Laser Line Research Articles

An Improved Multi-point Chord Reference Measurement Device and Error Correction Method for Corrugation Measuring in Sharp Curves

Background: The traditional chord reference method and its device have faced challenges matching the sharp curve track. Thus, it is of utmost importance to research and develop a measurement device and method that can obtain accurate and comprehensive information regarding rail running band corrugation. Aims: It provides a solution for the measurement of the multi-point chord reference method on sharply curved rails and, at the same time, meets the demand for data richness and accuracy in theoretical studies on the causes of rail corrugation and wheel-rail contact relationships. Objective: This paper aims to research and design a measurement device based on the multi-point chord reference method for the rail running band corrugation. Meanwhile, the error in measuring the sharp curve rail is corrected and verified by simulation. Methods: The lateral information of rail running band is obtained by using a line laser profile sensor; the rail corrugation measurement model and error correction model of the rail running band area are established based on multi-point reference system; the simulation of the system model is carried out using Matlab; and the mechanical structure is built for static testing. Results: The measurement model based on the profile sensor and multi-point chord reference system can accurately obtain the rail corrugation waveform of any longitudinal measurement line in the running band area. The measurement results can be accurately corrected for a radius of 200m- 400m, the error parameters can be effectively improved, and the mechanical mechanism of the measurement system runs stably. Conclusion: The results show that the measurement model can accurately measure the rail corrugation of the sharp curve section, and the multi-waveform in the rail running band area has good measurement performance, but the mechanical structure can be optimized and improved in the light weight.

Observation of Extraneous Axial Cavity Modes of a Single-Mode Solid-State Laser Using Ultrahigh-Contrast Fabry–Perot Interferometry

Extraneous axial optical cavity modes produced by a single-mode frequency-doubled neodymium-doped yttrium orthovanadate (Nd:YVO[Formula: see text]) laser were observed in spectra obtained via ultrahigh-contrast Fabry–Perot interferometry. These modes, which are much weaker than the primary axial mode emission, are separated by [Formula: see text] GHz and display decreasing intensity with increasing shift from the primary laser line and with increasing laser output power. The possible presence of such modes in target sample spectra necessitates that caution be used in the interpretation of spectral peaks in laser spectroscopy studies, particularly Brillouin light scattering experiments. This work also showcases the remarkable capabilities of modern multipass Fabry–Perot interferometry in the detection of exceedingly weak optical signals shifted in frequency by only a few gigahertz from the primary laser emission line.

Laser hazard classification of a line laser with an astigmatic extended source

Since lasers are used in a large variety of applications, new laser products have become more complex. To increase performance, like range or brightness, it is important to consider the maximum optical output that will not exceed laser safety limits. Exposure to an extended source laser results in a larger retinal image and a simplification of treating it as a point source unnecessarily restricts system performance. For laser beams where the location of the apparent source (beam waist) is different in each axis (astigmatic beams), the retinal image is asymmetric and is also a function of eye accommodation. Lasers with astigmatic beams are often evaluated as point sources because accommodation on the source in either beam axis can indicate that the source in that axis is a point source; however, the eye can only focus (accommodate) on one distance at a time. For a single accommodation of the eye, the source may be extended, and extended source lasers are considered less hazardous than point source lasers of the same output power because of the reduction of retinal irradiance (the power is distributed over a larger area). For a line laser with an astigmatic beam, a particular laser hazard class may allow for a higher laser output power than would be allowed if it were a point source laser.

Hand-eye calibration of line structured-light sensor based on double-sphere constraints

Aiming at the complex problem of solving the positional relationship between the line laser sensor at the end of the robot wrist and the coordinate system of the end flange, a line laser hand-eye calibration method based on a double ball fixed target is proposed. Firstly, a double standard ball with known radius and center distance is used as a reference tool, and the point cloud data of a single contour line is collected several times, and the coordinates of the two ball centers under the camera coordinate system can be obtained according to the center coordinates of the circle obtained from the fitted circle combined with the Pythagoras theorem. Then, according to the principle that the two spherical centers are fixed under the robot base coordinate system, the rigid transformation matrix between the line laser sensor and the robot is successively solved. When solving the rotation matrix, the constraint of the distance between the spherical centers of the two balls is introduced to obtain a solution with better accuracy. Experimental results show that the method has better overall performance compared with the traditional single-ball hand-eye calibration method.

