Reconstruction Of Surface Topography Research Articles

Sea ice melt pond bathymetry reconstructed from aerial photographs using photogrammetry: a new method applied to MOSAiC data

Abstract. Melt ponds are a core component of the summer sea ice system in the Arctic, increasing the uptake of solar energy and impacting the ice-associated ecosystem. They were thus one of the key topics during the 1-year drift campaign Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) in the Transpolar Drift 2019/2020. Pond depth is a dominating factor in describing the surface meltwater volume; it is necessary to estimate budgets and used in model parameterization to simulate pond coverage evolution. However, observational data on pond depth are spatially and temporally strongly limited to a few in situ measurements. Pond bathymetry, which is pond depth spatially fully resolved, remains unexplored. Here, we present a newly developed method to derive pond bathymetry from aerial images. We determine it from a photogrammetric multi-view reconstruction of the summer ice surface topography. Based on images recorded on dedicated grid flights and facilitated assumptions, we were able to obtain pond depth with a mean deviation of 3.5 cm compared to manual in situ observations. The method is independent of pond color and sky conditions, which is an advantage over recently developed radiometric airborne retrieval methods. It can furthermore be implemented in any typical photogrammetry workflow. We present the retrieval algorithm, including requirements for the data recording and survey planning, and a correction method for refraction at the air–pond interface. In addition, we show how the retrieved surface topography model synergizes with the initial image data to retrieve the water level of individual ponds from the visually determined pond margins. We use the method to give a profound overview of the pond coverage on the MOSAiC floe, on which we found unexpected steady pond coverage and volume. We were able to derive individual pond properties of more than 1600 ponds on the floe, including their size, bathymetry, volume, surface elevation above sea level, and temporal evolution. We present a scaling factor for single in situ depth measurements, discuss the representativeness of in situ pond measurements and the importance of such high-resolution data for new satellite retrievals, and show indications for non-rigid pond bottoms. The study points out the great potential to derive geometric properties of the summer sea ice surface emerging from the increasingly available visual image data recorded from uncrewed aerial vehicles (UAVs) or aircraft, allowing for an integrated understanding and improved formulation of the thermodynamic and hydrological pond system in models.

In situ build surface topography determination in electron beam powder bed fusion

Electron optical imaging is the most promising process monitoring method in electron beam powder bed fusion. State of the art in modern machines is the installation of a single detector in the top center of the build chamber. Exemplary applications are the reconstruction of digital twins of manufactured parts to compare their dimensional accuracy or analysing the top surface of each layer to identify surface features like pores or material transport. Multi-detector systems are currently under research and have shown great potential in reconstructing the surface topography in situ. A recently developed ray tracing model, describing the image formation process, allows to formulate design guide lines for multi-detector systems and provides a method for the computation of the normal vector field of the build surface. This work utilizes the recent progress and presents a newly developed four-detector system and an updated computation chain, which enable build surface topography reconstruction in situ in every layer of a build process. The computation chain contains a normal integration algorithm, which employs Tikhonov regularization to cope with measurement irregularities. The integration method is validated with ex situ measured as-built surfaces. Additionally, first applications are demonstrated and connections to process parameter changes illustrated.

Reconstruction and analysis of surface topography of micro-indented surface texture by chi-square function

During surface texture micro-indentation processing, the texture around the contact area will form protrusions. The morphology of these protrusions can change the actual contact area of the contact surface and affect the functional surface. To accurately describe the morphology of surface texture protrusions during the micro-indentation process, scaled chi-square functions are proposed to fit and further analyze their morphology. By simulation, the surface protrusion curve is generated by the micro-indenter head in different materials and depths. The scaled chi-square function is used to fit the extracted curves, and the fitted n value is used as an important characteristic parameter of the protrusion morphology. The study shows that the morphology of the protrusions is related to the material’s elastic modulus, yield strength, power law hardening exponent, and forming depth. Based on our results, it is convenient to judge the highest position and maximum height of the protrusions. The research findings will aid in the holistic design of micro-indentation surface textures, predicting their morphology, and selecting appropriate processes, while also being relevant for evaluating material performance post-micro-indentation with broad application prospects.

