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In this paper, the topography of 6082 aluminium alloy specimens after fatigue bending tests was studied with a comprehensive evaluation of measurement noise caused by vibration. Roughness results were acquired by contactless Focus Variation Microscopy (FVM). Studied data were pre-processed, removing the non-measured points and outliers with regular methods, respectively, and high-frequency noise was considered. The variations in ISO 25178 roughness parameters were studied. Based on the previous studies, it was found that surfaces after fatigue bending tests can be difficult to consider when analyzing the measurement noise in a selected bandwidth. Some advantages of profile data extraction in selected directions, like horizontal, vertical or crack, were found deficient, even in studies by various functions, like autocorrelation, power spectral density, or texture direction ratio. When noise suppression methods depend on the details studied, boundary areas were extracted to compare and highlight the presence of high-frequency data characteristics. The proposed method was validated when contrasting standardised Gaussian or median filtering techniques with the spline filtering approach. A proper filter for the reduction of vibrational noise from the results of FVM topography measurements was suggested based on the proposed procedure. Finally, it was proposed how use the new method for reducing errors caused by high-frequency measurement noise in the surface topography of specimens after fatigue bending tests. • The surfaces of 6082 aluminium alloy specimens after fatigue tests were characterised. • The surface topography was measured by the focus variation microscopy (FVM) technique. • High-frequency noise removal methods were supported by specified profile data extraction. • The improvement in measurement noise reduction was received by boundary areas studies. • The accuracy of the ISO 25178 parameter analysis can be improved by the proposed method. [ABSTRACT FROM AUTHOR]

The topography of surfaces produced by metal additive manufacturing is a challenge for optical measurement systems such as focus variation microscopes. These irregularities can lead to artifacts, such as incorrectly measured protrusions or spikes, hampering reliable topographic characterization. In order to eliminate this problem, we introduce a new algorithm based on dual convolving a vertical Sobel operator with cross sections of an image stack parallel to the scanning direction of the so-called depth scan. This has proven beneficial in order to distinguish the focus region from out-of-focus areas where outliers are frequently detected. This paper introduces a method for deriving self-adaptive thresholds from the convolution result and compares the effects of different operators in creating self-adaptive thresholds. Additionally, a simulation model of focus variation microscopy is introduced to validate both the measuring system and the proposed algorithm, thereby enhancing the overall performance of focus variation microscopy. Finally, comparisons of measurement results on rough metal additive manufacturing workpieces with and without self-adaptive thresholds are discussed to demonstrate the algorithm's effectiveness.The utilization of self-adaptive thresholds demonstrably reduces the uncertainty range in roughness parameter calculations. For example, in the case of an additive manufactured metal sample due to outlier elimination, the S z roughness value reduces from 543 µm to 413 µm. [ABSTRACT FROM AUTHOR]

Additive manufacturing of copper enables enhanced design freedom which allows for improved performance of components in thermal management and electrical applications. Joining via soldering provides ideal electrical and thermal connections, but the solderability of complex additively manufactured surfaces is poorly understood. In the present work, the solderability of nominally pure copper coupons manufactured by three additive manufacturing techniques (laser powder bed fusion, laser engineered net shaping, and bound powder extrusion) was experimentally assessed using the wetting balance technique and pin pull testing. Coupons produced by each method were tested as built and after surface modification by dry electropolishing. Contact angles and wetting times were calculated from wettability testing. Peak tensile loads required to remove pins soldered to coupons were also recorded for each surface condition. The dipped coupons and solder joint fracture surfaces were examined with optical and scanning electron microscopes. It was found that nonuniform wetting and excessive wicking of solder can result in weak joints, and surface modification positively affected overall solderability in all cases. All surfaces were shown to be wettable, but bound powder extrusion was found to produce the most solderable copper surfaces among the additive manufacturing methods tested. [ABSTRACT FROM AUTHOR]

