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We propose a new commercial laser triangulation sensor modification to enable the measurement of slots or bores side distance. The study showed the possibility of extending the sensor depth range for a slot or bore side distance measurement using a bypass of the illumination laser beam compared to a simple single mirror attachment to the sensor probe. We derived relations allowing for evaluation of the modified sensor side measurement range in desired depth based on the sensor parameters and the reflective mirror size and position. We demonstrated the functionality of the proposed measurement arrangement with an attachment to the commercial laser triangulation sensor and assessed the side-wall distance measurement. The results show the correct measurement depth and range prediction and the ability to perform side surface distance measurements at depths of more than 3.5 times the slot size. [ABSTRACT FROM AUTHOR]

In recent years, the research interest in the application of remote sensing technology to highly aerated flows has been increasing because this technology holds the ultimate promise to enable safe and accurate measurements of real-world air–water flows in natural and human-made environments. Despite the increasing number of publications, some fundamental questions, such as "what do we measure" or "what can we measure," have not been answered conclusively. In this study, we hypothesize that laser distance sensors can measure the concentration of entrapped air, which we demonstrate using two seminal air–water flow types, namely a submerged hydraulic jump and flows down a stepped spillway. By converting our free-surface signals into time series of instantaneous air concentrations, we also show that a dual laser triangulation setup enables the extraction of basic air–water flow parameters of the upper flow region, comprising interface count rates, interfacial velocities, and turbulence levels, whereas we acknowledge that some sensor characteristics, such as beam diameters, can lead to measurement biases. Overall, this study represents a major advancement in the remote measurement of air–water flow properties. Future collective research effort is required to overcome remaining challenges. [ABSTRACT FROM AUTHOR]

Material Extrusion (MEX) currently stands as the most widespread Additive Manufacturing (AM) process, but part quality deficiencies remain a barrier to its generalized industrial adoption. Quality control in MEX is a complex task as extrusion performance impacts the consistency of mechanical properties and the surface finish, dimensional accuracy, and geometric precision of manufactured parts. Recognizing the need for early-stage process monitoring, this study explores the potential of integrating Laser Triangulation Sensors (LTS) into MEX/P manufacturing equipment for layer-wise 3D inspections. Using a double-bridge architecture, an LTS-based sub-micrometric inspection system operates independently from the manufacturing process, enabling comprehensive digitization and autonomous reconstruction of the target layer's topography. Surface texture is then computed using standardized indicators and a new approach that provides insight into layer quality uniformity. A case study evaluating two alternative extruder head designs demonstrates the efficacy of this integrated approach for layer quality characterization. Implementing a generalized layer-wise procedure based on this integration can significantly mitigate quality issues in MEX manufacturing and optimize process parameter configurations for enhanced performance. [ABSTRACT FROM AUTHOR]

Measurement of vibration without having contact with the target is crucial for many applications. However, real time vibration signals are frequently mixed with various levels of dynamic noises. In this research, a non-contact type vibration measurement system based on laser triangulation method is proposed by using a PSD (Position sensitive detector) and here a single axis Brüel and Kjaer piezoelectric accelerometer is used to validate the experimental results. The primary goal of this measurement system is to develop a Gabor Transform based signal denoising technique, in order to eliminate noise from the real-time vibration data. Furthermore, PSD platform vibration, which might cause unanticipated inaccuracies in the detected vibration data, has also been eliminated by utilizing a self-vibration compensation approach using an ADXL-345 three-axis accelerometer. The self-vibration compensated vibration measurement technique has been designed using an NI (national instruments) cRIO (CompactRIO) 9074 real-time FPGA (field programmable gate array) based embedded controller. Consequently, a Gabor Transform and Expansion-based Signal Processing Technique is designed using NI cRIO-9074 real time platform to reduce external noise from the self-vibration compensated vibration data. It has been observed that the implementation of Gabor Transform has improved the performance of the system in term of enhancing the SNR (Signal-to-noise ratio). [ABSTRACT FROM AUTHOR]