Three-dimensional Element-by-element Surface Topography Reconstruction of Compound Samples Using Multisegment Silicon Drift Detectors.

Elemental surface topography information in microscopic material characterization contributes to a better understanding of surfaces, interfaces, substrates, and their applications. Here, a general approach based on microbeam proton-induced X-ray emission (micro-PIXE) to reconstruct the three-dimensional (3D) elemental surface topography using the annular multisegment silicon drift detector has been demonstrated. The proposed method includes four main steps: acquiring four two-dimensional elemental concentration maps using the multichannel spectrometer, reconstructing the local inclination angle from the atomic model of ion-matter interaction, calculating the two independent topography gradient components, and numerical surface topography integration. In this study, the general algorithm to obtain the gradient components has been successfully tested on a four-segment configuration to reconstruct the 3D surface topography of compound alloys with different microstructure scales. In synchrotron and accelerator facilities dealing with elemental X-ray mapping where the development of customized multisegment detectors is needed, the introduced method is applicable to elemental surface/interface roughness reconstruction in microscale for cultural heritage samples, fusion plasma-facing materials, and microelectronic devices.

Application of four-segments annular Silicon drift detector for 3-D surface topography reconstruction by micro-PIXE

Information about the surface topography is very important to achieve the correct elemental concentrations from the 2D X-ray intensity maps in micro-PIXE. Previously, an innovative approach of stereo-PIXE has been introduced to reconstruct the surface topography using two X-ray spectrometers in the lateral direction of the detector positions. Here, we developed the stereo-PIXE method to the four-segment Silicon drift detector (SDD), mounted at the Jožef Stefan Institute (JSI) microprobe, by considering a set of stereovision maps acquired by orthogonal segments to reconstruct the surface topography both in the lateral and longitudinal directions of the scanned area. To this aim, X-ray intensity disparity from the opposing segments was simulated for an ideal flat inclined model of the sample to infer the inclination angle across the opposing segments. Then, the obtained two gradient components of the surface topography from the inclination angles, along the axes that connect the two opposing segments, were reoriented along the scanned area with a proper rotation angle. Thus, to reconstruct the 3-D sample surface topography profile, the integration of the surface topography gradient was numerically performed in the two dimensions along the sample surface. The feasibility of the method is demonstrated on the pure Ti sample with scratched structures.

Fast Measurement of Surface Topographies Using a Phase-Measuring Deflectometric Microscopy

With the fast development in the fields of photovoltaics and integrated circuits, the measurement of surface topographies and micro-scaled defects has attracted intensive interests. However, existing measurement methods are time-consuming and unsuitable for in-situ detection. Therefore, a fast topographic measurement method is developed based on the deflectometric microscope system. Microscopic deflectometry is an attractive tool due to its high sensibility to surface slopes and large dynamic range of measurement. For the quantitative reconstruction of surface topographies from slopes, an integration method is developed based on the minimum spanning tree, and the integration path is designed based on a sparse representation and a curl map. The robustness and accuracy of the integration method are validated by numerical simulation and experiments. This method can achieve a high measurement accuracy with a high lateral resolution and a depth of field of 90 μm, hereby improving the manufacturing efficiency and quality of opto-electronics functional devices.

Interface Wetting Driven by Laplace Pressure on Multiscale Topographies and Its Application to Performance Enhancement of Metal-Composite Hybrid Structure

