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。     

红外变焦投影光学系统的设计

根据外场测试要求,设计一套精确变焦的大口径投影光学系统,为系统性能测试评估提供远场至近场的目标成像模拟,系统由精确变焦系统和大口径投影系统两部分组成。根据被测系统口径及所成像点大小要求,在保证光瞳衔接和口径匹配的前提下,对大口径投影光学系统和精确变焦系统进行了光学参数计算和像质优化。变焦系统工作波段为8 m ~12 m,变倍比为16x,大口径投影光学系统口径为300 mm,模拟实验结果表明,该系统在变焦过程中像面稳定,各焦距位置MTF曲线接近衍射极限,满足外场测试实验要求。     

30 mm~300 mm轻型变焦物镜光学系统设计

设计了一组长焦距轻量型变焦光学系统,焦距为30 mm ~ 300 mm, 视场角为1.1°~ 11.4°,F数为3.5。由于变焦系统焦距较长,并且需要在控制口径的前提下减轻质量,经过对变焦理论进行分析并结合实际情况,采用正组补偿,运用Zemax软件,对变焦系统同时进行像质优化与轻量化设计,优化过程中加入非球面,达到简化结构,提高像质的作用; 在不影响像面照度的情况下,对轴外光线进行了适当的拦光,使得有效口径尽量变小,同时对系统的部分透镜材料进行替换,平衡了高像质与轻质量间的矛盾,最终使系统的总体质量从937 g减小到584 g,且系统像质良好,轴上调制传递函数在120 lp/mm处大于0.3,轴外调制传递函数在120 lp/mm处大于0.2,各视场的调制传递函数在40 lp/mm处大于0.5,畸变小于1%。根据变焦运动方程,运用Matlab软件进行编程计算,得到反映变倍组与补偿组运动过程的凸轮曲线,在变焦的过程中像面比较稳定,调焦顺畅。     

6倍制冷型中红外连续变焦光学系统设计

提出了一种求解变焦方程的新方法,并针对中红外320×256元制冷型焦平面阵列探测器,设计了一个3.7～4.8 μm波段的透射式红外连续变焦距光学系统,其F数恒定为2,最小焦距值为22 mm,变倍比为6。系统由变焦物镜和二次成像系统构成,包括7片硅、锗透镜,并引入非球面以校正系统各种轴外像差,同时利用两个平面反射镜折叠光路以减小尺寸。在空间频率16 lp/mm处和全焦距范围内,系统各个视场的光学调制传递函数均大于0.55;在接收面为30 μm×30 μm的探测器敏感元内,能量集中度大于80%。因此该系统具有较好的成像质量。     

用于光具座自动测量焦距的变焦光学系统设计

为了提高光具座自动测焦距时的测量精度,设计一套连续变焦光学系统。该系统包括自准直组件和变焦组件两部分,可以调节CCD靶面上接收到的图像大小,得到最佳测量结果。根据设计指标要求,在控制系统总长的基础上进行初始结构选择和像质优化。设计完成后的自准直组件焦距200 mm,变焦组件焦距200 mm~20 mm,对接后的变焦系统可实现图像大小1~10连续调节。模拟实验表明:变焦系统像质良好,MTF曲线接近衍射极限,弥散斑小于CCD像元大小,可以满足实际检测需求。     

一种新型复合变焦光学系统

基于复合变焦光学系统原理,提出了一种新型复合变焦光学系统结构。该结构将连续变焦与两档变焦结合,可以增大变焦光学系统的焦距变化范围,实现更大的搜索范围和更远的跟踪距离。建立了新型复合变焦系统光学设计的数学模型。在该模型的指导下,针对像元数为320×240,像元尺寸为30μm×30μm的长波红外非制冷焦平面探测器,设计了一款新型复合变焦光学系统。该系统工作波段为8~12μm,焦距变化范围为10~360mm,在10~60mm时,F数为2,在60~360mm时,F数为4。对光学系统凸轮曲线和性能进行了分析。结果表明,该系统具有变倍比大、结构简单、像质好和变焦轨迹平滑等优点,验证了该数学模型的有效性。     

双波段大变倍比连续共变焦光学系统设计

为了提高变焦光学系统在复杂环境下的高分辨率探测能力,解决现有多波段光学系统中光路转换和波段切换耗时长、系统反应慢、不同波段目标信息存在差异的问题,设计了一种可见光(0.38~0.76μm)、中红外(3~5μm)共口径连续共变焦光学系统,系统工作焦距为7.52~98.35mm,变焦比为13×.基于正组补偿变焦理论分析了任意变焦位置处可见光、中红外变焦比的差异及其变化规律,推导了三片薄透镜消色差理论和双波段焦距补偿表达式.对变倍组和补偿组的光焦度进行合理匹配,使系统在任意变焦位置处的焦距及变焦比都相同,提高了双波段目标信息的一致性.根据使用要求,采用光学被动式完成双波段光学系统在-40~+60℃温度范围内的消热差设计.设计结果表明,系统结构紧凑,反应速度快,整体成像质量良好,可实现昼夜全天候工作.     

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。     

紧凑型大变倍比中波红外连续变焦光学系统设计

针对致冷型中波红外640×512凝视型焦平面探测器，设计了一个30×连续变焦光学系统。介绍了由无后固定组的变焦物镜组和中继透镜组组成的连续变焦系统的设计思路，不仅给出了系统在短焦、中焦、长焦3个位置的像质情况，还分析了反映全焦距范围内像质的离焦量和畸变。实验结果表明:该系统工作波段3.7 μm~4.8 μm，可以实现18 mm~540 mm连续变焦，全焦距范围内的离焦量都在焦深以内，长焦段最大畸变接近于0，短焦段最大畸变小于3%。该系统具有大变倍比、结构紧凑、变焦轨迹平滑、变焦行程短等优点，可用于红外光电探测和跟踪系统。     

8倍非制冷型红外折/衍射连续变焦系统设计

针对长波用320×240元非制冷焦平面阵列探测器,设计了8～12 μm波段折射/衍射混合红外连续变焦光学系统,其相对孔径大,F数为1.3,系统变焦倍率为8.变焦系统采用锗和硫化锌两种材料,通过引入二元面和非球面校正系统色差和轴外像差,在空间频率18 lp/mm处,全焦距范围内调制传递函数(MTF)均在0.5以上,接近衍射极限;系统在接收半径为17.5 μm的探测器敏感元内,能量透过率大于78%,表明该变焦系统具有良好的成像质量.     

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.