微光夜视鱼眼镜头的研究与设计

为了满足在夜晚低照度环境下对鱼眼镜头的需求,利用ZEMAX光学软件设计出了一款适用于2 inch微光夜视相机的微光夜视鱼眼镜头。该结构包含窗口透镜,共由7组10片透镜组成,其中除窗口外,其余全部为光学玻璃,而且选用的玻璃材料均为常用、性能良好、价格便宜的牌号。有效焦距为9.5 mm,相对孔径为1/1.8,视场角为170°,像高为21mm,光学系统总长为90 mm,最大口径为56 mm,后工作距离为10.4 mm。在分辨率46 lp/mm处,全视场范围内的MTF值均大于0.36,全视场f-θ畸变量的绝对值小于30%,场曲小于0.15 mm,镜头有较好的成像质量。     

大面阵CCD航空数码相机光学系统设计

充分考虑航空CCD相机工作环境和成像特点,设计了一款具有5000万像素的航空CCD数码相机光学系统,焦距75 mm,F数为4,畸变小于0.1%,工作温度-40℃～60℃.通过重点研究环境温度变化对数码相机光学系统成像质量的影响,提出通过无热优化的方法,保证相机在宽温度范围内具有良好的温度适应性.这种方法既能有效减小光学...     

高分辨率微型星载相机光学系统的设计及应用

为了克服太空环境的复杂性，满足航天工程的空间使用要求，研制一款2 500万像素宽光谱共焦成像的微型星载相机光学系统。该系统适应卫星发射和在轨道运行的恶劣环境，具有抗冲击震动、耐太空高温差强辐射，体积小，质量轻等优点。设计的系统可在450 nm～800 nm的谱段内清晰成像，焦距181 mm，入瞳口径45 mm，视场角10.4°，边缘相对照度0.81，轴上点MTF:0.57@55 lp/mm，0.33@110 lp/mm，畸变1.2%，镜头质量622 g，外形尺寸Φ58.3 mm×117 mm，抗辐照性能≥5 krad。通过温度适应性的模拟和优化，用户进行?30 ℃～+70 ℃光学镜头热真空试验，可正常工作。该系统已成功应用于天宫二号伴飞卫星相机中，获得的图像清晰稳定，为空间遥感实验观测发挥了重要的作用。     

一种高分辨力空间相机的光学设计

针对某一种光学设计指标要求的高分辨力空间相机,在计算分析光学系统参数的基础上,利用Zemax光学设计软件设计了同轴三反射镜(TMC)系统,二次成像离轴三反射镜(Cook TMA)系统和一次成像离轴三反射镜(Wetherell TMA)系统3种光学系统,均满足了指标要求。对比分析了三种光学系统的优缺点,在综合考虑光学系统的加工、检测和装调能力以及空间相机技术发展先进性的基础上选定了将Wetherell TMA系统作为最终方案,相机外形尺寸为1600 mm×1230 mm×545 mm,系统焦距为4375 mm,相对孔径为1:9.94,视场角为2°。对该光学系统的性能进行了模拟和验证,计算分析了光学系统的传递函数、像差、畸变等,各项指标性能优异,最后对该系统的光阑和杂光消除进行了分析并对光学系统的公差进行了合理的分配。     

新型三反射光学系统设计

随着空间光学技术的发展,对于空间相机地元分辨率的要求越来越高,而且必须具有多光谱成像能力,因此空间相机光学系统的设计要满足视场大和畸变小的要求.本文以共轴三反射光学系统为基础,研究了一种新型的三反射光学系统.该系统不仅中心遮拦小、光学畸变低,而且实现了全色和多光谱CCD的合理排布.设计结果表明:当光学系统的焦距为f=12 000 mm、F数为12、成像谱段位于450~900 nm时,视场角可以达到1.6°,光学系统的线中心遮拦比低于1/3,光学畸变量小于0.5%,在50 lp/mm处调制传递函数优于0.47,成像质量达到衍射极限,可以满足多光谱高分辨率空间相机对地遥感的使用需求.     