Surface topography reconstruction is extensively used to address the issue of weak bonding at the polymer-metal interface of metal-composite hybrid structure, while enhancement from this approach is seriously impaired by insufficient interface wetting. In this study, the wetting behavior of polymer on aluminum surfaces with multiscale topographies was theoretically and experimentally investigated to realize stable and complete wetting. Geometric dimensions of multiscale surface topographies have a notable impact on interfacial forces at the three-phase contact line of polymer/air/aluminum, and a competition exists between Laplace pressure and bubble pressure in dominating the wetting behavior. Laplace pressure facilitates the degassing of trapped air bubbles in grooves, bringing more robust interfacial wettability to grooves than dimples and grids. Conversely, dimples with excessive dimensions generate interfacial pores, and this intrinsic mechanism is theoretically unraveled. Moreover, different degrees of interface wetting cause variations in bonding strength of polymer-aluminum interface, which changes from ∼18% improvement to ∼17% reduction compared to original strength. Finally, groove topography perfectly achieved complete wetting between polymer and aluminum and consequently improved flexure performance by over 11% for the aluminum-carbon fiber hybrid side impact bar, which verifies the importance of complete wetting at a part scale. This study deepens the understanding of wetting behavior and clarifies the intrinsic correlation between interfacial bonding performance and surface topography.

A divide and conquer approach for machined surface topography reconstruction in peripheral milling inconel 718

This paper proposes a reconstruction procedure to characterize the texture of milled surfaces following the principle of a divide and conquer algorithm. It is a combination of a numerical simulation of the systematic component of the surface topography with the stochastic features of surface roughness. Firstly, the milled surface topographies are decomposed into kinematic and random components, both of them are calculated separately. Then, the kinematic components are numerically simulated based on relative motion between milling tool and workpiece. The random components are numerically simulated by fast Fourier transform (FFT) and the Johnson transform system. The measured and kinematic topographies are aligned fitting orientation and position by point clouds registration. Finally, the milled surface topographies are reconstructed by superposition of kinematic and random components based on the alignment datum. The proposed approach is applied to surface topography simulation and surface roughness prediction in peripheral milling Inconel 718. The milled surface topographies can be simulated by using the milling parameters as input parameters of the proposed model. The validation tests were carried out in Inconel 718 peripheral milling. The results show that the proposed approach has high accuracy in topography simulation and roughness prediction. The relative errors of predicted S a values are less than 7.55% in all the case studies of this paper. The effect of cutting parameters on roughness S a is sorted as follows, radial cutting depth > cutting speed > feed rate. In addition, the feed rate greater than 0.01 mm tooth−1 should be selected as far as possible in milling Inconel 718.

Method for reconstruction of axisymmetric capillary wave surface topography using inverse ray-tracing of refracted laser sheet

Capillary waves can be used to measure the fundamental fluid properties such as surface tension as well as, potentially, the viscosity of Newtonian fluids. This requires the measurement of various wave parameters, mainly wavelength, amplitude, and decay coefficient. However, the different scales of magnitudes make it a challenging task. Optical methods are well suited to analyze such problems due to their non-intrusive nature and high dynamic measurement resolution in both space and time. These methods are further categorized as point methods for a single probe measurement and space–time methods for transient measurement of the complete surface. Dynamic space–time methods are preferred despite the associated complex post-processing since they enable reconstruction of the wave surface. Some existing methods are discussed, and an improved method is then proposed to actually solve the associated inverse optics problem. In the method, an axisymmetric wave surface is re-constructed by analyzing the refracted laser sheet. The assumptions, simplifications, and constraints are taken to be compatible with experimental aspects for future validation. It is derived using the fundamental concepts in physics and the only major assumption of the axisymmetric nature of wave surface. The method exploits the underlying symmetry in the topography, making it more versatile, and suited for linear and non-linear capillary waves and waves with planar wavefront. The impact of parameters on the final result is determined through numerical simulations. Very low error (average and maximum) values are observed between reference and reconstructed topography for damped and undamped wave surfaces with a wide range of curvatures. Optimum values of critical parameters and associated reasoning are presented.

