High-resolution Surface Topography Research Articles

An integrated DEM code for tracing the entire regolith mass movement on asteroids

ABSTRACT This paper presents a general strategy for tracking the scale-span movement process of asteroid regolith materials. It achieves the tracking of the mass movement on the asteroid at a realistic scale, under conditions of high-resolution asteroid surface topography (submeter level) and actual regolith particle sizes. To overcome the memory exponential expansion caused by the enlarged computational domain, we improved the conventional cell-linked list method so that it can be applied to arbitrarily large computational domains around asteroids. An efficient contact detection algorithm for particles and polyhedral shape models of asteroids is presented, which avoids traversing all surface triangles and thus allows us to model high-resolution surface topography. A parallel algorithm based on Compute Unified Device Architecture for the gravitational field of the asteroid is presented. Leveraging heterogeneous computing features, further architectural optimization overlaps computations of the long-range and short-range interactions, resulting in an approaching doubling of computational efficiency compared to the code lacking architectural optimizations. Using the above strategy, a specific high-fidelity discrete element method code that integrates key mechanical models, including the irregular gravitational field, the interparticle and particle-surface interactions, and the coupled dynamics between the particles and the asteroid, is developed to track the asteroid regolith mass movement. As tests, we simulated the landslide of a sand pile on the asteroid’s surface during spin-up. The simulation results demonstrate that the code can track the mass movement of the regolith particles on the surface of the asteroid from local landslides to mass leakage with good accuracy.

Optical path optimization of chromatic line confocal displacement sensor for high resolution and wide range.

This study introduces the optical path-optimized dual-grating chromatic line confocal imaging (DG-LCI) technique for high-resolution and wide-range surface topography measurements. Chromatic line confocal imaging (LCI) finds extensive applications in high-speed 3D imaging of surface morphology, roughness analysis in industrial production, and quality inspection. A key advantage of LCI is its ability to achieve a large depth of focus, enabling the imaging system to measure a wide range in the Z direction. However, the challenge lies in the trade-off between the measurement range and resolution. Increasing the measurement range reduces the resolution, making it unsuitable for precise measurements required in industrial processing. Conversely, enhancing the resolution limits the measurement range, thereby sacrificing the advantage of LCI systems' broad measurement capabilities. Addressing this limitation, we propose a dual optical path dual-grating structure using a simplified and ingenious optical path optimization design. This design overcomes the challenge of sacrificing the millimeter-level measurement range while simultaneously improving the resolution. Rigorous simulations and experiments validate the effectiveness and validity of our proposed method.

Tactile Sensor Structure Optimized for Sliding Motion With High Resolution Recording of Surface Topography

The demand for tactile devices with human-like exquisiteness has recently been increasing in various fields. Among the various parameters that humans feel through the tactile system, temperature and surface topography are the most important parameters to achieve artificial tactile devices with human level precision. Here, we present a new tactile sensor with high resolution surface topography recording and temperature measurement. Our tactile sensor was designed to have a surface topography sensing part driven by P(VDF-TrFE) and a thermistor part for temperature sensing. Even though the sensor touched the same temperature object, the sliding condition showed different resistance change values. Therefore, the correlation factors of the sliding velocity to temperature were defined with a simple relation function. To achieve high resolution recording, ‘zig-zag’ arrayed tactile sensor can overcome the limitations of simple matrix cell design. The design eliminates empty spaces between sensor cells. By using these systems, a resolution of ~500μm to x-direction was achieved. This tactile sensor has linear sensitivity to pressure with a superior response time of 10ms for dynamic sensing. By integrating the dynamic piezoelectric signals during the sliding motion, we can reconstruct the surface topography of various objects.

Line laser scanning microscopy based on the Scheimpflug principle for high-resolution topography restoration and quantitative measurement.