A study on real-time path planning method for skin machining based on frame feature extraction and chronological feature optimization

Skin, as the crucial component of aircraft, should be milled along the edges of the frame to ensure the mounting accuracy. Traditional skin milling uses visual measurement and offline planning to generate a machining path that corresponds to the overall shape of the frame edge. To enhance adaptability and processing efficiency, an online planning method is proposed. However, it imposes greater demands on the computational efficiency, accuracy, and stability of the algorithm. In this paper, a real-time path planning method based on frame feature extraction and chronological feature optimization is proposed for the milling of attached frame-skin. The method uses a line laser to scan the surface features of both skin and frame structures, facilitating real-time extraction of feature structures. Periodic calculations of position and posture are conducted based on the time series, and a non-fitting method is used to generate a smooth and high-precision machining trajectory. The efficacy in achieving real-time path planning for the milling module is verified by experiments on prototypes of aircraft skin. The algorithm exhibits a duration of less than 8 ms in a run cycle, while maintaining accuracy within ±0.5mm.

Generation of Multiwavelength Fibre Laser based on Erbium-Doped Fibre Amplifier with Lyot Filter

A ring cavity setup consisting of erbium-doped fibre amplifier (EDFA) as the optical pump and lyot filter aids in the production of a multiwavelength spectrum. The wavelength of EDFA pumps in photons range of 1530 nm to 1560 nm, respectively. Using maximum power of 18 dBm and a single mode fibre (SMF) of 10 km length, the number of peak lasing lines produced between 3 dB spectral range is 51. Tuning of the polarization controller (PC) to a specific angle helps provide the most stable lasing line. Stability test is done on the output multiwavelength fibre laser (MWFL) over a time period to analyze the wavelength stability.

Aptamer-conjugated gold nanoparticles for portable, ultrasensitive naked-eye detection of C-reactive protein based on the Tyndall effect

BackgroundC-reactive protein (CRP) represents an early clinical biomarker that indicates the presence of inflammatory or infectious conditions in the human body. Today's procedures approved by the Food and Drug Administration (FDA) imply expensive equipment and highly trained personnel to perform the test. Therefore, a new diagnostic method with high detection efficiency and less cost is urgently needed for delivering rapid and timely results in point-of-care (POC) service. ResultsHerein, we propose a new, equipment-free, and portable sensing method for the future POC detection of CRP based on the Tyndall effect (TE). In our study, aptamer-conjugated citrate-stabilized gold nanoparticles (apta-AuNPs) are exploited as the sensing platform. The apta-AuNPs’ interaction with CRP in a saline environment leads to their aggregation, thus enhancing the scattering of light when the solution is exposed to a 640 nm pointer laser line. Firstly, the enhancement of the scattering light as a function of increasing concentration of CRP in solution is measured spectroscopically using a typical 90-degree angle spectrofluorometer and then the measurements are compared to the classic colorimetric detection using an UV–Vis spectrophotometer. Finally, to achieve high portability and accessibility, we demonstrate that the measurement of CRP concentration can be performed with similar accuracy but in a more direct and inexpensive way by using a laser pointer pen as the excitation source and a camera of a low-budget smartphone as a quantitative reader instead of most expensive spectrofluorometer. SignificanceThe portable TE-based assay exhibits a wide linear dynamic range (1–60 μg/mL) for the detection of CRP with a limit of detection (LOD) of 92 ng/mL The proposed method is capable to integrate both standard and high-sensitivity CRP analysis in a single procedure with increased sensitivity and prompt delivery of analysis results. Moreover, the sensing procedure is significantly faster than the FDA approved ones with a detection time of only 10 min. Finally, as a proof-of-concept, our findings demonstrate excellent recovery for CRP detection in spiked and diluted urine samples, highlighting the strong potential of this sensing method for POC applications.

