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Recent developments in keratoconus diagnosis
摘要： Introduction: Keratoconus and ectatic corneal diseases represent a hot area of research. The need to enhance diagnosis in order to recognize milder forms of the disease and identify inherent predisposition for ectasia progression has gained significant importance because of refractive surgery and also due to the development of new treatment modalities to treat ectatic corneal diseases. This article discusses the nomenclature related to the diagnostic tests used to characterize keratoconus and ectatic corneal diseases, providing a prospective discussion on the latest developments for the diagnosis and follow up of these conditions, including imaging modalities, biomechanical assessments, and an outlook in genetics and molecular biology. Areas covered: We performed an extensive Pubmed literature search, considering the latest developments in the diagnosis of keratoconus and additional ectatic corneal diseases. Expert Commentary: Corneal ectasia is characterized by biomechanical failure and stromal thinning, causing corneal bulging with subsequent visual impairment due to irregular astigmatism. Moderate and advanced stages are easily recognized, but the identification of mild or subclinical forms remains a challenge. Keratoconus is the most common ectatic corneal disease, being a bilateral, typically asymmetric and progressive corneal dystrophy. Corneal ectasia may occur unilaterally due to the impact from the environment, such as eye rubbing. The advent of refractive surgery and the development of new treatment modalities augmented the need for the diagnosis of milder forms of ectatic corneal disease and to document ectasia progression. Placido disc based corneal topography is sensitive to detect mild ectatic patterns in patients with relatively normal DCVA and biomicroscopy. However, the limitations of this technology are realized by the occurrence of post-refractive keratectasia despite normal anterior curvature maps and cases with suspicious topographic patterns that proceeded with LCV, based on advanced corneal imaging, resulting in documented stable outcomes. Corneal tomography, biomechanical assessment, and ocular wavefront analysis are among the diagnostic tools that enhance our ability to diagnose milder stages of keratoconus, or, even, to characterize ectasia susceptibility. Artificial intelligence and machine learning algorithms have been successful to integrate data and develop novel more accurate indices with enhanced sensitivity and specificity. This article discusses the latest developments in the diagnosis of keratoconus, including imaging modalities, biomechanical assessments, and an outlook in genetics and molecular biology.
关键词： ectasia,tomography,biomechanics,keratoconus,topography
更新于2025-09-23 15:19:57
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Improving the Reliability of Interference Measurements by using Several Wavelengths
摘要： Methods are proposed to improve the reliability of interference measurements of surface nanotopography with sharp height gradients that lead to ambiguity in determining the phase of interference signals. The effect of the total measurement error on the range of multiwavelength measurements is considered. The results of field experiments demonstrating an increase in the range of measurements of nanotopography by the proposed methods in comparison with single-wavelength measurements are given.
关键词： multiwavelength measurements,surface topography,interference measurements,partially coherent interferometry
更新于2025-09-19 17:15:36
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Terahertz Polarization Imaging and Its Applications
摘要： This review focuses on several recent research activities regarding precise and fast polarization-sensitive terahertz time-domain spectroscopy systems for imaging purposes, and explains three interesting application examples. Owing to modulation techniques that have recently been developed for the evaluation of the instantaneous terahertz electric-field (E-field) vector, fast and precise terahertz polarization imaging becomes feasible. This terahertz technology enables high-resolution surface topography, precise understanding of the spatial E-field vector distribution of the focused terahertz pulse, and examination of strain-induced birefringence in polymeric materials. These examples constitute a new application area of terahertz photonics with emphasis on both fundamental optics and industrial applications.
