SPRITE探测器调制传递函数测试方法研究

研究和测量SPRITE探测器调制传递函数(MTF),是为了分析、评价该探测器的空间分辨性能.先前的研究论文己报道了多种测试方法,本文据此进行了分析、研究,提出了基于平面干涉条纹的空间正弦波响应测试方法.该方法能消除光源、测试目标和光学成像系统引入的测量偏差,而且便于多光谱段的SPRITE探测器MTF测试.     

微光ICCD相机的动态调制传递函数理论模型研究

在微光像增强型电荷耦合器件(Intensified Charge-coupled Device,ICCD)积分时间内,空间振动影响微光ICCD相机的成像,导致成像质量下降.对于振动环境下微光ICCD相机成像,采用动态调制传递函数(modulation transfer function,MTF)评价空间振动对成像质量影响.结合微光ICCD相机特有结构,提出微光ICCD相机的动态MTF理论模型,分析低频正弦振动及高频正弦振动中,振动幅度、振动周期、积分时间等不同因素对成像质量的影响.     

液晶显示器件动态调制函数的测量与计算

为了降低液晶显示运动模糊,人们提出了各种方法,包括过驱动、背光扫描、高帧频等技术.如何客观准确地评价液晶显示的运动模糊程度,比较不同方法的优劣,对液晶显示的开发与应用至关重要.论文借鉴了光学系统中传统调制传递函数的概念,引入了动态调制函数作为液晶显示运动模糊的评价参数,详细讨论了动态调制函数的物理意义、测量计算及具体应用.     

基于调制传递函数的激光反射层析成像质量评价方法

激光反射层析成像技术作为实现空间目标远距离、高精度探测的有效途径之一,其成像质量的优劣对目标的探测精度有着很大的影响。将调制传递函数引入到激光反射层析成像质量评价中,通过求解激光反射层析成像系统的调制传递函数,得到变量为距离分辨率的调制传递函数曲线,在无需先验图像的情况下实现了对激光反射层析成像质量的定量评价,并搭建实验系统进行了验证。实验结果表明,基于调制传递函数曲线得到的距离分辨率与实验系统距离分辨率的理论计算值基本一致,该评价方法能够准确直观地描述激光反射层析成像质量。     

基于调制传递函数(MTF)的LCDs运动模糊研究

当运动图像在以LCDs为典型代表的保持型显示器上显示时,会产生诸如运动模糊之类的伪像这种图象质量的下降可以解释为LCDs显示运动图像时表现出的MIF低通特性.本文介绍了调制传递函数理论及其在像质评价中的应用方法,并运用调制传递函数理论从频域的角度分析了LCDs运动图像的显示特性、LC响应时间对运动模糊的影响以及背光闪烁的方法改善运动模糊的效果.     

数字式透镜调制传递函数测试系统设计

设计了一种数字式透镜调制传递函数(MTF)测试系统,分析了MTF测试算法,开发了CCD数据采集与处理系统,提供了用户操作界面;利用设计的测试系统,对已标定透镜的MTF值进行了测量,测试误差低于6%.     

紫外像增强器的调制传递函数测试系统设计

紫外像增强器是紫外成像系统的核心器件,其成像质量决定了对紫外光学信号的探测和成像能力。调制传递函数（Modulation Transfer Function,MTF）反映了系统对图像不同频率信息的传递能力,是像质评定的一种客观指标。本文基于狭缝成像和傅里叶分析的调制传递函数测试原理,设计了一套紫外像增强器的调制传递函数测试系统。然后对3支紫外像增强器进行了调制传递函数测试实验,得到3支紫外像增强器的MTF曲线截止频率均在32~34 lp/mm之间,并根据MTF曲线对3支紫外像增强器成像质量进行对比分析。最后经过重复测试得到几个重要频率点MTF测试值的标准差均低于0.02。     

工业用光学镜头调制传递函数快速检测系统

调制传递函数(MTF)是评价光学系统成像质量的重要指标。根据光学传递函数测量的理论基础,以狭缝、刀口作为目标物,搭建了一套适用于工业用光学镜头的调制传递函数(MTF)测量、成本低、结构简单、精度高、稳定性好的测量光路,并根据光路特点编译了相关测量软件。测量软件根据自动聚焦的基本原理进行了自动调焦的开发,在兼顾效率和精度的前提下,分别采用爬山法和传统方法作为粗调焦和细调焦的调焦搜索算法,并根据不同物镜的成像特点采取不同聚焦函数进行聚焦判定。通过实验显示,该MTF快速检测系统具有良好的稳定性。     

