Surface Measurement System Research Articles

Surface characterization of structural and stereo isomeric amino acids using sorption techniques and Raman spectroscopy

Event Abstract Back to Event Surface characterization of structural and stereo isomeric amino acids using sorption techniques and Raman spectroscopy Daniel Burnett1, Majid Naderi1, Anett Kondor1 and Manaswini Acharya1 1 Surface Measurement Systems, Ltd., United States Introduction: Amino acids are found in proteins and enzymes, which perform essential roles in nature. Different forms of compounds are known to have different physiological and therapeutic effects and therefore various effective methods are required to provide insight in their physical properties.[1] Considering that hydration is a major factor in determining the structural and isomeric forms of amino acids, the interaction with water vapor would provide fundamental information. Materials and Methods: Alanine samples were obtained from Across Organics. A unique combination of a fiber optic Raman probe with Dynamic gravimetric Vapor Sorption (DVS) was used to monitor the real-time transformation of different forms of Alanine. The sample was exposed to a particular RH while monitoring the change in mass. In-situ Raman spectra were collected during sorption experiments. Total surface free energies of different forms of Alanine were determined using IGC-SEA (Surface Measurement Systems Ltd.). IGC-SEA provides surface energy profiles of particulate/fibrous samples unlike conventional techniques which only yield a single average valued property. Results and Discussion: The combined water sorption/Raman spectroscopy results for ß-Alanine and DL-Alanine show significant characteristics in the region 800 – 1600 cm-1 for both materials. There are no changes in the Raman bands of ß-Alanine during the sorption process up to 90% RH. However, after the 90% RH stage and during the desorption stage the Raman Spectra show irreversible changes in ß-Alanine structure. The water sorption data for DL-Alanine indicates a relatively low uptake and confirms a stable material in agreement with the Raman spectrum. The difference of 125× in moisture uptake levels is attributed to water absorption into the bulk of ß-Alanine, which causes a phase change in ß-Alanine, whereas in the case of DL-Alanine there is no phase or structural changes. The dispersive and specific surface energy profiles at 0% RH indicate ß-Alanine has the higher total surface energy, thus is the most active and have higher affinity for water. At 90% RH, the acid-base surface energy of both samples is increased while the dispersive surface energy did not change significantly. Thus, the polarity, for both alanine samples increases with the relative humidity due to an increase in the acid-base surface energy of both samples. The wettability as the measure of the intermolecular interaction between the solid sample and water can is determined by the thermodynamic work of adhesion with water molecules (Figure 1). The higher work of adhesion shows higher the wettability (more hydrophilic). It is clearly observed that the wettability of both alanine samples increases with the RH, but the increase is more significant in the case of the ß-Alanine. Figure 1. Wettability of (a) DL-Alanine and (b) -Alanine at 0% RH (blue) and 90% RH (red). The work of adhesion values were calculated at 0.005 surface coverage (n/nm). Conclusions: IGC-SEA was able to measure the significant differences in surface chemistry for the ß-Alanine and DL-Alanine at 0 and 90% RH. These results correlate directly with water sorption behavior. The combination of gravimetric vapor sorption with Raman spectroscopy and IGC-SEA allows for better understanding of vapor-induced structural changes of biologically active ingredients.

Characterization of sorption behavior and mass transfer properties of four central africa tropical woods: Ayous, Sapele, Frake, Lotofa

