TOD Performance Theoretical Model for Staring Thermal Imagers

The TOD (triangle orientation discrimination threshold) metric, as a promising sensor performance measure, is suitable for all types of thermal imaging systems and corresponds to the field performance very well. Since this method was proposed, a great progress has been made in some aspects, such as experimental validation, field performance, and TOD sensor performance model. However, what is still missing is a TOD curve prediction model similar to MRTD (minimum resolvable temperature difference) equation. Here, an equation-based TOD performance model was first developed focusing on staring thermal imagers. Specifically, spatial distribution of the triangle standard test pattern is described quantitatively. Resolution transfer characteristic of the staring infrared imagers is modeled with linear system theory, and system noise is characterized with the introduction of three-dimensional noise model. The modulation effect of overall subsystem of staring thermal imager on the non-periodic triangle standard pattern is analyzed. The matched filter idea is adopted to characterize quantitatively the spatial integration of the eye to signal and various noise components over the triangle pattern area, and the perceived signal-to-noise ratio of the staring thermal imager is derived. Then, the TOD performance theoretical model is established. Comparing with experimental results, this theoretical model gives reasonable prediction of the TOD performance curve of staring thermal imagers. Although more tests and modifications are required, these preliminary results suggest that this model can be developed into a model that predicts the TOD for all kinds of sensors.     

Application des Capteurs Automatises DTO,COT et DCO au Dosage des Hydrocarbures dans L'Eau

Abstract

Among the objectives of this study was the determination of the oxidation yields for pure hydrocarbons in water (alkanes, alkenes, aromatics), following the TOD, TOC and COD methods, and the extraction efficiency of carbon tetrachloride followed by infra-red dosage (NFT90203).

For the global oxidative pollution tests, the best oxidation yields were obtained with TOC, followed by the TOD; COD results were clearly poor. The solvent extraction procedure afforded reliable results.

Correlation studies with the methods proposed enable the grouping of hydrocarbons in two main categories, according to the oxidation criteria: aliphatics and aromatics. Generally, it can be said that the correlations found were satisfactory.     

短波跳频通信中基于时间信息TOD的自同步法

本文提出了适用于短波跳频通信的基于时间信息TOD的自同步法，设计了实现该同步方法的系统原理框图。本系统的关键有两个：一是发送端发送的同步头包含时间信息TOD；二是接收端的频率合成器有两个工作状态，跳频工作状态和快速扫描驻留工作状态。本文还对这种同步方法在缩短同步捕获时间和增强抗干扰能力方面进行了分析。     

用于三角方向鉴别测量的客观判别模型

为减小人为因素对三角方向鉴别测量的影响,有效提高测量效率,研究了以机器视觉系统替代观察者进行三角方向鉴别测量的途径,建立了一种专门针对三角方向鉴别测量的客观判别模型。该模型以人眼视觉系统对信号的处理过程以及人眼视觉系统的主要效应为基础,利用方向通道滤波器实现图像信号分解,通过计算视觉特征矢量相关度,实现三角形靶标方向的判别。结合凝视型成像系统虚拟样机提供的三角形靶标,进行了客观判别模型与观察者的判别性能对比实验,并给出三组不同靶标尺寸下的对比实验结果。实验结果表明,客观判别模型很好地预测了观察者的判别性能。     

一种表征红外成像系统性能的新方法

介绍了一种评估红外成像系统性能的新方法--三角方向辨别(TOD)法.通过对TOD法进行分析,阐述了TOD法的基本思想,研究了TOD曲线和TOD准则的产生机理及其在红外成像系统现场性能评估方面的实现方法.比较了最小可分辨温差(MRTD)法与TOD法各自的优缺点.展望了TOD法在未来红外成像系统现场性能评估和测试领域的应用.     

TOD在红外成像系统性能表征中的应用

针对具有图像增强技术的传感器,提出了一种基于TOD的成像系统性能表征算法。首先,将经过红外成像系统仿真模型作用之后的效应样条存入数据库;然后,组织观测者对效应靶标样条和图像增强之后的样条进行判断;最后,拟合判别结果,并比较分析。     

基于模糊模式识别红外成像系统TOD 参数测量

介绍了用于红外热成像系统性能评估的三角方向辨别阈值(TOD)法。通过对TOD参数测试理论的分析，探讨基于模糊模式识别的客观法红外热成像系统TOD测试的基本方法和硬件组成，给出实现客观法TOD测量的图像处理、特征提取和模糊综合评判方法。     

Spatial chirp and angular dispersion of the nonlinear crystal for a femtosecond OPO

In this paper spatial chirp and angular dispersion are calculated theoretically and analyzed for a four-mirror, standing-wave cavity femtosecond OPO. The analytical expression of spatial chirp in the nonlinear crystal is deduced. The analytical expressions of second- and third-order dispersion including angular dispersion of the nonlinear crystal are presented, for the noncollinear type-I phase-matched Fs BBO OPO using angle tuning. Moreover, variations of GDD and TOD with cavity parameters are calculated exactly. The analysis method and the obtained result also are efficacious for a same type Fs OPO.     

光纤放大器中的自相似抛物脉冲

本文研究在含有增益色散、增益饱和、三阶色散、自频移、自陡峭等效应的光纤放大器中自相似抛物脉冲的产生和传输。结果表明,在渐近约束条件下,自相似脉冲的中心区域可用倒置的抛物脉冲来描绘,并且它的有效脉宽和功率都是线性增长的,而峰值振幅和频谱宽度保持常量。数值模拟结果与理论预期符合的非常好,这表明:在光纤放大器中,在适当的条件下初始输入脉冲可自相似地演化为抛物脉冲。     

基于TOD信息的长周期跳频序列产生及其性能分析

在跳频通信中,收发双方需要根据约定实时地产生跳频序列,以完成跳频同步。不同于通常设计中采用的加入同步码或使用精确时钟等方式,利用可实时获取且精度较高的GPS时间统一信息作为收发双方的参考TOD,依赖FPGA的高速运算能力,可以产生性能较好的调频序列。根据某跳频通信系统的设计需求,设计基于TOD信息的长周期跳频序列产生方法,给出GPS时统信息的提取方法和用于构造跳频序列的m序列寄存器状态计算方法,以及宽间隔化处理实现方法,同时分析了系统的计算时间与生成的跳频序列的性能。