Optical Roughness Research Articles

Effect of mechanical polishing on the surface structure of glasses studied by grazing angle neutron reflectometry

Grazing angle neutron reflectometry, optical and mechanical roughness profilometry techniques have been used to study the effects of the polishing operations on the surface of Borkron Schott glass (special borosilicate glass for neutron optics applications) as the polishing tool pressure P and the mean grain size of the polishing powder Φ. The neutron reflectivity investigations have shown that there is formation of a layer at the surface glass substrate. This layer is less dense than the bulk substrate and its thickness is around 60 Å. The optical and mechanical profilometry measurements have shown that both roughness and waviness decrease with P and Φ. All the experimental results show a good correlation between the neutron refractive index, the thickness and the roughness of the surface layer and the waviness of the glass surface with the two mechanical polishing parameters. The previous techniques have been completed by secondary ion mass spectroscopy and atomic force microscopy measurements.

Corrosion-wear study of 304 stainless steel in various NaCl solutions

The corrosion-wear behaviour of 304 stainless steel in various NaCl solutions with various loading conditions was qualitatively studied. A ‘dynamic corrosion-wear cell’ was designed. This apparatus was pin-on-disk type and constructed to meet the purpose of this work. In the process of experiments, potentiostatic and potentiodynamic methods were utilized to determine the effects of the environments and rubbing motion under load on the wear and corrosion of 304 stainless steel. Optical microscopy and surface roughness measurements were conducted on the samples. It was observed, firstly, that chloride ions enhance the corrosion-wear. Secondly, increasing the loadings and quantity of chloride ions reduces the polarization resistances. It was stated that the higher loading created a larger metal surface, thus leading to the formation of more active regions.

Statistical analysis of optical Fourier transform patterns for surface texture assessment

An optical method for surface texture assessment is developed. This technique utilizes the grey-level histogram of the optical Fourier transform pattern of the surface to derive statistical parameters which are subsequently correlated with the surface roughness as obtained from a stylus instrument. An optical roughness parameter R is obtained for the surface roughness characterization. It is found that it also correlates well with surface roughness for test samples of different materials and also from different machining processes. Optical roughness calibration curves are obtained for the measurement of finishing surfaces with Ra values up to 0.8 mu m. In addition, the method is found capable of detecting the presence of flaws on machined surfaces. This technique provides a fast noncontact method for surface texture assessment of 2D surfaces which could not normally be measured by most other techniques.

A model of an optical roughness-measuring instrument

We have developed a nonlinear model of a commercial optical instrument for measuring the root-mean-square slopes of rough surfaces. The model improves upon previous ones in that it accounts for certain instrumental factors which affect the optical roughness measurements.

Effect of temperature on the deposition rate and properties of hydrogenated amorphous carbon films

Abstract Hydrogenated amorphous carbon (a-C:H) films were grown from a hydrocarbon vapor (HCV) by the r.f. (13.56 MHz) self-bias method. The temperature increase of 76.2 mm silicon or quartz wafers during film deposition was maintained over a narrow range (1–20 °C) by clamping the wafers to a temperature-controlled cathode and admitting helium between the back side of the wafer and the cathode. Without wafer clamping and helium back-side cooling, wafer temperatures increased as much as 70–100 °C during deposition, depending on the HCV pressure P and negative d.c. self-bias voltage Vb. Films were deposited over ranges of Vb (from −0.4 to −1.8 kV), P (from 6.7 to 40 μbar) and initial wafer temperature Ti (from −10 to 90 °C). At a given P and Vb (i.e. constant ion energy) the deposition rates of a-C:H increased linearly with decreasing Ti, while the film density, Knoop microhardness HK and compressive stress decreased with decreasing Ti. In general, the values of film density, HK and stress were significantly lower for the temperature-controlled depositions than for films deposited in earlier work without temperature control, but at the same or even lower ion energy. The hydrogen content [H], optical gap ET and surface roughness of the films (measured by scanning force microscopy) increased with decreasing Ti. The effect of lower Ti on the deposition rate and film properties is consistent with a film structure containing a significant fraction of voids. These voids are postulated to form as a result of the lower mobilities of impacting species on the surface of the growing film which prevents densification of the film and retards sputtering or loss of hydrogen.

An optical roughness sensor for real-time quality measurement

As part of the intelligent processing efforts of the Spray Forming Technology Group at the David Taylor Research Center, a laser stripe sensor has been implemented to monitor preform characteristics. The preform surface roughness is measured in real time and the correlation to preform quality in terms of porosity levels is assessed. The laser stripe method is not a direct indicator of quality, but it can be used with other sensors and advanced control techniques for control of the spray-forming process.

