White Light Interference Research Articles

Characterisation of group behaviour surface texturing with multi-layers fitting method

Surface texturing was widely applied in improving the tribological properties of mechanical components, but study of measurement of this technology was still insufficient. This study proposed the multi-layers fitting (MLF) method to characterise the dimples array texture surface. Based on the synergistic effect among the dimples, the 3D morphology of texture surface was rebuilt by 2D stylus profiler in the MLF method. The feasible regions of texture patterns and sensitive parameters were confirmed by non-linear programming, and the processing software of MLF method was developed based on the Matlab®. The characterisation parameters system of dimples was defined mathematically, and the accuracy of MLF method was investigated by comparison experiment. The surface texture specimens were made by laser surface texturing technology, in which high consistency of dimples’ size and distribution was achieved. Then, 2D profiles of different dimples were captured by employing Hommel-T1000 stylus profiler, and the data were further processed by MLF software to rebuild 3D morphology of single dimple. The experiment results indicated that the MLF characterisation results were similar to those of Wyko T1100, the white light interference microscope. It was also found that the stability of MLF characterisation results highly depended on the number of captured cross-sections.

WEAR BEHAVIOUR AND SURFACE ROUGHNESS OF POLYMER INFILTRATED CERAMIC MATERIAL COMPARED TO PRESSABLE GLASS CERAMIC

Abstract: Introduction: Multiple restorative materials with various chemical, mechanical and physical characteristics are used as permanent dental restorations. The appropriate selection of a restorative material is crucial for preserving the occlusal harmony and normal masticatory function. Several aspects during selection of restorative materials should be considered, among which are the wear behaviour and abrasive nature of the restorative materials and natural enamel. Objectives: The study determines the two-body wear and surface roughness measurement, of polymer infiltrated ceramic (Vita Enamic) and pressable lithium disilicate based ceramic (IPS e.max press). Materials and methods: Two-body wear was investigated in custom made tooth wear brushing machine (60,000 cycles, 20 N and 60 cycle/min). The test specimens were divided into two groups, each group consisted of 8 ceramic specimens and 8 enamel cusp antagonists. Quantitative analysis of wear was carried out with subtractive weight loss of all specimens before and after wear test. Surface roughness measurements were evaluated before and after the wear test using a white light interference microscope. The data was collected and statistically analyzed using Mann-Whitney (U) test. Results: Statically significant differences were found for two-body wear, with Vita Enamic samples show lower wear loss than IPS e.max press samples and cause less enamel wear loss. The Vita Enamic showed lower surface roughness and caused less surface roughness to enamel cusp antagonist than IPS e.max press samples. Conclusions: Vita Enamic revealed lower wear loss contributed by terms of weight loss and surface roughness change than IPS e.max press. IPS e.max press contributed to more surface roughness and wear loss of opposing enamel than Vita Enamic. Keywords: CAD/CAM - Two-body wear - Tooth brushing wear - Surface Roughness

Design, fabrication, characterisation of optical imaging cylindrical micro-lens array based on liquid crystal

The electrical adjustment of the optical performance of liquid crystal cylindrical micro-lens array of 128×128, which is based on the field controlling effect of liquid crystal dielectric behaviour, is realised through constructing smart liquid crystal electro-optic structure, and orderly modulating the refractive index of liquid crystal material and its spatial distribution. According to the elastic continuum theory of liquid crystal, it is firstly described on the formation of specific refractive index spatial distribution of liquid crystal molecules, which is driven by applied electric-field. Furthermore, the white-light focusing, the far-field white-light interference and the monochromatic laser interference are all measured extensively and discussed in details.