The accurate depth imaging of piled products provides essential perception for the automated selection of individual objects that require itemized food processing, such as fish, crabs, or fruit. Traditional depth imaging techniques, such as Time-of-Flight and stereoscopy, lack the necessary depth resolution for imaging small items, such as food commodities. Although structured light methods such as laser triangulation have high depth resolution, they depend on conveyor motion for depth scanning. This manuscript introduces an active dual line-laser scanning system for depth imaging static piled items, such as a pile of crabs on a table, eliminating the need for conveyor motion to generate high-resolution 3D images. This advancement benefits robotic perception for loading individual items from a pile for itemized food processing. Leveraging a unique geometrical configuration and laser redundancy, the dual-laser strategy overcomes occlusions while reconstructing a large field of view (FOV) from a long working distance. We achieved a depth reconstruction MSE of 0.3 mm and an STD of 0.5 mm on a symmetrical pyramid stage. The proposed system demonstrates that laser scanners can produce depth maps of complex items, such as piled Chesapeake Blue Crab and White Button mushrooms. This technology enables 3D perception for automated processing lines and offers broad applicability for quality inspection, sorting, and handling of piled products. [ABSTRACT FROM AUTHOR]

Process Analytical Technology (P A T) plays a crucial role in the design of today's manufacturing lines as continuous manufacturing becomes more important. Until now P A T tools to measure the ribbon solid fraction (S F r i b b o n ) in-line are not commonly used in roll compaction. The aim of this study was therefore to establish a new approach as P A T for in-line ribbon solid fraction determination. Different placebo formulations with different binders and one formulation containing active pharmaceutical ingredient were investigated using in-line laser triangulation measurement to detect the ribbon thickness after compaction. With this the ribbon elastic recovery was determined in-line (E R i n − l i n e ) while the ribbons are attached to the roll surface. It was found that the ratio (E R r a t i o ) between the total elastic recovery and E R i n − l i n e is formulation specific and not influenced by any process parameters. This enables E R r a t i o as prediction tool for S F r i b b o n , if the solid fraction at gap (S F g a p ) width is known. S F g a p was determined with ribbon mass flow measurement or based on the Midoux model, a simplified Johanson model, gaining two prediction models for S F r i b b o n . Both models showed good agreement of the predicted S F r i b b o n and the measured one. [Display omitted] • Novel in-line laser triangulation measurement of ribbon elastic recovery in roll compaction. • In-line prediction of ribbon solid fraction as Process Analytical Technology (PAT). • Ribbon mass flow and Midoux number based model were established. • Prediction model based on Midoux number showed superior results and applicability. [ABSTRACT FROM AUTHOR]

We propose a new commercial laser triangulation sensor modification to enable the measurement of slots or bores side distance. The study showed the possibility of extending the sensor depth range for a slot or bore side distance measurement using a bypass of the illumination laser beam compared to a simple single mirror attachment to the sensor probe. We derived relations allowing for evaluation of the modified sensor side measurement range in desired depth based on the sensor parameters and the reflective mirror size and position. We demonstrated the functionality of the proposed measurement arrangement with an attachment to the commercial laser triangulation sensor and assessed the side-wall distance measurement. The results show the correct measurement depth and range prediction and the ability to perform side surface distance measurements at depths of more than 3.5 times the slot size.

The most important step in finalizing a production process is precise quality control of the manufactured product. For products manufactured with a high degree of precision, under strict tolerances, precise quality inspection is essential. In modern production, it is desirable for such processes to be accurate, reliable, repeatable, and above all, automated. Our work focuses on the design and development of a measuring cell, that precisely measures the surface roughness, and detects geometrical defects of a smaller workpiece, which was manufactured with a high level of precision and quality. For conducting precise measurements, the apparatus employs only a pair of displacement sensors, that measure a single point on touch-sensitive surfaces, using laser triangulation. Although such sensors are very accurate, their main drawback lies in the fact that they can perform measurements on only a single point. Thus, the measuring cell enables the sensors to move on the x and y axis, while also clamping the workpiece and allowing it to rotate to a desired position. [ABSTRACT FROM AUTHOR]

