【作者】 乔利锋；

【导师】 张永明；

【作者基本信息】 中国科学技术大学 ， 安全技术及工程， 2008， 博士

【摘要】 火灾探测是感知火灾发生和减轻火灾损失的关键技术之一,光电感烟探测器在火灾探测中发挥着越来越重要的作用,然而光电感烟探测器存在着不能有效区分火灾烟颗粒与非火灾烟颗粒如粉尘等而发生误报的突出问题。常规的光电感烟探测器利用烟颗粒对非偏振光的散射原理进行火灾探测,而颗粒对偏振光散射包含颗粒性质更丰富的信息,因此,研究火灾烟颗粒与干扰源颗粒对偏振光的散射特征,并由散射特征估计颗粒的特征,对烟颗粒与干扰源颗粒加以区分,将可能在减少光电感烟探测器误报方面具有重要的应用价值,同时可以推动颗粒光散射理论及利用光散射特征估计颗粒特性方法的发展。论文从颗粒光散射的基本约束方程及解的表示形式分析颗粒偏振光散射特征的主要影响因素:颗粒的大小、形貌和折射率,而这些影响均可以使用颗粒对偏振光散射的Muller矩阵进行描述;利用分析颗粒SEM(Scanning ElectronMicroscopy)图像的方法,对烟颗粒及粉尘颗粒的大小、形貌特征进行研究,建立烟颗粒与粉尘颗粒的形貌模型,利用国内外已有对颗粒性质的研究成果分析烟颗粒与粉尘颗粒折射率的区别;根据烟颗粒与粉尘颗粒形貌特征及尺度大小,使用颗粒光散射计算的DDA(Discrete Dipole Approximation)方法,对不同形貌、大小、折射率的颗粒的光散射Muller矩阵进行计算,分析了颗粒不同特征引起的散射Muller矩阵元素随散射角分布的变化,由此分析利用颗粒光散射Muller矩阵差别估算颗粒性质差别的方法。改造和发展已有的基于电光调制器、波片、偏振片等光偏振态变换器件的烟颗粒光散射Muller矩阵测量系统,改进其光学系统与数据采集方式,提出使用偏振调制的光标定波片、偏振片等光学器件光轴方向的方法,对测量系统进行校准、测试与测量精度的估算,利用该测量系统,完成对典型烟与粉尘颗粒光散射Muller矩阵的实际实验测量。研究结果表明,烟颗粒与粉尘颗粒由于颗粒大小、形貌、折射率引起的对偏振光散射的Muller矩阵随散射角的分布不同可以通过理论计算得到,并可以被实验检测到;通过颗粒光散射Muller矩阵的不同元素随散射角的变化,可以估计颗粒大小、形貌、折射率等颗粒性质的差异。因此,若感烟探测器依据颗粒对偏振光散射原理工作,通过检测光散射Muller矩阵元素随散射角的变化对检测的颗粒做更细致的分类,有可能在有效降低光电探测器的误报率方面取得突破。更多还原

【Abstract】 Fire detection is an essential way to preventing the occurrence of a fire, and photoelectric smoke detectors are playing an increasing important role in fire detections. Normally, photoelectric smoke detectors use scattering of non-polarized by smoke particles to sensing the exists of smoke in the detector chamber, and false alarms are commonly met for in the using photoelectric smoke detectors, because they can not distinguish between smoke and other nuisance aerosols, like dust. It is possible to obtain more detail information of the characteristics of the particles with the polarized light scattering method, so it can be an effect way and valuable practically and theoretically to draw the false alarm rate by studying the polarized light scattering properties by different particles, analyzing the cause factors of different light scattering patterns which is equivalents to analyzing the particle characteristics using the light scattering pattern.The work begin with the introductions of the basic equations and the form of the solutions of light scattering, and then the factors that can influence the polarized light scattering patterns which can be presented by the light scattering Muller matrices were analyzed, that is the particles’ size, morphologies, and complex refract indices. The study on the morphologies and size of smoke and dust particles were carried out using the particles’ SEM(Scanning Electron Microscopy) images, and the shape models for smoke and dust particles were established, the difference between smoke and dust’s complex refract indices were investigated based on the existing research results. The calculation of particles with different size, morphologies, and complex refract index were implemented using the DDA(Discrete Dipole Approximation) method, with the resulting Muller matrices, the different scattering pattern between particles with different size, morphologies, and complex refract index were analyzed using the statistics methods, and the possible methods to estimate the size, morphologies and complex refract index with the scattering pattern were discussed.The platform which measure the light scattering Muller matrices of smoke particles based on light polarization state transformation devices such as the electronic optical modulator, polarizer, quad wave plates and polarization analyzer were improved, including the improvement of the optical system and the signal equitation methods. The methods to calibrate the alignments and orientations of the quad wave plates and the polarization analyzer using the polarization modulated light were established with which the system were carefully calibrated, and the system were tested with estimating the precisions of the measurements, and the light scattering Muller matrices of several typical smoke and dust particles were measured using the platform.The research results showed that, the different Muller matrices distribution patterns on the scattering angles of particles with different size, morphologies and complex refract indices can be predicted using the calculations and measurements with the experiment platform, and the the properties of particle size, morphologies, complex refract indices can be inferred from the Muller matrices as the functions of scattering angles. It can be concluded that using polarized light scattering, the smoke detectors could be used to distinguish between different particles, and the false alarm rate could be reduced, and could induce breakthrough achievements for photoelectric smoke detection.更多还原