水下距离选通成像系统调制传递函数模型分析

随着国家对水下成像探测、水下资源勘查等应用需求增加,建立符合实际情况的水下光电成像模型,成为目前水下成像研究者的目标。为了探究水下距离选通成像系统性能,建立了距离选通成像系统各个模块调制传递函数模型,以及总的系统调制传递函数模型。对目前市场上主流成像系统所采用的超第二代、第三代像增强器的选通成像性能进行理论对比仿真分析,完成了对水下距离选通成像系统性能模型的仿真。结果表明,前向散射光调制传递函数以及后向散射光调制传递函数随着探测距离以及选通时间的增加呈现逐渐下降趋势,并且前向散射光调制传递函数下降的速度更快;系统调制传递函数随着探测距离、选通时间和空间频率的增加而逐渐下降,并且通过理论模型分析得到典型的第三代像管的性能比超第二代像管的性能在水下距离选通成像过程中更具优势。     

CCD调制传递函数测量方法的改进

本文对目前所采用的测量ＣＣＤ调制传递函数方法进行了分析,并此基础上提出了改进的测量方法,改进后的方法不仅继承了原来方法的优点,同时其测量和测量结果的可靠性都有较大的提高。     

A simple method for determining the modulation transfer function in digital radiography

The authors developed a simple method for determining the presampling modulation transfer function (MTF). which includes the unsharpness of the detector and the effect of the sampling aperture, in digital radiographic (DR) systems. With this method, the presampling MTF is determined by the Fourier transform of a ;finely sampled' line spread function (LSF) obtained with a slightly angulated slit in a single exposure. Since the effective sampling distance becomes much smaller than the original sampling distance of the DR system, the effect of aliasing on the MTF calculations can be eliminated. The authors applied this method to the measurement of the presampling MTF of a compound radiographic system and examined the directional dependence, the effect of exponential extrapolation, and the effect of different sampling distances. It is shown that the technique of multiple slit exposure and exponential extrapolation of the LSF tail, which has been commonly used in analog seven-film systems, can be employed in DR systems. The authors determined the glare fraction in order to estimate the component of low-frequency drop mainly due to ;glare'     

红外图像转换器传递函数测试方法

红外图像转换器是红外成像制导武器半实物仿真系统红外成像目标模拟器的重要组成部分,用于产生动态红外目标/干扰环境特性图像。图像传递函数是评价图像转换器性能优劣的一项综合性技术指标,包含了图像在不同等效黑体温度条件下,不同分辨率对应的图像调制度。叙述了红外图像转换器图像传递函数的定义和测试方法,用经过标定的热像仪和光学放大系统对红外图像转换器产生的图像进行放大,测试了亮、暗条纹的辐亮度,计算了条纹对的对比度。描述了红外热像仪的标定方法和使用注意事项,给出了256×256元MOS电阻阵列红外图像转换器图像传递函数的测试结果。该文可作为红外图像转换器性能考核的参考。     

Efficient WISH in an indoor environment

With the diffusion of wireless connections to Internet, the number of complex operations carried out from mobile users is increasing. To cope with bandwidth limitations and with disconnections, data caching is the most used technique. However for complex operation like dynamic searching a better solution is to take advantage of the multichannel property offered by CDMA protocol. In this case, cached documents can be allocated on distinguished channels in a dynamic way to obtain a better utilization of the radio communication links. We study a particular caching strategy suitable to be integrated with a radio-channel policy. We consider a semantic caching for intranet queries (or intranet searching) that takes advantage of data semantics by caching query answers instead of pages in order to exploit similarities between different queries. In fact, in a WLAN scenario, Internet activity is frequently composed by intranet searching operations characterized by local queries that aim to explore documents stored in a neighbor of the home site. We study benefits from a channel allocation strategy applied to intranet searching with semantic caching. Simulation experiments are carried out by considering an indoor scenario model where mobile clients perform keyword-based queries answered by local Web servers running application we refer to as WISH (Wireless Intranet SearcHing), an intranet searching tool based on semantic caching. The results show a 12% improvement in radio channel usage for 20% of users that share cached documents.     

