基于米氏散射及夫朗和费衍射的FAM激光测粒仪

提出了综合动用夫朗和费衍射和米氏散射，即在大粒径范围内采用夫朗和费衍射理论，而在小粒径范围内采用米氏散射理论，来改善小粒径范围内的测量精度，保证激光测粒仪在整个粒径范围的测量精度。     

激光衍射法中光学模型对B4 C粉末粒度分布测量结果的影响

选了四种不同平均粒径的B4C粉末分别用激光衍射法仪中Fraunhofer（夫朗和费）衍射和Mie（米氏）散射光学模型测量其粒度分布和平均粒度，结果表明，对于粒径界于10－15μm之间的粉末，无需知道材料对光的折射率和吸收率，其应用Fraunhofer衍射理论测理的结果与应用Mie散射理论测得的结果近似，但分布线有一定的区别，对于＞15μm粉末，在两种模型下分布曲线与平均粒径皆接近；而对于＜10μm的粉末，必须采用Mie散射光学模型，并需预先知道材料的光学特性。     

同轴度误差的非接触精密测量方法

根据夫朗和费单缝衍射原理，以激光作光源，采用线阵CCD获取衍射条纹图像，实现同轴度误差的非接触自动测量。通过对比测量和精度分析表明该方法测量精度高，测量装置结构简单，具有实用价值。     

经典Mie散射的数值计算方法改进

在光散射颗粒测量技术中,Mie散射理论的计算非常重要。本文介绍一种改进的Mie散射数值计算方法,通过对Mie散射系数进行重新构造,找到参量来控制Mie计算的收敛和计算精度。对各有关参量选用合适、稳定的递推关系进行计算。数值计算结果表明该方法具有快速、稳定的优点,可以在极大的颗粒粒径和折射率范围内得到合理结果。     

雾粒粒度测试技术研究

阐述了脱硫塔内喷雾雾场研究的必要性，分析了雾场的环境条件，应用夫朗和费衍射原理设计制造了适于大雾场内进行测试的仪器，并叙述了仪器的特点，讨论了雾粒测定仪进入脱硫塔内测试的有关技术问题，文章还介绍了雾粒测定仪在脱硫塔内测试的情况，分析了测试结果。     

闭环控制原理的粒径分布测量方法

颗粒粒径在制药、食品加工等领域中都是一个重要的参数,通过测量、控制颗粒粒径可以有效地提高生产力、产品质量和过程效率。该文研发设计了一种衍射式粒径分布测量装置,并根据积分变换反演方法,利用小角度内的衍射光信息,通过基于闭环控制原理的粒径分布重建方法进行粒径分布测量计算。解决了积分变换反演方法在Fraunhofer衍射式粒径分布测量的应用中,克服了原积分变换反演方法重建精度低、分辨能力差的缺点,而且结构简单,容易实施。     

激光粒度仪的系统实现及展望

以夫朗和费衍射为理论依据，以自扫描光电二极管阵列（SSPA）和NI公司的M系列的数据采集卡PCI6220为主要硬件设备，以先进的虚拟仪器技术LabVIEW8．0作为软件平台，系统地研究了激光粒度仪的实现过程。并就现有的软硬件系统，结合实际运用需要讨论了一些可行的改进方法。     

雾粒粒度测试技术研究

阐述了脱硫塔内喷雾雾场的研究的必要性，分析了雾场的环境条件，应用夫朗和费衍射原理设计制造了适于大雾场内进行测试的仪器，并叙述了仪器的特点，对论了雾粒测定仪进入脱硫塔内测试的有关技术问题，文章还介绍了雾粒测定仪在脱硫塔内测试的情况，分析了测试结果。     

颗粒层状结构对散射特性及激光粒度测量的影响

根据Aden-Kerker理论,对双层颗粒前向散射特性进行了研究。在此基础上,分别用衍射理论、Mie理论和Aden-Kerker理论计算了散射系数矩阵并采用非独立模式算法进行反演。数值计算结果表明,双层颗粒的散射光强由颗粒折射率和内外径决定,在实际的激光前向散射粒度测量中,如果沿用Fraunhofer衍射理论或Mie理论计算系数矩阵,在测量双层颗粒时,反演结果会有一定的误差。相比于Mie理论,衍射理论的反演误差更大。     

CCD测量动态范围的扩展技术

介绍利用曝光量控制和图像融合处理技术扩大CCD测量动态范围的原理与方法。用电子快门控制曝光时间,得到强度范围不同的图像,即用低曝光量得到高强度信息,用高曝光量得到同一场景中低强度信息。利用最小二乘法求解CCD响应曲线,引入权重因子融合多幅图像中的有效像素值得到动态范围扩展的图像。在实验中用CCD对小孔的夫朗和费衍射图像进行测量,利用扩展技术得到了能全面反映衍射效应细节的高动态范围图像。     

A STUDY OF THE ACCURACY OF OPTICAL FRAUNHOFER DIFFRACTION SIZE ANALYZER

In this paper the discrepance of scattered light between Mie theory and Fraunhofer diffraction is showed at different refractive indexes and sizes of particle. The accuracy of the Malvern particle size analyzer is discussed when it is used to measure small particles and some advice is proposed for its use.     