关键词： topography,birefringence,polarization,parabolic mirror,terahertz spectroscopy
更新于2025-09-19 17:15:36
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Disorder in H <sup>+</sup> -irradiated HOPG: effect of impinging energy and dose on Raman D-band splitting and surface topography
摘要： Disorder was induced in pristine highly oriented pyrolytic graphite (HOPG) by irradiation with H+ ions with energies of 0.4 MeV and 1 MeV, and doses of 1014 ions/cm2 and 1016 ions/cm2. Raman spectroscopy was used as the main technique to characterize different samples and gain new insights on the splitting of the D band into two components (D1 and D2), trying to correlate this feature of the vibrational spectrum with the impinging energy and dose. An increased ID2/IG ratio in comparison with ID1/IG was observed in the irradiated samples. This behavior indicates that the impinging energy mainly affects the D1 component, while the D2 component is strongly dominated by the dose. We expect a larger contribution of defects (originating from the rupture of C–C sp2 symmetry through the formation of C–H sp3 bonds) to the D2 component than to the D1 component. SQUID measurements of the irradiated samples showed an enhancement in the normalized remanence, as well as an increment in coercivity compared to pristine HOPG, consistent with H+-induced point-like defects as well as C–H bonds. AFM scanning after Raman and SQUID characterization showed a distribution of surface defects, which were ascribed to the burst of hydrogen blisters formed as a consequence of the irradiation process. The results presented in this work contribute to the current trend in nanotechnology in areas devoted to the control of properties by defect engineering in carbon-based materials.
关键词： ion–solid interactions,highly oriented pyrolytic graphite (HOPG),topography,Raman spectroscopy,disorder
更新于2025-09-19 17:15:36
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Non-intrusive measurements of free-water-surface profiles and fluctuations of turbulent, two-phase flow using 2-D laser scanner
摘要： For measuring free-water surfaces conventional methods, such as resistance-type probes, U-manometers, point gauges, ultrasonic sensors, etc. are still most commonly used in modern hydro engineering. These methods give accurate results at suitable flow conditions, but are insufficient when the water surface is characterized by turbulence and two-phase flow, with fast dynamics. This paper presents the use of laser scanning as a measurement method for the acquisition of free-water-surface profiles of hydraulic phenomena with turbulent, non-stationary, and non-homogeneous free-surface flows. Results shows that laser scanning can provide accurate measurements of free-water-surface profiles with high spatial and temporal resolution, even in cases of turbulent flows with high vertical fluctuations on the water surface. The comparison with the reference values determined by analysing the images taken with the high-speed camera showed that measurement uncertainty ranges from ±5 mm to ±10 mm, which is more than an order of magnitude smaller than the range of local vertical water-surface fluctuations. The average profiles, envelopes of vertical water surface fluctuation around the mean value, as well as the construction of complex water surface topography of intensive waving can be determined by processing laser scanning data. The results contribute to the wider use of this non-contact measurement method, which provides important information on water flow properties to many fields of hydro-engineering. The application of 2-D laser scanning for free-water-surface acquisition was conducted in the model of supercritical junction flow, where the development of standing waves leads to the phenomenon of self-aerated flow.
关键词： fluctuations,water surface topography,laser scanning,turbulent, two-phase flow
更新于2025-09-19 17:13:59
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Impact of pixel surface topography onto thin-film encapsulated top-emitting organic light-emitting diodes performances
摘要： Two di?erent designs of top-emitting green OLEDs (Organic Light-Emitting Diodes) have been studied. The ?rst one presents a planar OLED architecture. The second one presents an OLED having a topographic surface, so as to simulate a pixel partitioning of a display using an electrically insulating, 200 nm-thick, resist. It has been observed that the topography has a large impact on OLED performances. Studying devices using an ALD (Atomic Layer Deposition)-deposited Al2O3 barrier ?lm shows that topographic OLEDs have a lower stability under storage in 65 °C/85% RH conditions compared to planar ones, with a di?erence in ageing models between the two devices. As the ALD deposition technology has a high conformity, which implies that ALD-deposited Al2O3 barrier ?lms should be as good on topographic devices as on planar ones, we inferred that the topographic OLED Achilles’ heel lies rather in the OLED structure rather than in the Al2O3 encapsulation itself. Thus, topographic and planar unencapsulated OLEDs (without Al2O3) were studied: interestingly, it has been observed that planar OLEDs can live several weeks, while topographic OLEDs show a very short shelf lifetime (in laboratory atmosphere, at 21 °C/50% RH), of only a couple of hours. It will be shown that the topographic OLED surface tends to reduce the thickness of the PVD (Physical vapour Deposition)-deposited layers in the OLED, as this is expected for a non-conformal deposition PVD technique, on tapered angle regions of the resist (pixel edges). While this thickness variation would not be critical for thick electrodes, as for instance for bottom-emitting devices made on glass substrates, this thickness reduction turns out to be a critical point for the ultrathin, 15 nm, silver cathode, used as semi-transparent electrode in this top-emitting architecture and will therefore be discussed in the framework of using OLED top-emitting architectures in (micro)display technology.