Coherence scanning interferometry (CSI), based on the principle of interference, can achieve sub-nanometer precision for height measurements. On the other hand, focus variation microscopy (FVM), combining the small depth of field of the objective, is a widely used surface topography measurement method suited to surface topography that is mostly optically rough. In this paper, we propose a method to simultaneously obtain the interferometric fringe data and focus variation FVM image stack, from a single vertical scanning process, using a CSI instrument without any hardware modifications. Using a 3D Fourier transform, the FVM signal, looks takes the form of a "bowtie" and the CSI signal resembles two "umbrellas" that are separated in 3D K-space. The signal is recovered using a 3D inverse Fourier transform and the surface topography can be determined by fusing the CSI and FVM signals. Since both signals come from the same instrument and scanning process, there is no need for coordinate registration and data interpolation during the data fusion process. Our method combines the features of CSI and FVM measurement, thereby improving the robustness and data coverage of the measurement. An all-in-focus surface topography map can also be generated using this method. This focusing feature has the potential to significantly improve the defect detection and quality control ability of CSI instruments. • Extracting focus variation data from coherence scanning interferometry without any hardware modifications. • No need for coordinate registration and data interpolation during the data fusion process. • Combining the features of CSI and FVM measurement, thereby improving the robustness and data coverage of the measurement. • All-in-focus surface topography map can be generated using this method for defect detection and quality control. [ABSTRACT FROM AUTHOR]

Stitching methods allow one to measure a wider surface without the loss of resolution. The observation of small details with a better topographical representation is thus possible. However, it is not excluded that stitching methods generate some errors or aberrations on topography reconstruction. A device including confocal microscopy (CM), focus variation (FV), and coherence scanning interferometry (CSI) instrument modes was used to chronologically follow the drifts and the repositioning errors on stitching topographies. According to a complex measurement plan, a wide measurement campaign was performed on TA6V specimens that were ground with two neighboring SiC FEPA grit papers (P#80 and P#120). Thanks to four indicators (quality, drift, stability, and relevance indexes), no measurement drift in the system was found, indicating controlled stitching and repositioning processes for interferometry, confocal microscopy, and focus variation. Measurements show commendable stability, with interferometric microscopy being the most robust, followed by confocal microscopy, and then focus variation. Despite variations, robustness remains constant for each grinding grit, minimizing interpretation biases. A bootstrap analysis reveals time-dependent robustness for confocal microscopy, which is potentially linked to human presence. Despite Sa value discrepancies, all three metrologies consistently discriminate between grinding grits, highlighting the reliability of the proposed methodology. [ABSTRACT FROM AUTHOR]

Stitching methods allow one to measure a wider surface without the loss of resolution. The observation of small details with a better topographical representation is thus possible. However, it is not excluded that stitching methods generate some errors or aberrations on topography reconstruction. A device including confocal microscopy (CM), focus variation (FV), and coherence scanning interferometry (CSI) instrument modes was used to chronologically follow the drifts and the repositioning errors on stitching topographies. According to a complex measurement plan, a wide measurement campaign was performed on TA6V specimens that were ground with two neighboring SiC FEPA grit papers (P#80 and P#120). Thanks to four indicators (quality, drift, stability, and relevance indexes), no measurement drift in the system was found, indicating controlled stitching and repositioning processes for interferometry, confocal microscopy, and focus variation. Measurements show commendable stability, with interferometric microscopy being the most robust, followed by confocal microscopy, and then focus variation. Despite variations, robustness remains constant for each grinding grit, minimizing interpretation biases. A bootstrap analysis reveals time-dependent robustness for confocal microscopy, which is potentially linked to human presence. Despite Sa value discrepancies, all three metrologies consistently discriminate between grinding grits, highlighting the reliability of the proposed methodology.