A line laser scanning microscopy system with a larger depth of field based on the Scheimpflug principle is proposed for high-resolution surface topography restoration and quantitative measurement on miniature non-transparent samples. An imaging model based on the Scheimpflug principle is established, and a calibration method without system parameters is derived, which is further extended to a microscopic system. The measuring range of the system is 5m m×4m m×x m m, where x is the movement distance of the displacement stage. In the z-axis direction, the relative error of measurement is about 1% when z is of the millimeter level and less than 7% when z is of the micron level, and the spatial resolution is better than 3.8µm. In the y-axis direction, the relative error of measurement is less than 5%. Finally, three-dimensional scanning of two samples with different surfaces is carried out to verify the feasibility of the system. The experimental results show that our system has the capability of high-resolution topography restoration and can be applied in industrial production scenarios such as automatic measurement and intelligent identification.

Fault Damage Zone Effects on Ground Motions during the 2019 Mw 7.1 Ridgecrest, California, Earthquake

ABSTRACT We have simulated 0–3 Hz deterministic wave propagation in the Southern California Earthquake Center Community Velocity Model (CVM) version CVM-S4.26-M01 for the 2019 Mw 7.1 Ridgecrest earthquake. A data-constrained high-resolution fault zone model (Zhou et al., 2022) is incorporated into the CVM to investigate the effects of the near-fault low-velocity zone (LVZ) on the resulting ground motions, constrained by strong-motion data recorded at 161 stations. The finite-fault source used for the simulation of the Ridgecrest event was obtained from the Liu et al. (2019) kinematic inversion, enriched by noise following a von Karman correlation function above ∼1 Hz with a f−2 high-frequency decay. Our results show that the heterogeneous near-fault LVZ inherent to the fault zone structure significantly perturbs the predicted wave field in the near-source region, in particular by more accurately generating Love waves at its boundaries. The fault zone decreases the 0.1–0.5 Hz mean absolute Fourier amplitude spectrum bias to seismic recordings for all sites in the model and in the Los Angeles basin area (∼200 km from the source) by 16% and 26%, respectively. The fault zone structure generally improves modeling of the long-period features in the data and lengthens the coda-wave trains, in better agreement with observations. The favorable fit to data was obtained with a model including high-resolution surface topography, a 700-m-thick geotechnical layer and frequency-dependent anelastic attenuation in the model domain, with QS=0.1VS and QS(f)=0.1VSf0.5 (VS in m/s) for frequencies lower and higher than 1 Hz, respectively. We recommend that a data-constrained fault zone velocity structure, where available, be included in ground-motion modeling to obtain the least-biased fit to observed seismic data.

Angle-based wavefront sensing enabled by the near fields of flat optics

There is a long history of using angle sensors to measure wavefront. The best example is the Shack-Hartmann sensor. Compared to other methods of wavefront sensing, angle-based approach is more broadly used in industrial applications and scientific research. Its wide adoption is attributed to its fully integrated setup, robustness, and fast speed. However, there is a long-standing issue in its low spatial resolution, which is limited by the size of the angle sensor. Here we report a angle-based wavefront sensor to overcome this challenge. It uses ultra-compact angle sensor built from flat optics. It is directly integrated on focal plane array. This wavefront sensor inherits all the benefits of the angle-based method. Moreover, it improves the spatial sampling density by over two orders of magnitude. The drastically improved resolution allows angle-based sensors to be used for quantitative phase imaging, enabling capabilities such as video-frame recording of high-resolution surface topography.

Process design for 5-axis ball end milling using a real-time capable dynamic material removal simulation

For repairing turbine blades or die and mold forms, additive manufacturing processes are commonly used to build-up new material to damaged sections. Afterwards, a subsequent re-contouring process such as 5-axis ball end milling is required to remove the excess material restoring the often complex original geometries. The process design of the re-contouring operation has to be done virtually, because the individuality of the repair cases prevents actual running-in processes. Hard-to-cut materials e.g. titanium or nickel alloys, parts prone to vibration and long tool holders complicate the repair even further. Thus, a fast and flexible material removal simulation is needed. The simulation has to predict suitable processes focusing shape deviations under consideration of process stability for arbitrary complex engagement conditions. In this paper, a dynamic multi-dexel based material removal simulation is presented, which is able to predict high-resolution surface topography and stable parameters for arbitrary processes such as 5-axis ball end milling. In contrast to other works, the simulation is able to simulate an unstable process using discrete cutting edges in real-time.