A pressure-volume diagram is often used to determine the indicated work of a Stirling engine. In this study, both the laser triangulation and hybrid Harris corner detection methods are proposed. The volume variations in the Stirling engines can be measured directly without complicated calculations. The variations in the pressure of the working fluid in the engine are measured by a piezoresistive pressure sensor. To confirm the proposed methods, a flat alpha-type Stirling engine was tested. In the laser triangulation method, a laser sensor is used to measure the variation in the crank angle of the shaft. In the hybrid Harris corner detection method, the crank angle of the shaft is obtained by analyzing the images of the mechanism recorded by a high-speed camera. The volume of the working spaces is obtained according to the geometry of the driving mechanism as well as the engine speed. In this study, the pressure-volume diagram of the proposed engine under different operating speeds is measured and compared. The results indicate that the difference in the engine speed and phase angle measured by both methods is 2.3 % and 2.9 %, respectively. The indicated powers of the engine measured by both methods with a heating temperature of 500 °C at 765 ± 5 rpm are 5.789 W and 6.904 W, respectively. The relative difference between the volume variations measured by both methods is lower than 0.5 %. The hybrid Harris corner detection method can obtain more precise results than the laser triangulation method.

Material Extrusion (MEX) currently stands as the most widespread Additive Manufacturing (AM) process, but part quality deficiencies remain a barrier to its generalized industrial adoption. Quality control in MEX is a complex task as extrusion performance impacts the consistency of mechanical properties and the surface finish, dimensional accuracy, and geometric precision of manufactured parts. Recognizing the need for early-stage process monitoring, this study explores the potential of integrating Laser Triangulation Sensors (LTS) into MEX/P manufacturing equipment for layer-wise 3D inspections. Using a double-bridge architecture, an LTS-based sub-micrometric inspection system operates independently from the manufacturing process, enabling comprehensive digitization and autonomous reconstruction of the target layer’s topography. Surface texture is then computed using standardized indicators and a new approach that provides insight into layer quality uniformity. A case study evaluating two alternative extruder head designs demonstrates the efficacy of this integrated approach for layer quality characterization. Implementing a generalized layer-wise procedure based on this integration can significantly mitigate quality issues in MEX manufacturing and optimize process parameter configurations for enhanced performance.

The accurate depth imaging of piled products provides essential perception for the automated selection of individual objects that require itemized food processing, such as fish, crabs, or fruit. Traditional depth imaging techniques, such as Time-of-Flight and stereoscopy, lack the necessary depth resolution for imaging small items, such as food commodities. Although structured light methods such as laser triangulation have high depth resolution, they depend on conveyor motion for depth scanning. This manuscript introduces an active dual line-laser scanning system for depth imaging static piled items, such as a pile of crabs on a table, eliminating the need for conveyor motion to generate high-resolution 3D images. This advancement benefits robotic perception for loading individual items from a pile for itemized food processing. Leveraging a unique geometrical configuration and laser redundancy, the dual-laser strategy overcomes occlusions while reconstructing a large field of view (FOV) from a long working distance. We achieved a depth reconstruction MSE of 0.3 mm and an STD of 0.5 mm on a symmetrical pyramid stage. The proposed system demonstrates that laser scanners can produce depth maps of complex items, such as piled Chesapeake Blue Crab and White Button mushrooms. This technology enables 3D perception for automated processing lines and offers broad applicability for quality inspection, sorting, and handling of piled products.