Rapid Prototyping of Multi-Scale Electrodes on Polymer Surfaces

Rapid prototyping of multi-scale electrodes on polymer surfaces Multiscale electrodes that combine features in multiple lengthscales – from the millimetre to the nanometer scale – are essential for developing a wide range of electrical and optoelectronic devices including solar cells1 and biosensors2. While nanomaterials, used in the active region of such devices, have shown to enhance device performance, these often have to be interfaced with wires and contact pads in the milimeter or micrometer lengthscales for use in practical devices3. Although electrodeposition is a simple, inexpensive and rapid method for the fabrication of tunable nanomaterials, it often has to be combined with templates for organizing the nanostructures in the desired device-specific geometries4. Templates created by machining or lithographic processing often add significantly to the complexity and cost of the manufacturing process, and require long design to production times. Self-assembled templates are simple and inexpensive and can be rapidly created; however, they often have shortcomings in terms of controllability of geometry and size5. Here we demonstrate a facile method for developing multiscale electrodes by combining electrodeposition with templates created using benchtop and rapid prototyping methods. Macroscale patterning is performed using a craft cutter to define electrode patterns on a self-adhesive vinyl film immobilized on a pre-stressed polystyrene substrate. Microscale patterning is induced by shrinking metallic thin films through heating the pre-stressed substrate. Tunable nanostructuring is achieved by manipulating the parameters of the electrodeposition process. The surface structure of these electrodes was characterized using scanning electron microscopy and white light interference microscopy, while their electrical and electrochemical properties were characterized using the four-point-probe and voltammetric methods. The multiscale electrodes fabricated here were shown to be tunable in terms of structure, sheet resistance, and electroactive surface area. Furthermore, complex electrode structures were created for a variety of biomedical applications including electrochemical detection, magnetic separation, and bacterial lysis with a design to fabrication time of a few hours. (1) Battaglia, C.; Escarré, J.; Söderström, K.; Charrière, M.; Despeisse, M.; Haug, F.-J.; Ballif, C. Nanomoulding of Transparent Zinc Oxide Electrodes for Efficient Light Trapping in Solar Cells. Nat. Photonics 2011, 5, 535–538. (2) Soleymani, L.; Fang, Z. C.; Sargent, E. H.; Kelley, S. O. Programming the Detection Limits of Biosensors through Controlled Nanostructuring. Nat. Nanotechnol. 2009, 4, 844–848. (3) Soleymani, L.; Fang, Z.; Sun, X.; Yang, H.; Taft, B. J.; Sargent, E. H.; Kelley, S. O. Nanostructuring of Patterned Microelectrodes to Enhance the Sensitivity of Electrochemical Nucleic Acids Detection. Angew. Chem. Int. Ed. Engl. 2009, 48, 8457–8460. (4) Plasmonic, T. N.; Halpern, A. R.; Corn, R. M. Lithographically Patterned Electrodeposition of Gold , Silver , and Resonances. 2013, 1755–1762. (5) Fan, Z.; Razavi, H.; Do, J.; Moriwaki, A.; Ergen, O.; Chueh, Y.-L.; Leu, P. W.; Ho, J. C.; Takahashi, T.; Reichertz, L. a; et al. Three-Dimensional Nanopillar-Array Photovoltaics on Low-Cost and Flexible Substrates. Nat. Mater. 2009, 8, 648–653. Figure 1

Investigation of spectral shifts in a white light interferometer with a single interference peak

When the optical path difference between the two arms of an interferometer is so small that only one peak exists within the measurable interference spectrum, traditional white light interference demodulation techniques based on two adjacent interference peaks are not a suitable choice. We report an experimental approach to measure the peak wavelength shifts with only a single interference peak in a fiber white light interferometer. The temperature measurement experiments prove a linear relationship between the peak wavelength and the temperature. The temperature resolution is 0.1°C in theory.

Study on Spatial Frequency Domain Algorithm and White Light Interference System Based on NMM

White light interference technique for topography measurement effectively avoids phase ambiguity in phase-shifting interferometry. The spatial frequency domain algorithm based on scanning white light interference technique has the advantage of insensitivity to noise and higher calculation accuracy compared with other methods. The white light interference sensor is constructed based on nano positioning and nano measuring machine (NMM), the calibrated step height standard of 100±3nm is measured. The spatial frequency domain algorithm is adopted for data processing, the repetitive test result of 97.9nm and standard deviation of 0.48nm are achieved. To verify the measuring ability of complex device, the number ‘242’ on ink box is measured and three-dimensional reconstruction is conducted. The high precision and traceable measurements of micro/nano scale step height standard and complex devices are realized by the white light interference system based on NMM with steady frequency laser interferometer built-in.