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In line with engineering research focusing on metal tools, techniques to record the attribute of 'edge sharpness' on stone tools can include both mechanical and micro-geometric approaches. Mechanically-defined sharpness techniques used in lithic studies are now well established and align with engineering research. The single micro-geometrically-defined technique—tip curvature—is novel relative to approaches used elsewhere, and has not explicitly been tested for its ability to describe the attribute of sharpness. Here, using experimental flakes produced on basalt, chert, and quartzite sourced at Olduvai Gorge (Tanzania), we investigate the relationship between tip curvature and the force and work required to initiate a cut. We do this using controlled cutting tests and analysis of high-resolution microCT scans. Results indicate cutting force and work to display significant dependent relationships with tip curvature, suggesting the latter to be an appropriate metric to record the sharpness of lithic tools. Differences in relationship strength were observed dependent on the measurement scales and edge distances used. Tip curvature is also demonstrated to distinguish between the sharpness of different raw materials. Our data also indicate the predictive relationship between tip curvature and cutting force/work to be one of the strongest yet identified between a stone tool morphological attribute and its cutting performance. Together, this study demonstrates tip curvature to be an appropriate attribute for describing the sharpness of a stone tool's working edge in diverse raw material scenarios, and that it can be highly predictive of a stone tool's functional performance. [ABSTRACT FROM AUTHOR]

The topography of surfaces produced by metal additive manufacturing is a challenge for optical measurement systems such as focus variation microscopes. These irregularities can lead to artifacts, such as incorrectly measured protrusions or spikes, hampering reliable topographic characterization. In order to eliminate this problem, we introduce a new algorithm based on dual convolving a vertical Sobel operator with cross sections of an image stack parallel to the scanning direction of the so-called depth scan. This has proven beneficial in order to distinguish the focus region from out-of-focus areas where outliers are frequently detected. This paper introduces a method for deriving self-adaptive thresholds from the convolution result and compares the effects of different operators in creating self-adaptive thresholds. Additionally, a simulation model of focus variation microscopy is introduced to validate both the measuring system and the proposed algorithm, thereby enhancing the overall performance of focus variation microscopy. Finally, comparisons of measurement results on rough metal additive manufacturing workpieces with and without self-adaptive thresholds are discussed to demonstrate the algorithm’s effectiveness.The utilization of self-adaptive thresholds demonstrably reduces the uncertainty range in roughness parameter calculations. For example, in the case of an additive manufactured metal sample due to outlier elimination, the Sz roughness value reduces from 543 µm to 413 µm.

• Address application limitations of traditional focus variation microscopy. • Determine the optimal parameters for active illumination mode. • Measurement noise immunity enhanced from 8.7 nm to 1.1 nm (50 × objective). • Reconstruct the surface topography of microchannels through transparent encapsulation layer. Optical measurement methods for surface topography offer the advantages of high accuracy, rapid measurement, and non-destructiveness. Each method has its own suitable application scenarios. Among them, focus variation microscopy is extensively employed in precision manufacturing, aerospace, and medical industries due to its ability to measure rough and large slopes surfaces. However, since the measurement depends on local grayscale differences between focused and blurred images, it cannot measure surfaces with low reflectivity or insufficient texture information. In this work, we propose an active illumination mode for focus variation method that utilizes a digital micromirror device (DMD) to generate a checkerboard pattern. This method introduces additional texture information, resulting in a usable local gradient of image grayscale. Additionally, we analyze the selection criteria for the checkerboard pattern parameters, including the period and light-dark ratio. Furthermore, measurements of two standard steps with different heights demonstrate that the measurement repeatability of the proposed method can reach the nanometer level, rendering it suitable for high-precision measurements. More importantly, the measurement noise results indicate significantly superior performance of active illumination mode compared to the uniform illumination mode. Finally, we reconstruct the surface topography of the microchannels in a microfluidic chip through the encapsulation layer, demonstrating the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

