cameras have great increase in recent years, face recognition makes a perfect fit for searching targeted individuals within the vast amount of video data. However, the performance of such searching depends on the quality of face images recorded in the video signals. Since the surveillance video cameras record videos without fixed postures for the object, face occlusion is very common in everyday video. The proposed system builds a model for occluded faces using fuzzy principal component analysis (FPCA), and reconstructs the human faces with the available information. Experimental results show that the system has very high efficiency in processing the real life videos, and it is very robust to various kinds of face occlusions. Hence it can relieve people reviewers from the front of the monitors and greatly enhances the efficiency as well. The proposed system has been installed and applied in various environments and has already demonstrated its power by helping solving real cases.     

基于光学变换的平面龙伯透镜天线

龙伯透镜天线具有高增益、低副瓣和宽带特性,可以实现多波束,进行大角度扫描等优点,主要应用于卫星通信、电子对抗等领域。但因其体积大、重量大和球形结构不易固定等缺点,在实际应用中受到很大的限制。本文基于光学变换原理设计了一种新型的全介质平面龙伯透镜天线,半径为60 mm,厚度为20 mm,在15 GHz时,天线增益为23 dB,半功率波束宽度为12°,第一副瓣电平低于-23 dB。同时设计了平面和圆弧馈源阵列,在70°范围内实现了较好的多波束覆盖。     

计算"Top-hat"端面抽运晶体热透镜焦距的改进方法

在激光二极管(LD)端面抽运的固体激光器中,热效应是设计中必须考虑的重要参量之一。研究激光工作物质内热效应的最方便的方法是等效热透镜(TL)法。前人给出的公式算出的热透镜焦距比实验值小。针对“Top-hat”抽运光,在找出了导致计算值与实验值差距的原因后,给出了能够得出更为精确热透镜焦距值的改进方法,并进行了数值计算,根据计算结果给出了拟合方程。研究结果显示,热透镜焦距不仅仅是抽运功率的函数,还是激光半径与抽运光半径比的函数,并且在激光和抽运光半径大致相当的时候,热透镜焦距大约是原来公式计算值的1.6倍。在相同的抽运条件下,热效应造成的衍射损耗同用原来热透镜焦距计算的结果相比要小很多,同样和激光半径、抽运光半径有关。实验证明新理论比旧理论更接近实验结果。