Laser Profile Research Articles

Mineralogy and lithology of the Upper Cretaceous Niobrara Formation determined by hyperspectral core imaging

Sections of the Upper Cretaceous (Coniacian to Campanian) Niobrara Formation in two cores from Kansas and Colorado, the Amoco Rebecca Bounds and USGS Portland 1, respectively, were examined by hyperspectral core imaging and analysis. A spectral imaging system combining high-resolution photography (50 μm), 3D laser profiling (20 μm), and near-visible + short-wave infrared reflectance spectroscopy (wavelengths from 450 to 2500 nm, 500 μm pixel size) was applied to these cores to provide spectral and textural data facilitating creation of continuous mineral and lithology class maps. In addition, compositing of pixel-based results to group pixels to create mineralogical and lithological logs (0.5-ft resolution) was performed to facilitate comparisons to other geochemical datasets. The results show general correspondence in trends identified by previous geochemistry studies, with some exceptions due to instrumental limitations related to low reflectance of some rock intervals and the limited range of infrared wavelengths examined. This study provides a cursory overview of an extensive dataset meant to demonstrate the utility of hyperspectral core scanning to studies of mudrocks in petroleum systems as well as the kinds of information this technique can provide for detailed examination of stratigraphic features in sedimentary systems more generally.

Laguerre-Gaussian Mode Laser Heater for Microbunching Instability Suppression in Free-Electron Lasers.

Microbunching instability (MBI) driven by beam collective effects is known to be detrimental to high-brightness storage rings, linacs, and free-electron lasers (FELs). One known way to suppress this instability is to induce a small amount of energy spread to an electron beam by a laser heater. The distribution of the induced energy spread greatly affects MBI suppression and can be controlled by shaping the transverse profile of the heater laser. Here, we present the first experimental demonstration of effective MBI suppression using a LG_{01} transverse laser mode and compare the improved results with respect to traditional Gaussian transverse laser mode at the Linac Coherent Light Source. The effects on MBI suppression are characterized by multiple downstream measurements, including longitudinal phase space analysis and coherent radiation spectroscopy. We also discuss the role of LG_{01} shaping in soft x-ray self-seeded FEL emission, one of the most advanced operation modes of a FEL for which controlled suppression of MBI is critical.

Convolutional neural networks for pavement roughness assessment using calibration‐free vehicle dynamics

AbstractRoad roughness is a measure of how uncomfortable a ride is, and provides an important indicator for the needs of roadway maintenance or repavement, which is closely tied to the state and federal budget prioritization. As such, accurate and timely monitoring of deteriorating road conditions and following maintenance are essential to improve the overall ride quality on the road. Various technologies, including vehicle‐mounted laser profiling systems, have been developed and adopted for road roughness (e.g., IRI—International Roughness Index) measurement; however, their high cost limits their use. While recent advances in smartphone technologies allow us to use their embedded accelerometers for road roughness monitoring, the complicated process of necessary vehicle calibration hinders the widespread use of the technology in the actual practices. In this work, a deep learning IRI estimation method is proposed with the goal of using anonymous (i.e., calibration‐free) vehicles and their responses measured by smartphones as road roughness sensors. A state‐of‐the‐art deep learning algorithm (i.e., CNN—convolutional neural network) and multimetric vehicle dynamics data (i.e., accelerometer, gyroscope), possibly measured by drivers’ smartphones, are employed for the purpose. Optimized CNN architecture and data configuration have been investigated to achieve the best performance. The efficacy of the proposed method has been numerically validated using real road IRI information (i.e., Speedway, Tucson, AZ), real driving speed profiles, and four different types of vehicle data with associated uncertainties.

Time-dependent 3D modeling of the thermal analysis of the high-power diode laser hardening process

In this paper, the thermal analysis of the high-power diode laser hardening process was modeled on AISI 4130 steel. Afterward, the depth and width of hardness were predicted based on the complete austenite temperature (AC3). Due to the dimensions and output beam power of the diode laser stack (DLS), it is impossible to achieve the suitable power density (103-105 W/cm2). Furthermore, the output intensity profile of the DLS is not homogeneous because of the pitch between the emitters. Thus, to achieve a suitable power density and a uniform beam profile, an optical layout was designed. The beam profile was experimentally obtained by a beam profiler at different distances from the focal plane and was compared with the modeling results. Due to the agreement between the modeling and experimental results, the intensity value of each mesh of the laser profile was extracted from the ZEMAX software. Then, for the thermal analysis of the laser hardening process (LHP), it was entered as a heat flux input into the COMSOL Multiphysics software.