In-situ process monitoring and adaptive quality enhancement in laser additive manufacturing: A critical review

Laser Additive Manufacturing (LAM) presents unparalleled opportunities for fabricating complex, high-performance structures and components with unique material properties. Despite these advancements, achieving consistent part quality and process repeatability remains challenging. This paper provides a comprehensive review of various state-of-the-art in-situ process monitoring techniques, including optical-based monitoring, acoustic-based sensing, laser line scanning, and operando X-ray monitoring. These techniques are evaluated for their capabilities and limitations in detecting defects within Laser Powder Bed Fusion (LPBF) and Laser Directed Energy Deposition (LDED) processes. Furthermore, the review discusses emerging multisensor monitoring and machine learning (ML)-assisted defect detection methods, benchmarking ML models tailored for in-situ defect detection. The paper also discusses in-situ adaptive defect remediation strategies that advance LAM towards zero-defect autonomous operations, focusing on real-time closed-loop feedback control and defect correction methods. Research gaps such as the need for standardization, improved reliability and sensitivity, and decision-making strategies beyond early stopping are highlighted. Future directions are proposed, with an emphasis on multimodal sensor fusion for multiscale defect prediction and fault diagnosis, ultimately enabling self-adaptation in LAM processes. This paper aims to equip researchers and industry professionals with a holistic understanding of the current capabilities, limitations, and future directions in in-situ process monitoring and adaptive quality enhancement in LAM.

Quickly Formed Continuously Tuneable Laser in the Full Visible Spectrum Using Cholesteric Liquid Crystal Cells Based on the Electrothermal Effect

AbstractWavelength‐tuneable lasers can play a crucial role across many fields, and their applications continue to expand with advancements. Cholesteric liquid crystal (CLC) devices are developed, enabling good wavelength‐tuneable lasers. In CLC devices, pitch control is required to tune the desired wavelength. However, pitch control takes a long time and is difficult, which limits the speed and range of laser wavelength tuning. Here, by applying a voltage once and forming an electric field gradient along the wedge direction in the CLC wedge cell, we could realize CLC pitch gradient arrays that achieve continuous wavelength tuning over 500 nm in only 10 min through the electrothermal effect while continuously generating laser lines in the full visible spectrum. The laser wavelength could be rapidly tuned over the full visible spectrum by moving within the array in the wedge cell. The study of CLC cells for electric field application in real time is able to observe the dynamic process of pitch change directly. This new laser device and strategy has potential in many fields that require active laser tuning and is expected to lead to innovative changes in the development of future practical laser devices in the optical industry.

Real-time and non-contact estimation of state of charge for lithium-ion battery using laser ultrasonics

Lithium-ion batteries (LIBs) are widely used in portable electronics, electric vehicles, and stationary storage systems due to their high power and high energy. Monitoring the status of LIBs, particularly the state of charge (SOC), is crucial to ensuring battery performance and safety. Non-destructive ultrasonic approaches are recently emerging as a promising method for estimating the battery state and improving safety. However, current battery state estimation methods require contact and the use of a couplant, limiting their practicality and real-time applications. This study presents a non-contact laser ultrasonic system for monitoring the battery state during charge/discharge cycles. The experimental setup utilizes a line laser source to generate ultrasonic waves and an interferometer to detect the wave signal in a pitch-catch mode. Various ultrasonic features, including time-of-flight (TOF) and signal amplitude (SA), are analyzed in the time and frequency domains, respectively, at different degradation rates. The results show significant changes in the ultrasonic features in response to battery SOC and cycling degradation. The proposed non-contact ultrasonic method has the capability to determine the internal status of LIBs, enabling real-time monitoring of battery safety.