Electrochemical Dissolution Behavior and the Residue Formation Mechanism of Laboratory Made Carbonyl Nickel

The anodic dissolution of two laboratory-made Ni samples obtained using the carbonyl method was investigated to understand the origin of residue formation in the anode basket in an electroplating tank. The first sample was obtained with 3ppm addition of carbonyl sulfide to introduce a small amount of sulfur (CN-S sample). The second was obtained without sulfur impurities (CN sample). Linear sweep voltammetry and chronopotentiometry were applied to characterize the dissolution of these samples. The dissolution of the CN-S sample took place in the active region at low overpotentials. This behavior is determined by the presence of sulfur impurities that break down the passive layer and facilitate Ni dissolution. The CN sample without sulfur was dissolved at high overpotentials. The overpotential-time plots displayed regular large amplitude oscillations in which the overvoltage periodically moved between the transpassive and passive regimes. The anodic dissolution of this sample was controlled by two competing processes: breakdown and formation of the passive layer. Scanning electron microscopy and white light interference microscopy were applied to monitor the morphological changes of the two samples as a function of the dissolution time. The results of these studies showed that the CN-S sample dissolved uniformly across the surface. However, the roughness and the aspect ratio of the protruding features on the surface increased with time. This sample produced a fine residue due to detachment of small protruding crystallites. In contrast, the dissolution of the CN sample involved pit formation and took place predominantly from the bulk of the pits. The dissolution of this sample left a porous skeleton of more passivated Ni. The residue in this case consisted of large, porous chunks of the skeleton.

Effect of ocular transverse chromatic aberration on detection acuity for peripheral vision.

We examined the effect of transverse chromatic aberration (TCA) on detection acuity for white-light interference fringes seen in Maxwellian view at various orientations and locations in the visual field. A circular patch (3.5° diameter, 3.2 log Trolands) of nominally high-contrast fringes was produced on the retina by a commercial instrument (the Lotmar Visometer, Haag Streit) mounted on a gimbal for controlled positioning of the stimulus in the visual field from 0° to 35° eccentricity. Detection acuity for white light fringes for all meridians and eccentricities ≥15° was maximum when fringes were oriented parallel to the visual meridian line. This meridional effect disappeared when a narrow-band filter was used to eliminate TCA. The meridional effect also disappeared when the interferometric stimulator was displaced laterally to align the instrument with the eye's local achromatic axis. Modelling confirmed that TCA is the major factor responsible for white-light meridional bias, with minor contribution arising from higher-order monochromatic aberrations and neural factors.

Tribological performance of femtosecond laser-induced periodic surface structures on titanium and a high toughness bearing steel

Laser-induced periodic surface structures (LIPSS, ripples) were processed on steel (X30CrMoN15-1) and titanium (Ti) surfaces by irradiation in air with linear polarized femtosecond laser pulses with a pulse duration of 30fs at 790nm wavelength. For the processing of large LIPSS covered surface areas (5mm×5mm), the laser fluence and the spatial spot overlap were optimized in a sample-scanning geometry. The laser-processed surfaces were characterized by optical microscopy (OM), white light interference microscopy (WLIM) and scanning electron microscopy (SEM). Spatial LIPSS periods between 450 and 600nm were determined. The nanostructured surface regions were tribologically tested under reciprocal sliding conditions against a 10-mm diameter ball of hardened 100Cr6 steel. Paraffin oil and engine oil were used as lubricants for 1000 sliding cycles at 1Hz with a normal load of 1.0N. The corresponding wear tracks were analyzed by OM and SEM. In particular cases, the laser-generated nanostructures endured the tribological treatment. Simultaneously, a significant reduction of the friction coefficient and the wear was observed in the laser-irradiated (LIPSS-covered) areas when compared to the non-irradiated surface. The experiments reveal the potential benefit of laser surface structuring for tribological applications.

자유 곡면 형상 측정을 위한 백색광 주사 간섭계의 정확도 향상 및 시스템 오차 분석

Scanning white-light interferometry is an important measurement option for many surfaces. However, serious profile measurement errors can be present when measuring free-form surfaces being highly curved or tilted. When the object surface slope is not zero, the object and reference rays are no longer common path and optical aberrations impact the measurement. Aberrations mainly occur at the beam splitter in the interference objective and from misalignment in the optical system. Both effects distort the white-light interference signal when the surface slope is not zero. In this paper, we describe a modified version of white-light interferometry for eliminating these measurement errors and improving the accuracy of white-light interferometry. Moreover, we report systematic errors that are caused by optical aberrations when the object is not flat, and compare our proposed method with the conventional processing algorithm using the random ball test.

A new dual-plate slipometer for measuring slip between molten polymers and extrusion die materials.