Post-event surface deformation of Amyntaio slide (Greece) by complementary analysis of Remotely Piloted Airborne System imagery and SAR interferometry

The results of structure from motion photogrammetry and SAR interferometry as complementary techniques for measuring ground deformation induced by the massive open-pit landslide in Amyntaio, Greece (June 10, 2017), is presented in this paper. This unexpected slide damaged the entire westernmost marginal area of the pit, significant number of buildings, and infrastructures of the nearby village of Anargiri. The described methodology includes the generation of a multi-temporal dataset (from Sept. 2017 to Sept. 2018) of very high-resolution surface topography (at 10 cm), based on the analysis of imagery collected by Remotely Piloted Airborne Systems (RPASs). Satellite observations involved interferometric processing of TerraSAR-X data for a complementary estimation of ground displacement rates. Height differences from consecutive aerial photography campaigns as well as space-borne measurements provided valuable information on the evolution of the deformation and its spatial characteristics during the post-event period, an important aspect for future hazard and risk considerations.

Atmospheric response to high-resolution topographical and radiative forcings in a general circulation model of Venus: Time-mean structures of waves and variances

Thermal tides, stationary waves, and general circulation are investigated using a T63 Venus general circulation model (GCM) with solar and thermal radiative transfer in the presence of high-resolution surface topography, based on time average analysis. The simulated wind and static stability are very similar to the observed ones (e.g., Horinouchi et al., 2018; Ando et al., 2020). The simulated thermal tides accelerate an equatorial superrotational flow with a speed of ~90 m s−1 around the cloud-heating maximum (~65 km). The zonal-flow acceleration rates of 0.2–0.5 m s−1 Earth day−1 are produced by both horizontal and vertical momentum fluxes at low latitudes. In the GCM simulation, strong solar heating above the cloud top (>69 km) and infrared heating around the cloud bottom (~50 km) modify the vertical structures of thermal tides and their vertical momentum fluxes, which accelerate zonal flow at 103 Pa (~75 km) and 104 Pa (~65 km) at the equator and around 103 Pa at high latitudes.Below and in the cloud layer, surface topography weakens the zonal-mean zonal flow over the Aphrodite Terra and Maxwell Montes, whereas it enhances the zonal flow in the southern polar region. The high-resolution topography produces stationary fine-scale bow structures at the cloud top and locally modifies the variances in the geographical coordinates (i.e., the activity of unsteady wave components). Over the high mountains, vertical spikes of the vertical wind variance are found, indicating penetrative plumes and gravity waves. Negative momentum flux is also locally enhanced at the cloud top over the equatorial high mountains. In the solar-fixed coordinate system, the variances (i.e., the activity of waves other than thermal tides) of flow are relatively higher on the nightside than on the dayside at the cloud top. Strong dependences of the eddy heat and momentum fluxes on local time are predominant. The local-time variation of the vertical eddy momentum flux is produced by both thermal tides and solar-related, small-scale gravity waves.

Multi-view fringe projection system for surface topography measurement during metal powder bed fusion.

Metal powder bed fusion (PBF) methods need in-process measurement methods to increase user confidence and encourage further adoption in high-value manufacturing sectors. In this paper, a novel measurement method for PBF systems is proposed that uses multi-view fringe projection to acquire high-resolution surface topography information of the powder bed. Measurements were made using a mock-up of a commercial PBF system to assess the system's accuracy and precision in comparison to conventional single-view fringe projection techniques for the same application. Results show that the multi-view system is more accurate, but less precise, than single-view fringe projection on a point-by-point basis. The multi-view system also achieves a high degree of surface coverage by using alternate views to access areas not measured by a single camera.