Spectral line confocal sensor signal analysis and correction: Unlocking reflectance difference sample measurements

Spectral line confocal imaging (LCI) technology enables high-resolution, rapid 3D surface morphology analysis of transparent materials and other samples, positioning it as a leading optical measurement tool. Nevertheless, where the sensor measures samples with significant variations in surface reflectance, the peak signals of the acquired images exhibit low signal-to-noise ratios or become distorted, hampering the peak extraction algorithm from accurately locating their peak positions. Consequently, it's arduous to reconstruct their precise surface topography. To enhance the sensor's dynamic measurement range and adaptability, this paper introduces an adaptive correction approach. It utilizes a regularized non-negative matrix to decompose images with various grey levels. This is followed by weighted frequency filtering and Gaussian enhancement of all the grey layers. Eventually, these layers are fused into one image with high contrast and uniformity. Using this approach, the sensor is capable of achieving precise 3D reconstruction with high-quality peak signals. Additionally, this study experimentally demonstrates the efficacy of the suggested approach by measuring the interdigital electrode and printed circuit boards (PCB). It should be noted that the technique presented in this paper is not limited to spectral line confocal instruments and is also effective for line laser and line structured light instruments.

Intergranular stress and plastic strain formation during laser scanning of additively manufactured stainless steel: An experimentally-driven thermomechanical simulation study

A novel experiment-driven modelling and simulation approach is proposed to study the formation of intergranular stresses and plastic strains during laser scanning of additively manufactured 316L stainless steel. Recently, laser scanning experiments were performed using a unique coupling between a continuous-wave laser and a scanning electron microscope. These experiments form the basis for the development of a thermo-elasto-viscoplastic polycrystal model endowed with the minimum necessary physics of the problem in order to facilitate simulating sufficiently large domains to obtain reasonable stress magnitudes. The case of a single laser line scan performed in vacuum is analyzed in detail. Polar dislocation density magnitudes and distribution predicted from the simulation are compared with those measured experimentally. Results reveal that for 93% of the grains in the lasered zone, a statistical measure of the predicted polar dislocation density (Nye’s) tensor lies within a factor of 2 (higher or lower) of the experimental one; this result sets a benchmark for future experiment-simulation comparisons. Subsequent investigation studies the origin of the local residual stresses and plastic strains. On the lasered surface, the grain surface-averaged normal residual stress component and plastic strain component along the scan direction reaches a value ∼1.7GPa and 0.04, respectively. The contribution of elastic anisotropy, plastic heterogeneity and strengthening due to microstructure refinement after laser scanning on the formation of stresses and plastic strains is studied in detail.

Elucidating the effects of surface wettability on boiling heat transfer using hydrophilic and hydrophobic surfaces with laser-etched microchannels

This study explores the nuanced interplay between surface wettability and morphology in nucleate boiling heat transfer. Surfaces with identical microstructures but varying wettability are created on copper substrates using laser texturing and a hydrophobic agent. The spacing between laser-etched microchannels is adjusted to achieve different contact angles and percentages of laser-textured areas. Boiling performance is assessed with variations in channel spacing and surface coverage, revealing significant differences between hydrophilic and hydrophobic surfaces. The critical heat flux (CHF) enhancement mechanisms are identified, emphasizing either enhanced liquid replenishment or separate boiling and liquid-supply regions. A critical laser line spacing of 100 μm is determined, where hydrophobic and hydrophilic variants exhibit similar CHF. Interestingly, hydrophilic surfaces show a weak correlation between the heat transfer coefficient (HTC) and contact angle, while hydrophobic surfaces demonstrate a strong correlation. This separation of surface morphology and wettability confirms that lower wettability promotes early nucleate boiling and high HTC, whereas hydrophilic variants contribute to enhanced CHF with lower HTC. These distinctions are most prominent at high coverage with laser-textured areas and diminish as coverage decreases. The findings provide valuable insights into optimizing surface properties for efficient boiling heat transfer applications.