In this work, we study the slip behaviors common to plastics die extrusion metals or platings using a new instrument called a dual-plate slipometer. By dual-plate, we mean that whereas the stationary plate incorporates a local shear stress transducer, the moving plate does not. The stationary plate and transducer are made of one stainless steel, but the moving plate is made from, or plated with, different extrusion die materials under study. This new instrument allows slip velocity to be measured without having to build a new shear stress transducer from each extrusion metal or plating under study. We explore the effect of extrusion die composition and die metal surface morphology on the slip properties of polyolefins using a sliding plate rheometer. In this work, we studied the slip behaviors of polyolefins on four common plastics die extrusion metals or platings, without having to build a new shear stress transducer from each. Specifically, our new method replaces the moving plate; with each of the four die metals or platings under study without changing the stainless steel material of the shear stress transducer and its stationary plate. Our experiments include high-density polyethylene, low-density polyethylene, and polypropylene (PP) on four different die metals or platings. We use steady simple shear to obtain shear stress versus nominal shear rate for different gaps, from which we can then deduce the slip velocity using the Mooney analysis. We then fit four slip models to our experimental measurements, and we find the Hatzikiriakos hyperbolic sine model to be accurate, even for the measured inflections in the slip velocity as a function of shear stress curves. Our analysis includes detailed characterization of the die metal plating surfaces, including measurements of the composition of the sliding plates by energy dispersive spectroscopy, surface energy by contact angle goniometry, and surface roughness by both white light interference and stylus profilometries. We use our slip measurements to evaluate the Allal-Vergnes equation for the critical shear stress for slip [A. Allal and B. Vergnes, "Effect of die surface on the onset of stick-slip transition in the flow of molten linear polymers," J. Non-Newtonian Fluid Mech. 167-168, 46-49 (2012)]. We conclude our analysis by dedimensionalizing slip, and we then use these dimensionless groups to analyze slip. This paper provides a set of reference data for extrusion die designers for polyolefins.

Study on Phase Shifting Algorithm and System of White Light Interference

The white-light interferometry (WLI) has been widely used in 3D topography measurement. This paper introduces a white light phase shifting method for interferometry with the combination of Hariharan phase shifting and WLI. A micro/nanolevel mechanic system was designed and built for the experiments. To verify system accuracy and feasibility, a 100nm step height standard was measured by the designed system and the metrological nanomeasurement machine (NMM). Results of 102.7nm and 102.5nm are obtained respectively. En value of 0.14 is calculated, demonstrating the reliability of result measured by the system. Based on classic nanoquantity traceability system, the measurement results can effectively traced back to the definition of nanometer magnitude, which can improve the accuracy of measurement.

Femtosecond laser-induced periodic surface structures on steel and titanium alloy for tribological applications

Laser-induced periodic surface structures (LIPSS, ripples) were generated on stainless steel (100Cr6) and titanium alloy (Ti6Al4V) surfaces upon irradiation with multiple femtosecond laser pulses (pulse duration 30 fs, central wavelength 790 nm). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning geometry for the processing of large surface areas (5 × 5 mm2) covered homogeneously by the nanostructures. The irradiated surface regions were subjected to white light interference microscopy and scanning electron microscopy revealing spatial periods around 600 nm. The tribological performance of the nanostructured surface was characterized by reciprocal sliding against a ball of hardened steel in paraffin oil and in commercial engine oil as lubricants, followed by subsequent inspection of the wear tracks. For specific conditions, on the titanium alloy a significant reduction of the friction coefficient by a factor of more than two was observed on the laser-irradiated (LIPSS-covered) surface when compared to the non-irradiated one, indicating the potential benefit of laser surface structuring for tribological applications.

White light differential interference contrast microscope with a Sagnac interferometer

A new technique for producing a white light differential interference contrast (DIC) image using a lateral shearing, rotation phase shifting Sagnac interferometer (SI) is proposed. The SI, placed in the image space after the tube lens of a microscope system with spatially coherent white light Kohler illumination, splits the image forming beam into coherent components with small lateral shear. Phase shifts, between the interfering components, which can be considered as biased phase difference (BPD), are introduced by applying small angular rotation of the SI in its own plane. This variable BPD between the interfering white light components produces a uniform intensity colored background. The object related phase shift, due to the height difference between two close points on the object surface with separation on the order of least resolvable separation of the microscope objective, in addition to the BPD would produce a change in intensity/hue/color against a uniform background due to the BPD. Thus a DIC image is formed and the variable BPD provides an excellent means of improving the contrast of the image.

