大孔径变焦投影镜头设计

为了实现某一大孔径定焦投影镜头作为初始结构, 经过优化设计后成为大孔径变焦投影镜头, 根据设计目标的DMD对角线尺寸, 利用AUTOCAD对选择的定焦距系统的初始结构尺寸进行测绘, 初步选择各镜材料, 规划成5组元变焦系统, 利用各种操作数对镜头的基本参数和外形尺寸进行限制, 并合理利用2个非球面, 在光学设计软件Zemax与CODE V中往返优化, 得到一款在可见光波段内, 短焦距为14.61 mm、视场角为60°、F数为1.5, 长焦距为29.31 mm、视场角为30°、F数为1.6的变焦投影镜头。设计结果表明:各视场的传递函数(MTF)值在截至频率60 lp/mm处不低于0.46, 各焦距处的弥散角不超出1.6', 镜头具有良好的像质。该镜头系统由11块透镜和1块平行平板组成, 其中透镜2使用了非球面镜, 该镜头片数较少, 透镜折射率不高, 材料容易选择。     

双远心数字条纹投影的光学系统设计

针对3D自动检测PCB板缺陷的实际应用问题,设计了一款高分辨率、大景深、大视场的双远心数字条纹投影光学系统,实现了大面积区域均匀投影。分析了基于0.65 WQXGA DMD的双远心数字条纹投影系统的工作原理及设计指标;设计了基于复眼透镜阵列的LED匀光照明系统,在DMD照明面内的照明均匀性为90.5%,且能量利用率为45.8%;设计了双远心结构的投影光学系统,投影视场为66.5mm×37.5mm,并在全视场范围内分辨率在8lp/mm处的MTF值大于0.5。利用光学软件建立双远心数字投影整体系统模型,仿真结果表明,被投影区域均匀性为90.8%,投影条纹在+/-7.5mm的离焦范围内投影清晰且周期均匀,综合提高了3D自动检测系统的投影质量。     

一款大靶面消热差鱼眼镜头设计

为了满足信息化时代对高清鱼眼镜头的应用需求,利用CODE V和Zemax光学软件设计了一款匹配16 mm(1英寸)CCD的大孔径玻塑混合鱼眼镜头。该系统可在光谱为486 nm～656 nm以及850 nm范围内清晰成像,视场角为210°,F数2.0,焦距为4.1 mm, F-Theta畸变小于7%,边缘照度大于68%。常温下,该系统在奈奎斯特频率91 lp/mm处0.707视场MTF大于0.5,全视场MTF大于0.35。-40℃～+75℃状态下0.707视场MTF大于0.3,全视场MTF大于0.2,满足高低温环境下的使用要求。系统采用7片式玻塑混合的结构形式,具备大视场角、大靶面、大光圈等特征,可广泛应用于高清摄像、安防监控、工业生产等领域。     

90°视向角口腔内窥镜光学系统设计

基于实际应用设计了一个90°视向角的光学系统,可用于1/4″CCD口腔内窥镜成像.系统具有62°视场角,孔径为F/7,各视场的光学传递函数在80 lp/mm处取值良好、景深大、像面照度均匀,整个系统的最大镜头口径小于4.6 mm.     

变焦结构光成像系统的光学设计

为了实现快速低成本改变光学系统焦距,设计了基于液体透镜的变焦结构光三维成像镜头和微透镜阵列。系统采用7片球面玻璃镜片和1片液体透镜结构, F#为3.2,全视场大小为10 mm,总长180 mm,焦距变化范围54 mm~61 mm。结果表明:该系统能实现投影距离227 mm~256 mm调节,调焦过程中目标表面清晰,细节分辨率高,系统在整个变焦区域内,在40 lp/mm时,全视场MTF优于0.2,系统场曲小于0.2,畸变小于0.2%。柱面微透镜阵列整体尺寸为10 mm×10 mm,周期宽度为1 mm,厚度为1 mm。随着投影距离的增长,光学系统成像质量先上升后下降,在237 mm处成像质量最优,随着投影距离的增加,光学系统的放大倍率增大,光学系统整体相对照度不均匀性小于0.2。     

二元变焦内窥镜光学系统设计

根据高斯光学原理,以液体透镜为核心元件,研究了无移动镜组变焦系统的设计方法。从医用内窥镜的使用要求出发,设计了一种二元变焦内窥镜系统。该系统可通过气压或液压控制液体透镜表面曲率变化,实现1.5倍变倍比,在1.8 mm和2.7 mm焦距下都获得了良好的成像质量。     

头盔显示器自由曲面光学组件的优化设计

根据设计要求计算了非共轴球面光学系统的初始结构,选定泽尼克多项式为自由曲面面型,利用正交泽尼克多项式与像差的关系,调整曲面参数校正系统的像差,运用CODE V进行系统优化。通过设计实例对比了直接优化和分步优化方法,由对比结果可知,分步优化更适用于自由曲面光学组件的设计。仿真结果表明:系统在整个视场范围内,点列斑直径小于27 m,网格畸变的最大值为-7.15%,30 lp/mm处的MTF大于0.197。     

紧凑式多光谱成像系统设计和优化

针对快照式多光谱系统存在体积大、光路复杂的问题,从孔径分割多光谱成像系统模型出发,设计出由复合前置光学元件、阵列孔径光阑、微透镜阵列、阵列滤光片和图像传感器组成的紧凑式多光谱成像系统,总体尺寸优于12.4×8×8(mm)³。利用阵列孔径光阑克服了垂轴色差大、视场小和光能利用率低的问题。系统在480～650nm波长范围内视场角20°、F/#0.4、焦距2.5mm、总长12.4mm、单通道MTF在153lp/mm大于0.35、畸变小于0.23%。与现有技术对比,该系统兼顾了像素分辨率、光谱分辨率和时间分辨率,实现了单通道500×400的像素分辨率和6.8nm的光谱分辨率。与计算重构成像系统相比,其直接成像的方式确保了系统的高时间分辨率;且具备小型化、轻量化和低成本的特点。     

小口径大视场工业内窥镜光学系统设计

近年来,内窥镜广泛应用于复杂环境下小尺寸零件缺陷检测,该文设计一种用于航空发动机叶片检测的工业内窥镜光学系统。系统基本结构采用二次成像,物镜采用非对称反远距结构,将大视场光线收束进小口径腔体中,适配镜将物镜所成一次实像放大21倍,后接对角线长42 mm高速相机。系统基于Zemax设计软件进行系统优化、公差分析和像质评价,最终系统具有大视场(120°)、细孔径(3 mm)、耐高温(25℃～180℃)等特点。由于对视场、孔径和适配镜放大率有较高要求,因此合理引入非球面提高系统成像质量,入瞳直径提高至0.5 mm,系统空间截止频率在17 lp·mm^-1处,全视场调制传递函数值均大于0.28,最大畸变值小于21.2%。     

90°视向角内窥远心测量仪的光学设计

针对深腔内深孔、微小孔或盲孔等, 由于受到腔体尺寸形状和腔体结构的限制,导致对腔体内表面的检测及腔体内孔径形位信息的检测有很大的难度, 设计了一种检测腔内小孔特征以及腔内状态的内窥镜光学探头。该探头为具有90°视向角、20 mm大景深、高分辨率的细径内窥镜,其放大倍率为-0.71×,最大畸变为0.5%,全视场MTF在166 lp/mm处接近0.1,孔径检测精度为0.01 mm,分辨率为0.005 mm,且光学系统外径小于5 mm,可用于对腔体直径范围15 mm~45 mm、孔径直径范围0.01 mm~4 mm的腔体零件内微小孔径形位信息的检测。     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.