TDI CMOS图像传感器曝光时间优化方法研究

为了提高时间延迟积分互补金属氧化物半导体(TDI CMOS)图像传感器的成像质量,研究了TDI CMOS图像传感器中曝光时间的选取对成像质量的影响。基于行滚筒曝光读出原理,分别分析了曝光时间对信噪比(SNR)和调制传递函数(MTF)的影响机理,根据分析结果,提出在级数已选定的情况下,曝光时间的选取存在最优值,此时得到的图像质量较好。为验证结论,基于自主研发的TDI CMOS图像传感器芯片及现场可编程门阵列(FPGA)开发板,搭建了TDI CMOS图像传感器成像测试系统。实验中采用MTF×SNR作为评价图像质量的指标,实验结果表明,在选定的相机参数下,积分级数为8级,光强为20 lx时,TDI CMOS图像传感器曝光时间选取64 ms时所得到的图像质量最好,此时MTF×SNR最大。     

时间延迟积分型面阵CMOS图像传感器MTF速度失配模型研究

研究了时间延迟积分型面阵互补金属氧化物半导体(CMOS)图像传感器调制传递函数(MTF)速度失配特性,在分析累加级数、像素尺寸、镜头放大倍数、行周期及电机运动速度失配等影响因素的基础上,建立了MTF速度失配模型。基于现场可编程门阵列(FPGA)开发板,搭建面阵CMOS图像传感器实现线阵时间延时积分(TDI)的CMOS测试系统。实验结果表明,在光强为3lx,速度失配M(ΔV/V)<2,8级时间延迟积分与面阵成像相比,MTF值提高50%;当累加级数为8级,速度失配满足M(ΔV/V)=2的速度失配容限时,奈奎斯特频率处的MTF值下降10%,当速度失配达到M(ΔV/V)=10时,MTF值下降35%。     

数字域时间延迟积分CMOS遥感相机动态传函建模分析

调制传递函数（MTF）是遥感相机的重要评价指标,但是目前对于数字域TDI CMOS相机动态MTF特性研究十分有限,为了深入研究其像质下降机理,结合数字域TDI CMOS成像原理,建立了像元、电子快门、曝光时间、振动引起的数字域TDI成像MTF下降数学模型。结合推导模型开展了预估分析和实验验证。结果表明：传感器的有效像元区域分布会影响图像MTF,且开口率越小影响越大;CMOS传感器的卷帘快门会导致数字域TDI成像MTF下降,卷帘速度越慢影响越严重,其中卷帘速度从6μs变为10μs时,对应的图像MTF从0.191下降为0.177;曝光时间越短则MTF越高,尤其当存在低频像移失配时更为明显,曝光时间从180μs减小为100μs时,图像MTF从0.126提高为0.155,但同时也会影响图像信噪比,因此在实际应用中应合理选择曝光时间。     

基于空间相机时间延迟积分传感器拼接区图像的像移测量

为了对由飞船姿态不稳或隔振装置的振动抑制残余量等因素产生的宽频带像移进行测量,提出了基于时间延迟积分(TDI)传感器拼接区所成图像的像移测量方法。定义了偏移系数,用以衡量成像期间像移速度与TDI传感器积分时间之间的失配度,以调制传递函数(MTF)为相机成像质量评价指标,分析了失配度与成像质量之间的关系,确定了满足成像质量的像移测量方法的精度范围;利用两片TDI传感器拼接区所拍图像存在相同内容、拍摄时刻不同的特点,阐述了基于TDI传感器拼接区图像的像移测量原理。实验结果表明测量精度达到0.2377pixel,测量频带达到228Hz,证明该方法能够对宽频带、高精度的像移进行有效测量。     

卷帘快门对数字域TDI成像的影响分析EI北大核心CSCD

数字域时间延迟积分(TDI)互补金属氧化物半导体(CMOS)成像以其成本低、功耗小、操作灵活等优势,近几年逐渐引起研究关注。然而CMOS传感器的卷帘快门存在运动失真,为了深入研究其对数字域TDI的影响,结合卷帘快门工作原理,建立了卷帘快门效应对数字域TDI引起的像移及调制传递函数(MTF)下降的数学模型。并结合推导模型开展了预估分析和验证实验。结果表明:卷帘快门效应会对数字域TDI算法带来较大的影响;读出时间越长像移量越大、MTF下降越严重;另外行周期越短影响也越严重,其中行周期从200 us变为100 us时,对应的数字域TDI图像MTF从0.6144下降为0.4807。     

