基于自相关函数的非平面表面粗糙度的图像纹理研究

采用自相关函数对不同加工工艺形成的非平面工件表面粗糙度进行了研究。讨论了自相关函数及其扩展度参数与图像纹理特性的关系,构建了实验装置,利用图像处理软件对实验所得的激光散斑图像进行了处理,得到了自相关函数及其扩展测度参数随表面粗糙度的变化曲线。为研究非平面工件的粗糙度,提供了一种新的方法。     

基于多色散斑延长效应的表面粗糙度测量及影响因素分析

粗糙表面在多波长激光束照射下形成的多色散斑场显示出散斑延长效应,利用此效应可以测量表面粗糙度,并且测量结果在一定条件下不受粗糙表面横向特征的影响。通过模拟计算随机粗糙表面的多色散斑场,以空间平均的多色散斑场局部自相关函数研究了平均散斑延长率〈χ〉对表面轮廓均方根偏差σh的依赖关系,分析了测量系统因素,如入射激光波长组合、成像器件光敏单元尺寸和动态范围对测量结果的影响。结果表明,以空间平均的局部自相关函数代替集平均的散斑自相关函数描述多色散斑延长效应是有效的;为达到一定的粗糙度测量精度,应选择合适的入射激光波长组合和合适的成像器件光敏单元尺寸。     

光学薄膜表面复型电子显微照片的计算机处理

用计算机处理薄膜表面复型电子显微照片,得到表面高度轮廓,提出了计算机定标方法,并计算了薄膜表面微结构参量.     

The autocorrelation of speckles in deep Fresnel diffraction region and characterizations of random self-affine fractal surfaces

This paper studies the correlation properties of the speckles in the deep Fresnel diffraction region produced by the scattering of rough self-affine fractal surfaces. The autocorrelation function of the speckle intensities is formulated by the combination of the light scattering theory of Kirchhoff approximation and the principles of speckle statistics. We propose a method for extracting the three surface parameters, i.e. the roughness w, the lateral correlation length ξ and the roughness exponent α, from the autocorrelation functions of speckles. This method is verified by simulating the speckle intensities and calculating the speckle autocorrelation function. We also find the phenomenon that for rough surfaces with α= 1, the structure of the speckles resembles that of the surface heights, which results from the effect of the peak and the valley parts of the surface, acting as micro-lenses converging and diverging the light waves.     

Analysis of roughness of Cs surfaces via evaluation of the autocorrelation function

At low temperature prepared quench-condensed Cs surfaces are analysed on a nanometer scale via scanning tunneling microscopy. The analysis of surface roughness is presented with the help of the evaluation of their autocorrelation function. In order to extract the correct autocorrelation function we present the requirement regarding the scan resolution of scanning probe microscopy (SPM) images in general. This is supported by a ‘numerical experiment’. Furthermore, we present some methods of deducing higher orders of autocorrelation lengths, which are needed to evaluate SPM images with non-random distribution of roughness amplitudes. These characteristic values of the autocorrelation function could play the key role in further statistical calculations, e.g., on how surface roughness alters the wetting behaviour of liquid helium adsorbed on the cesium surfaces.     

粗糙表面对散斑统计特性的影响

为研究高速摄影中激光相干噪声的影响因素,降低激光照明中散斑噪声对高速摄影成像质量的影响,对激光照射表面的粗糙程度与形成的散斑场统计特性之间的关系进行了研究。基于菲涅尔-基尔霍夫衍射原理,分析了高斯光束入射在随机粗糙表面上经反射形成的散斑图样,通过对大量散斑图样的数据统计,得出了激光散斑的信噪比、自相关函数、概率密度函数与入射表面粗糙度之间的变化关系。计算结果表明：粗糙度的增大使散斑场信噪比降低、相干程度减小、概率密度降低,即表面越粗糙散斑噪声越严重。     

A study of the interface roughness effect in Si nanowires using a full 3D NEGF approach

The effect of interface roughness in ballistic Si nanowires is investigated using a full 3D non-equilibrium Green's Functions formalism. The current density, the electron density and the transmission function are calculated for nanowires with different interface roughness configurations. Interface roughness is randomly generated using an exponential autocorrelation function. The interface roughness profile in nanowires with 2 nm diameter and 6 nm length is reflected in the current density landscape showing macroscopic 3D patterns. These macroscopic patterns affect the transmission probability causing resonances coming from the constrictions in the channel. The shape of the electron density in cross-sections along the wire follows the distortion of electron transversal wave function.     