Microstructure and mechanical properties of Ti6Al4V/W bimetallic structure via selective laser melting

The titanium alloy Ti–6Al–4V (TC4) and tungsten (W) possess excellent complementary properties that would be useful for a wide range of industrial applications if they could be suitably combined. Selective laser melting was applied to prepare TC4/W specimens with a bimetallic structure. A strong bond without interfacial macrocracks was obtained by adjusting the laser line energy density to <0.75 J/mm. The bond interface of the bimetallic structure reached a microhardness of 503 ± 20 HV, which was harder than that of the two base materials, and the transverse and longitudinal ultimate compressive strengths were 1510 ± 40 MPa at strains of 20%–22.5%. Three-point bending experiments showed that when TC4 was used as the base material, the flexural strength of the specimen was 2210.5 ± 44.5 MPa. The high strength of the bond interface was attributed to sufficient agitation of the molten pool and reinforcement by fine crystalline grains. The agitation was provided by the melting and elemental diffusion of TC4 owing to the high energy input during the formation of W, and the fine crystalline grains were obtained by the dispersed W particles providing multiple nucleation sites for liquid TC4. The bimetallic structure retained the strength of W and toughness of TC4, which bodes well for its industrial application.

Development of a vision system integrated with industrial robots for online weld seam tracking

This paper develops a laser-structured light vision system for the industrial welding manipulator. The designed structured light vision system consisting of a line laser projector and an industrial camera is a decent 3D object data acquisition platform. By applying the principle of triangulation, the depth value of the object can be obtained via the laser plane in the captured image. According to hand-eye calibration and the principle of triangulation, the 3D position of the objects in the robot coordinate system is calculated. Based on the discriminated convolution tracker and deep reinforcement learning that increases the accuracy and processing time of the tracker, allowing simultaneous scanning for seam data acquisition and welding along the weld path, a real-time seam tracking algorithm is developed to handle the square-groove butt joint with small gaps (i.e., <1 mm). Experiments are undertaken using a Yaskawa industrial welding robot integrating the designed laser-structured light vision system. Experiment results show the significant performance of the developed system in welding square-groove butt joints with curved profiles and small gaps, i.e., the welding absolute mean error is 0.31 mm, whereas in the case of using convolution tracker only, the welding absolute mean error 1.7 mm.

Microstructures and mechanical properties of copper-to-glass laser transmission welding employing a nanosecond pulsed laser

This study focuses on the interfacial characteristics of glass/copper welds achieved through laser transmission welding, utilizing a nanosecond pulsed laser. The investigation explores key processing parameters, specifically laser line energy intensity and total scan numbers, and their impacts on weld performance. Through meticulous analysis covering bond strength, cross-sectional surface morphologies, micro- and nano-structures, phase formations, and elemental compositions, the study systematically addresses the weld formation mechanism. The research elucidates potential reasons for diverse bonding characteristics, emphasizing the formation of Cux+-O-Si compounds (primarily Cu+-O-Si and Cu2+-O-Si) at the glass/copper interfacial region, as revealed by the XPS spectrum and HR-TEM images. These findings highlight redox reactions facilitated by strong intra-mixing through diffusion and convection during welding. The shear force separation test unveils an impressive maximum bond strength of 34.9 MPa, surpassing previously reported results, despite the indication of a brittle fracture in the separated surface morphologies. The correlation between a larger weld zone, abundant eutectic Cux+-O-Si compounds, and a uniformly re-solidified glass region is closely linked to the resulting high weld strength. This study underscores the direct relationship between laser irradiating energy and the extent of the weld zone, while the number of repeated scans proved to be an effective approach for regulating the elemental composition and microstructures in the weld. Overall, these findings contribute valuable insights into the weld formation mechanism and offer practical considerations for optimizing glass/copper welds through laser transmission welding.