一种用于模拟电路测试与修调的方法

针对模拟电路中一些基准量的测试与修调,本文提出了一种通过管脚复用技术和单多晶的EEPROM相结合的方法对模拟电路中的基准电压进行了测试与修调,然后通过仿真验证了该方法实现的电路功能。     

Towards an analog system design environment

An analog circuit design environment and its key features are presented. These are multifunctionality, advanced modeling, novel simulation approaches, general sizing algorithms, hierarchy, and automatic and interactive layout generation capabilities. Also, several developments in the field of analog design automation are discussed     

A dynamic CMOS multiplier for analog VLSI based on exponentialpulse-decay modulation

A clocked, charge-based, CMOS modulator circuit is presented. The circuit, which performs a semilinear multiplication function, has applications in arrayed analog VLSI architectures such as parallel filters and neural network systems. The design presented is simple in structure, uses no operational amplifiers for the actual multiplication function, and uses no power in the static mode. Two-quadrant weighting of an input signal is accomplished by control of the magnitude and decay time of an exponential current pulse, resulting in the delivery of charge packets to a shared capacitive summing bus. The cell is modular in structure and can be fabricated in a standard CMOS process. An analytical derivation of the operation of the circuit, SPICE simulations, and MOSIS fabrication results are presented. The simulation studies indicate that the circuit is inherently tolerant to temperature effects, absolute device sizing errors, and clock-feedthrough transients     

A deterministic frequency-domain model for the indoor power line transfer function

The characterization of the transfer function of the power line (PL) channel is a nontrivial task that requires a truly interdisciplinary approach. Until recently, a common attribute and limitation of existing models for the PL channel transfer function lay in the phenomenological or statistical approach usually followed. This approach allows one to describe the channel only partially, e.g., as dominated by multipath-like effects, and prevents one from unveiling special properties of it. Multiconductor transmission line (MTL) theory was recently found by the authors to be a useful and accurate tool in modeling the PL transfer function while, at the same time, taking into account the wiring and grounding practices mandated by several regulatory bodies for commercial and residential premises. Crossing several layers of abstraction and following a bottom-up approach, complex circuit-level models originating from MTL theory can be manipulated and represented in terms of cascaded two-port networks (2PNs), thus allowing one to compute a priori and in a deterministic fashion the transfer function of any PL link. In the present contribution, we present additional analysis and data that validate the accuracy of the MTL approach and further justify its use in the PL channel context. Moreover, we also describe in detail the methodology to follow for modeling both grounded and ungrounded PL links in a unified framework. A consequence of the validity of the proposed modeling is that it can facilitate the process of standardization of the PL transfer function, an important step toward the availability of a commonly agreed upon (set of) channel transfer functions.     

Characterization of the modulation transfer function of discrete filtered backprojection

A mathematical expression for the modulation transfer function (MTF) of image reconstruction by discrete filtered backprojection (DFBP) is derived. A simulation study is used to investigate the dependence of the MTF of DFBP on: (1) the number of projection views; (2) the type of ramp filter used; (3) the interpolation method used during backprojection; and (4) the position of the object. These results were compared to MTFs calculated from point-source single-photon-emission computed tomographic (SPECT) acquisitions in air. The experimentally obtained MTFs contained much of the same structure as the MTFs of DFBP obtained through simulation. It is shown that the discretization of the filtered backprojection process can cause the tomographic transfer function to be anisotropic and nonstationary. However, through proper selection of the methods used in reconstruction, a nearly isotropic and stationary MTF can be obtained.     

一种小型室内环境智能监测仪器的设计

基于人们对室内空气质量监测的需求,设计一种以STM32F103C8T6微控制器作为核心控制器的一套室内环境智能检测系统,它能够实时、准确并有效地监测当前室内的温度、湿度以及空气中的悬浮颗粒(PM10)和有毒有害气体等,并通过蓝牙把当前室内的环境情况传送到电脑端显示出来,及时向人们警示,避免对人体健康产生危害。该系统具有体积小、方便可靠以及操作简单等特点,可广泛应用在室内环境检测领域。