像元间隔对亚像元动态成像系统MTF的影响

亚像元动态成像系统的调制传递函数MTF主要取决于像元尺寸及像元间隔等因素的影响。分析了像元间隔对亚像元动态成像系统的调制传递函数的影响，并给出了数值分析的结果：像元间的隔对亚像元动态成像系统MTF的影响总的趋势是随着像元间的增大而增大。     

图像传感器调制传递函数的矩形模板接触测量

为了方便地测量图像传感器的调制传递函数(MTF),在正弦模板法基础上,提出了矩形模板接触测量的方法。该方法将矩形模板紧贴于图像传感器,使矩形模板直接投射到图像传感器上,从而对图像传感器MTF进行测量。根据模板函数的一个周期占据图像传感器像元的数量情况,对采用正弦模板测得的调制传递函数值,与采用矩形模板测得的调制传递函数值,进行了理论推导和比较,找出了两者的数量关系。采用空间频率为25lp/mm的矩形模板、1280像素×1024像素的CMOS图像传感器进行实验,在对结果进行系数π/4修正后,测得图像传感器在该空间频率处的调制传递函数值为0.25。     

高级像差对人眼成像质量和视觉的影响

定量地研究高级像差对人眼成像质量和视觉的影响对人眼像差矫正具有重要的实验和临床意义.利用Hartmann-Shack波前传感器人眼像差仪测量了正常人眼6mm瞳孔的波前像差,由波前像差计算出人眼光学系统的光学调制传递函数MTF和Strehl比率,并由MTF和视网膜空间像调制度AIM曲线计算出人眼视锐度和对比敏感度函数CSF.根据MTF和Strehl比率分析了高级像差对人眼成像质量的影响,根据视锐度和对比敏感度函数CSF分析了高级波像差对视觉的影响.研究表明Zernik前6级像差对人眼成像质量和视觉的影响是不可忽略的,更高级的像差对人眼成像质量和视觉的影响较小,甚至可以忽略.对Zemik前6级像差进行矫正,可以得到相当好的视觉.     

刃边法计算在轨卫星图像MTF的仿真分析

调制传递函数（MTF）较之仅凭借某一个数字量（分辨率、清晰度等）来对成像系统进行质量评价更具有权威性。刃边法适合卫星在轨的特性，易于实现，无需人工对在轨遥感器输入激励信号。本文在实现刃边法计算图像MTF的算法的基础上，通过仿真，分析了像移、刃边角度、噪声对MTF计算结果的影响，并对算法精度进行了检验。仿真结果表明，本文的计算在轨卫星图像MTF的方法具有较高的精度，并且能较好地抵抗噪声。     

测量视觉系统MTF的一种客观方法

视觉系统的光学调制传递函数( MTF ),通常采用以大脑知觉为基准,对客观物理刺激进行主观评价的心理物理方法来测量。利用哈特曼-夏克波前传感器测量视觉系统的波像差,再由波像差和瞳函数的自相关,即可得出视觉系统的MTF。与心理物理方法相比,该方法不受被测试者情绪和心理状态的影响,并克服了测量过程繁琐的缺陷,具有客观、简便、快捷的特点,测量的全过程仅需3分钟。     

两种排列方式光纤传像束的像质评价

根据调制传递函数对比度定义,推导了线列光纤传像束调制传递函数(MTF)的数理关系,建立了光纤直径有随机误差的线列光纤传像束MTF仿真模型,对MTF进行数值分析。通过考虑在光纤传像束中输入信号与光纤的位相匹配对MTF的影响,分析了V型槽排列和紧密排列两种不同方式的光纤传像束的平均MTF。结果显示,有随机误差的光纤束的平均MTF值分别分布于理想传像束平均MTF曲线附近,表明了光纤自身的误差对传像束的平均MTF影响不大;V型槽排列的线列光纤束的像质优于紧密排列方式的线列光纤束。     

掠入射光学系统成像质量评价

为了能够全面评价掠入射光学系统的成像质量,基于像差理论和傅里叶光学原理,使用Matlab 编程语言编写了针对掠入射系统的像质评价程序,并利用此程序结合ZEMAX 软件对用于太阳观测的Wolter I 型和双曲面-双曲面(H-H)型掠入射系统的成像质量做了详细的分析.结果表明,该像质评价程序能够计算不同口径和焦距的掠入射系统在不同视场,不同工作波长时的点扩散函数、能量集中度、线扩散函数和调制传递函数,对掠入射系统的设计和优化具有指导作用.     