This study provides the sorption isotherm, its hysteresis and their mass transfer properties of four Central Africa Tropical woods widely used for building construction: frake (Terminalia Superba), lotofa (Sterculia Rhinopetala), sapele (Entandrophragma Cylindricum) and ayous (Triplochiton Scleroxylon). Characterization of these four species in particular and Central Africa tropical woods in general were necessary to develop conservation and treatment of wood after first transformation using the drying. Also, moisture transport on wooden material used such as wall buildings can be facilitating to found the thermal comfort. Measurements of isotherms were performed using a dynamic vapor sorption apparatus (Surface Measurement Systems) at 20 and 40°C with air relative humidity ranged from 0% to 90%. Mass diffusivity was determined in steady state using a specific vaporimeter. Air permeability was determined using a specialized device developed to measure over a wide range of permeability values. Permeability and mass transfer properties were determined in the tangential direction with a ‘’false’’ quartersawn board (sapele and lotofa) and in the radial direction with a flatsawn board (ayous and frake). Samples of sapele, ayous and frake are heartwood when lotofa contains as well as heartwood than sapwood. Results obtained showed that the temperature effect on sorption behavior was quite low. We observed also a low difference between the sorption behavior of these different species and hysteresis of sorption decreases when temperature increases. Hailwood-Horrobin model’s explains plausibly the experimental sorption isotherms data. Results on characterization of mass transfer properties showed that, in the steady state, mass diffusivity decreases exponentially when basal density increases. Mass diffusivity was higher in desorption than in adsorption phase. The gaseous permeability of these species was between than those of Australian hardwoods and temperate woods. It was difficult to define a relationship between permeability and mass diffusivity.

Deformation verification and surface improvement of active stressed lap for 4 m-class primary mirror fabrication.

The surface shape accuracy of the active stressed lap impacts the performance of grinding and polishing in the fabrication of large mirrors. We introduce a model of active stressed lap for the fabrication of a 4 m f/1.5 mirror based on finite element analysis (FEA), and the lap surface accuracy achieves RMS<1.8 μm in the FEA method. Using the lap surface measurement system, experimental verification is put forward, and the RMS of the measured lap surface is within 2 μm in practice. A general improvement in lap surface accuracy using the Zernike polynomial is shown. After compensating the calculation errors, the lap surface accuracy is improved by 8%-23%, and achieves RMS<1.5 μm, which is appropriate for practical grinding and polishing.

Applicationof Computer Visionfor Polishing RobotinAutomotive Manufacturing Industries

Polishing is a highly skilled manufacturing process with a lot of constraints and interaction with environment. In general, the purpose of polishing is to get the uniform surface roughness distributed evenly throughout part’s surface. In order to reduce the polishing time and cope with the shortage of skilled workers, robotic polishing technology has been investigated. This paper studies about vision system to measure surface defects that have been characterized to some level of surface roughness. The surface defects data have learned using artificial neural networks to give a decision in order to move the actuator of arm robot. Force and rotation time have chosen as output parameters of artificial neural networks. Results shows that although there is a considerable change in both parameter values acquired from vision data compared to real data, it is still possible to obtain surface defects characterization using vision sensor to a certain limit of accuracy. The overall results of this research would encourage further developments in this area to achieve robust computer vision based surface measurement systems for industrial robotic, especially in polishing process.Keywords: polishing robot, vision sensor, surface defects, and artificial neural networks

The Design of Anti-aliasing Analog Filter for Data Acquisition in the Surface Measurement

In the surface measurement system, the data acquisition is key part and the anti-aliasing analog filter is necessary. This paper deals with the design of the anti-aliasing analog filter. Based on the principle of anti-aliasing filtering, the parameters of filter are computed, the filter circuit is designed, and the frequency characteristic is drawn. Combined with digital filter, the filtering can maintain the low frequency components very well and suppress effectively the high frequency signals in the original surface profile, which reduces the distortion caused by noise and makes the filtering effect better. This method has been applied in the surface measurement system and the actually measured data verified the performance of the filter.

Corrections to “Limitation of a Line-of-Light Online Paper Surface Measurement System” [Aug 13 2715-2724

Corrections to “Limitation of a Line-of-Light Online Paper Surface Measurement System” [Aug 13 2715-2724

Surface measurements by white light spatial-phase-shift imaging interferometry.

A novel method of common-path imaging interferometry, the White Light Spatial-Phase-Shift (WLSPS) for object surface measurements, is discussed here. Compared to standard White Light Interferometry (WLI), which uses a reference mirror, the interferometry of WLSPS is obtained by creating manipulations to the light wavefront reflected from an object's surface. Using this approach, surface measurements can be obtained from any real object image, and do not need to be taken directly from the object itself. This creates the ability for a surface measurement tool to be attached to any optical system that generates a real image of an object. Further, as this method does not require a reference beam, the surface measurement system contains inherent vibration cancelation.