Improving MRI's slice selectivity in the presence of strong, metal-derived inhomogeneities

PurposeTo develop schemes that deliver faithful 2D slices near field heterogeneities of the kind arising from non-ferromagnetic metal implants, with reduced artifacts and shorter scan times. MethodsAn excitation scheme relying on cross-term spatio-temporal encoding (xSPEN) was used as basis for developing the new inhomogeneity-insensitive, slice-selective pulse scheme. The resulting Fully refOCUSED cross-term SPatiotemporal ENcoding (FOCUSED-xSPEN) approach involved four adiabatic sweeps. The method was evaluated in silico, in vitro and in vivo using mice models, and compared against a number of existing and of novel alternatives based on both conventional and swept RF pulses, including an analogous method based on LASER's selectivity spatial selectivity. ResultsCalculations and experiments confirmed that multi-sweep derivatives of xSPEN and LASER can deliver localized excitation profiles, centered at the intended positions and endowed with enhanced immunity to B0 and B1 distortions. This, however, is achieved at the expense of higher SAR than non-swept counterparts. Furthermore, single-shot FOCUSED-xSPEN and LASER profiles covered limited off-resonance ranges. This could be extended to bands covering arbitrary off-resonance values with uniform slice widths, by looping the experiments over a number of scans possessing suitable transmission and reception offsets. ConclusionsA series of novel approaches were introduced to select slices near metals, delivering robustness against Bo and B1+ field inhomogeneities.

Road profile estimation and half-car model identification through the automated processing of smartphone data

This paper proposes a robust road profile estimation method and vehicle parameter identification method through an optimization with an objective function and constraint conditions on estimated profiles. The methods require only vehicle response measurements, enabling easy and inexpensive, yet effective, road condition monitoring through the automated processing of smartphone data. A half-car (HC) model, representing both bouncing and pitching motions, is employed for the profile estimation. The road profiles at the front and rear tire locations are included as state variables in the augmented state vector and are estimated by combining the augmented Kalman filter (AKF), Robbins–Monro (RM) algorithm, and Rauch–Tung–Striebel (RTS) smoothing. The two independent state variables, however, correspond to a single physical profile, while their distance coordinates differ by the wheelbase. Therefore, the vehicle parameters are optimized through the minimization of the difference between the identified road profiles at the front and rear tire locations using a genetic algorithm. Three objective functions and three constraint conditions are proposed to automatically select the best vehicle parameters. With this HC model, the road profile is subsequently estimated by combining the AKF, RM, and RTS methods. Through numerical simulations, the accuracy of the profile estimation and validity of the parameter identification are clarified. The influences of different drive speeds and difference between the left and the right profiles are numerically investigated. Drive tests with three different vehicles and a reference laser profiler show that the algorithm can automatically compensate for differences among vehicles with different drive speeds and estimate profiles accurately.

Real-time filtering on parallel SIMD architectures for automated quality inspection

Surface metrology in automated quality inspection is a field, among many others, affected by noise and thus requiring filtering. In surface metrology, filtering is required to remove undesired information from data in order to extract surface features and relevant properties necessary for quality control. Moreover, filtering requires immediate results, while the product is being manufactured. This way, quick correcting actions can be directly applied to solve possible manufacturing issues. This work proposes different strategies to filter height maps in real-time acquired using laser profilers, the most widely used inspection method in industrial applications. Different models to apply the filtering operations are considered, particularly assessing different alternatives to store previous samples in memory, which are required for data filtering. FIFO, double FIFO, circular and double circular buffers are evaluated. Furthermore, CPU parallelism, SIMD instructions and cache-line friendly data structures are analyzed. The proposed methods are extremely efficient, capable of filtering laser profiles at extremely high acquisition rates. The proposed methods are designed for real-time surface metrology, but they are very likely to find potential applications in different areas. The filters are compared in terms of accuracy and speed, including other well-known filters such as the spline filter. Tests analyze execution time, including cache efficiency and filtering accuracy. Results with synthetic data and real data obtained from steel strips show excellent performance, providing accurate results at very high speeds.