Acoustic and optical sensing modalities represent two of the primary sensing methods within underwater environments, and both have been researched extensively in previous works. Acoustic sensing is the premier method due to its high transmissivity in water and its relative immunity to environmental factors such as water clarity. Optical sensing is, however, valuable for many operational and inspection tasks and is readily understood by human operators. In this work, we quantify and compare the operational characteristics and environmental effects of turbidity and illumination on two commercial-off-the-shelf sensors and an additional augmented optical method, including: a high-frequency, forward-looking inspection sonar, a stereo camera with built-in stereo depth estimation, and color imaging, where a laser has been added for distance triangulation. The sensors have been compared in a controlled underwater environment with known target objects to ascertain quantitative operation performance, and it is shown that optical stereo depth estimation and laser triangulation operate satisfactorily at low and medium turbidites up to a distance of approximately one meter, with an error below 2 cm and 12 cm, respectively; acoustic measurements are almost completely unaffected up to two meters under high turbidity, with an error below 5 cm. Moreover, the stereo vision algorithm is slightly more robust than laser-line triangulation across turbidity and lighting conditions. Future work will concern the improvement of the stereo reconstruction and laser triangulation by algorithm enhancement and the fusion of the two sensing modalities. [ABSTRACT FROM AUTHOR]

Rolling noise is a significant contributor to railway noise. Wheel and rail roughness are decisive for the emitted noise level. An optical measurement method installed on a moving train is suitable for closer monitoring of the rail surface condition. A measurement setup based on the chord method requires the sensors to be positioned in a straight line along the direction of measurement and in a stable lateral position. Measurements should always be performed within the shiny and uncorroded running surface, even when there are lateral movements of the train. In this study, concepts for the detection of the running surface and the compensation of lateral movements are investigated in a laboratory setting. The setup consists of a vertical lathe with a ring-shaped workpiece that incorporates an implemented artificial running surface. The detection of the running surface based on laser triangulation sensors and a laser profilometer is investigated. It is shown that the running surface can be detected using a laser profilometer that measures the intensity of the reflected laser light. It is possible to detect the lateral position and the width of the running surface. A linear positioning system is proposed to adjust the lateral position of the sensors based on the running surface detection of the laser profilometer. When the lateral position of the measuring sensor is disturbed by a movement with a wavelength of 18.85   m , the linear positioning system can keep the laser triangulation sensor inside the running surface for 98.44 % of the measured data points at a velocity of approximately 7.5   km   h − 1 . The mean positioning error is 1.40   mm . By implementing the proposed system on the train, future studies can be conducted to examine the lateral position of the running surface as a function of the various operational parameters of the train. [ABSTRACT FROM AUTHOR]

In recent years, welding feedback control systems and weld quality estimation systems have been developed with the use of artificial intelligence to increase the quality consistency of robotic welding solutions. This paper introduces the utilization of an intelligent welding system (IWS) for feedback controlling the welding process. In this study, the GMAW process is controlled by a backpropagation neural network (NN). The feedback control of the welding process is controlled by the input parameters; root face and root gap, measured by a laser triangulation sensor. The NN is trained to adapt NN output parameters; wire feed and arc voltage override of the weld power source, in order to achieve consistent weld quality. The NN is trained offline with the specific parameter window in varying weld conditions, and the testing of the system is performed on separate specimens to evaluate the performance of the system. The butt-weld case is explained starting from the experimental setup to the training process of the IWS, optimization and operating principle. Furthermore, the method to create IWS for the welding process is explained. The results show that the developed IWS can adapt to the welding conditions of the seam and feedback control the welding process to achieve consistent weld quality outcomes. The method of using NN as a welding process parameter optimization tool was successful. The results of this paper indicate that an increased number of sensors could be applied to measure and control the welding process with the developed IWS. [ABSTRACT FROM AUTHOR]