A STUDY OF THE ACCURACY OF OPTICAL FRAUNHOFER DIFFRACTION SIZE ANALYZER

ABSTRACT

In this paper the discrepance of scattered light between Mie theory and Fraunhofer diffraction is showed at different refractive indexes and sizes of particle. The accuracy of the Malvern particle size analyzer is discussed when it is used to measure small particles and some advice is proposed for its use.     

激光粒度测量的应用与前景

激光粒度仪是一种应用广泛而又比较有发展前途的粒度测量设备.介绍了激光粒度仪的测量原理,介绍和对比了Fraunhofer衍射和Mie散射理论在激光粒度仪中的应用,探讨了如何评价激光粒度仪以及在线测量的一些技术难题,并展望了激光粒度仪的应用前景和发展方向.     

The development of the measurement of particle concentration using a commercial laser diffraction particle size analyzer

A laser diffraction particle size analyzer based on the Fraunhofer diffraction theory has the advantages of real-time measurement of particle size distribution over a broad range. However, the dispersed particle number concentration is not displayed in commercially available analyzers. The method of measuring the dispersed particle number concentration was investigated for different particles having various shapes, i.e. spherical, cubical and prismoidal with a log-normal distribution, by considering the characteristics of the measured voltage of the set detector in relation to the diffracted light intensity using a commercial laser diffraction particle size analyzer. As a result, an approximate equation for the particle number concentration was proposed expressing the measured median diameter and the highest voltage measured by the detector. This equation was applicable to particles having various shapes, i.e. spherical, cubical and prismoidal. Furthermore, this technique can be used for the continuous measurement of the particle number concentration of growing crystals in the crystallizer for crystallization operation.     

Reconstruction of particle-size distributions from light-scattering patterns using three inversion methods

By means of a numerical study we show particle-size distributions retrieved with the Chin-Shifrin, Phillips-Twomey, and singular value decomposition methods. Synthesized intensity data are generated using Mie theory, corresponding to unimodal normal, gamma, and lognormal distributions of spherical particles, covering the size parameter range from 1 to 250. Our results show the advantages and disadvantages of each method, as well as the range of applicability for the Fraunhofer approximation as compared to rigorous Mie theory.     

Size distribution of mineral aerosol: using light-scattering models in laser particle sizing

The size distribution of semitransparent irregularly shaped mineral dust aerosol samples is determined using a commonly used laser particle-sizing technique. The size distribution is derived from intensity measurements of singly scattered light at various scattering angles close to the forward-scattering direction at a wavelength of 632.8 nm. We analyze the results based on various light-scattering models including diffraction theory, Mie calculations for spheres with various refractive indices, and T-matrix calculations for spheroidal particles. We identify systematic errors of the retrieved size distribution when the semitransparent and nonspherical properties of the particles are neglected. Synthetic light-scattering data for a variety of parameterized size distributions of spheres and spheroids are used to investigate the effect of simplifying assumptions made when the diffraction model or Mie theory is applied in the retrieval.     

Forward light scattering for arbitrary sharp-edged convex crystals in Fraunhofer and anomalous diffraction approximations

Fraunhofer diffraction is a well-known physical model for describing forward light scattering from opaque particles much larger than the wavelength of the light. Analytical expressions exist for diffraction from circular- or rectangular-shaped apertures. An expression is derived for diffraction by apertures of a general polygonal shape. From this expression the exact solution for anomalous diffraction by arbitrary convex crystals is calculated. These expressions are useful in characterizing crystal size and shape, by laser diffraction instruments, when measured in a solution.     

Estimating and correcting mie scattering in synchrotron-based microscopic fourier transform infrared spectra by extended multiplicative signal correction

We present an approach for estimating and correcting Mie scattering occurring in infrared spectra of single cells, at diffraction limited probe size, as in synchrotron based microscopy. The Mie scattering is modeled by extended multiplicative signal correction (EMSC) and subtracted from the vibrational absorption. Because the Mie scattering depends non-linearly on alpha, the product of the radius and the refractive index of the medium/sphere causing it, a new method was developed for estimating the Mie scattering by EMSC for unknown radius and refractive index of the Mie scatterer. The theoretically expected Mie contributions for a range of different alpha values were computed according to the formulae developed by Van de Hulst (1957). The many simulated spectra were then summarized by a six-dimensional subspace model by principal component analysis (PCA). This subspace model was used in EMSC to estimate and correct for Mie scattering, as well as other additive and multiplicative interference effects. The approach was applied to a set of Fourier transform infrared (FT-IR) absorbance spectra measured for individual lung cancer cells in order to remove unwanted interferences and to estimate ranges of important alpha values for each spectrum. The results indicate that several cell components may contribute to the Mie scattering.     

Fraunhofer Diffraction by Koch Fractals

Abstract

Analytical expressions are derived for the complex amplitude in the Fraunhofer diffraction field of an arbitrary Koch fractal with a finite range of self-similarity. Results of the numerical evaluation for the intensity distribution of Fraunhofer diffraction patterns are compared with those obtained experimentally. It is shown that the diffraction pattern of the Koch fractal can be divided into two areas, a central fractal area and a periodic area, and that the former is surrounded by the latter. The existence of the periodic area is a consequence of the finite inner cut-off of the self-similarity of the object fractal. On the other hand, the outer cut-off gives rise to a small core area at the centre of the diffraction pattern.