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Handheld pocket-size Fourier transform profilometry using projector-enabled smartphone
摘要： Surface Fourier transform profilometry (FTP) is a technique used for reconstructing three-dimensional (3-D) surface topography using light. It has been widely used in machine vision for biomedical and biometric automations, providing solutions beyond conventional 2-D imaging. This paper proposes an implementation of the handheld pocket-size FTP for 3-D surface profile imaging using a projector-enabled Samsung Galaxy Beam smartphone. In the implementation, a crossed-optical-axes geometry of the FTP is formed by using a mirror positioned over the phone’s projector via an adjustable tilt mounting bracket. Experimental proof-of-concept of the proposed profilometry is done by implementing conventional and non-phase shifting FTPs with different diffuse test objects. The experimental results obtained by using the non-phase shifting technique are in good agreement with those of the direct contact measurement. Besides having superiority of compactness, the proposed profilometry paves the way for the development of real-time 3-D profiling and printing through internet or Bluetooth interconnection.
关键词： 3-D profilometry,non-phase shifting technique,contrast function,sinusoidal grating,projector-enabled smartphone,3-D surface topography,Samsung galaxy beam,Fourier transform,shape measurement
更新于2025-09-23 15:21:01
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Effect of Scanning Strategy During Selective Laser Melting on Surface Topography, Porosity, and Microstructure of Additively Manufactured Ti-6Al-4V
摘要： The effect of the scanning strategy during selective laser melting (SLM) of Ti-6Al-4V was investigated. An optimized cellular scan strategy (island scan modeled) was compared to a simple cellular scan strategy (island scan stripes) and a simple antiparallel line scanning strategy (line scan). Surface texture was investigated by optical three-dimensional (3D) surface measurements, which when combined with light optical microscopy (LOM), revealed deflections caused by the thermal stresses during the build process. Elevated edges caused by the edge-effect dominate the surface texture of all investigated specimens. The scanning strategy determines the surface texture, and the lowest surface roughness was obtained by the line scan strategy. Porosity was investigated with X-ray computed tomography-imaging. Mainly spherical porosity was observed for the line scan and island scan modeled specimens, while the island scan stripes strategy showed more lack-of-fusion defects and a higher total porosity amount. Microstructure was investigated with LOM and scanning electron microscopy (SEM). The microstructure in Ti-6Al-4V was largely martensitic α’ and prior β grains. The morphology is different for the various scan strategies, and decomposition of α’ into lamellar α/β was observed in the bottom part of the island scan specimen. Accordingly, the hardness decreased in the decomposed part of the specimen.
关键词： scanning strategy,porosity,surface topography,selective laser melting,powder bed fusion,microstructure,SLM,Ti-6Al-4V
更新于2025-09-23 15:21:01
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Structured-illumination Makyoh-topography: optimum grid position and its constraints
摘要： Complementing conventional Makyoh topography with structured illumination using a sparse square grid, the large-scale surface shape can be calculated with a deflectometry approach, while the sample’s morphology can still be imaged. However, the grid’s image must be sharp not to mask the Makyoh image of the sample morphology. In this paper, the instrumental conditions for the grid sharpness are established. The two main types of Makyoh set-ups (lens and mirror based) are analysed. It is shown that the lens-based set-ups allow the position of the grid to be sharp on the Makyoh image. However, for mirror-based set-ups this is not possible because of geometrical instrumental constraints. The calculations are corroborated with experiments.