This work aims to develop a novel method for on-line monitoring of coating quality during the Extreme High-speed Laser Cladding (EHLA) process. JG-11 coating was prepared by EHLA, and microstructure, microhardness, corrosion performance, and scratch resistance were investigated. To analyze the influences of fluctuations in processing parameters on coating quality, a single-factor experiment scheme was designed and an on-line monitoring system based on laser triangulation was built. Furthermore, a new forming method for the surface profile of EHLA coating was proposed, and a new comprehensive evaluation index of surface morphology was accordingly designed. Benefitting from the extremely high cooling rate, EHLA JG-11 coating had fine grains, high hardness, and better corrosion resistance and scratch resistance than those of Electroplating Hard Chromium (EHC). The results revealed that the surface morphologies presented different characteristics due to the fluctuations of process parameters, such as high surface flatness, deep pits, small peaks, poor directionality, etc. The comprehensive evaluation index composed of Sa, Ssk, and Str could effectively characterize the surface morphology of EHLA coating, which proved that the monitoring system and evaluation method could realize on-line monitoring of the process parameters during the EHLA process. [ABSTRACT FROM AUTHOR]

[Display omitted] Ribbon porosity is a critical parameter to monitor in the roller compaction process. In this study, six techniques for measuring the porosity of solid compacts, i.e., manually by caliper (Caliper), X-ray microtomography (µCT), off-line near-infrared spectroscopy (NIR), laser triangulation (Laser), mercury intrusion porosimetry (MIP), and GeoPyc, were compared using a set of rectangular ribblets of microcrystalline cellulose (MCC). These ribblets, which were compressed at 8–130 MPa on a compaction simulator, exhibited porosities over the range of 0.09 – 0.52. Subsequently, porosities of MCC ribbons made on a roller compactor at specific roll forces of 1.8 kN/cm and 8.8 kN/cm were measured. The Caliper method is convenient for samples with a simple shape but not suitable for real ribbons. The accuracy of GeoPyc measurement relies on accurate conversion factor (unit in cm3/mm), sample shape and size, and sufficient sample volume percentage in the medium. The µCT data is more accurate at lower porosities (< 0.2), while the MIP data is more accurate at higher porosities (> 0.4). The Laser method has good accuracy and is more reproducible compared to other methods in the ribblets measurement. The NIR method is fast, which makes it suitable for in-line monitoring of changes in ribbon quality, but porosity quantification is sensitive to sample presentation, such as surface curvature and roughness. These insights could assist in the choice of the most appropriate method for monitoring ribbon porosity to guide the development and optimization of a roller compaction process for a given formulation. [ABSTRACT FROM AUTHOR]

In 3D printing, as in other manufacturing processes, there is a push for zero-defect manufacturing, mainly to avoid waste. To evaluate the quality of the printed parts during the printing process, an accurate 3D measurement method is required. By scanning the part during the buildup, potential nonconformities to tolerances can be detected early on and the printing process could be adjusted to avoid scrapping the part. Out of many, shape-from-focus, is an accurate method for recovering 3D shapes from objects. However, the state-of-the-art implementation of the method requires the object to be stationary during a measurement. This does not reconcile with the nature of 3D printing, where continuous motion is required for the manufacturing process. This research presents a novel methodology that allows shape-from-focus to be used in a continuous scanning motion, thus making it possible to apply it to the 3D manufacturing process. By controlling the camera trigger and a tunable lens with synchronous signals, a stack of images can be created while the camera or the object is in motion. These images can be re-aligned and then used to create a 3D depth image. The impact on the quality of the 3D measurement was tested by analytically comparing the quality of a scan using the traditional stationary method and of the proposed method to a known reference. The results demonstrate a 1.22% degradation in the measurement error. [ABSTRACT FROM AUTHOR]

Laser measurement technique has been widely explored and applied in various fields in recent years due to its advantages of high measurement precision and resolution. However, applications in frontier fields such as MEMS motion measurement and robotics control pose have requirement for higher precision and resolution, which promote further studies in improving the performance of this technique. Many advanced techniques have been proposed and applied in the laser measurement system to optimize its performance, and the optimized measurement system has found its way in state‐of‐the‐art applications. In this invited paper, we focus on the latest investigations and new applications of the improved laser measurement methods, especially present recent research works regarding the laser triangulation measurement and the laser heterodyne vibration measurement. At the end, we have discussed further developments and challenges of laser measurement technique. [ABSTRACT FROM AUTHOR]