消畸变、长焦距相机光学系统设计

随着空间光学技术的不断发展,时间延时积分电荷耦合器件(TDI-CCD)相机得到了广泛的应用,TDI-CCD图像传感器的应用不仅提高了相机系统的信噪比而且使相机的光机结构更加紧凑,但光学系统的畸变在推扫过程中会造成像移,并最终导致图像模糊,因此对光学系统的设计提出了新的要求。分析了光学系统畸变对TDI-CCD推扫成像时的影响,研究了空间相机光学系统设计中消除畸变的方法,并进行了光学系统设计。设计了谱段位于450～900nm,焦距f=6000mm,F数为10的三反射消畸变光学系统。设计结果表明,当光学系统视场角为1.6°时,光学系统的畸变量小于0.01%,当面中心遮拦为0.06时,Nyquist频率(50lp/mm)处调制传递函数优于0.50,成像质量达到衍射极限,可以满足高分辨率TDI-CCD空间相机的使用要求。该光学系也适用于多光谱、立体成像和立体测绘等对光学系统畸变有严格要求的相机系统。     

大F数长焦距空间相机光学系统设计

随着空间技术的不断发展,地元分辨率不断提高,空间相机光学系统的设计不断提出新的要求。分析了长焦距空间相机光学系统设计过程中需要考虑的问题,研究了大F数、长焦距空间光学系统的设计原理,并进行了光学系统设计。设计了谱段位于500~800 nm,焦距f=7200 mm,F=14.4的大F数、长焦距的折轴三反光学系统。结果表明,光学系统视场角达到1.6°,在450 km的轨道上,地面幅宽可以达到12.5 km,像元尺寸为10μm时,地面像元分辨率达到0.62 m,当中心遮拦为6%时,Nyquist频率(50 lp/mm)处调制传递函数(MTF)优于0.38,成像质量达到衍射极限,光学系统畸变量优于0.5%,可以满足高分辨率空间相机对地观测的使用要求,同时也验证了大F数、长焦距光学系统的设计原理。     

多光谱相机光学系统公差分析与研究

光学系统公差的合理制定是影响相机总体性能的主要因素。首先针对光学系统设计的指标要求,综合考虑空间环境适应性、结构布局等因素,采用像方远心光路,设计离轴三反多光谱相机光学系统;运用公差的灵敏度分析和反转灵敏度分析,计算系统内各公差参数对相机各谱段成像质量的影响,给出合理的公差要求及合适的补偿调整参数。按给定的公差要求,加工、装调了具有较高成像质量的光学系统。实验检测结果表明,相机静态传递函数在全视场所有谱段的实测值均在0.243以上,满足指标要求,制定的公差合理、可行,验证了公差分析与研究方法的正确性。     

高分辨率空间相机共轴三反光学系统实现形式研究

为了设计出高分辨率空间相机的光学系统,研究了反射式光学系统中存在次镜对主镜的中心遮拦等问题.通过对共轴三反射光学系统结构参数和最终视场在像面上的分布情况的分析,提出了半视场、全视场和环形视场3种光学形式,设计了焦距为3000mm、F数为10的3种形式的共轴三反光学系统.设计结果表明:3种共轴三反光学系统在有效视场角内成像质量均接近衍射极限,可以满足高分辨率空间相机不同的使用要求,指出半视场共轴三反光学系统适合于线阵CCD推扫成像,全视场共轴三反光学系统可用于面阵CCD凝视成像,环形视场共轴三反光学系统可实现一台相机上全色和多光谱成像的要求.     

空间微重力下离轴三反相机离焦范围

由三块反射镜组成的光学系统在轨道空间微重力的影响下,其反射镜面间隔、曲率半径往往发生改变,对系统的后截距产生较大的影响,最终导致相机离焦,成像质量下降。通过分析三反系统的等效高斯光学系统,得到其后截距公式;通过齐次坐标变换,得到反射镜面刚体位移公式;通过采用最小二乘算法拟合计算得到微重力环境下的镜面半径,计算出相机在空间环境下的离焦量为0.04 mm,为调焦机构的设计提供了理论依据。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

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.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.