关键词： Dark spots,Physical vapour deposition,Atomic layer deposition,Organic light-emitting diodes,Topography,Degradation
更新于2025-09-19 17:13:59
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Influence of double pulse ablation on the film topography in picosecond pulsed laser deposition of nickel
摘要： An approach to achieve co-axial picosecond laser pulsed pair is proposed. Instead of introducing additional optical devices, this method involves the adjustment of switching-out dynamics in the regenerative amplification process. Experimental results concerning the dependence of laser output behavior on the duration of the quarter-wave voltage applied on the Pockels cell are reported. The influence of ablation mode (single pulse or double pulse) on the morphology of deposited Nickel-films is studied. A significant improvement in the surface morphology with the double pulse mode is observed. Fewer nanoparticles are observed and the thin film appears to be smoother with lower roughness.
关键词： double pulse ablation,nickel,film topography,picosecond pulsed laser deposition
更新于2025-09-19 17:13:59
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Hydraulic Engineering Topographic Mapping and Modeling Based on Three Dimensional Laser Scanning Technology
摘要： Topographic mapping and modeling is one of the most basic and important work in hydraulic engineering construction. This paper present a work flow which contains data measurement, pre-process and post-process with three dimensional laser scan technology. By adopting B-tree and its expansion structure, a multi-level point cloud management and storage method has been established. Then propose a contour generation method based on scan data and the equivalent point interpolation data. A self-adaptive mesh Delaunay algorithm is introduced with point cloud data in order to generate triangular irregular network digital elevation model. Finally, the modeling accuracy and error has been analysis, the results proves this method is with high efficient and accuracy and can be provide assistance for the project construction.
关键词： topography,contour,hydraulic engineering,3D laser scan,3D model
更新于2025-09-16 10:30:52
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Topographic Measurement of Individual Laser Tracks in Alloy 625 Bare Plates
摘要： Additive manufacturing (AM) combines all of the complexities of materials processing and manufacturing into a single process. The digital revolution made this combination possible, but the commercial viability of these technologies for critical parts may depend on digital process simulations to guide process development, product design, and part qualification. For laser powder bed fusion, one must be able to model the behavior of a melt pool produced by a laser moving at a constant velocity over a smooth bare metal surface before taking on the additional complexities of this process. To provide data on this behavior for model evaluations, samples of a single-phase nickel-based alloy were polished smooth and exposed to a laser beam at three different power and speed settings in the National Institute of Standards and Technology Additive Manufacturing Metrology Testbed and a commercial AM machine. The solidified track remaining in the metal surface after the passing of the laser is a physical record of the position of the air–liquid–solid interface of the melt pool trailing behind the laser. The surface topography of these tracks was measured and quantified using confocal laser scanning microscopy for use as benchmarks in AM model development and validation. These measurements are part of the Additive Manufacturing Benchmark Test Series.
关键词： Additive manufacturing,Welding,Nickel-based superalloys,Topography data,Laser melt pool,Metals
更新于2025-09-16 10:30:52
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Surface dynamic deformation of LY2 aluminum alloy subjected to a laser shock wave planishing technique with different kinds of contacting foils
摘要： In this paper, a laser shock wave planishing technique (LSWP) was used to treat the LY2 aluminum alloy surface with corrugated structures, and the influence of contacting film material on the planishing effect was studied. The dynamic response characteristics of surface micro-features under different physical parameters of contacting foils were simulated by finite element simulation (FEM), and experimental verification was carried out. A close match between the experimental results with these simulation results in FEM was found. The planishing of surface micro-protrusions can reduce the surface roughness of treated sample, and the lifting of bottom materials can ensure the surface profile accuracy. The results demonstrate that the planishing effect on micro-protrusions improves with the density of the contacting foil decreasing; The lifting effect on the bottom material enhances with the strength of the contacting foil increasing. A high modulus of elasticity contacting foil also facilitates the bottom material bulging.
关键词： Micro-features,Aluminum alloy,Finite element modeling,Surface topography,Laser shock wave,Dynamic response
更新于2025-09-16 10:30:52