In-situ 3D reconstruction of worn surface topography via optimized photometric stereo

Since worn surfaces contain rich information of the wear mechanisms, in-situ measurements of surface topography can characterize ongoing wear degradation in machines. With the help of photometric stereo vision, three-dimensional (3D) topography of worn surfaces is obtained with a monocular microscope. However, the accuracy of the reconstructed surfaces remains low due to the non-Lambertian reflections of worn surfaces and noise in the image acquisition equipment. To address this issue, an optimized photometric stereo approach is proposed for the improvement of worn surface reconstruction. To accommodate the non-Lambertian reflections, a multi-branch network is constructed to estimate normal vectors from both the photometric images and the incident illumination directions. The estimated normal vectors are adopted to reconstruct worn surface topography by embedding prior knowledge. With this design, the overall distortion caused by image noise is effectively suppressed. The proposed method is verified by comparing with the Laser Scanning Confocal Microscopy (LSCM). As the main result, over 88% similarity on the worn surface roughness can be obtained.

A Single Image 3D Reconstruction Method Based on a Novel Monocular Vision System.

Three-dimensional (3D) reconstruction and measurement are popular techniques in precision manufacturing processes. In this manuscript, a single image 3D reconstruction method is proposed based on a novel monocular vision system, which includes a three-level charge coupled device (3-CCD) camera and a ring structured multi-color light emitting diode (LED) illumination. Firstly, a procedure for the calibration of the illumination’s parameters, including LEDs’ mounted angles, distribution density and incident angles, is proposed. Secondly, the incident light information, the color distribution information and gray level information are extracted from the acquired image, and the 3D reconstruction model is built based on the camera imaging model. Thirdly, the surface height information of the detected object within the field of view is computed based on the built model. The proposed method aims at solving the uncertainty and the slow convergence issues arising in 3D surface topography reconstruction using current shape-from-shading (SFS) methods. Three-dimensional reconstruction experimental tests are carried out on convex, concave, angular surfaces and on a mobile subscriber identification module (SIM) card slot, showing relative errors less than 3.6%, respectively. Advantages of the proposed method include a reduced time for 3D surface reconstruction compared to other methods, demonstrating good suitability of the proposed method in reconstructing surface 3D morphology.

Gait parameters during the Timed Up-and-Go dual-task test: A validation study of video-recorded data

Surface topography can be used for the evaluation of spinal deformities without any radiation. However, so far this technique is limited to posterior trunk measurements due to the use of a single posterior camera.Purpose of this study was to introduce a new multi camera surface topography system and to test its reliability and validity.The surface topograph uses a two-camera system for imaging and evaluating the subjects front and back simultaneously. Inter- and intra-rater reliability was tested on 40 human subjects by two observers. For validation human, subjects were scanned by MRI and surface-topography. For additional validation we used a phantom with an anthropomorphic body which was scanned by CT and surface topography.Inter- (0.97−0.99) and intra-rater reliability (0.81−0.98) testing revealed good and excellent results in the detection of the body surface structures and measurement of areas and volumes. CT based validation revealed good correspondence between systems in the imaging and evaluation of the phantom model (0.61–10.52 %). Results on validation of human subjects revealed good to moderate results in the detection and measurements of almost all body surface structures (1.36–13.34 %). Only measurements using jugular notch as a reference showed moderate results in validity (0.62–27.5%) testing.We have introduced a novel and innovative surface topography system that allows for simultaneous anterior and posterior trunk measurements. The results of our reliability and validity tests are satisfactory. However, in particular around the jugular notch region further improvements in the surface topography reconstruction are needed.

Introduction and evaluation of a novel multi-camera surface topography system

BackgroundSurface topography can be used for the evaluation of spinal deformities without any radiation. However, so far this technique is limited to posterior trunk measurements due to the use of a single posterior camera. Research questionPurpose of this study was to introduce a new multi camera surface topography system and to test its reliability and validity. MethodsThe surface topograph uses a two-camera system for imaging and evaluating the subjects front and back simultaneously. Inter- and intra-rater reliability was tested on 40 human subjects by two observers. For validation human, subjects were scanned by MRI and surface-topography. For additional validation we used a phantom with an anthropomorphic body which was scanned by CT and surface topography. ResultsInter- (0.97−0.99) and intra-rater reliability (0.81−0.98) testing revealed good and excellent results in the detection of the body surface structures and measurement of areas and volumes. CT based validation revealed good correspondence between systems in the imaging and evaluation of the phantom model (0.61–10.52 %). Results on validation of human subjects revealed good to moderate results in the detection and measurements of almost all body surface structures (1.36–13.34 %). Only measurements using jugular notch as a reference showed moderate results in validity (0.62–27.5%) testing. SignificanceWe have introduced a novel and innovative surface topography system that allows for simultaneous anterior and posterior trunk measurements. The results of our reliability and validity tests are satisfactory. However, in particular around the jugular notch region further improvements in the surface topography reconstruction are needed.