Dispensing and seam sealing in the manufacturing industry cause some problems related to human health, time consumption and material waste because of inconsistent sealers. However, at present, in small- and medium-sized factories, manual performance by workers and teaching manipulators by using teach-pendant to recognize seam sealing trajectories, especially for 3D complex seam curves, are still the two main approaches. To improve spraying quality, productivity, and repeatable consistency while reducing cost, this research presents an effective method of using robot and computer vision for autonomous detection of the seam sealing curve. First, the camera calibration methodology is proposed based on the laser triangular algorithm. Then, the coordinates of the seam curve are computed by applying the image processing algorithm. After that, the coordinates are processed and converted to the coordinates of the robot and transmitted to the controller to perform the task. By using this methodology, the robot can perform the gluing task without knowing the trajectory in advance; moreover, the system is not overly complicated and has high accuracy as well as a fast processing speed. The efficiency of the system is proven through experiments on 2D and 3D complex curves. [ABSTRACT FROM AUTHOR]

Copyright of Technisches Messen is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A non-contact measuring system is designed in this paper. In this system, a high-performance laser displacement senor and an additional turntable are integrated for acquiring the full dimensional data of complex surface. Due to the massive number of point clouds collected by the system, valid path planning methods are introduced in consideration of efficiency. As a result, the effectiveness of this system and measurement techniques for complex surface inspection are proved through various experiments. [ABSTRACT FROM AUTHOR]

Optical system parameter design is of great importance to ensure the accuracy of asymmetry systems such as laser triangulation ranging systems. However, the system parameter determination often depends on the experience and manual attempts of designers, which is not only time-consuming but also inevitable to introduce human errors. Therefore, in this paper an automatic optimization design method based on nonlinear programming genetic algorithm with elitism strategy (E-NPGA) is proposed, to accurately and fast determine the optimal system parameters of laser triangulation ranging systems assisting in improving the measurement accuracy. Firstly, an optimization model of system parameters is developed under the Scheimpflug rule establishing the constraints for various measurement resolutions and ranges. An image size constraint is constructed for the first time to improve and evaluate the parameter optimization. Secondly, the E-NPGA is proposed with nonlinear optimization and elitism strategy, which can determine the optimal system parameters in 15 iterations avoiding local extremum. In design examples, using the E-NPGA determined system parameters ZEMAX simulation and experimental results of the parameters depended image spot size show a slight relative difference below 0.6%. Moreover, the experiment results demonstrate the sensor system designed by using the E-NPGA enables a distance measurement with submicron absolute error and 1 0 − 4 relative uncertainty. The automatic optimization method proposed in this paper is compared with the conventional GA method and PSO method, and it is validated that the convergence accuracy of the proposed method is much higher than the conventional ones. • An optimization design model of laser triangulation ranging systems is proposed. • An image size constraint is constructed to improve system parameter optimization. • An enhanced genetic algorithm is developed to determine optimal system parameters. • The designed sensor system enables a distance measurement with 1 0 − 4 uncertainty. • Potential applications on other more complex asymmetric optical systems. [ABSTRACT FROM AUTHOR]

Rolling noise is a significant contributor to railway noise. Wheel and rail roughness are decisive for the emitted noise level. An optical measurement method installed on a moving train is suitable for closer monitoring of the rail surface condition. A measurement setup based on the chord method requires the sensors to be positioned in a straight line along the direction of measurement and in a stable lateral position. Measurements should always be performed within the shiny and uncorroded running surface, even when there are lateral movements of the train. In this study, concepts for the detection of the running surface and the compensation of lateral movements are investigated in a laboratory setting. The setup consists of a vertical lathe with a ring-shaped workpiece that incorporates an implemented artificial running surface. The detection of the running surface based on laser triangulation sensors and a laser profilometer is investigated. It is shown that the running surface can be detected using a laser profilometer that measures the intensity of the reflected laser light. It is possible to detect the lateral position and the width of the running surface. A linear positioning system is proposed to adjust the lateral position of the sensors based on the running surface detection of the laser profilometer. When the lateral position of the measuring sensor is disturbed by a movement with a wavelength of 18.85 m, the linear positioning system can keep the laser triangulation sensor inside the running surface for 98.44% of the measured data points at a velocity of approximately 7.5 km h−1. The mean positioning error is 1.40 mm. By implementing the proposed system on the train, future studies can be conducted to examine the lateral position of the running surface as a function of the various operational parameters of the train.