中红外AOTF前置光谱相机折/衍射混合变焦光学系统

设计了基于AOTF器件的中波红外光谱相机前置变焦系统,针对AOTF器件和探测器的特性,系统采用折/衍射混合设计,用6片透镜即实现了25~300 mm连续12×变焦,并用ZEMAX软件对则汇集结果进行优化和像质评价。结果表明,该光学系统各个波段上在空间频率14 lp/mm处调制传递函数(MTF)值接近衍射极限,能量集中度大于90%。可用于大多情况下中红外光谱成像分析以及中红外的目标探测及识别。     

图像传感器单粒子效应脉冲激光实验研究

针对设计研制的512×512 CMOS APS图像传感器,采用聚焦脉冲激光束研究了其空间单粒子效应特性。试验结果表明,CMOS APS器件图像传感器存在单粒子翻转（SEU）和单粒子锁定（SEL）现象。验证了CMOS APS图像传感器抗单粒子锁定设计的有效性。当对图像传感器移位寄存器区进行照射时,同时发生单粒子翻转和单粒子锁定,器件其它区域也有类似现象。分析了器件单粒子效应的敏感性,获得了器件发生单粒子翻转和锁定的脉冲激光能量阈值及器件锁定电流大小。     

电视图像传感器检测平台的研制

为了准确、客观评价面阵CCD器件和整机多项性能参数,研制了电视图像传感器试验检测平台系统.整套系统装置采用组合式的设计理念,由两部分构成,电视图像传感器性能参数测试系统测量噪声、响应度、饱和照度、阈照度、动态范围、系统信噪比(SNR)、信号传递函数(SiTF)、均匀性等,其测试系统误差为4.28%;电视图像传感器成像系统组件定标与试验检测系统测量系统调制传递函数(MTF)、系统畸变、视场角与焦距、系统分辨率、系统光学同轴度等,其系统误差为4.48%.     

圆孔阵列对“猫眼”目标成像质量的影响分析

利用圆孔阵列光强调制作用可以有效减弱光学窗口的“猫眼”效应,同时也会对“猫眼”目标成像质量产生一定不利影响.考虑到利用调制传递函数(MTF)可对光电仪器成像质量进行综合评价,分别给出了测试望远系统和微光夜视系统MTF的数学模型,利用自行研制的光学仪器MTF数字化检测系统,实现了这两种典型“猫眼”目标MTF的数字化检测.结果表明,圆孔阵列在全空间频率上均使“猫眼”目标的MTF有所下降,且孔径较小、孔阵较密的圆孔阵列对“猫眼”目标MTF的影响较小,这为合理设计圆孔阵列结构以减小对“猫眼”目标成像质量的影响提供了可靠的实验数据.     

Method for the measurement of the modulation transfer function of sampled imaging systems from bar-target patterns

A rigorous and simple method for the determination of the modulation transfer function (MTF) of a sampled imaging system is presented. One calculates the MTF by imaging bar patterns and calculating the reduction in amplitude of the fundamental frequency components. The optimal set of bar-pattern frequencies that reduce errors from aliased frequency components is derived. Theoretical and experimental data are presented.     

Evaluation of silicon active pixel sensors for alpha particle detection

Alpha particles can be used as a test stimulus offering several advantages for probing materials of micrometre thicknesses. In this work a silicon CMOS Active Pixel Sensor (APS) is evaluated for alpha particle detection and imaging. These devices can replace traditionally used solid-state track detectors, giving advantages of increased sensitivity, improved linearity and higher dynamic range. CMOS APSs offer high detection efficiency, low noise and digital readout. Qualitative and quantitative analysis of the back-illuminated back-thinned (BT) and standard sensor response to 5.5 MeV alpha particles is presented. Alpha particle detection efficiency was estimated and energy resolution was measured. Imaging capabilities were assessed and quantified. Cluster centroiding algorithms were implemented for image quality improvement.     

中波红外全景成像仪线扩散函数的模拟分析与验证

线扩散函数是评价成像系统成像质量的一个重要参数,线扩散函数的模拟分析与验证对成像仪的研制至关重要。本文首先分析中波红外全景成像仪探测器所接收到的辐亮度,从理论上估算了全景成像仪的线扩散函数,然后通过斜缝法加以验证,试验结果证实了理论模型的正确性。并对线扩散函数经离散傅里叶变换计算而得MTF传递函数,结果与理论得出的系统MTF基本符合,进一步证明了这种模拟分析方法的可行性。     

当代照相市场及未来的发展

本文叙述了传统感光材料的现状，包括技术、ＡＰＳ和大公司的投资情况，数字成像的基本特征和应用领域，最后从质量和成本的角度，用发展的眼光分析了未来照相市场的基本走势。     