[Display omitted] • The amount of PEO and excipient type and ratios impact drug release and swelling properties. • Surface roughness (Smr2) indicates higher hydration rates for PEO:lactose ratios. • Higher PEO content results in reduced porosity and increased compact hardness. • PEO:excipient compacts show faster drug release compared to pure PEO compacts. • UV dissolution imaging provides insights into swelling and drug dissolution phenomena. The use of dissolution imaging in analysing the behaviour of hydrophilic matrices and various types of excipients is examined in this study. The main aim was to investigate how different ratios of excipients with different solubility properties, such as lactose, microcrystalline cellulose, and dicalcium phosphate impact on the swelling properties and propranolol hydrochloride (PPN) release characteristics of polyethylene oxide matrix compacts. The surface properties of the compacts were investigated using a focus variation microscope after which dissolution studies were conducted to determine compact swelling and drug release properties. Smr2 , a surface parameter representing the percentage of deeper valley structures on the surface, was used to calculate the proportion of the compact surface available for retaining lubrication (dissolution media in this case). Smr2 values of 83 and 84 were measured for the 1:1 and 1:3 PEO lactose compacts, respectively. This parameter utilised in this experiment gives an indication of the compact surface available for the initial hydration process and suggests a higher rate of hydration for the 1:1 and 1:3 PEO lactose compacts. The swelling studies revealed that a higher PEO ratio (3:1) resulted in more extensive gel layer formation as compared to the 1:3 compacts. All PEO:excipient compacts exhibited faster drug release than the compacts comprising PEO as the sole excipient. The quantity of PEO present was thus crucial in influencing the capacity of the matrix to control the release of PPN. This study underscores the potential for modifying drug release by altering the quantity of the matrix gel-former (PEO in this case) as well as the type or ratio of excipient used. The study also highlights the novelty of using UV dissolution imaging to image and quantify swelling and drug dissolution processes as well as providing qualitative observations such as channel formation which can support formulation optimisation and mechanistic understanding. [ABSTRACT FROM AUTHOR]

Many methods of ballistic toolmark comparison rely upon comparison using 2D greyscale imaging. However, newly emerging analysis methods such as areal surface analysis now utilise an extra dimension of measurement allowing the surface heights/depths of unique toolmark features to be recorded in a densely populated (x,y,z) array for a 3D/areal quantitative comparative analysis. Due to this step change, the colloquialism in referring to the crater produced at the centre of the primer during firing as a "firing pin impression" has become a misnomer, leading some to believe that this toolmark is produced via a single process, where the critical variable is the condition of the firing pin. Furthermore, current forensic ballistic methodology relies on the microscopic differences between individual fired bullets and cartridge cases produced as a result of the manufacturing process of a particular firearm, in this case "matched toolmarks" confirm a ballistic match to a specific firearm. However, very rarely is it considered that the ammunition itself possesses minute differences produced during manufacture that could affect the ballistic match efficacy. This study examines the discharge process of conventional centrefire ammunition and concludes that the unique toolmarks upon the cartridge primer are definitively produced in two defined stages. This conclusion suggests that the factory loading and quality control tolerances of the cartridge itself should now be considered to be a more significant contributing factor to the production of cartridge primer toolmarks than has previously been accepted. • Cartridge primer toolmarks are produced in an impression stage and an extrusion stage. • Backpressure has an observable impact on post discharge cartridge primer toolmarks. • Manufacturing tolerances play a role in the production of cartridge primer toolmarks. [ABSTRACT FROM AUTHOR]

