稀疏孔径光学系统成像的图像恢复算法研究

提出两种稀疏孔径光学系统成像的图像恢复模型.分析维纳滤波、最小二乘方滤波和极大似然法盲去卷积三种图像恢复算法的适用条件.针对存在噪声干扰的稀疏孔径光学系统,通过实验对比,指出维纳滤波和最小二乘方滤波把相机光学传函当作系统传函,其理论推导能够达到最优.盲去卷积把大气传输函数和相机光学传函作为系统传函进行恢复,其恢复结果优于维纳滤波带入常数K和最小二乘方滤波调整参量结果.     

空间变光学信息处理述评

一、引 言 近几年来国内外对空间变光学信息处理的研究已有若干进展. 1975年我们曾用一种非相干光方法,处理转动大模糊图象,实验和理论文章已发表[1].在文献[2,3]中论述了用平面光学元件列实现一般线性光学变换以及用迭代法求解.此后,我们对此类系统又做了一些讨论和具体计算. 正如大家所熟悉的,线性光学系统输出函数g(x,y),与输入函数f(x,y)的关系,由迭加积分表述:h(x,y;x',y')是光学系统的点扩展函数,它表示系统在输出平面上(x,y)点对于输入平面上(x',y')点δ函数的响应.当它具有h(x-x'.y-y')形式时,则此系统被称为“空间平移不变的”,或…     

全息滤波光学图像相减

基于傅里叶光学二次滤波技术,本文提出了一种新的光学图像相减方法,即全息滤波光学图像相减法,该方法需用图像的逆转和匹配两种滤波器和一个8f光学系统,实验表明,作为一种新的图像相减方法,避免了以往实时法对光程的精细控制,因而降低了对辅助设备和环境的要求.     

窗函数对光学空间滤波效果的影响分析

为改善光学空间滤波的效果，分析说明了低通滤波器窗函数对光学空间滤波效果的影响。提出了相同通频区域下选择窗函数的两个要求即更窄的频谱主瓣宽度和更小的旁瓣高度，并运用MATLAB模拟了基于4f系统的光学空间滤波。结果表明，窗函数频谱主瓣宽度直接影响滤波结果的轮廓可见度，频谱旁瓣直接影响着频域截断带来的吉布斯波纹的大小。为如何选择滤波器透过率分布提供了理论参考。     

空间滤波的实验研究

运用空间域和频率域方法讨论了阿贝-波特实验和空间滤波实验中光波分别经过单透镜2f系统和4f系统时透镜的傅里叶变换和物体的频谱,探究了物体成像过程中的分频和合频过程,分析了空间滤波实验中透镜孔径对实验的影响.应用Matlab仿真模拟了低通滤波、方向滤波、显色滤波等图像处理技术,验证了夫琅禾费衍射下的巴比涅原理.     

高斯光束的4F光学系统空间滤波效应模拟与实验验证

以频谱的傅立叶变换与空间滤波理论为基础,对高斯光束经过4F光学系统的空间滤波后光强、相位调制进行了理论分析;利用MATLAB数学软件模拟了"光"字屏经过4F系统频谱面高通、低通滤波后形成的图像;自行设计微分屏,通过改变衍射光的相位实现了边缘增强的动态效果模拟,实验现象与以上模拟结果完全吻合。理论模拟可以生动、深入地揭示高斯光束在4F光学系统中傅立叶变换与空间滤波物理内涵,其模拟方法与效果展示可以为功能型滤波器的设计提供参考。     

信息光学实验装置的调整

4f′光学滤波系统是信息光学实验中最常用的光学系统。它要求正变换透镜L_1的后焦面与付里叶逆变换透镜L_2的前焦面重合,并要求确定L_1的前焦面、谱面、L_2的后焦面。本文介绍一种快速准确定位的莫尔条纹法。     

基于调制传递函数的光学低通滤波器评价模型与实验研究

为了量化评价光学低通滤波器(optical low pass filter,OLPF),利用调制传递函数(modulation transfer function, MTF)建立了一个包含OLPF的二维数字光学成像系统模型,并以此模型为基础构建了OLPF的评价函数.应用该评价函数,计算三种典型OLPF的滤波特性,计算结果表明随着理想光学系统空间截止频率的增大,三种OLPF的滤波性能均有先微弱增强,后迅速减弱的趋势;当光学系统F数大于44时,采用嵌入“两层四点”式OLPF的数字成像系统的低通 关键词： 光学低通滤波器 调制传递函数 评价函数 空间频率     

一种新型离轴三反式光学系统的设计

在三反射镜光学系统的几何光学理论的基础上，设计了一个焦距f=1000 mm,相对孔径D/f=1/4，视场角2w=3°的离轴非球面三镜反射系统，讨论了优化方法和各参量对系统结构和像差的影响.     

空间滤波实验中光路和傅里叶变换透镜孔径对实验的影响

运用空间域和频率域方法讨论了阿贝-波特实验和空间滤波实验中光波分别经过"4f系统"、双透镜系统(两种)和单透镜系统时透镜的傅里叶变换和物体的频谱,分析了空间滤波实验中光路和傅氏透镜孔径对实验的影响.     