关键词： Makyoh topography,surface defects,structured illumination,deflectometry,geometrical optics,flatness testing
更新于2025-09-23 15:21:01
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3D auto-context-based locality adaptive multi-modality GANs for PET synthesis
摘要： Positron emission tomography (PET) has been substantially used recently. To minimize the potential health risk caused by the tracer radiation inherent to PET scans, it is of great interest to synthesize the high-quality PET image from the low-dose one to reduce the radiation exposure. In this paper, we propose a 3D auto-context-based locality adaptive multi-modality generative adversarial networks model (LA-GANs) to synthesize the high-quality FDG PET image from the low-dose one with the accompanying MRI images that provide anatomical information. Our work has four contributions. First, different from the traditional methods that treat each image modality as an input channel and apply the same kernel to convolve the whole image, we argue that the contributions of different modalities could vary at different image locations, and therefore a unified kernel for a whole image is not optimal. To address this issue, we propose a locality adaptive strategy for multi-modality fusion. Second, we utilize 1×1×1 kernel to learn this locality adaptive fusion so that the number of additional parameters incurred by our method is kept minimum. Third, the proposed locality adaptive fusion mechanism is learned jointly with the PET image synthesis in a 3D conditional GANs model, which generates high-quality PET images by employing large-sized image patches and hierarchical features. Fourth, we apply the auto-context strategy to our scheme and propose an auto-context LA-GANs model to further refine the quality of synthesized images. Experimental results show that our method outperforms the traditional multi-modality fusion methods used in deep networks, as well as the state-of-the-art PET estimation approaches.
关键词： Image synthesis,Positron emission topography (PET),Locality adaptive fusion,Generative adversarial networks (GANs),Multi-modality
更新于2025-09-23 15:21:01
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Irregular Astigmatism and Higher-Order Aberrations in Eyes With Dry Eye Disease
摘要： Visual disturbances were included in the de?nition of dry eye disease in the 2007 Dry Eye Workshop report. As a result, quality of vision (QoV) in dry eye patients has received increased attention. Corneal topography and wavefront sensors have been used to objectively and quantitatively evaluate optical quality, with data showing increases in irregular astigmatism and higher-order aberrations (HOAs) in dry eye patients. Furthermore, ocular optical characteristics are in?uenced by the tear ?lm, which constantly ?uctuates over time. Therefore, dynamic quantitative assessments of optical quality with continuous measurements are essential to understanding QoV in dry eye patients. This review summarizes what is known and what advances have been made in evaluating and understanding QoV in dry eye patients. In particular, corneal topographic and wavefront analyses, conducted both overseas and in Japan, are described.
关键词： wavefront sensor,dry eye,higher-order aberrations,corneal topography,irregular astigmatism
更新于2025-09-23 15:21:01
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Crystal growth and optical properties of Ca <sub/>3</sub> TaGa <sub/>3</sub> Si <sub/>2</sub> O <sub/>14</sub> single crystals
摘要： Transparent yellowish Ca3TaGa3Si2O14 single crystals were grown in Ar+(0.5–3)% O2 along the Y-axis by the Czochralski technique. The structural perfection of Ca3TaGa3Si2O14 samples was studied by X-ray topography and rocking curve methods. Topograms and rocking curves along the surfaces of the Y- and Z-cuts were studied before and after surface treatments (polishing and etching). Transmittance spectra were measured in the wavelength range of 200–3300 nm. Optical anisotropy was studied along the X- and Z-axes, and dichroism along the X-axis. The dispersions of the refractive index No and speci?c rotation of the polarization plane were determined using spectrophotometric methods.
关键词： optical properties,Czochralski technique,single crystals,Ca3TaGa3Si2O14,X-ray topography
更新于2025-09-23 15:21:01
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Assessment of anterior and posterior corneal indices using two Scheimpflug analyzers
摘要： Purpose: To assess the agreement between the elevation and curvature measurements of the anterior and posterior corneal surfaces obtained using the Galilei Dual Scheimpflug Analyzer and those obtained using the Pentacam single Scheimpflug system. Methods: This prospective, noninterventional, diagnostic study was conducted at the Department of Ophthalmology at the American University of Beirut (Medical Center) and included 60 eyes of 60 consecutive patients. Measurements were obtained using 2 different Scheimpflug analyzers (Galilei and Pentacam). The best-fit sphere was set at 8 mm in both machines. Pachymetry (CCT), anterior elevation (AE) and posterior elevation (PE), and curvature were assessed. Pearson’s correlation coefficients, comparison of means, and Bland-Altman plots were used to evaluate agreement between the 2 systems. Results: The average CCT (at the corneal apex) was 533 ± 35 μm and 532 ± 37 μm (p=0.980), the average central AE was 1.25 ± 3.95 μm and 2.29 ± 5.28 μm (p=0.964), and the average central PE was 4.19 ± 8.18 μm and 5.42 ± 14.05 (p=0.956) μm with the Galilei and Pentacam, respectively. Conclusion: The Scheimpflug analyzers correlated well in the assessment of pachymetry, elevation, and curvature.