대형 금형의 품질관리를 위한 이동식 측정기 개발

지금까지 금형의 표면관리를 위해 단순 현미경이나 표면 거칠기 측정기를 이용한 측정방법들은 구조적인 문제로 산업현장에서 적용하는 데 효율성이 떨어진다. 이에 따라 장소에 구별 없이 다양한 크기의 금형 측정과 품질관리 효율성을 높일 수 있는 측정시스템 및 분석시스템은 매우 필요하다. 본 연구는 이와 같은 필요성을 만족시키기 위한 현장맞춤형 이동식 표면측정 시스템 개발을 목표로 수행하였다. 측정시스템은 지지대(Base), 몸체(Body), 광학계(Opticalsystem)등 3부분으로 분리할 수 있도록 기구적으로 설계 및 제작하였다. 측정시스템의 실험결과 표면거칠기는 94.9~99.9%의 정확성을 나타냈으며, 원의 측정 값에 대한 편차는 <TEX>$2{\mu}m$</TEX> 이내로 신뢰성을 확보하였다. Existing measurement methods using microscopes or surface roughness measurement instruments for surface control in manufacturing die are low in their efficiency when they are applied in industrial fields due to structural problems. Therefore, it is very important to develop a measurement and analysis system which can enhance efficiency in the measurement of different-sized manufacturing dies and provide quality control regardless of location. This study aimed at the development of a portable surface measurement system to satisfy this need. This measurement system was designed and manufactured in such a way as to divide it into three parts: the Base, the Body, and the Optical system. As a result of testing the system, the surface roughness was measured with an accuracy between 94.9 and 99.9%, and the deviation in the measurement value of a circle was within <TEX>$2{\mu}m$</TEX>.

An active three-dimensional vision system for automated detection and measurement of surface defects

There is a growing need to perform automated visual surface inspection in various manufacturing processes due to increased emphasis on quality control. A number of high-resolution three-dimensional metrology products are commercially available, but they are all very limited in their fields of view. The small field of view of the scanners makes inspection of relatively large parts a time-consuming operation, which has significant negative impacts on throughput. This article presents a two-stage inspection process in which a machine vision system, based on the photometric stereo principle, is used to detect potentially defective regions on parts over a much wider field of view than the one covered by the commercial products. The suspicious regions are then inspected using a high-resolution commercial three-dimensional surface measurement system, ignoring areas that are perceived to be defect free. Experimental tests on planar steel samples, having known surface defects, show that this approach is effective and it reduces the overall inspection time significantly.

基于波前传感法的立方相位板面形测量

A surface measurement system is designed according to the features of cubic phase plate surface based on wavefront sensing technology.A mapping model from reflected wavefront to surface shape is presented,and in order to measure surface with greater curvature,an algorithm based on image processing method is proposed to improve the dynamic range of the wavefront sensor.Simulation analysis shows that the conversion accuracy of the proposed mapping model is 2~3 times better than traditional algorithm and the dynamic range is increased nearly 4times.Finally,an experimental system is built to measure the surface of an actual cubic phase plate,the result compared with the data achieved by Wyko white light interferometer verifies the correctness and accuracy of the measurement system.

A New Optical Surface Measurement Method with Iterative Sparsity-Constrained Threshold Phase Retrieval Algorithm

Due to its low complexity and acceptable accuracy, phase retrieval technique has been proposed as an alternative to solve the classic optical surface measurement task. However, to capture the overall wave field, phase retrieval based optical surface measurement (PROSM) system has to moderate the CCD position during the multiple-sampling procedure. The mechanical modules of CCD movement may bring about unexpectable deviation to the final results. To overcome this drawback, we propose a new PROSM method based on spatial light modulator (SLM). The mechanical CCD movement can be replaced by an electrical moderation of SLM patterns; thus the deviation can be significantly suppressed in the new PROSM method. In addition, to further improve the performance, we propose a new iterative threshold phase retrieval algorithm with sparsity-constraint to effectively reconstruct the phase of wave field. Experimental results show that the new method provides a more simple and robust solution for the optical surface measurement than the traditional techniques and achieves higher accuracy.

