基于变焦系统的红外成像目标模拟器研究

随着红外对抗技术的发展,红外成像制导已成为光电精确制导技术的一个发展方向。简要介绍了红外成像制导武器系统半实物仿真的发展现状。针对目前半实物仿真采用一弹一仿的问题,提出了基于五轴转台的新型仿真方案。通过采用变焦距投影系统目标模拟器,使得不同视场、不同焦距、不同型号的导引头可采用同一套仿真系统进行仿真测试,提高了仿真系统的效费比。设计了衍射受限长波红外变焦投影光学系统,系统变倍比为2 3,弥散斑直径小于50μm。     

红外搜索跟踪系统的半实物仿真系统设计

信息处理组件的设计与验证是红外搜索与跟踪系统研制过程中的关键环节;设计了一个基于嵌入式多媒体系统的红外信息处理组件半实物仿真测试系统,能够通过嵌入式系统完成红外目标场景视频流的实时生成、伺服控制模型的在线解算,软件仿真环境通过以太网与实物系统交互,实现针对红外信息处理组件的半实物闭环仿真测试,为信息处理组件的设计、仿真验证和性能评估提供了集成验证环境,将能够有效缩短整个系统的研制周期,提高研制质量。     

红外仿真变焦光学系统设计

针对目前半实物仿真采用一弹一仿的问题,提出采用变焦距投影系统的五轴转台仿真方案,使得不同视场、不同焦距、不同型号的导引头可以采用同一套仿真系统进行仿真测试,提高了仿真系统的效费比。分析了红外半实物仿真用变焦光学系统的特点,设计了（8～12）μm波段衍射受限红外变焦光学系统,系统入瞳直径80mm,变倍比为3.0,弥散斑直径小于50μm。     

一种红外场景/点源目标模拟器技术研究

研究了一种红外场景/点源目标模拟器。模拟器由一路红外场景、一路点源目标和四路点源干扰组成。模拟器包括点源目标/干扰通道、中继光学系统、成像通道、多目标复合系统、运动控制系统和机械支撑及连接结构,可以同时模拟一路点源目标,四路点源干扰和一路红外场景。对模拟器进行实验研究,模拟器所生成红外图像的空间分辨率达到10 lp/mm,模拟器点源光斑尺寸最小为42μm,最大为499μm。该模拟器已经成功应用到半实物仿真试验中。     

室温下低温背景红外场景生成方法实验研究

针对高空红外场景模拟的需要,提出了模拟低温背景红外场景的新物理概念和半实物仿真实验装置.将锗单晶制作的初始透明的半导体屏放置于低温系统前端,通过控制其小于禁带宽度的局部辐射系数,在室温下(≥27℃)得到低温背景(≥-30℃)的红外场景.对液氮槽和半导体致冷器生成的冷背景的效果、辐射功率差随写入光功率的变化及低温背景和目标的温度对比度进行了实验测试.实验结果表明,液氮生成的冷背景可达-30℃,半导体致冷器为3℃;在一定范围内增大写入光的功率可以提高半导体屏的转换效率,写入光功率过高会造成辐射功率值的饱和;随着写入光功率的增加,温度对比度也大幅升高.     

动态目标模拟器用视景仿真镜头光学设计

研究一种基于液晶光阀的动态光学目标模拟器用视景仿真镜头,给出了视景仿真镜头的设计实例。动态光学目标模拟器由内置液晶显示系统、视景仿真镜头、外置投影仪、计算机、电缆、调整机构组成。测试设备将命令发送到计算机,计算机根据接收的指令生成模拟地形图并控制液晶光阀将图像显示出来,液晶光阀位于视景仿真镜头的焦平面位置,视景仿真镜头对液晶光阀成像后形成平行光出射,可在有限距离上产生无限远效果模拟观测结果,光学敏感器接受模拟器的出射光线并成像完成模拟试验,视景仿真镜头采用二次成像的反远结构,同时为保证与液晶光阀出射光相互匹配,采用了远心光路的结构形式。视景仿真镜头的焦距f=-22.447 1 mm,视场角是对角线视场为45,有效视场为301.5301.5;全视场畸边＜1％,在Nyquist频率42.5 lp/mm处MTF＞0.45,系统长度325 mm;视景仿真镜头与敏感器镜头配合后在敏感器像面上的照度均匀性不小于95.4％。最后给出了视景仿真镜头的测试结果。     

武器红外传感器系统实时仿真概述

红外传感器系统的性能取决于系统操作时的环境,如复杂的地形、背景环境和大气条件等,用传统的飞行试验方法来作为系统性能的测试手段已不适应.采用半物理闭环仿真方法,在实验室建目标模拟器,可实时产生动态逼真的交战时所观察到的红外场景,为具有红外探测能力武器系统在研制、集成、测试、系统性能有效评价、武器系统的开发等方面提供精确可重复的实验途径.仿真系统包括目标特性及与红外场景有关的数据库、图像生成计算机、红外目标发生器、红外场景投影光学系统、飞行模拟器、仿真计算机.目前目标发生器产生的红外图像分辨率已达到512×512,帧频100Hz,辐射波段3～5μm、8～12μm,适用于目前红外制导系统制导过程的分析和评价.     

基于大屏幕的可见光目标模拟器技术研究

介绍了在电视制导武器半实物仿真系统中基于平面直角大屏幕的可见光目标模拟器的组成和工作原理,利用视景仿真软件Vega和MFC实现了视景生成软件的设计与开发,并将其应用于电视导引头的半实物仿真中。仿真结果表明,所提出的目标模拟器及其视景软件能够满足电视导引头半实物仿真的需求。     

弹道终端飞机目标红外图像瞄准点识别方法

依据飞机目标红外图像的特点,将飞机机头选定为跟踪瞄准点。利用弹道终端目标未充满视场前的红外序列图像、视场中心角、弹目距离等,建立了弹体坐标系下飞机轴线方向的求解模型。采用MAT、Hough变换等技术,对目标充满视场后的红外序列图像进行处理,检测出了飞机轴线,识别出了飞机机头。利用从弹道终端的两个序列图像中抓取出来的四帧红外图像进行了仿真,并给出了实验结果。     

红外场景投射器双波段投影光学系统设计

为了使红外场景投射器投射出的红外场景更加逼真,设计了一入瞳距800mm、入瞳100mm和视场为±2.5°的双波段红外场景投射器投影光学系统。研究了红外场景投射器双波段投影光学系统的设计过程,分析了初始结构选择的方法。该系统可以模拟主要发出波长为3~5μm的高温物体和波长为8~12μm的常温物体,可以分别使用3~5μm波段红外探测器和8~12μm波段红外探测器进行观测,并对该系统进行了像质评价和公差分析。     

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.     

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.     

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.     

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.