Texture analysis of rough surfaces using optical Fourier transform

An optical Fourier transform technique was developed in conjunction with a machine vision system to study the texture of machined surfaces having a wide range of roughness. Surface-ground samples of different materials were used in the study. The spectra obtained by the optical method were compared with those obtained by the stylus method in terms of spectrum peak and RMS value. Correlation curves were obtained to indicate the relationship between the texture parameters and the average roughness Ra for different materials. Optical roughness correlation curves were also obtained for roughness measurement along the lay direction and subsequently for specimens coated with oil.

Infrared optical constants and roughness factor functions determination: the HTHRTR method

This method was developed to determine the complex infrared optical constant of a single free-standing partially absorbing plate as wellas a thin solid film eposited on it. The method is based on exact formulas for normal transmittance T and near-normal reflectance R of the substrate as well as the film-substrate double layer. Coherent multiple reflections throughout the film and incoherent multiple reflections in the substrate as well as the intensity losses on the rough surface are taken into account. The influence of various data on the solution of the inverse problem is discussed by a contour map study. The method is explained using examples of both- and single-side-polished silicon wafers where the transmission and reflection roughness factor functions H(T),H(R) are determined for the rough surface. The thin-film example has been the silicon oxide film formed on the single-side-polished silicon substrate by chemical vapor deposition.

Epitaxial Al(110) Films Grown On Heavily-Doped Si(100) by Cluster Beam Deposition.

ABSTRACT:Epitaxial Al films have been grown on heavily doped Si(100) by neutral cluster beam deposition. The Al films were evaluated by RBS, RHEED, optical interference roughness maps and STM imaging. The results were consistent with the formation of epitaxial Al (110) bi-crystals similar to films grown by ionized cluster beam deposition on lightly-doped Si

Smoothing Characteristics of Optical Stylus.

An optical roughness sensor employing the critical angule method has two displacement sensitive ranges which are called the precision range and the wide range. In the present paper ; the smoothing characteristics of a large ortical spot were investgated using four kinds of objectives with different specifications. The large spot can smooth periodic curves such as a grating and a machined surface which has both periodic and random components. The smoothing effects in the experimental results were less than the theoretical ones obtained by averaging the profiles over the spot area. The large spot in the wide range can therefore be used as displacement sensor to measure straightness error in scanning motion, to make a datum line for in-process profile measurements and to make an optical skid in the optical roughness sensor.

Coefficients of friction for arch wires in stainless steel and polycrystalline alumina bracket slots. I. The dry state

The surface roughness and the coefficients of friction were measured for sixteen arch wire-bracket combinations. The sample included one rectangular arch wire product from each of the four principal alloy groups and one bracket product from among the stainless steel and polycrystalline alumina inventory. Although subsamples representing both the 0.018-inch and the 0.022-inch slot sizes were evaluated, no differences were observed in their rankings. When tested over a series of eight incident angles, the optical surface roughness of representative stainless steel and alumina brackets averaged 0.148 and 0.193 microns, respectively. After testing at a single angle (82 degree) and referencing a nomogram, the roughness of the stainless steel, cobalt-chromium, beta-titanium, and nickel-titanium arch wire surfaces averaged 0.053, 0.129, 0.137, and 0.247 microns, respectively. When the various arch wire-bracket couples were pressed against an 0.010-inch stainless steel ligature wire at 34 degrees C and otherwise prevailing atmospheric conditions, the coefficients of friction ranged from stainless steel (lowest) to cobalt-chromium, nickel-titanium, and beta-titanium (highest)--regardless of bracket product or slot size. These results corroborated earlier observations in which the same arch wire products were drawn between stainless steel or alumina contact flats. In the current research, the average coefficient of kinetic friction for the stainless steel couple (0.139) was less than that for the stainless steel arch wire against a polycrystalline alumina bracket (0.174).

Growth mechanism and morphology of semiconducting FeSi2 films

Semiconducting β-FeSi2 films grown on (100)-oriented Si and on (11̄02)-sapphire substrates are investigated by x-ray diffraction, Nomarski optical microscopy, stress, and surface roughness measurements. As a result of an exothermic, nucleation controlled reaction, we observe a characteristic ring-shaped surface pattern of the silicide. Surface roughness and stress in β-FeSi2 are less pronounced for films grown at lower temperatures and cooling rates. Sapphire substrates result in smoother surfaces than Si due to the match of the thermal expansion coefficient of sapphire to the silicides.

Optical roughness measurement of ground surfaces by light scattering

An optical method is investigated for the roughness measurement of the ground surfaces in the range of 0.025–1.6 μm R q values. The method is based upon the principle of light scattering with an aim to in situ application. Computer simulation and experimental work is conducted in order to establish the scattering behaviours from the ground surfaces. From the results, an optical measuring strategy is suggested and proved by comparing the optical results with those of stylus instrument.