Nanosecond pulsed laser irradiation of titanium: Oxide growth and effects on underlying metal

Titanium oxide/oxynitride coatings were created on the polished surface of commercially pure, grade 2 titanium substrates by irradiating samples in air using a nanosecond-pulsed, infrared (1064nm) fiber laser. Coatings consist of three distinct layers, including a thin TiO2 rutile cap, a TiO middle layer, and an inhomogeneous bottom layer that is composed of TiOxN1−x and possibly oxygen-intercalated phases such as Ti6O. The combined thickness of TiO2 and TiO layers was varied from ~10 to 120nm by increasing the accumulated laser fluence. Laser-grown coatings exhibit different colors, which vary with oxide thickness. The observed color is attributed to the interference of incident white light reflected from the upper and lower boundaries of the TiO2 capping layer.

Multi-Function Fusion Measurement Method for Surface Texture

The texture and characteristics of surface have been becoming the leading factors to achieve the designed function of products successfully. So the measurement of surface texture is more and more important. A kind of new multi-function fusion measurement method for surface texture is presented in the paper. Four kinds of different scale measurement methods such as microscopy image measurement, vertical scanning white light interference measurement, white light interference nanoprobe measurement and white light interference diamond-probe measurement are fused for the surface texture multi-function fusion measurement in this method.

Wear behavior of a NiCr/AgVO3 self-lubricating composite

NiCr/AgVO3 self-lubricating composite was prepared by powder cold-pressed method with the NiCr alloy as the matrix and 10 wt.% additive of AgVO3 as solid lubricant. The AgVO3 additive powder was synthesized by the precipitation method which exhibits a melting point of 460 °C. Microstructure, phase composition and thermal properties of the AgVO3 powder, as well as the composite of NiCr/AgVO3 were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The friction and wear behavior of the specimens from room temperature (R.T.) to 800 °C was evaluated using a ball-on-disk tribometer and 3D white light interference (WLI). The results showed that the friction coefficient of this material under atmosphere decreases with temperature increasing from R.T. to 800 °C. However, the wear rate firstly increases from R.T. to 200 °C, almost remains stable from 200 °C to 600 °C, and then decreases with further increasing the temperature up to 800 °C. It is also found that the prepared composite materials show a better frictional behavior than NiCr alloy over the whole range of temperatures, which is mainly attributed to solid lubrication of AgVO3 exhibiting a lamella-slip structure at temperatures below 460 °C and forms liquid-film at elevated temperatures above the melting point.

Corrosion behavior of each phase in low carbon microalloyed ferrite–bainite dual-phase steel: Experiments and modeling

In situ observation of the initial corrosion behavior of a low carbon microalloyed ferrite–bainite dual-phase steel showed that the corrosion originated from the inside of ferrite and ferrite boundary. In addition, a model for describing the corrosion behavior of each phase in multiphase steel was established. Based on this model, a method to quantitatively assess the corrosion rate of each phase was presented by white light interference, and the relationship between the surface roughness and corrosion morphology was also established. Meanwhile, the galvanic corrosion at phase-scale and the influence of phase distribution on service safety of multiphase steel were discussed.

High-resolution corneal topography and tomography of fish eye using wide-field white light interference microscopy

Topography and tomography of fish cornea is reconstructed using high resolution white light interference microscopy. White light interferograms at different depths were recorded by moving the object axially. For each depth position, five phase shifted interferograms were recorded and analyzed. From the reconstructed phase maps, the corneal topography and hence the refractive index was determined and from amplitude images the cross-sectional image of fish cornea was reconstructed. In the present method, we utilize a nearly common-path interference microscope and wide field illumination and hence do not require any mechanical B-scan. Therefore, the phase stability of the recorded data is improved.

Research on Characterization Methods of Nano Dimension Standards

This paper develops one method to characterize nano dimension standards using Scanning White Light Interference Sensor (SWLIS) based on Nano Measurement Machine (NMM). The experimental results show the average value of SHS8-440 low step height standard is 44.15 nm and SHS8-100.0 high step height standard is 100.29 μm, with a standard deviation of 0.30 nm and 0.03 μm, respectively. Also, SWLIS is performed to measure and characterize step height standards, which cover most of the conventional step height standards produced by VLSI Standards Incorporated (VLSI). Additionally, atomic force microscope (AFM) is used as a beneficial supplement due to low lateral resolution of optical methods. The average value of TGZ1_PTB 1D grating from NT-MDT Company is 3000.2 nm with a standard deviation of 0.3 nm by AFM.