近贴X射线成像系统调制传递特性联合检测方法

利用光学调制传递函数评价原理,在建立了各个成像子系统信号传递关系的基础上,提出了一种近贴式X射线成像光学调制传递特性检测方法。从像增强器约束、射线源约束和噪声约束这3个角度对近贴式X射线成像系统光学调制传递函数进行理论定标。将近贴式X射线成像系统后端的CCD望远系统换成CCD显微系统并对不同空间分辨率的铅栅进行成像与对比度拟合。实验结果表明:时域均衡可以有效提高拟合精度。其拟合结果表明空间分辨率为10线对/mm时其调制传递函数仍有10%,与理论定标结果基本一致。故传统近贴式X射线成像系统的望远光学镜头分辨率才是真正的成像瓶颈。     

Atmospheric modulation transfer function in the infrared

In high-resolution ultranarrow field-of-view thermal imagers, image quality over relatively long path lengths is typically limited by atmospheric degradation, especially atmospheric blur. We report our results and analyses of infrared images from two sites, Fort A. P. Hill and Aberdeen Proving Ground. The images are influenced by the various atmospheric phenomena: scattering, absorption, and turbulence. A series of experiments with high-resolution equipment in both the 3-5- and 8-13-microm regions at the two locations indicate that, as in the visible, image quality is limited much more by atmosphere than by the instrumentation for ranges even of the order of only a few kilometers. For paths close to the ground, turbulence is more dominant, whereas for paths involving higher average elevation, aerosol modulation transfer function (MTF) is dominant. As wavelength increases, turbulence MTF also increases, thus permitting aerosol MTF to become more dominant. A critical role in aerosol MTF in the thermal infrared is attributed to absorption, which noticeably decreases atmospheric transmission much more than in the visible, thereby reducing high-spatial-frequency aerosol MTF. These measurements indicate that atmospheric MTF should be a basic component in imaging system design and analysis even in the infrared, especially as higher-resolution hardware becomes available.     

Experimental investigation of the influence of the relative position of the scattering layer on image quality: the shower curtain effect

The imaging quality of optical systems in a turbid environment is influenced not only by the content of the turbid layer between the object and the optical receiver but also by the inhomogeneity of that medium. This is important, particularly when imaging is performed through clouds, nonhomogeneous layers of dust, or over vertical or slant paths through the atmosphere. Forward small-angle scattering influences image quality and blur more severely when the scattering layer is closer to the receiver. In this study it is the influence of the relative position of the scattering layer on the image quality and modulation transfer function (MTF) that is investigated. The scattering layer in controlled laboratory experiments consists of calibrated polystyrene particles of known size and quantity in a small cuvette. A point source was imaged by a computerized imaging system through a layer containing polystyrene particles, and the point-spread function (PSF) was recorded. The aerosol MTF was calculated using the measured PSF. The MTF was measured as a function of changing relative distance of the scattering layer from the receiver, whereas the object-plane-to-receiver distance was constant. The experimental results were compared to theoretical shower curtain effect models based on the solution from radiative transfer theory under the small-angle approximation. Although the general trend of the experimental results certainly agrees with the theoretical models, it could be that the small-angle approximation method might be of limited validity at such low spatial frequencies. Aggregation also causes some disagreement with predictions from theory.     

Design, optimization, and performance analysis of new photodiode structures for CMOS active-pixel-sensor (APS) imager applications

The dark current in the active-pixel-sensor (APS) cell of a CMOS imager is known to be mainly generated in the regions of bird's beak after the local oxidation of silicon process as well as the surface damage caused by the implantation of high doping concentration. Furthermore, shallow and deep pn-junctions can improve the photo-sensitivity for light of short and long wavelengths, respectively. In this paper, two new photodiode structures using p-substrate and lightly-doped sensor implant SN- as pn-junction photodiode with the regions of bird's beak embraced by SN- and p-field implants, respectively, are proposed and analyzed to reduce dark current and enhance the overall spectral response. 5 /spl mu/m/spl times/5 /spl mu/m APS cells fabricated in a 0.35-/spl mu/m single-poly-triple-metal (1P3M) 3.3-V CMOS process are designed by using the proposed photodiode structures. As shown from the experimental results, the two proposed photodiode structures of 5 /spl mu/m/spl times/5 /spl mu/m APS cells have lower dark currents of 30.6 mV/s and 35.2 mV/s at the reverse-biased voltage of 2 V and higher spectral response, as compared to the conventional structure and other photodiode structures. Thus, the two proposed new photodiode structures can be applied to CMOS imager systems with small pixel size, high resolution, and high quality.