研磨ベルト仕上面の装飾品位に関する研究 ＩＩ 光学特性粗さＳＮと３次元粗さ形状特性値との関連性

The geometrical meaning of the optical characteristic roughness SN is discussed for the purpose of the use as the scale parameter to estimate the quality of the belt sanded surface. The experiments were carried out under the various grinding conditions by the platen type belt grinder. The ground surface is constructed by the long crested asperities which will be important estimation for quality. The surface roughness parameters such as density of summits, the mean curvature and the mean slope of asperities, the number of peaks and the zero-crossings were calculated by the profile and surface spectral moments. The functional relationship between an SN and the geometrical roughness parameters were derived statistically by the regression analysis. It was found that an SN has strongly correlated with the surface invariants of the spectral moment which indicate the curvature and the slope of the asperity at the same time.

ベルト研磨面に関する視覚評価と３次元粗さ形状特性値の因子分析

This paper presents the quantitative relationship between one's visual estimation and the analytical data of the high quality surface texture. The quality of belt sanded surface is investigated systematically by 50 panelers. The test pieces are ground under the various grinding conditions using the platen type belt grinder. The results of factor analysis point out clearly that there are strong relationships between high quality and the properties of surface geometry based on the correlation diagram. The physical meaning of high quality estimation are explained by the range of (1) mean curvature, (2) mean slope of asperity, (3) optical characteristic roughness SN, (4) center-line average height Ra, (5) the number of peaks, and (6) the number of zero-crossings, respectively. It was found that the irregularity of long crestedness perpendicular to grinding direction can be estimated by ARMA (4, 3) model of SN due to 0.2 mm beam.

Laser optical roughness measurement

A method for non-contacting profile assessment and roughness measurements of engineering surfaces is presented. The well known effect of focusing a light beam on the surface is used, at the same time compensating for the effect on the measuring results of varying material colours by appropriately processing the measuring signal. The sensor and the transducer are connected with the data-processing unit of a stylus instrument, which provides for a simple procedure of recording the roughness profile and calculating standard roughness parameters from it. The measuring results thus obtained agree well with the results of traditional stylus instruments.

Microstructure of boron-doped silicon layers prepared by low pressure chemical vapour deposition

The microstructures of silicon layers 0.55–0.60 μm thick with boron contents of about 10 17 or 10 20 atoms cm -3, prepared by low pressure chemical vapour deposition at 570 or 620°C on thermally oxidized silicon wafers, were characterized in the as-grown condition and after chemical thinning. The microstructural characteristics obtained from transmission electron microscopy examination on cross-sections, reflection high energy electron diffraction patterns, Raman spectrometry at 488 nm and UV absolute reflectance measurements as well as the optical and mechanical roughness of the sample surfaces were compared. The results showed the following. 1. (i) The layers are polycrystalline throughout their depth, with an external region of columnar character, intense twinning and 〈110〉 texture, and with a near-interface zone 50–100 nm thick of randomly oriented grains of size not greater than 10nm. 2. (ii) The thickness of the interfacial zone decreased as the deposition temperature increased. In the external region the texture became more developed as the level of boron doping and the deposition temperature increased, whereas the twinning, dislocation density, vacancy and/or impurity concentrations (from Raman results) and excess volume fraction (from absolute reflectance results) appear to be enhanced by increases in doping and decreased by increases in temperature. 3. (iii) The surface roughness was also clearly higher for layers with lower boron contents.

Practical and theoretical aspects of applied image analysis

It is demonstrated how special industrial measurement tasks can be solved by Image Analysis Systems. Software for Vision Systems is discussed. Especially the Image Analysis Software Library developed at the Fraunhofer Institute for Manufacturing, Engineering and Automation (IPA) is presented and compared with other libraries. Some examples are given concerning scale invariant pattern recognition as well as the description of structures by their fractal dimension. The concept of fractal dimension is applied to optical surface roughness measurements. First results are very surprising and it is suggested to increase the efforts to introduce this concept in wider fields of measurement.

Statistical properties of the speckle phase in the optical imaging system

First-order statistics of the speckle phase are studied on an axis of the imaging system under the assumption of Gaussian statistics for the formation of the speckle field. It is found that the speckle phase is most widely distributed at the image plane owing to the noncircularity of the speckle field. Asymmetry of the probability-density distribution of the speckle phase also appears to be due to the inclination of the joint probability density of the complex speckle amplitude. These statistical characteristics of the speckle phase are enhanced for relatively small values of the optical roughness of the object.

Some properties of reactively sputtered tin lead oxide films

Reactive d.c. sputtering was used to produce thin oxide films of Pb x Sn 1− x O 2, where x was in the range from 0 to 0.6. The optical transmission and reflection spectra were measured at wavenumbers between 1.3 × 10 4 and 3.5 × 10 4 cm -1. From these data the optical constants, surface roughness and thicknesses of films were derived. The results show that the optical constants depend on the composition of the source material used in sputtering. Measurements of the electron energy losses show that, in addition to the basic phase of Pb x Sn 1− x O 2, the films contain other phases of lead oxides as well as pure lead (for x different from zero).