The validity of high-pass angular spectrum filter in solid immersion lens system

应用矢量方法计算了具有高通角谱滤波器的固体浸没透镜（SIL）系统的焦场分布。数值结果显示，对于径向（角向）偏振输入光，高通角谱滤波器可以减小SIL系统的光斑（暗斑）大小。然而，对于线性偏振输入光，简单的高通角谱滤波器不能够优化SIL系统的光场分布，也不能够改进系统的光存储密度。     

基于四叉树的光学小波滤波器轴心定位的研究

精度问题制约了光学小波变换的广泛应用。若要扩展其应用领域,必须提高变换精度。在二维光学小波变换4f系统中,小波滤波器轴心的精确定位至关重要。提出了一种基于四叉树搜索方法的光学小波滤波器轴心定位方法。所用的加载滤波器载体为空间光调制器(SLM),定位精度可达到SLM的一个像素大小。为加快搜索速度,提出了一种基于四灰度级并行处理的改进方法。     

基于光子晶体光纤中受激布里渊散射的光载波抑制

设计了一种基于光子晶体光纤中受激布里渊散射的载波滤波器.该滤波器利用两个环形器和一段光子晶体光纤构成了一个环形腔,这种腔结构有效地降低了光纤中受激布里渊散射的阈值.理论分析了光子晶体光纤载波滤波器对提高光调制深度和射频增益的影响.利用25 m的高非线性光子晶体光纤作为受激布里渊增益介质,当入射载波功率为70 mW时,微波光子信号的射频增益为5.38 dB,实验结果与理论计算相吻合.     

数字全息变焦系统的研究及应用

从4f系统及照像机变焦镜头的设计思想出发,提出并设计了一个由三面透镜组成的数字全息变焦系统.该系统具有4f系统的性能,且可以方便地改变横向放大率,适应实际检测物体尺寸及形状的变化.用几何光学表述了变焦系统的工作原理,基于矩阵光学理论介绍了变焦系统的设计方法,利用衍射的角谱理论对像空间波面重构计算方法进行了介绍.并且,给出了实验证明及应用实例.     

Improving the resolution of a solid immersion lens optical system using a multiphase Fresnel zone plate

We propose a method to improve the resolution of near-field optical system with a solid immersion lens by using a multiphase level Fresnel zone plate. The analyses are based on scalar angular spectrum theory. The results show that the multiphase Fresnel zone plate can not only decrease the spot size but also decrease the sidelobe intensity and enhance greatly the diffractive efficiency compared with annular amplitude filter or binary 2-, 3-, 4-zone phase filter.     

基于光学子波变换的SDF匹配滤波器

提出了一种基于光学子波变换的综合判别函数匹配滤波器(WFSDF),将光学子波变换和综合判别函数相结合,只用一个简单的4f系统就能实现输入图像和SDF子波变换的相关运算。采用计算全息的方法制作复数匹配滤波器。计算机模拟仿真结果表明,与传统的SDF匹配滤波器相比,WFSDF匹配滤波器,锐化了相关峰,提高了识别率,同时简化了光路,能够实现多目标的畸不变识别。     

Optical implementation of the Banyan network using the Wigner distribution approach

A new optical processor is proposed for implementing the Banyan interconnection network. The optical system is simple and compact since it only employs a phase filter to permute the data input. Based on a relation between the space-spatial frequency information of the input plane and that of the output plane, the required local phase variation of the filter is determined by means of the Wigner distribution function. Experimental verifications are presented for a one-stage four-channel interconnection.     

Passive and temporally continuous optical spectral analyzer of RF signals via wavelength coding

A novel approach realizing an optical spectrum analyzer for photonic detection of an unknown RF carrier signals is presented. The described module may be part of an electronic warfare system in which detection of a narrow band RF signal is required. Moreover, The RF signal is characterized by an unknown time varying carrier frequency embedded in wide band noise. The system uses a passive, fiber based photonic configuration. It allows the spectrum mapping of an incoming electronic RF signal modulated on an optical carrier. The spectral analyzer configuration uses a finite impulse response (FIR) filter that is realized by two different optical paths of parallel fibers which generate a spectral notch filter. Hence, a wavelength coding is realized by chromatic dispersion such that each wavelength is filtered by a different FIR filter. Therefore, the energy at a WDM demux output channels is actually proportional to the spectrum of the input RF signal. This spectral mapping is obtained without lose of temporal RF information.     

An approach to enhance the receiver sensitivity with SOA for optical communication systems

In this paper, we investigate an SOA (semiconductor optical amplifier) preamplifier structure by optimizing the carrier lifetime in order to reduce the amplified spontaneous emission (ASE) noise and crosstalk, with adequate gain increase. This proposed SOA optical preamplifier has no need of optical alignment and antireflection coating. This structure of SOA eliminates the need of optical filter, and exhibits large tolerance to the input light wavelength. The receiver sensitivity is investigated for single and multi channel transmission links. The received power of − 50.34 dBm is observed at bit error rate (BER) 10^− 12 for 10 Gb/s with PIN receiver. Further, the impact of gain, amplified spontaneous emission power and gain variation for different carrier lifetime with input power for OOK system is illustrated. The proposed SOA has constant gain of 30.06 dB up to gain saturation for carrier lifetime 0.18 ns. It is predicted that low value of carrier lifetime suffers less from ASE noise.     

Iterative Wiener deconvolution based method for phase retrieval from noisy intensities

To retrieve the phase from the noisy measured intensities in the diffraction planes, an iterative Wiener deconvolution based method is proposed. With the same iterative scheme as the iterative angular spectrum method (IAS), the propagation of the optical wave function between the input plane and the diffraction planes is calculated by Wiener deconvolution in this method. The angular spectrum convolution kernel used in the iterative angular spectrum method is incorporated into the Wiener filter. The simulation experiments show that the proposed method can reduce the impact of the noise on the retrieved phase and performed better than the pre-denoising method. Furthermore, the proposed method exhibits great advantage compared to IAS for retrieving the complicated phase distribution from two measured intensities.