高变倍比大相对口径长波红外变焦系统设计

针对传统红外连续变焦系统难以同时满足高变倍比和大相对口径的使用要求,通过采用复合变焦光学系统结构,增加传统红外连续变焦光学系统的变焦距范围和相对口径。基于长波红外320×240像元、25 μm×25 μm非制冷焦平面探测器,设计了一款高变倍比大相对口径长波红外变焦光学系统, 光学系统由一个连续变焦部分与两档变焦部分组成,通过引入衍射光学元件校正长焦端色差,工作波段为8 μm~12 μm,焦距变化范围为-9 mm~-272.25 mm,F数为1.4。该系统具有成像质量好、变倍比高、相对口径大、导程小和凸轮曲线平滑等优点。     

轻型车载大口径光电跟测系统光学设计

设计了一套能实现机动式布站的大口径车载可见光、红外、激光光电跟踪测量光学系统。其主光学系统采用共口径光谱分光方式工作,系统有效口径1.2m,各成像通道成像质量均达到衍射极限;捕获电视系统采用连续变焦距光学系统,视场范围0.31°～4.57°;激光测距通道设计作用距离达20km。光学设计结果表明,此套光学系统能够用于空中和空间目标的运动轨迹、成像测量和实况景象记录。     

中波红外长焦距折反光学系统设计

针对多模制导中长焦距红外光学系统结构紧凑及宽温度范围热稳定性的要求,设计了一种中波红外折反光学系统。该系统根据其它模式制导的要求,采用固定焦距和口径的主镜,通过二次成像,在保持长焦距的同时减小了透镜的口径,降低了到达中继成像系统主光线的高度,同时也降低了制造成本。设计了波长为3.7~4.8 μm、焦距f为300 mm、F数为2的中波红外成像系统。结果表明,该系统结构紧凑像质优良,各视场光学传递函数均大于0.6,接近衍射极限,并且在-50~70℃可实现光学被动消热差。针对该光学系统进行了公差分析并提出了抑制杂散辐射的方法,该系统满足实际加工和应用需求。     

大变倍比中波红外连续变焦光学系统设计

针对新一代光电吊舱对轻小型长焦距高清红外变焦成像系统的迫切需求,采用分辨率为1280×1024、像元尺寸为15μm大面阵中波制冷红外探测器,设计了一款变倍比为48、焦距范围为25～1200 mm的中波红外连续变焦光学系统。为了实现小型化设计,采用二次成像、正组机械补偿、平滑换根、结合后组温阑切换变F数,以及光路巧妙折转的设计思路及方法,在保证100%冷阑效率的同时,实现了红外变焦系统的大变倍比与小型化设计。结果表明,该光学系统在-40℃～+60℃温度范围内具有良好的成像质量,且光学最大口径为230 mm,光学总长仅为350 mm,该系统具有结构紧凑、变倍比大、焦距长、分辨率高、成像质量良好等优点,可满足新一代红外成像系统的要求。     

红外光学系统焦距测量装置校准规范说明

红外光学系统焦距测量装置是红外光学系统焦距校准和检测的技术手段之一。红外光学系统焦距测量装置校准规范不仅应用于计量部门，保证计量部门日常校准工作的准确性、一致性和可溯源性，同时为红外光学系统焦距测量装置生产部门提供了技术依据，满足红外光学系统焦距测量装置用户在申请各种认证过程中对红外光学系统焦距测量系统的要求。简要介绍红外光学系统焦距测量装置校准规范的主要构成和主要参数校准方法及不确定度评定。     

红外大变倍比连续变焦距系统光学被动式无热化设计

为了实现大变倍比连续变焦距红外光学系统的光学被动无热化设计,研究了连续变焦距系统的无热化设计基本理论及方法。提出了在大相对孔径大变倍比连续变焦距红外系统中采用光学被动式消热差的方法。推导出了连续变焦距系统光学被动消热差的计算方法。基于这种计算方法,设计了一个焦距30~150mm,长波红外工作波段在8~12μm,相对孔径1∶1.1的大变倍比、大相对孔径连续变焦距系统,并进行光学被动消热差设计,使系统在-30℃~60℃温度范围内MTF大于0.3满足成像要求。系统设计合理,成像质量满足要求,通过系统设计充分验证设计理论的可行性和实用性。     

大口径超长焦距紧凑型光学系统设计

为满足空间遥感光学系统结构紧凑、体积小以及高分辨率的需求,提出了一种长焦距紧凑型光学系统的设计方法。基于高斯光学和初级像差理论,创建了同轴四反射镜系统的初始结构,通过视场偏置的方法避免二次遮拦。对设计的大口径超长焦距同轴偏视场四反射光学系统进行优化,系统口径1 800 mm,有效焦距25 000 mm,全视场角1°×0.1°。设计结果表明,系统设计波像差优于λ/50(λ=632.8 nm),全视场相对畸变小于0.4%,光学筒长仅为有效焦距的1/10,结构简单紧凑,像质接近衍射极限,对大口径超长焦距空间遥感光学系统的设计具有一定的借鉴作用。     

红外光学系统焦距测量的研究

红外光学系统是红外系统的关键组件,而焦距是光学系统重要的参数之一,它的测量直接影响到红外系统的定位精度和打击目标的准确率。传统的测量焦距的方法一直沿用可见光照明的放大率法,其测量精度受很多因素的制约。研制的测量红外光学系统焦距的系统,采用倒置放大率法测量方式,直接用红外光源照明放置在被测光学系统物方焦面上的玻罗板,用线...     

大口径内扫描红外变焦光学系统设计

设计了一种大口径内扫描三档变焦光学系统。系统工作波段为7.7～10.3μm,焦距为65mm、130mm、390mm,变倍比为6∶1,系统F数为1.67,最大口径为240mm。系统具有较好的成像质量,且对冷反射和扫描温差进行了优化控制,这种变焦光学系统具有大口径、长焦距,能够用于对远距离小目标跟踪的特点,在高性能红外热像仪中得到较好的应用。     

双色红外共孔径消热差光学系统设计

针对红外搜索跟踪系统对目标的探测,为提高光学系统在复杂背景下的探测能力,设计了双色红外共口径光学系统。系统工作波段为红外中波3 m~5 m和红外长波8 m~12 m,采用分光型RC系统实现双波段共孔径清晰成像,总焦距为400 mm,相对孔径D/f=1/2,全视场角为2,为了抑制中波的热辐射杂光,对中波系统实现了二次成像,通过红外材料与光焦度的合理分配实现了折反式被动消热差设计。设计结果表明,系统在-40℃～+60℃工作温度下像质优良,能够满足红外搜索跟踪系统的使用需求。     

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.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

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.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

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.