Sensors Offer Nuclear Options

A 2D laser profile sensor is being used by the Nuclear Advanced Manufacturing and Research Centre (Nuclear AMRC) in a project to develop a smart robotic grinding/deburring solution for welded components.

Impact of laser stacking and photocathode materials on microbunching stability in photoinjectors

Microbunching instability is a well-known phenomenon that may deteriorate the performance of accelerators. The instability may be triggered by a shot-noise mechanism or by some initial intensity modulations at the generation of the electron bunch (or both) and can be amplified all along the machine. At SwissFEL, the free-electron laser (FEL) facility operating at the Paul Scherrer Institute (PSI), the initial design stipulated a shaping of the photocathode laser output to obtain a flat-top longitudinal profile. This scheme is attractive in terms of the uniformity of the beam properties along the bunch. The drawback of this approach is that some unavoidable modulations are generated along the laser pulse. We investigate, both experimentally and by numerical simulations, the longitudinal dynamics of a beam obtained illuminating a copper cathode with a laser profile shaped by the stacking technique. We repeat the analysis for several compression factors and initial laser profile modulations. We find that the microbunching instability gain renders the use of the stacking technique not efficient to run a free-electron laser facility using as photocathode a material with a short response time. We experimentally demonstrate that the use of a material with a longer response time efficiently damps the structures originating from the laser profile obtained with stacking, and helps to improve the performance of the facility. In general, this is an approach to minimize the microbunching instability at any FEL (also not using stacking) or at least reduce the use of other countermeasures, which, such as the laser heater, may degrade the final FEL performance.

Efficient terahertz (THz) generation by nonlinear mixing of bicolor top-hat lasers in hot plasma

We report a theoretical model of radially polarized terahertz (THz) wave emission by nonlinear mixing of bicolor, radially polarized lasers having a top-hat envelope profile [s (profile index)≥1] in density modulated hot plasma. We investigate the effect of the laser profile index on the emitted THz field profile and found that THz field amplitude and peak location changes with the laser profile index. Our numerical investigations show that THz field amplitude is the highest around ωp≈ω1−ω2 (where ωp is the plasma frequency and ω1 and ω2 are the laser frequencies). We observe that phase matching can be achieved with the help of the plasma density modulation wave number. The plasma density modulation wave number increases with electron temperature and decreases with the frequency mismatch between ωp and ω1−ω2. We found that the conversion efficiency is maximum at ω1−ω2≈ωp and increases fivefold with an increase in electron thermal velocity (vth) from vth=0 to vth=0.2c, where c is the speed of light.

Light Drone-Based Application to Assess Soil Tillage Quality Parameters.

The evaluation of soil tillage quality parameters, such as cloddiness and surface roughness produced by tillage tools, is based on traditional methods ranging, respectively, from manual or mechanical sieving of ground samples to handheld rulers, non-contact devices or Precision Agriculture technics, such as laser profile meters. The aim of the study was to compare traditional methods of soil roughness and cloddiness assessment (laser profile meter and manual sieving), with light drone RGB 3D imaging techniques for the evaluation of different tillage methods (ploughed, harrowed and grassed). Light drone application was able to replicate the results obtained by the traditional methods, introducing advantages in terms of time, repeatability and analysed surface while reducing the human error during the data collection on the one hand and allowing a labour-intensive field monitoring solution for digital farming on the other. Indeed, the profilometer positioning introduces errors and may lead to false reading due to limited data collection. Future work could be done in order to streamline the data processing operation and so to produce a practical application ready to use and stimulate the adoption of new evaluation indices of soil cloddiness, such as Entropy and the Angular Second Moment (ASM), which seem more suitable than the classic ones to achieved data referred to more extended surfaces.

