五角棱镜补偿法加工工艺研究

由于五角棱镜两B棱的投影夹角对第二光学平行差影响倍率较大且加工过程中无法测量该夹角,从而导致棱镜加工合格率较低。通过分析侧面垂直度误差及Δ45°对五角棱镜光学平行差的影响,提出一种新的五角棱镜加工工艺方法:利用最后一个加工面对前3个已加工面存在的角度误差进行一次性补偿,从而降低了对各加工面的加工误差要求。实践证明:该方法能够有效地提高五角棱镜加工的合格率和生产效率,减小加工难度,并能显著降低对加工和检测设备的精度要求。     

五角棱镜光束转向波前误差的分析与检测

从分析五角棱镜的角度制造误差产生的光学平行差入手,建立起五角棱镜的光输出平面波前与运动误差和角度制造误差产生的扫描激光束转向的波前改变量之间的关系.采用渥拉斯顿棱镜型双频激光干涉仪实时测量五角棱镜的运动误差,即可计算出扫描激光束转向的波前误差,以便在大型望远系统波前测量时对此误差加以修正.     

五角棱镜的光束转向误差对波前测量的影响

从分析五角棱镜的角度制造误差产生的光学平行差入手，推导出确定入射光线和棱镜调整的表达式；利用棱镜转动定理建立了五角棱镜的光输出平面波前与其角度制造误差和导轨引起的运动误差之间的关系；并用计算机模拟试验分析了五角棱镜的角度制造误差和导轨引起的运动误差产生的扫描光束转向的波前误差。指出此研究结果有利于五角棱镜的加工和棱镜调整，还有利于大口径望远系统波前检测过程中扫描光束转向的波前误差的修正。     

变倾角移相法测量反射棱镜的光学平行差

为解决棱镜等效展开为玻璃平板后因腔长固定导致的移相困难问题,提出一种变倾角移相测量反射棱镜光学平行差的方法。通过改变光束在反射棱镜入射端面上的倾角在干涉图中引入移相量,实现干涉图中的相位提取。采用最小二乘法拟合相位计算反射棱镜的光学平行差。在实验中,测试了一块弦长为56.5mm的等腰直角棱镜,得到直角偏差Δ_(90°)为-2.1435″、锐角偏差δ_(45°)为-4.6216″、直角边对应棱差γ_C为0.3554″,而Zygo GPI干涉仪仅可得到棱镜直角偏差,与本文方法的测量值偏差在0.15″以内。所提方法移相光路设计简便,并可实现小尺寸反射棱镜的测量。     

五角棱镜制造角差及抖动对其转向角的影响

从五角棱镜的原理和特性出发,分析了在理想条件下五角棱镜的转向角不受入射角的影响,详细讨论由于五角棱镜加工角差和相对入射光束抖动对其转向角的影响,给出了相应的精确表达式。其中对于入射光在垂直于入射面抖动的情况,由于不能简单从二维几何光学关系分析,而采用了矢量分析方法,得出:当角差δβ=δθ时,入射角抖动对转向角偏差的影响可以忽略,而转向角偏差与制造角差几乎成线性关系。为五角棱镜用于计量测试误差分析提供了理论依据。结论对五角棱镜的制造也有很大理论指导的意义。     

五角棱镜角度误差对建立大尺寸平面基准的影响

用一准直光束作为基线，通过９０°折转的五角棱镜扫描，建立一个参考基准面在大尺寸测量中是一种行之有效的方法。在理想条件下，五角棱镜的折转角不受入射角的影响。由于有加工误差，光束的折转角将偏离９０°，且入射光线与扫描轴间的角运动也会影响该偏转角。本文分析了五角棱镜角度误差和扫描精度对光束折转角的影响。结果表明，五角棱镜的制造误差和工作状态将引起测量带误差，该误差是一个固定的系统误差，可以通过预先对所用的五角棱镜进行标定，在数据处理中予以修正。实验结果表明，修正后的结果具有很高的精度     

共孔径偏振耦合分光系统中反射镜造成的相位延迟差的测量

 激光信标共孔径发射接收偏振分光系统的动态相位补偿需要测量望远镜各反射镜对s光和p光的相位延迟差。利用Stokes矢量和Mueller矩阵建立了物理模型，并推导出用测得的回光功率计算相位延迟差的解析式。提出一种通过实验测量回光功率计算反射镜相位延迟差的方法，解决了在0～2p范围内唯一确定反射镜相位延迟差的问题。实际测量了两块反射镜的相位延迟差，并将测量结果用于动态相位补偿偏振分光实验，验证了该方法的正确性。分析了偏振分光棱镜、法拉第旋光器以及近似计算这3个主要的测量误差源，并估计总测量误差约为1°。     

用“棱镜体”加工高精度棱镜

随着光学技术的发展,越来越需要广泛地采用高精度棱镜,这就给棱镜加工工艺提出了更高的要求。而现在,许多工厂对高精度棱镜的90°角大都采用“长方体”加工,但“长方体”不能解决棱镜任意角和同时解决两种光学平行差的精度要求。“棱镜体”就是将“长方体”加工棱镜90°角的原理推广到加工任意角棱镜的一种光学工具。     

大场景光学运动捕捉系统标定方法研究

为解决大场景下光学运动捕捉系统精度检测困难的问题,提出利用全站仪标定大场景下光学运动捕捉系统定位精度的方法。首先在光学运动捕捉系统的四个分区域均匀选取若干公共点,其次利用同尺寸同心靶球解决全站仪和光学运动捕捉系统测量点不一致的问题,之后通过全站仪和光学运动捕捉系统分别测量得到公共点的真实值和测量值,基于罗德里格矩阵的抗差最小二乘迭代方法计算全站仪坐标系到光学运动捕捉系统坐标系的位姿变换矩阵,最后坐标系统一并计算光学运动捕捉系统在分区域和整体区域下的定位精度。同时,基于该方法实现了度量运动捕捉系统和Vicon运动捕捉系统的外参标定。实验结果表明：光学运动捕捉系统在四个分区域的定位精度分别为2.385 mm、0.877 mm、1.787 mm、2.890 mm,整体区域下光学运动捕捉系统的定位精度为8.126 mm。说明大场景下光学运动捕捉系统的定位精度明显降低,验证了利用全站仪进行光学运动捕捉系统标定和运动捕捉系统外参标定的可行性和有效性。     

五角棱镜在建立大尺寸平面基准中的应用

从五角棱镜的原理和特性出发，叙述了利用五角棱镜扫描建立大平面基准过程中，由于加工角差和当五角棱镜相对入射光束有相对运动时其出射光束的横移对平面基准的影响，提出了用衍射成像技术消除光束横移，数据计算修正棱镜的角度差的影响。     

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.