Online reconstruction of surface topography along the entire cutting path in peripheral milling

This paper presents a novel method for online reconstruction of 3D surface topography in peripheral milling. Compared with the traditional surface topography modeling only focusing on local features as well as losing the time and location information, the presented method can accurately depict not only the variation of dynamic characteristics and the topography features within the local scope, but also along the entire cutting path. Meanwhile, the actual machining time and workpiece location information are introduced in surface topography modeling by using sensor information. The multi-sensor information, including cutting force signals and the eddy current sensor information in multiple directions, is employed to model dynamic factors, namely the vibration relating to deflection of cutting tool and the machining system characteristics, respectively. Two parts of work are carried out on modeling the vibration relating to deflection along the entire cutting path. First, a method based on the Kolmogorov-Smirnov test is applied to the real-time force signals, where the force signals between the entrance and exit points of the cutting teeth along the entire cutting path can be automatically extracted. Second, combining with an axial weight distribution model of the instantaneous cutting thickness, the extracted force signals can be transformed into the required force factors and correspondingly nonlinearly distributed along the instantaneous cutting depth. A piecewise cubic Hermite algorithm is then introduced to create the discrete values of the dynamic factors as continuous models without losing original precision. The continuous models are successfully coupled into ideal cutting edge trajectory equation to form a surface topography model. Further, a numerical algorithm with the characteristics of self-searching function is performed to solve the surface topography model, any point on the workpiece surface can be precisely reconstructed and thus formed the reconstructed surface topography. Eventually, cutting experiments were conducted to validate the effectiveness of the proposed method by comparing the measured and reconstructed results. A good agreement on all the quantitative and qualitative indicators is found. The results demonstrate that the proposed method can accurately realize an online reconstruction of the surface topography along the entire cutting path, and is also an appropriate monitoring approach for a number of features on surface topography (e.g., surface roughness, form deviation).

Reverse reconstruction of surface topography from residual stress after chip‐forming machining of the material

AbstractResidual stress is induced in the sample of a material stressed by external forces (tension, pressure, thermal stress, etc.) from the beginning of the stress. An instantaneous level is a function of the intensity of the external deformation work, the time and speed of the deformation, and the degree of immediate surface and volume deformation. It is proportional to the individual deformation limits, i. e., the elastic limit, yield point, flexural strength and breach limit; the maximum is reached at the level of the breach limit. Furthermore, it is dependent on the physical‐mechanical properties of the material and on the method, i. e., the technology of straining, or machining. The same applies to the roughness distribution and other topographical features on the machined surface. The tension that has not been exhausted is partly returned to the volume of the sample and partly acts in contact with space, within a certain distance and time. This paper aims to present a reverse reconstruction of the surface topography from residual stresses after chip‐forming machining of the material. Our original approach to the solution fully exploits the rules of roughness distribution and other topographic features of the surfaces of the given materials after machining, not only by chip‐forming machining.

Effect of Hydrogen Plasma on the Bismuth Single Crystal Surface

The data of atomic force microscopy studies of the cleavage surface morphology of a bismuth single crystal after exposure to atomic hydrogen are presented. It has been established that as a result of exposure to atomic hydrogen, nanocrystalline formations appear on the cleavage plane. The mechanism and features of the surface topography reconstruction are discussed. New data on the hierarchy of nano-formations are presented.