Profile Measurement Based on Focus Variation Method for Geometrical Defect Evaluation: A Case Study of Cold Forged Propeller Blade

Geometrical defect is one of the main problems that will affect performance and perfect mating of produced parts. Coordinate measurement machine (CMM) is commonly used for the measurement, but the use of this machine is limited because of the small size and complexity of the component or features. This study aims to evaluate the defect that occurs on an AA6061 cold forging blade produced using cold forging process based on profile measurement technique. A systematic approach based on focus variation was proposed to evaluate two features, that is, roundness error and twist deviation. The profile was obtained with the use of InfiniteFocus Alicona 3D surface measurement system. Specific algorithms were developed for different cases as the evaluation of the features is discrete and the results were validated.

Quality control of injection molded eyewear by non-contact deflectometry

Occupational eye wear such as safety spectacles are manufactured by injection molding techniques. Testing of the assembled safety spectacle lenses in transmission is state of the art, but there is a lack of surface measurement systems for occupational safety lenses. The purpose of this work was to validate a deflectometric setup for topography measurement, detection of defects and visualization of the polishing quality, e.g. casting indentations or impressions, for the production process of safety spectacles. The setup is based on a customized stereo phase measuring deflectometer (PMD), equipped with 3 cameras with f’1,2 = 16 mm and f’3 = 8.5 mm and a specified measurement uncertainty of ± 3 µm. Sixteen plastic lenses and 8 corresponding injection molds from 4 parallel cavities were used for validation of the deflectometer. For comparison an interferometric method and a reference standard (&lt; λ/10 super polished) was used. The accuracy and bias with a spherical safety spectacle sample was below 1 µm, according to DIN ISO 5725-2.2002-12. The repeatability was 2.1 µm and 35.7 µm for a blind radius fit. In conclusion, the PMD technique is an appropriate tool for characterizing occupational safety spectacle and injections mold surfaces. With the presented setup we were able to quantify the surface quality. This can be useful and may optimize the quality of the end product, in addition to standardized measuring systems in transmission.

3D Electronic Products Surface Measurement System Based on Machine Vision

Adopting high-speed line scan industrial camera, through window function of the software to capture interested areas scanning by linear structured light, through image processing algorithms and splicing technique to extract 3D feature information of the detected object surface, combined with the camera calibration technology, calculated the three-dimensional coordinates of the detected object, and real-time displayed intuitive pseudo color map, monitored picture signal and weeded out unqualified products. Compared with similar systems at home and abroad, the system are real-time pseudo color graphics display, open system and lower cost.

Online measurement based tool path generation toward integrated robotic laser cladding

PurposeRefurbishing may be the most practical approach under the low volume production. This effort aims to achieve robotic laser cladding with the main purpose of achieving maximum processing flexibility, predictably high quality, lower maintenance and operating costs. This study aims to focus on online measurement and cladding path generation toward automatic laser cladding.Design/methodology/approachBased on the specific requirements of automatic laser cladding, an approach was proposed toward an automatic laser cladding with powder injection for the refurbishment of components with free‐form surfaces. This study assessed the feasibility of integrating a non‐contact free‐form surface measurement system, an industrial robot, and an algorithm for generating cladding tool paths seamlessly.Findings3D laser scanning and laser cladding systems can be embedded into an existing robot motion control system. Online measurement based 3D surface reconstruction is a practical approach toward cladding tool path generation for on‐site refurbishment.Practical implicationsRobotic laser cladding may be a potential application by integrating other measurement devices, such as temperature sensor based monitoring system.Originality/valueRefurbishing worn‐out components could have significant economic benefits. This study indicates that robotic laser cladding may potentially facilitate improved refurbishment of oversized components.