Multi-scale measurement of high-reflective surfaces by integrating near-field photometric stereo with touch trigger probe

Precision measurement of large scale surface topography is a challenging task for high-reflective parts. This paper presents a multi-sensor system to address this issue by integrating the technical merits of touch trigger probe and photometric stereo. The probe is used to extract a set of high-precision sparse points for an initial surface construction, which is then applied to drive a near-field photometric stereo for recovering dense surface normal of the surface. By fusing the sparse discrete points with the dense surface normal, high-resolution surface topography can be obtained accordingly. Experiments confirm the state-of-the-art performance of the proposed method.

Cover Image, Volume 11, Issue 1

Cover Photograph: (Top Left) The polarization optical microscope images show the formation of crystalline microarchitectures in Na2Mn0.9Fe0.1P2O7 glass formed by laser irradiation. Formed crystal is one of the promising cathode active materials for sodium‐ion batteries. There are two structural polymorphs (beta‐ and layered‐ ) and can selectively form either of them according to the power of laser irradiation. Honma et al. DOI: 10.1111/ijag.14102. (Bottom Right) The apparent indentation fracture toughness of the silver and enamel layers deposited onto a glass substrate have been evaluated via SEM and high resolution surface topography images of the hardness imprints. The imprints are generated by nano‐indentation technique using a cube‐corner indenter. The determination of the fracture toughness by indentation consists in measuring the lengths of the cracks at the corners of the hardness impression. The absence of radial‐median cracks at the indents performed onto sintered silver provides clear evidence of the higher fracture toughness compared to enamel and glass, but prohibits a quantitative comparison. The soda‐lime silicate glass substrate has a homogeneous microstructure ensuring high repeatability onto the radial‐median cracks lengths resulting from the indentation. The average fracture toughness of the enamel layer is relatively complex to assess due to the multiphase microstructure. Walch and Roos DOI: 10.1111/ijag.13875. image

Polarimetric SAR Signatures for Characterizing Geological Units in the Canadian Arctic

This study investigates the polarimetric radar signatures of geological units in the Canadian Arctic to characterize their physical surface properties. It focuses on the Tunnunik and Haughton meteorite impact structures using RADARSAT-2 quad polarimetric synthetic aperture radar (SAR) data. The geological units show different three-dimensional (3-D) polarimetric SAR signature plots (i.e., radar backscattering responses according to the orientation and the ellipticity of a polarization state). We analyzed the quantitative relationship between the polarimetric SAR signatures of the geological units and their surface roughness. The pedestal height and the standard deviation of linear copolarization responses (SDLP) were calculated from the 3-D copolarization power signature plot, and then compared to in situ surface roughness measurements derived from LiDAR scanned high-resolution surface topography. The results show that the pedestal height has a positive correlation coefficient of ∼0.6 with surface roughness, while the SDLP has a negative correlation coefficient of ∼0.8 with surface roughness. The variation between the different polarization responses is highly dependent on the surface roughness of the geological units. The SDLP is thus suggested as a promising parameter to characterize surface roughness, in addition to the pedestal height that has been commonly used.

Voltage-controlled formation of short pitch chiral liquid crystal structures based on high-resolution surface topography.

Chiral nematic liquid crystals (CLCs) offer interesting perspectives for device applications and are fascinating materials to study because of their ability to self-assemble into complex structures. This work demonstrates that narrow lines of electron-beam resist on top of an ITO coated glass surface can dramatically influence the formation and growth of short pitch chiral superstructures in the bulk. By applying a voltage to the cell, directional growth of CLC structures along the corrugated surface can be controlled. Below the electric unwinding threshold, chiral structures start to grow along the grating lines with their helical axis parallel to the substrates. This results in a uniform lying helix-like structure at intermediate voltages and a chiral configuration with periodic undulations of the helical axis at low voltages.

Terahertz Polarization Imaging and Its Applications

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.

基于白光干涉频域分析的高精度表面形貌测量

基于白光干涉频域分析的高精度表面形貌测量

Marangoni Convection Assisted Single Molecule Detection with Nanojet Surface Enhanced Raman Spectroscopy.

