逆透视映射公式的误差分析及准确度验证

从数学上分析了目前普遍使用的逆透视映射公式的误差,给出重新推导的逆透视映射数学公式.设计实验验证了采用本文公式进行逆透视映射的效果,并与现有两公式的效果进行了比较.实验结果表明:无论相机内外参量如何变化,本文推导出的公式其IPM变换效果均好于现有公式,在相机架设高度等参量确定的条件下,采用改进后的公式,逆透视映射变换的...     

Ф2020 mm口径空间红外相机主反射镜设计

针对某Ф2 020 mm主反射镜,为了保证空间红外相机主反射镜具有良好的面形精度及较高的一阶固有频率,对其支撑结构进行了针对性研究。根据反射镜的尺寸形状和面形精度要求,确定了反射镜的背部支撑方案。设计了采用两种柔性方式串联的柔性结构用于主反射镜的支撑,并确定了柔性环节的应力最大位置。采用有限元方法对反射镜组件在力热耦合状态下进行了仿真分析,结果表明反射镜全口径最大面形误差RMS值为27.02 nm,组件一阶谐振频率为95 Hz。对相机处于装调状态装星状态时反射镜的面形进行了有限元分析,结果表明满足总体对主反射镜的设计要求。     

同步辐射聚焦镜压弯机构设计与面形误差分析

基于同步辐射聚焦镜的原理，对压弯机构进行设计，对压弯理论进行介绍, 并推导了压弯镜理论面形的计算过程；根据设计理论建立了基于柔性铰链的压弯机构的模型，并对压弯机构的参数进行计算，有效长度为84.9 mm，最大力矩为259.8×10-3 N·m。设计并校核了压弯机构，满足了压弯机构在材料力学上的要求；最后针对压弯镜存在的理论面型误差，通过对压弯镜进行有限元仿真得到模拟值，与理论值进行对比，分析了不同的因素对面型误差的影响。     

交汇测量系统线阵相机标定方法

为了提高大靶面交汇测量系统的测量准确度,分析了交汇测量原理,推导出脱靶量坐标公式.根据脱靶量公式分析其各项参量,利用几何关系建立像元坐标与偏移角度之间的映射模型.根据映射模型,利用光栅尺设计了一种针对线阵相机的标定方法,该方法不考虑相机参量,将整个光学系统看作一个整体,基于整体参量直接对像元坐标和它所对应的偏移角进行标定.实验结果表明,标定后的交汇测量系统在1.4m处的平均测量误差为0.4mm,最大测量误差优于0.6mm.该方法简单高效,可提高系统标定的速度,且标定误差满足系统交汇测量准确度的要求.     

空间相机调焦机构运动同步性误差分析

研究了空间相机调焦机构的运动同步性误差对成像质量的影响。针对某型空间相机的大尺寸焦面调焦机构,分析了运动同步性误差产生的原因。按照其光学系统参数计算得出当系统光学传递函数下降不超过5％时,调焦机构运动同步性误差的最大允许值为0.02 mm。针对其采用的调焦机构,推导出运动同步性误差计算公式,并计算得到该调焦机构的最大运动同步性误差为0.015 mm。最后,对该调焦机构进行了实际测试。测试结果显示,该调焦机构的运动同步性误差在振动实验前后分别为0.012和0.013 mm,表明该机构的运行非常稳定。理论分析以及实验结果证明了该调焦机构完全满足应用要求。     

空间光学遥感器主镜加工过程中疲劳寿命研究

针对空间光学遥感器主镜镜面加工过程中,磨盘与主镜间磨削动作往复运行引起的主镜柔性支撑结构疲劳寿命问题,通过建立主镜组件的有限元模型,利用MSC.Fatigue软件按应力-寿命(S-N)法对主镜组件进行了疲劳寿命分析,确定了支撑结构的薄弱部位,并对仿真过程进行了误差分析,讨论了影响仿真结果的各个因素.对比热真空试验和动力学试验前后主镜镜面面型数据,验证了支撑结构加工、设计参量的合理性.通过疲劳寿命仿真分析,可以有效预示光学结构在加工过程中的疲劳情况,为空间光学遥感器结构的设计、加工提供理论依据和参考.     

空间光学遥感器主镜加工过程中疲劳寿命研究

针对空间光学遥感器主镜镜面加工过程中,磨盘与主镜间磨削动作往复运行引起的主镜柔性支撑结构疲劳寿命问题,通过建立主镜组件的有限元模型,利用MSC.Fatigue软件按应力-寿命(S-N)法对主镜组件进行了疲劳寿命分析,确定了支撑结构的薄弱部位,并对仿真过程进行了误差分析,讨论了影响仿真结果的各个因素.对比热真空试验和动力学试验前后主镜镜面面型数据,验证了支撑结构加工、设计参量的合理性.通过疲劳寿命仿真分析,可以有效预示光学结构在加工过程中的疲劳情况,为空间光学遥感器结构的设计、加工提供理论依据和参考.     

逆透视映射公式的误差分析及准确度验证

从数学上分析了目前普遍使用的逆透视映射公式的误差,给出重新推导的逆透视映射数学公式.设计实验验证了采用本文公式进行逆透视映射的效果,并与现有两公式的效果进行了比较.实验结果表明:无论相机内外参量如何变化,本文推导出的公式其IPM变换效果均好于现有公式.在相机架设高度等参量确定的条件下,采用改进后的公式,逆透视映射变换的相对误差平均为0.85%,较现有的公式准确度有较大提高,能更好地满足智能导航和路面状况勘测等对近距离图像的逆透视映射变换应用要求.     

微粒子观测相机调焦机构设计

为满足微粒子观测相机对光学系统的要求,提出了一种基于滚珠丝杆驱动的传动式调焦机构,介绍了其独特的直线运动结构形式。针对调焦机构承受的静载荷工况和温度工况,用有限元模拟法仿真分析了它的应力和变形情况,得到的最大静力变形为0.001 mm,最大热变形为0.002 mm。通过分析该结构各个传动件误差及装配误差,给出了结构总的理论相对误差值为2.2%。在样机的装调检测中实现了步进分辨率为0.005 mm,平均空回误差步距角为0.2个,完全可以满足整机对调焦机构的要求。     

星敏感器测试用微调整机构设计（英文）

针对高精度星敏感器在地面标定实验中与测试设备准确对接的实际要求,设计一种纳米级星敏感器标定用五维微调整机构.详细分析了光轴对准误差对敏感器测试的影响.为保证对接精确性,提出了搭积型调整架机械结构的设计思想;论述了二维平移和三维调整模块的设计方案;对调整机构进行了仿真建模和力学分析.对设计的微调整机构进行验证性实验,结果表明:位移分辨力可以达到25nm,角度分辨力可以达到0.1角秒,且稳定性高.设计的微调整机构可以满足星敏感器与测试设备准确对接的技术指标要求,确保了星敏感器定标结果的可信度.     

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.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.