Surface roughness measurements from coherent light scattering

Results are presented of surface roughness measurements obtained by applying Beckmann's theory on the scattering of electromagnetic waves from rough surfaces to the scattering of laser light from ground glass surfaces. Measurements of the variance of surface height obtained in several scattering geometries and also from stylus measurements are presented and shown to agree closely for each surface. Also results are presented which show that the usual assumption of a Gaussian form for the autocorrelation function of surface height does not apply to the surfaces being studied here.     

Size-dependent reactivity of aluminum cluster cations toward water molecules

Using the autocorrelation of speckles in the deep Fresnel region is a novel approach to measuring surface parameters of a rough surface. In this letter, we construct a scanning system using a fibre-optic probe for detecting the speckle field with excellent resolution. By relating the autocorrelation function of the speckle intensity and the surface height with the Kirchhoff approximation theory, we realise the measurement of the surface parameters. Three parameters, i.e. the roughness w, the lateral correlation length ξ and roughness exponent α are extracted. We measure two sample surfaces in the experiment, and the results are consistent with those measured by atomic force microscope (AFM).     

银薄膜对光学基底表面粗糙度及光散射的影响

为了研究金属银薄膜与光学基底表面粗糙度和光散射的关系,提出了通过对光学薄膜矢量散射公式积分来获得界面粗糙度完全相关模型和完全非相关模型下其表面的总反射散射的方法.理论计算了光学基底上两种模型在不同厚度银膜下的总反射散射和双向反射分布函数.结果表明,当沉积在光学基底上的银薄膜的厚度大于80 nm后,两种模型下计算的银薄膜的表面总反射散射都等于基底的总积分散射,银薄膜能较好地复现出基底的粗糙度轮廓.实验研究表明为了复现基底的粗糙度,银薄膜的最佳厚度应在80~160 nm之间.     

An optical method and neural network for surface roughness measurement

The measurement of surface roughness using stylus equipment has several disadvantages. A non-contact optical method is needed for measuring the surface roughness of engineering metals with improved accuracy. One candidate for an optical method is the use of a laser source, where the laser light intensity reflected from the surface represents the surface roughness of the illuminated area. A relation can be developed between the reflected laser beam intensity and the surface roughness of the metal. The present study examines the measurement of the surface roughness of the stainless steel samples using a He-Ne laser beam. In the measurement a Gaussian curve parameter of a Gaussian function approximating the peak of the reflected intensity is measured with a fast response photodetector. In order to achieve this, an experimental setup is designed and built. In the experimental apparatus, fiber-optic cables are used to collect the reflected beam from the surface. The output of the fiber-optic system is fed to a back-propagation neural network to classify the resulting surface profile and predict the surface roughness value. The results obtained from the present study are then compared with the stylus measurement results. It is found that the resolution of the surface texture improves considerably in the case of optical method and the neural network developed for this purpose can classify the surface texture according to the control charts developed mathematically.     

An optical method and neural network for surface roughness measurement

The measurement of surface roughness using the stylus equipment has several disadvantages. A non-contact optical method becomes demanding for measuring the surface roughness of the engineering metals with improved accuracy. One of the candidates for the optical method is the use of a laser source in which case the reflected laser light intensity from the surface may represent the surface roughness of the illuminated area. Consequently, a relation can be developed between the reflected laser beam intensity and the surface roughness of the metals. The present study examines the measurement of the surface roughness of the stainless-steel samples using a He–Ne laser beam. In the measurement, a Gaussian curve parameter of a Gaussian function approximating the peak of the reflected intensity is measured with a fast response photodetector. To achieve this, an experimental setup is designed and realized. In the experimental apparatus, fiber-optic cables are used to collect the reflected beam from the surface. The output of the fiber-optic system is fed to a backpropagation neural network to classify the resulting surface profile and predict the surface roughness value. The results obtained from the present study is, then, compared with the stylus measurement results. It is found that the resolution of the surface texture improves considerably in the case of optical method and the neural network developed for this purpose can classify the surface texture according to the control charts developed mathematically.     

Experimental characterization of a random metallic rough surface by spectrophotometric measurements in the visible range

Back-reflected light from a random rough surface is studied with the purpose of characterising the surface statistical properties. A new goniospectrophotometer with optic fibres is presented and a random rough copper surface is analysed. The probability density of the surface normal and the h/l ratio (r.m.s. roughness/autocorrelation length) are so obtained. Optical results are compared with mechanical ones, performed with a profilometer. For the first time, Abel's transform method is used to connect the two-dimensional statistical information deduced from optical measurements and the one-dimensional profiles.     