Many single-molecule (SM) label-free techniques such as scanning probe microscopies (SPM) and magnetic force spectroscopies (MFS) provide high resolution surface topography information, but lack chemical information. Typical surface enhanced Raman spectroscopy (SERS) systems provide chemical information on the analytes, but lack spatial resolution. In addition, a challenge in SERS sensors is to bring analytes into the so-called "hot spots" (locations where the enhancement of electromagnetic field amplitude is larger than 103). Previously described methods of fluid transport around hot spots like thermophoresis, thermodiffusion/Soret effect, and electrothermoplasmonic flow are either too weak or detrimental in bringing new molecules to hot spots. Herein, we combined the resonant plasmonic enhancement and photonic nanojet enhancemnet of local electric field on nonplanar SERS structures, to construct a stable, high-resolution, and below diffraction limit platform for single molecule label-free detection. In addition, we utilize Marangoni convection (mass transfer due to surface tension gradient) to bring new analytes into the hotspot. An enhancement factor of ∼3.6 × 1010 was obtained in the proposed system. Rhodamine-6G (R6G) detection of up to a concentration of 10-12 M, an improvement of two orders of magnitude, was achieved using the nanojet effect. The proposed system could provide a simple, high throughput SERS system for single molecule analysis at high spatial resolution.

Dual interferometer for dynamic measurement of corneal topography.

The cornea is the anterior most surface of the eye and plays a critical role in vision. A thin fluid layer, the tear film, coats the outer surface of the cornea and serves to protect, nourish, and lubricate the cornea. At the same time, the tear film is responsible for creating a smooth continuous surface, where the majority of refraction takes place in the eye. A significant component of vision quality is determined by the shape of the cornea and stability of the tear film. A dual interferometer system for measuring the dynamic corneal topography is designed, built, verified, and qualified by testing on human subjects. The system consists of two coaligned simultaneous phase-shifting polarization-splitting Twyman–Green interferometers. The primary interferometer measures the surface of the tear film while the secondary interferometer tracks the absolute position of the cornea, which provides enough information to reconstruct the absolute shape of the cornea. The results are high-resolution and high-accuracy surface topography measurements of the in vivo tear film and cornea that are captured at standard camera frame rates.

Layer-dependent quantum cooperation of electron and hole states in the anomalous semimetal WTe2.

The behaviour of electrons and holes in a crystal lattice is a fundamental quantum phenomenon, accounting for a rich variety of material properties. Boosted by the remarkable electronic and physical properties of two-dimensional materials such as graphene and topological insulators, transition metal dichalcogenides have recently received renewed attention. In this context, the anomalous bulk properties of semimetallic WTe2 have attracted considerable interest. Here we report angle- and spin-resolved photoemission spectroscopy of WTe2 single crystals, through which we disentangle the role of W and Te atoms in the formation of the band structure and identify the interplay of charge, spin and orbital degrees of freedom. Supported by first-principles calculations and high-resolution surface topography, we reveal the existence of a layer-dependent behaviour. The balance of electron and hole states is found only when considering at least three Te–W–Te layers, showing that the behaviour of WTe2 is not strictly two dimensional.

High resolution topography utilizing a line scan stereo vision technique

High-resolution surface topography measurement using two line scan CCDs was proposed for full-field optical inspection of surface geometry and defects. Based on traditional stereo vision technique, a new configuration of dual linear CCD system was constructed and a novel algorithm for correspondence matching based on digital image correlation (DIC) technique was proposed for the determination of 3D coordinates. Depending on the desired resolution, a user-defined template was employed in the algorithm to accurately select the correspondence pairs in the line scan image. The OpenGL™ database was used to reconstruct the surface topography from the corresponding matched points. Experimental results show that the accuracy and repeatability in the sub-micrometer scale were established with the proposed technique, which can be further improved depending on the pixel resolution of the line CCD. Since larger specimen can be inspected at high-speed by the use of larger arrays with smaller pixel size, the dual vision system can be easily used for high-resolution 3D profile measurement and defect inspection in-line.