Parametric optimization of pulse-echo laser ultrasonic system for inspection of thick polymer matrix composites

One of the main challenges of using laser ultrasonic techniques for non-destructive testing applications is the typically low signal-to-noise ratio of the laser ultrasonic signals. In the case of thick composite structures, this is even more problematic since composite materials have very strong sound attenuation. This article investigates the effects of laser beam size and profile to the amplitude of pulse-echo laser ultrasonic signals with the constraint that the peak energy density (fluence) must be kept constant under the thermal damage threshold of material like polymer matrix composites. Such constraint is very important for the non-destructive feature of non-destructive testing, yet in a number of the existing parameter studies of laser ultrasonics, it was not fully investigated. In this article, a series of A-scan and C-scan experiments on thick composite specimens shows that the amplitude of the direct waves and the reflected waves increases with the increase in laser beam size with constant peak energy density. This amplitude enhancement significantly improves the propagation depth, thereby optimizing the system for inspection of thick composite structures. The validity of experimental results is verified theoretically by solving the thermoelastic model of epicenter displacement using Laplace–Hankel transformation.

Error Analysis and Calibration for a Novel Pipe Profiling Tool

Integrity of industrial pipework is ensured through routine inspection. Internal visual inspection tools are capable of characterising degradation in the form of corrosion, pitting, erosion and cracking. The accuracy of such inspection systems has a direct impact on decisions regarding the remaining lifetime of the asset. By minimising error margins, the asset may be operated with confidence for longer, with less uncertainty. This paper considers a probe system consisting of a laser profiler and camera that produces a textured 3D model of the internals of 2 – 6 inch pipework. The accuracy of the system is defined by the ability to extract laser projections from an image as it travels down the pipe, to accurately reconstruct these projections into 3D and to estimate the probe trajectory as it travels through the pipe. This paper presents an error model of the laser profiler. It then presents a novel calibration routine to reduce the error caused by misalignment and tolerances during fabrication of the system. A key advantage of the proposed calibration technique over alternatives is that we can calibrate for errors without manually adjusting the probe, which enables fabrication of a smaller more robust measurement system. In lab-based trials our calibration technique reduced peak sizing errors from 2.7 mm to 0.14 mm in 120 mm diameter pipes.

The tribological properties of bearing alloys under oil lubrication

In this article, the tribological behaviors of CuPb24Sn under different load and oil lubrication conditions were studied. The worn surface, material transfer, and debris of the material were analyzed by the scanning electron microscopy and energy-dispersive X-ray spectrometer. In addition, the wear rate of CuPb24Sn was measured by means of a laser microscopic 3D and profile measurement apparatus. The results show that the soft phase lead wears preferentially from the sample surface under both light and heavy load conditions. Under the light load condition, the wear rate of the soft phase lead is low. Therefore, in this condition the samples are lubricated by oil and surface residual lead, and the wear mechanism is mainly abrasive wear. However, under heavy load conditions, the soft phase lead is quickly consumed. The lubricating oil film is thinner and the asperities contact is increased. And then the surface temperature and oxidation of samples are increased too. In this case, the main wear mechanisms of samples are adhesive wear and oxidation wear. At the same time, with the depletion of lead, cracks begin to form and propagate at the interface between lead and copper, and then peel off from the matrix to form wear debris, which further accelerates the wear of the sample.

Premier League Effort

Two companies demonstrate their leading-edge credentials by acquiring UK technology firsts: ESP Laser Cutting with a 12 kW Bystronic laser profiler and GF Laser, which is applying a Trumpf TruLaser Cell 5030 5-axis profiler

Dynamic laser beam shaping for laser aluminium welding in e-mobility applications

High demanding novel laser welding applications are currently encountered in e-mobility sector such as overlap joint of thin aluminium alloys without full penetration for battery coolers and battery boxes. In this work, high dynamic laser profiles enabled by unique CIVAN proprietary Coherent Beam Combining (CBC) and Optical Phase Array (OPA) technologies are explored. Experimental investigation of overlap welding of 3003 aluminium alloy plates of 0.8mm thickness at speeds over 10m/min and the study of main process parameters, various beam shapes and oscillation patterns at high frequency up to MHz are undertaken. Effects of laser beam intensity profiles, oscillation frequencies in resulting seam shapes are presented. Process optimization is carried out in terms of weld seam geometry width and depth of penetration avoiding defects as porous, cracks and voids in the interface. Quality of weld joints is evaluated by cross sections macrographs and metallographic examination.