In recent years, welding feedback control systems and weld quality estimation systems have been developed with the use of artificial intelligence to increase the quality consistency of robotic welding solutions. This paper introduces the utilization of an intelligent welding system (IWS) for feedback controlling the welding process. In this study, the GMAW process is controlled by a backpropagation neural network (NN). The feedback control of the welding process is controlled by the input parameters; root face and root gap, measured by a laser triangulation sensor. The NN is trained to adapt NN output parameters; wire feed and arc voltage override of the weld power source, in order to achieve consistent weld quality. The NN is trained offline with the specific parameter window in varying weld conditions, and the testing of the system is performed on separate specimens to evaluate the performance of the system. The butt-weld case is explained starting from the experimental setup to the training process of the IWS, optimization and operating principle. Furthermore, the method to create IWS for the welding process is explained. The results show that the developed IWS can adapt to the welding conditions of the seam and feedback control the welding process to achieve consistent weld quality outcomes. The method of using NN as a welding process parameter optimization tool was successful. The results of this paper indicate that an increased number of sensors could be applied to measure and control the welding process with the developed IWS.

The speckle-induced measurement uncertainty is one of the major bottlenecks to achieve high measurement accuracy in laser triangulation sensors (LTS). Conventional methods for improving uncertainty focus on suppressing speckles and refining centroid extraction algorithms, overlooking the potential information about object motion that speckles inherently contain. To address this deficiency, a dynamic speckle correlation (DSC) method is proposed to reduce speckle-induced measurement uncertainty in laser triangulation systems. This method uses the correlation between speckle patterns and the movement of the object being measured, thereby enabling real-time error compensation without any speckle reduction mechanisms. To verify the effectiveness of the DSC method, we have designed a compact LTS based on oblique incident laser. Extensive experiments demonstrate that, for displacement measurement of objects with surface roughness ranging from R a 0. 4 to R a 3. 2 , the DSC method can effectively reduce the root mean square (RMS) measurement error to 3 ∼ 5 μ m. Compared with using the traditional grayscale centroid method alone, the measurement accuracy after DSC compensation is improved by at least 20%. • Speckle-induced measurement uncertainty is reduced by analyzing speckle features. • The speckle correlation in laser triangulation contains valuable information about object motion. • The dynamic displacement measurement accuracy on optical rough surfaces is improved. [Display omitted] [ABSTRACT FROM AUTHOR]

A non-contact optical inspection method for detecting voids in translucent composites is presented. Structured laser light is used to illuminate the inspected part. As the light penetrates the matrix, it scatters and is reflected from internal structures, rendering them perceptible in close proximity of the laser illumination. A systematic image acquisition and scanning approach is employed along with image processing to reconstruct and visually represent the internal composition of the inspected part. Experiments involving translucent epoxy and polyester based composites demonstrate capability to detect voids with depths reaching up to 5 mm. The detection depth is predominantly influenced by the light transmittance properties of the matrix, as well as the density and quantity of fiber layers. The arrangement of the camera and laser on the same side of the inspected part facilitates the examination of parts with varying thicknesses. The presented method is intended for automated inspection in mass production by leveraging its non-contact characteristics and high operational velocity. • Voids are visible in close proximity to structured light illumination. • Void detection up to a depth of 5 mm, influenced by resin transparency and fiber density. • Independence of variations in part thickness. • Enables high-speed automated inspection in mass production. [ABSTRACT FROM AUTHOR]