Study of zinc-induced changes in lymphocyte membranes using atomic force microscopy,luminescence, and light scattering methods

Changes in the surface structure of lymphocyte membranes exposed to various concentrations of zinc ions are studied. It is found by atomic force microscopy that increasing the concentration of zinc ions leads to a reduction in the correlation length of the autocorrelation function of the roughness profile of a lymphocyte compared to control samples; this may indicate the existence of fine structure in the membrane surface. Fluorescence markers are used to observe a reduction in the microviscosity of the lipids in the outer monolayer of the lipid bilayer after lymphocytes are exposed to Zn ions, as well as the exposure of phosphatidylserine on the surface membrane, and the oxidation of HS-groups of membrane proteins. Calculations of the absorption coefficients of lymphocytes modified with zinc reveal the existence of absorption bands owing to the formation of metal-protein complexes and zinc oxide nanoparticles. These results indicate significant changes in the structural and functional state of lymphocyte membranes exposed to zinc ions.     

Eine neue Methode zur Bestimmung der Rauhigkeitsautokorrelationsfunktion von optischen Oberflächen

A New Method of Determining the Autocorrelation Function of Polished Optical Surfaces Starting with a general theory of light scattering a measuring procedure for determining the autocorrelation function of surface roughness of well polished substrates is deduced. In this method light intensity scattered into a fixed direction has to be measured in dependence on the dimensions of the scattering area. The results are tested for a glass surface polished by different methods.     

Talbot effect in metallic gratings under Gaussian illumination

Metallic gratings can be found in applications such as optical metrology. Due to their fabrication process, the surface presents a certain roughness. In this work, the effect of roughness on Talbot effect has been analyzed when the grating is illuminated with a Gaussian beam. A model based on Fresnel regime is used in order to determine the intensity distribution in the near field. Contrast of the self-images is obtained and it is found that it decreases in terms of the distance between the grating and the observation plane. When the autocorrelation function of roughness presents a Gaussian behaviour, the diffracted beams are still Gaussian although some of their properties change. For example, the width of the diffracted beams increases with respect to the case of the standard chrome on glass gratings. On the other hand, the power of each diffracted beam is independent on the roughness properties of the surface.     

The dynamic angle-limited integrated scattering (DALIS) method for measuring scattering of light from optical surfaces with random roughness

A new and simple dynamic angle limited integrated scattering (DALIS) method is developed to examine optically smooth reflective surfaces with defined surface form. Our experimental results from two systems show advantages over conventional angle resolved scattering measurement (ARS) methods. By collecting scattered light in a given solid angle, our methods do not require a detection unit with an extremely large dynamic range. Unlike in the common ARS measurement method, here we use a simple linear translation stage to scan scattered light. The power spectrum density function and the autocorrelation function of the surface roughness can be recovered from the measured scattering pattern. This method can be applied to in-workshop inspection of optical polishing processes.     

Anomalous Heat and Momentum Transport Arising from Surface Roughness in a Normal <Superscript>3</Superscript>He Slab

I discuss heat and momentum transport in a mesoscopic film of ³He, confined by rough walls in the normal Fermi liquid state. Inelastic binary quasiparticle scattering mediated by elastic scattering from the surface roughness gives rise to a coherent “mixed” scattering channel that drives anomalous transport over a range of temperature. I calculate the thermal conductivity and viscosity of the film in this regime and derive these in terms of the film thickness and autocorrelation function of the surface roughness, which enters the formulation as an independent input. This calculation can be useful in understanding and isolating the effects of confinement and surface roughness, especially in the context of exploring the superfluid state in the film.     

表面粗糙度干涉图像处理中的阈值优选

提出用于表面粗糙度自动干涉法测量过程中的一种有效的白光干涉图像阈值分割方法，分割后的二值图像经过干涉条纹边界线萃取后得到的被测表面输廓波形和表面粗糙度参数的计算结果与高精度ＴＡＬＹＳＵＲＦ６型表面粗糙度测量仪的测量结果十分吻合，此种图像分割方法同样也适用于粗糙表面激光干涉图像的二值化分割。     

Speckle from a cascade of two diffusers

Speckle patterns for single pieces of frosted glass and for pairs with controlled separation have been studied. Intensity versus frequency data are obtained at fixed positions in the Fresnel zone using a tunable dye laser for the illumination. From these intensity data, both the autocorrelation versus frequency and the spectral intensity are computed and shown to be sensitive to the detailed microstructure of the object's surface. Examples of diffuse surfaces adequately characterized by smooth distribution functions and those with glint-like facets requiring δ-function augmentation are presented. For the cascade the autocorrelation function drops initially as controlled by the fine-scale roughness of the separate diffusers, i.e., almost independently of their spacing which is varied from 20 to 110 μm. Its low frequency content is found to be dependent on this spacing.