Research on measurement method of grinding wheel profile based on image mosaic

Grinding is one of the most effective processing methods of hard and brittle materials. In the grinding process, measurement of the grinding wheel profile is of great significance for evaluating the grinding wheel processing accuracy, detecting wear and compensating machining errors. In this paper, a novel grinding wheel profile measurement method based on an image mosaic is proposed to realize fast non-contact profile measurement. A profile template matching approach based on the profile search algorithm is constructed according to the characteristics of the wheel profile, and the complete grinding wheel profile is obtained and measured by a fast and accurate mosaic of profile images. The experimental results show that the proposed algorithm is more efficient and accurate compared with the traditional image mosaic algorithm. On the basis of this method, a measurement system for the grinding wheel profile is established and cylindrical and hemispherical grinding wheels are measured. The high-resolution complete cross-sectional profiles are obtained and the results are compared with a 2D laser profiler. The root mean squared error of the cylindrical grinding wheel is 0.08%–0.1% of the nominal radius. The center position deviation of the hemispherical grinding wheel is between ±3 µm and the radius deviation is below 0.08% of the nominal radius. The measurement results indicate the feasibility and precision of this method, which can realize non-contact rapid measurement of the grinding wheel profile.

25 Years Ago December 1994

Industry & government talk training; Swedish machine tools; business recovering for UK-based machine tool firms; press brake and CO2 laser profiler innovation; toolmaker-to-OEM journey; past & present of flexible manufacturing cells

Automated Core Logging Technology for Geotechnical Assessment: A Study on Core from the Cadia East Porphyry Deposit

Abstract The Cadia East porphyry deposit, located approximately 20 km south of Orange, New South Wales, Australia, contains a significant resource of copper and gold. This resource is hosted within the Forest Reefs Volcanics and is spatially and temporally associated with the Cadia Intrusive Complex. To extract ore, the underground mine currently uses the block cave mining method. The Cadia East geotechnical model provides data inputs into a range of numerical and empirical analysis methods that make up the foundation for mine design. These data provide input into the construction of stress models, caveability models, ground support design, and fragmentation analysis. This geotechnical model encompasses two commonly used rock classification systems that quantify ground conditions: (1) rock mass rating (RMR) and (2) rock tunneling quality index (Q index). The RMR and Q index are calculated from estimates of rock quality designation (RQD), number of fracture sets, fracture roughness, fracture alteration, and fracture spacing. Geologists and geotechnical engineers collect information used to produce these estimates by manually logging sections of drill core, a time-consuming task that can result in inconsistent data. Modern automated core scanning technologies offer opportunities to rapidly collect data from larger samples of drill core. These automated core logging systems generate large volumes of spatially and spectrally consistent data, including a model of the drill core surface from a laser profiling system. Core surface models are used to extract detailed measurements of fracture location, orientation, and roughness from oriented drill core. These data are combined with other morphological and mineralogical outputs from automated hyperspectral core logging systems to estimate RMR and the Q index systematically over contiguous drill core intervals. The goal of this study was to develop a proof-of-concept methodology that extracts geotechnical index parameters from hyperspectral and laser topographic data collected from oriented drill core. Hyperspectral data from the Cadia East mine were used in this case study to assess the methods. The results show that both morphological and mineralogical parameters that contribute to the RMR and Q index can be extracted from the automated core logging data. This approach provides an opportunity to capture consistent geologic, mineralogical, and geotechnical data at a scale that is too time-consuming to achieve via manual data collection.

Preparation of two-dimensional thin films by backside irradiation pulsed laser deposition method using powder target

In this work, two-dimensional thin films were prepared by pulsed laser deposition (PLD) via backside irradiation. For this, a handmade transparent target holder made of quartz-glass was used to hold the powder targets. Visible-wavelength pulsed laser irradiation was applied from the holder side to the substrate. Using this new method, indium (In) and zinc (Zn)-concentrated thin films were prepared on a silicon substrate. The deposition rate of the film prepared with this method was calculated from the thickest position of the prepared film and the deposition time. The deposition rate was lower than for films prepared via conventional PLD. Two-dimensional profiles of the prepared films via backside irradiation PLD displayed a convex shape and its spatial resolution strongly depended on the laser profile. X-ray photoelectron spectroscopy measurements suggested that tailored In and Zn composition thin films could be prepared with this method using an In2O3 and ZnO powder target.