Calibration of revolution axis for 360 deg surface measurement

Two methods are proposed to calibrate the revolution axis of a 360 deg, multiview fringe projection system for surface measurement. The first method is based on minimizing the distance between calculated and measured points; the second method is based on minimizing the difference between thus obtained vectors. Both are able to retrieve the revolution axis of a turntable, which is then used to transform surface patches measured at different viewing angles to a common coordinate. In the point-based method, a nonlinear minimization problem has to be solved by the Levenberg-Marquardt algorithm; in the vector-based method, the minimization problem is resolved into several linear equations, and an analytic solution is obtained efficiently. Results of simulation and experiments show that the error of calibration can be less than 0.05 deg for the axis's orientation and 0.3 mm for the axis's position (a point on the axis), which is about 0.1% of the measured volume.

Inspection of freeform intraocular lens topography by phase measuring deflectometric methods

Manufacturing spherical, aspheric, and freeform surfaces requires testing throughout the development and production process. State-of-the-art topography measurement is limited in applicability for intraocular lenses (IOLs), and there is no dedicated commercial surface measurement system available for freeform IOLs. The purpose of this work was to validate a deflectometric setup for surface measurement, detection of defects, and shape fidelity analysis for the development and production of IOLs. The setup is based on a phase measuring deflectometer with a field-of-view of 80 mm×80 mm and a mean repetition accuracy of 1.6·10(-3) D. The technique is suitable for detection of global and local surface errors, extracted from geometry and topography analysis. For validation according to DIN ISO 5725:2002, spherical IOLs with radii of curvature of 10 and 20 mm, a commercial aspheric IOL, and single-sided freeform IOL samples were used.

Limitation of a Line-of-Light Online Paper Surface Measurement System

A new prototype device has been developed based on a laser triangulation principle to measure online surface topography in the paper and paperboard industries. It characterizes the surface in a wide spatial scale of topography from 0.09-10 mm. The prototype's technique projects a narrow lineof-light perpendicularly onto the moving paper-Web surface and scattered reflected light is collected at a low angle, low specular, and reduced coherent length onto the CCD sensors synchronized with the laser sources. The scattering phenomenon determines surface deviations in the z-direction. The full-width, at half-maximum of a laser line in cross section is sensitive in computation of the surface topography. The signal processing aspect of the image processing, for example, threshold and filtering algorithms are also sensitive in estimating the accurate surface features. Moreover, improper light illumination, intensity, reflection, occlusion, surface motion, and noise in the imaging sensor, and so forth, all contribute to deteriorate the measurements. Optical techniques measure the surface indirectly and, in general, an evaluation of the performance and the limitations of the technique are both essential and challenging. The paper describes the accuracy, uncertainty, and limitations of the developed technique in the raw profiles and in terms of the rms roughness. The achieved image subpixel resolution is 0.01 times a pixel. Statistically estimated uncertainty (2σ) in the laboratory environment was found 0.05 μm for a smooth sample, which provides a 95% confidence level in the rms roughness results. The depth of field of the prototype is ~2.4 mm.

In-Process Fast Surface Measurement Using Wavelength Scanning Interferometry

A wavelength scanning interferometry system for fast areal surface measurement of micro and nano-scale surfaces which is immune to environmental noise is introduced in this paper. It can be used for surface measurement of discontinuous surface profiles by producing phase shifts without any mechanical scanning process. White light spectral scanning interferometry, together with an acousto-optic tuneable filtering technique, is used to measure both smooth surfaces and those with large step heights. An active servo control system is used to serve as a phase compensating mechanism to eliminate the effects of environmental noise. The system can be used for on-line or in-process measurement on a shop floor.

Sphere-Based Geometrical Calibration Method for Structured Light Surface Measurement Systems

This paper proposes a sphere-based calibration method for the structured light system with unconstrained one projector &amp; one camera, regardless of pattern codification. A 1-pose example of such a method is also proposed and tested. In comparison with a traditional plane translation method of 15 poses, we note an increase in the consistency of more than 10% while the calibration time shrinks to 6% and the calibration accessory is reduced to the size of a flash-light. This method suits well for applications where mobility, speed and ease-of-use are important criteria.