卷帘快门对数字域TDI成像的影响分析

数字域时间延迟积分(TDI)互补金属氧化物半导体(CMOS)成像以其成本低、功耗小、操作灵活等优势,近几年逐渐引起研究关注。然而CMOS传感器的卷帘快门存在运动失真,为了深入研究其对数字域TDI的影响,结合卷帘快门工作原理,建立了卷帘快门效应对数字域TDI引起的像移及调制传递函数(MTF)下降的数学模型。并结合推导模型开展了预估分析和验证实验。结果表明:卷帘快门效应会对数字域TDI算法带来较大的影响;读出时间越长像移量越大、MTF下降越严重;另外行周期越短影响也越严重,其中行周期从200 us变为100 us时,对应的数字域TDI图像MTF从0.6144下降为0.4807。     

基于TDI-CCD的高速小目标交汇测量系统

介绍了TDI CCD图像传感器的工作原理和成像特点 ,提出了基于TDI CCD的交汇测量系统 ,初步分析了该交汇系统行扫描速率和目标运动速率的同步控制问题。同一般线阵CCD组成的交汇测量系统相比较 ,TDI CCD构成的交汇测量系统能够提高探测灵敏度、扩大动态探测范围、增大信噪比 ,从而大大提高系统对目标的捕获几率。同时亦可减小照明光源的亮度及功耗。对大靶面、高速小目标物体运动轨迹的精密测量具有重要意义。     

推扫式线阵TDI CCD扫描调制传递函数分析

 根据线阵TDI CCD离散采样的特点,以采样间距内成像调制度均值为基础,构建了推扫成像模式下线阵TDI CCD扫描方向的调制传递函数。该调制传递函数的数值分析表明：对于像元为10 μm的线阵TDI CCD,行转移驱动时钟相数为4, 3或2时,Nyquist频率处调制传递函数值分别为0.363,0.333或0.255;行频误差为1%及3%时,不同积分级数下调制传递函数变化曲线表明,增大行频误差及增加积分级数将使调制传递函数值减小,图像分辨率降低。成像实验结果符合所构建调制传递函数的定量分析结论。     

全局快门sCMOS图像传感器数字TDI微光成像技术

为实现高分辨率大动态范围的空间微光(LLL)成像,提出基于全局快门科学级互补金属氧化物半导体(sCMOS)图像传感器的数字域时间延迟积分(TDI)微光成像方法。通过推导数字域TDI成像数据处理方法,建立了系统信噪比(SNR)模型,提出了数字域TDI大动态范围成像方法,并分析了速度失配导致的调制传递函数(MTF)退化现象。实验结果表明,该方法能够明显提高微光成像质量,当数字域TDI积分级数为30时,系统SNR由未积分的5.04dB提高到19.78dB,动态范围比传统数字域TDI方法提升了29.54dB,为实现高分辨率大动态范围空间微光成像提供了保障。     

扫描镜稳定度对TDI CCD测量精度的影响

利用TDI CCD成像数值仿真模型,研究了TDI CCD测量系统的测角精度随扫描镜速度稳定度的变化规律。首先根据TDI CCD推扫成像的物理过程,建立了数值仿真模型,设计了从光学像和扫描镜稳定度到数字图像的仿真链路;然后利用图像重心计算方法求取图像中心坐标并得到目标点的角位置坐标;通过蒙特卡诺法进行海量打靶试验,对结果进行统计得到扫描镜各稳定度水平上的测量精度值;最后将某工程样机的扫描镜速度稳定度带入仿真模型,仿真结果表明：测试误差增大5.67 μrad,达到了像元角分辨率的1/4。在光学测量系统的系统设计时,需要考虑像元分辨率及扫描镜稳定度的综合影响,选用合适的扫描镜稳定度要求,使测量角分辨率满足用户需求。     

Multi-soliton generation with extremely narrow free spectrum range for multiplexed sensors via optical network

We propose a new system of multiplexer sensors using the localized soliton pulse generated by a microring resonator in optical networks. A large bandwidth signal is generated by a soliton pulse propagating within the microring resonator, which is allowed to form the multiplexed sensors. Two forms of soliton pulses are generated and localized, i.e. temporal and spatial solitons. The required soliton pulses with specified wavelengths can be localized and formed the sensing. This is formed by using an optical add/drop multiplexer incorporating in the optical network, where the localized soliton pulses are available for add/drop signals to/from the optical network. The change in physical parameter measured the change in soliton wavelength, which formed the measurement.     