Measuring the in-plane thermal diffusivity of anisotropic solids by lock-in infrared thermography: Laser-spot vs laser-line heating

A method is proposed to measure the in-plane thermal diffusivity of anisotropic solids along an arbitrary direction using laser-line lock-in thermography. In this method, the sample is heated by an intensity-modulated laser beam, which impinges on the sample surface with the shape of a narrow strip. The resulting temperature oscillations are recorded by a thermographic camera and a phase thermogram is obtained by lock-in processing the image sequence. The thermal diffusivity along the direction perpendicular to the laser line can be determined from the linear dependence of phase lag with the distance to the heating line using the slope method. Unlike laser-spot lock-in thermography, in which the slope method only provides the thermal diffusivity along the principal directions, in this configuration, the thermal diffusivity can be measured experimentally along any direction, just selecting the relative orientation of the sample with respect to the laser line. Moreover, this configuration allows averaging several parallel phase profiles leading to more reliable thermal diffusivity values. The experimental results are presented for a highly anisotropic material, namely, a unidirectional carbon fiber-reinforced polymer plate.

Highly Efficient Transfer of Quantum State and Robust Generation of Entanglement State Around Exceptional Lines (Laser Photonics Rev. 18(4)/2024)

Highly Efficient Transfer of Quantum State and Robust Generation of Entanglement State Around Exceptional Lines (Laser Photonics Rev. 18(4)/2024)

UGV에서 효율적인 노면 모니터링을 위한 퓨전 센서 시스템

Road surface monitoring is essential for maintaining road environment safety through managing risk factors like rutting and crack detection. Using autonomous driving-based UGVs with high-performance 2D laser sensors enables more precise measurements. However, the increased energy consumption of these sensors is limited by constrained battery capacity. In this paper, we propose a fusion sensor system for efficient surface monitoring with UGVs. The proposed system combines color information from cameras and depth information from line laser sensors to accurately detect surface displacement. Furthermore, a dynamic sampling algorithm is applied to control the scanning frequency of line laser sensors based on the detection status of monitoring targets using camera sensors, reducing unnecessary energy consumption. A power consumption model of the fusion sensor system analyzes its energy efficiency considering various crack distributions and sensor characteristics in different mission environments. Performance analysis demonstrates that setting the power consumption of the line laser sensor to twice that of the saving state when in the active state increases power consumption efficiency by 13.3% compared to fixed sampling under the condition of =10, =10.

Abstract 84: StarBright Dyes: Fluorophores with superior performance for multiplexing in flow cytometry and Western blotting

Abstract New StarBrightTM Dyes from Bio-Rad are bright fluorescent fluorophores ideal for many antibody-based applications, for example, western blotting and flow cytometry. Traditional fluorophores can be dim, have high cross laser excitation, or don’t work with all protocols, leading to poor data. StarBright Dyes have been designed to address these pain points. Western blotting secondary antibodies are available conjugated to StarBright Blue 700 and StarBright Blue 520 Dyes. Their brightness, the short exposure time required, and low background make them ideal for detection of a single target, or as shown here for multiplex detection of several proteins in combination with other common fluorophores. For flow cytometry, we have a full range of 32 StarBright Dyes excited by the most common laser lines: 355 nm, 405 nm, 488 nm, 561 nm, or 640 nm. They are available conjugated to highly cited clones against common immunophenotyping targets. Data shown here on the ZE5 Cell Analyser demonstrates how the features of StarBright Dyes can improve multiplexing immunophenotyping data. They have narrow excitation and emission spectral profiles, which reduce compensation and spread. This, combined with their exceptional brightness, enables high resolution of cell populations. They work in all buffers and fixatives, so including them in existing panels does not require a change in protocol. They can also be premixed in a master mix for over six months with no loss in performance. Premixes are ideal when using the same panel over an extended period, such as in clinical and longitudinal studies, to ensure reproducible results, also saving time and money. StarBright Dyes are ideal for multiplexing assays in both western blotting and flow cytometry. BIO-RAD and STARBRIGHT are trademarks of Bio-Rad Laboratories, Inc. in certain jurisdictions. All trademarks used herein are the property of their respective owner. Citation Format: Sharon Sanderson, Oliver Rosenwasser, Michael Blundell. StarBright Dyes: Fluorophores with superior performance for multiplexing in flow cytometry and Western blotting [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 84.