关键词： Corneal pachymetry,Photography/instrumentation,Cornea/pathology,Cornea/anatomy & histology,Corneal topography
更新于2025-09-23 15:21:01
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[Developments in Earth Surface Processes] Remote Sensing of Geomorphology Volume 23 || Landslide analysis using laser scanners
摘要： The advent of light detection and ranging (LiDAR) (see Table 1 for acronyms) has revolutionized the study of landslides and geomorphology because it provides an extraordinarily fine resolution topography (Carter et al., 2001). Electronic components and computers at affordable prices have made this technique widely available since the beginning of the 21st century. The number of geoscientific publications is increasing at a nearly exponential rate since around 1990 demonstrating its impact on geosciences (Abellan et al., 2016).
关键词： LiDAR,landslides,geomorphology,topography,laser scanning
更新于2025-09-23 15:19:57
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Investigations in the fabrication of surface patterns for wettability modification on a Zr-based bulk metallic glass by nanosecond laser surface texturing
摘要： Laser texturing has previously been employed to enhance the wettability of metallic alloys. Such studies reported that modifying the wettability of a surface is a result of changes in both its topography and its chemistry. In this paper, an investigation about laser-induced surface wettability modification is also reported but for a less studied type of material in this context. In particular, nanosecond (ns) laser processing was employed to texture two types of surface patterns, i.e. dimples and grooves, on the surface of a Zr-based bulk metallic glass (BMG) known as Vitreloy 105. The specific focus of the research was on understanding the role played by both surface topography and chemistry modifications in changing the wettability of the original surface. Using static contact angle measurements, it was found that groove patterns enhanced the hydrophilicity of the original BMG, while dimple patterns weakened it. Based on the obtained 3D surface measurements and XPS data, it is suggested that the reduced hydrophilicity of dimple-textured surfaces was driven by the decrease of hydrophilic C=O and O=C-O bonds post laser processing. While these bonds were also reduced for groove-textured patterns, the hydrophilicity was still enhanced following laser irradiation as a result of the dominant role that a much larger induced surface roughness should play in this case.
关键词： Surface topography,Bulk metallic glass,Nanosecond laser surface texturing,Surface chemistry.,Wettability
更新于2025-09-23 15:19:57
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Study on laser annealing of niobium films deposited on copper for RF superconducting cavities
摘要： Niobium sputtered copper cavities were proposed as a kind of promising next generation superconducting cavities, but were still challenged by the Q-slope effect under high acceleration gradients. Current solutions focus on improving the film quality to make it more bulk-like, for which a higher substrate temperature is required. However, due to the limitation of the melting point of the copper substrate, both the deposition process and the post-annealing process cannot be performed at a high temperature. The laser annealing mentioned in this paper uses nanosecond pulsed laser as the heat source, and the local temperature field generated within the thickness scale of the niobium film can anneal the film without affecting copper substrate. Laser annealing system has been set up in Peking University, and experiments with niobium thin film on copper (Nb/Cu) samples have been carried out. Superconducting performance, surface topography and other properties of Nb/Cu samples before and after annealing are compared. Recrystallization of niobium films happened and various factors that may cause Q-slope have been suppressed according to the results. All these indicate the effectiveness of laser annealing and the possibility of being used in niobium sputtered copper cavities in the future.
关键词： Surface topography,Surface roughness,Recrystallization,Niobium thin film,Superconducting cavity,Laser annealing
更新于2025-09-23 15:19:57