椭芯光纤干涉型多参量光纤传感技术

本文提出用椭圆纤芯高双折射光纤偏振干涉和双模干涉结合的双技术四参量以及双模干涉多参量同时测量的传感理论和实验原理，对交叉灵敏度作了分析，同时给出了误差分析，并结合理论模型对灵敏度矩阵的状态作了粗略估计。初步结果为：（１）灵敏度矩阵条件数不太大，可以采用迭代改善方法解线性方程组得到较好的解；（２）双模干涉传感器的灵敏度比偏振干涉传感器的灵敏度高两个数量级。     

The Anthracen-9-ylmethyloxy Unit: An Underperforming Motif Within the Fluorescent PET (Photoinduced Electron Transfer) Sensing Framework

Compound 2, which was designed to act as a fluorescent sensor for calcium according to the PET (Photoinduced Electron Transfer) principle, shows a relatively small Ca²⁺-induced fluorescence enhancement factor (FE) of 1.8 whereas its close relative 1 is known to display a far higher FE value of 16. Though designed as fluorescent PET sensors for solvent polarity, compounds 5 and 6 also show negligible fluorescence enhancement as their environments are made progressively less polar even though their relatives 3 and 4 show limiting FE values of 53 and 3, respectively. Indeed, 3 and 4 are useful since they are fluorescent sensors for solvent polarity without being affected by Bronsted acidity. The poor sensory performance of 2, 5, and 6 relative to their cousins is attributed to the presence of an oxygen proximal to the 9-position of an anthracene unit, which opens up a CT (charge transfer) channel. Normal PET sensing service is resumed when the offending oxygen is deleted.     

Coupling-Wave Structures for Optical Waveguide Sensors

An optical waveguide sensor structure, i.e. a coupling-wave structure, is presented and analyzed on the basis of a codirectional coupler. Potential uses for absorption-and fluorescence based sensors are theoretically explained by the group index method (D.-K. Qing, X-.M-. Chen, K. Itoh, M. Murabayashi: J. Lightwave Technol. 14 (1996) 1907). Refractive-index-based sensors were also analyzed. An actual coupling-wave structure was realized by combining the ion-exchange and the sol-gel methods. The coupling-wave structure that provides effective sensing interaction is easy to fabricate and can be used to realize optical waveguide chemical or biological sensors.     

CMOS vs. CCD sensors in speckle interferometry

In the field of interferometric metrology the use of high resolution CCD sensors with 1024×1024 to 2048×2048 pixels is predominant. Due to special features (e.g. random pixel access, characteristic curve) CMOS sensors with similar resolution can be an interesting alternative. We compare some characteristics of both sensor types that are important for interferometry and demonstrate two exemplary applications that are only possible by using CMOS cameras.     

Selected optoelectronic sensors in medical applications

Optoelectronic technology plays an important role in medical diagnosis. In the paper a review of some optoelectronic sensors for invasive and non-invasive human health test is presented. The main attention is paid on their basic operation principle and medical usefulness. The paper presents also own research related to developing of tools for human breath analysis. Breath sample unit and three gaseous biomarkers analyzer employing laser absorption spectroscopy designed for clinical diagnostics were described. The analyzer is equipped with sensors for CO, CH₄ and NO detection. The sensors operate using multi-pass spectroscopy with wavelength modulation method (MUPASS-WMS) and cavity enhanced spectroscopy (CEAS).     

Microbend fiber optic detection of continuously varying refractive index of chlorinated water

In this paper we report a simple microbend fiber optic sensor using a plastic fiber, LED and photodetector assembly for sensing minute variation of refractive index of chlorinated water. Chlorinated water has slightly higher refractive index and gradual release of chlorine from bleaching powder treated water causes a temporal decrease in refractive index of the solution. The evaporation of chlorine from water and the change in refractive index is found to follow a first order exponential decay function of time. Introducing microbends in an optical fiber is easier and less complex than etching of fiber cladding for traditional optical fiber sensors.     

Pulsed interferometric optical fibre sensor detecting wiretapping in long transmission lines

A modified optical fibre based Mach-Zehnder interferometer was applied as a sensor to detect wiretapping in long transmission optical fibre lines. The signal consisting of short pulses (around 1?ns) was launched to the input of the interferometer based on the polarization maintaining fibres and polarization elements. When the sensing line was undisturbed, detectors registered only a single pulse. The additional two side pulses appear, if the wiretapping attempt took place. For robust detection of any alarm situation we proposed two-criteria algorithm to minimize false alarm rate. Moreover, slow environmental fluctuations were continuously monitored and compensated by polarization controllers. We measured frequency characteristics of the sensor and performed a hundred wiretapping attempts, which proved high performance of the sensor.     

Proposal of the nano-sensing device and system using a nano-waveguide transducer for distributed sensors

We propose a new concept of a distributed sensing system using a nano-waveguide and an array waveguide. The small change in physical quantity affects the change in device parameters such as refractive index or length, which is relatively absorbed and observed by the resonant wavelength. In principle, the dense wavelength separation is generated by using a soliton pulse propagating within a ring resonator system, whereas a resonant signal can be stored within the nano-waveguide, i.e. a transducer, which is formed by the sensing device. Induced change in the resonant signal at each wavelength occurs, and can be detected by using the optical spectrum analyzer. Such a proposed device is suitable to perform the measurements in the nano-scale regime such as force, stress and temperature. Moreover, the distributed or multiplexed sensing applications are also available using the nano-waveguide sensing device incorporating the array waveguide, which is discussed in details. Quantum measurement using the same system is also described.