The surface of tissue paper is relatively complex compared to other paper grades and consists of several overlapping structures like protruding fibres, crepe and fabric-based patterns at different spatial frequencies. The knowledge of tissue surface characteristics is crucial when it comes to improvement with respect to surface softness and the perceptual handfeel of tissue products. In this work we used the optical based, non-contact measurement principle of focus variation for surface characterization of dry-creped, textured and through air dried (TAD) tissue. Based on the three tissue grades, a procedure which includes the characterization of the whole tissue surface throughout different scales within one setup, was developed. Surprisingly, focus variation was rarely used in tissue-related research, as it provides robust and reliable 3D surface information which can be used for further areal surface analysis. Special attention was given to the preparation and discussion of the raw data up to the final analysis including several spatial filtering steps. Enhanced surface parameters like the developed interfacial area ratio (Sdr) and the power spectral density (PSD) were used to describe the surface adequately. The surface roughness of the three tissue grades was compared, with the textured tissue showing the highest roughness in Sdr and PSD analysis. Although both methods are based on different principles, a high correlation in terms of evaluated roughness is evident. Regular structures like crepe and patterns are obtainable as peaks at the respective frequency with a certain intensity in the PSD evaluation. Apart from topography in terms of structures and roughness, the wide field of view of the focus variation measurement also allows assessment of effects related to flocculation and sheet formation. The developed procedure could also be appropriate for other fibre based materials and/or fabrics, which are similar to tissue with respect to optical properties such as for example nonwovens. [ABSTRACT FROM AUTHOR]

Numerous studies have focused on determining whether objective statistical methods can be used to discriminate between known matches and nonmatches when comparing laboratory prepared toolmarks. This study involved an analysis of striated toolmarks made as a function of varying vertical and horizontal angles of attack. Comparisons based on experimental data show that replicate toolmarks from the same tool show high correlation values at identical vertical and horizontal angles, with the correlation decreasing as the angular difference increases, especially for horizontal angular changes. Comparisons between nonmatching samples produce low correlation values that remain unchanged as horizontal angular differences increase. While complete statistical separation was not achieved between matching and nonmatching samples, there is evidence demonstrating that toolmarks can be identified if the variation in horizontal angle is within 10°. The experiment shows that computer-aided comparison techniques could be viable for identification with the proper statistical algorithm. [ABSTRACT FROM AUTHOR]

Abstract: As the field of use-wear analysis has developed, the number of different methodologies that address tool function has increased. Multiple new methods have been published in recent years, both in qualitative and quantitative approaches. This paper focuses on a recent development in quantitative microscopy, specifically focus variation microscopy. This microscope characterizes surface features and has the ability to generate measurements of surface roughness, particularly useful for lithic use-wear studies. This paper presents the results of some preliminary measurements taken on experimental tools, highlighting the strengths and weaknesses of this new method and how it can contribute to the growing field of use-wear quantification. Finally, it presents some of the new challenges facing archaeologists interested in the quantification of use-wear and future directions of research. [Copyright &y& Elsevier]

Abstract: The appearance of portable artistic objects during the Upper Palaeolithic is characterised by a combination of a wide choice of techniques, use of different materials and a diversity of iconographic expression, with many objects made of bone and antler decorated with animal representations. Taphonomic and experimental approaches have been systematically applied in an effort to understand the technical and artistic procedures followed. In this study, we applied a new combination of 3-dimensional microscopy (focus variation optical microscope) and micro-CT scanning to the analysis of two Magdalenian engraved specimens: a reindeer antler from the site of Neschers (France), engraved with the partial image of a horse in left profile, and a horse metatarsal from Courbet Cave, Penne (France), engraved with a horse head also in left profile. Results of the analysis suggest that both the Neschers and Courbet Cave engravings had been prepared before being carved. The overall contours of the horse body/head were incised first, while anatomical features were added afterwards. In the Neschers case, the incision resulted from the repeated scratching of a previously made incision in order to enlarge the engraving, possibly reflecting the engraver''s aesthetic sense. The combination of the techniques used in this study is applicable to fragile or unique archaeological specimens. Micro-CT scanning, in particular, provides non-invasive means for identifying engravings that are obscured by encrusted sediment. The application of these techniques can potentially open new avenues for the authentication, technical and gestural recognition and interpretation of incised forms and artistic creativity. [Copyright &y& Elsevier]