Low-Frequency Vibration Monitoring System Based on Optical Image Phase Method With Different Fringe Patterns

A rapid low-frequency vibration monitoring system based on fringe projection is introduced. Fourier transform profilometry is used to obtain the three-dimensional surface topography reconstruction of the vibrating object at each sampling moment. Then the height value of the selected point on the measured vibrating object at each moment is arranged by time and drawn as a trajectory curve. Finally, the frequency and the amplitude of the vibration could be calculated by the drawn trajectory curve and the sampling rate of the CCD camera. To confirm the reliability of this method, three different kinds of fringes are projected onto the measured object. It shows that the measurement results are more accurate when adopting sinusoidal wave as the fringe pattern, and the system could detect the vibration of whose frequency is above 0.01Hz or whose amplitude is more than $30\mu \text{m}$ . The study could be better introduced in this system to be applied to the field of industrial vibration measurement and dynamic vibration monitoring.

Three‐dimensional reconstruction of fluvial surface sedimentology and topography using personal mobile laser scanning

AbstractHigh‐resolution quantification of fluvial topography has been enabled by a number of geomatics technologies. Hyperscale surveys with spatial extents of <1 km2 have been widely demonstrated by means of terrestrial laser scanning (TLS) and structure‐from‐motion (SfM) photogrammetry. Recent advances in the development and integration of global navigation satellite system (GNSS), inertial measurement unit (IMU) and lightweight laser scanning technologies are now resulting in the emergence of personal mobile laser scanners (MLS) that have the potential to increase data acquisition and processing rates by one to two orders of magnitude compared to TLS/SfM, and thus challenge the recent dominance of these technologies. This investigation compares a personal MLS survey using a Leica Pegasus Backpack that integrates Velodyne Puck VLP‐16 sensors, and a multi‐station static TLS survey using a Riegl VZ‐1000 scanner, to produce digital elevation models (DEMs) and surface sedimentology maps. The assessment is undertaken on a 500 m long reach of the braided River Feshie. Comparison to 107 independent real‐time kinematic (RTK)‐GNSS check points resulted in similar mean error (ME) and standard deviation error (SDE) for TLS (ME = −0.025 m; SDE = 0.038 m) and personal MLS (ME = −0.014 m; SDE = 0.019 m). Direct cloud‐to‐cloud (C2C) comparison between a sample of TLS and personal MLS observations (2.8 million points) revealed that C2C distances follow a sharply decreasing Burr distribution (a = 2.35, b = 3.19, rate parameter s = 9.53). Empirical relationships between sub‐metre topographic variability and median sediment grain size (10–100 mm) demonstrate that surface roughness from personal MLS can be used to map median grain size. Differences between TLS and personal MLS empirical relationships suggest such relationships are dependent on survey technique. Personal MLS offers distinct logistical advantages over SfM photogrammetry and TLS for particular survey situations and is likely to become a widely applied technique. © 2019 John Wiley & Sons, Ltd.

Application of three-dimensional confocal x-ray fluorescence equipment in surface topography and depth contour scanning.

Three-dimensional microfocus x-ray fluorescence technology has been used to determine surface topography. The surface scanning technique initially facilitated surface topography reconstruction of the sample. This paper demonstrates the improved performance of its infrastructure, including a higher-precision translation platform, an ultrabright microfocus x-ray source and a rewritten scanning algorithm, leading to a new scanning technology that can depict the surface topography of samples with complex internal structures. The improved scanning technology can analyze the metal element information of layers at different depths. This paper presents studies of the surface and depth of coins and porcelain bottles from ancient times using this technique.

Research on 3D Reconstruction Technology of Tool Wear Area

The operators' poor adaptability on photos and difficulties of removing background point and noise point and other problems make the conventional focusing synthesis techniques difficult to get better application and promotion in the field of three-dimensional reconstruction. In this paper, a modified Laplacian operator was used as an evaluation basis to select focus points and the theory of three-dimensional reconstruction was discussed from the perspectives of image multilayer composite algorithm and height interpolation. To solve the problem of removing noise point and background point, a double threshold selection technique was proposed, which greatly improved the adaptability of focusing evaluation operator. Finally, a test on three-dimensional reconstruction of the tool wear's surface topography was conducted.