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In 3D printing, as in other manufacturing processes, there is a push for zero-defect manufacturing, mainly to avoid waste. To evaluate the quality of the printed parts during the printing process, an accurate 3D measurement method is required. By scanning the part during the buildup, potential nonconformities to tolerances can be detected early on and the printing process could be adjusted to avoid scrapping the part. Out of many, shape-from-focus, is an accurate method for recovering 3D shapes from objects. However, the state-of-the-art implementation of the method requires the object to be stationary during a measurement. This does not reconcile with the nature of 3D printing, where continuous motion is required for the manufacturing process. This research presents a novel methodology that allows shape-from-focus to be used in a continuous scanning motion, thus making it possible to apply it to the 3D manufacturing process. By controlling the camera trigger and a tunable lens with synchronous signals, a stack of images can be created while the camera or the object is in motion. These images can be re-aligned and then used to create a 3D depth image. The impact on the quality of the 3D measurement was tested by analytically comparing the quality of a scan using the traditional stationary method and of the proposed method to a known reference. The results demonstrate a 1.22% degradation in the measurement error.

In order to decrease the noise and vibration of operation in railway tracks, it is necessary to inspect the status of them frequently. A main task in inspection of railway tracks is measurement of rail corrugation. The rail corrugation occurs during operation due to wear. The dynamic component of the vertical wheel-rail contact force, as induced by rail corrugation is an important source to vibration. Also, according to the corrugation wavelength and railway vehicle speed, a dynamic excitation is generated which is an important source to noise. It is essential to utilize a system to check the rail corrugation. In this article, a new measurement system based on image processing is proposed to perform the corrugation measurement in a reliable manner, while traditional measurement systems are based on acceleration measurement or chord measurement and they are not reliable due to physical contact or need for knowing the characteristics of the track. The proposed system is based on laser triangulation principle using image processing to measure the rail corrugation precisely and quickly. This approach is an efficient technique for high-speed and high-accurate rail corrugation measurement. Experimental results show the capability of the system for practical usages. [ABSTRACT FROM AUTHOR]

Copyright of Laser Technology is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Technisches Messen is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a new type of 3D foot scanning system using rotational and translational 3D scanning stages. Commercial 3D foot scanning systems (or scanners) mostly employ the laser triangulation method and three or more linear stages to scan the entire 3D shape of the foot. We introduce a new foot scanning method using only two laser-camera triangulation sensors. The proposed scanning system consists of a 360° rotational and a linear translational 3D sensors. The rotational sensor employs two line lasers with a vision camera to solve an occlusion problem of the rotational stage and acquires the 3D shape of the upper part of the foot. The translational sensor consists of a line laser and a vision camera and acquires the 3D shape of the foot sole. The performance of the proposed scanning technique is verified using plastic models and human feet. In average, about 0.5 mm reconstruction accuracy is obtained by the proposed technique. [ABSTRACT FROM AUTHOR]

Limitations of the pinhole method and astigmatic defocus detection have difficulties in determining the direction of defocus and a restricted linear correction range. Here, a distance-measuring approach based on the laser triangulation principle is proposed with a corresponding mathematical model to overcome these problems and to satisfy the requirements of an industrial thin-film transistor liquid-crystal display (TFT-LCD) inspection microscope system in active auto-focus applications. The approach combines infrared light at a wavelength of 808 nm with visible light. The light reflected from the surface of the object reaches a CCD camera and forms a spot via a set of optical devices. To control a PZT to achieve real-time auto-focusing, a Gaussian curve fitting method is used to process the spot information with the presented mathematical model giving the relationship between the detection value and the defocus value focus error signal (FES). The preliminary experiments with a 50× objective lens show that the measured values are consistent with the theoretical values, have good linearity and possess a focusing accuracy of 0.2 μm within ±30 μm of the focal plane. The analysis of the experimental results proves the feasibility of using this method in industrial applications. Compared with the traditional method of microscope focus correction, this method has the advantages of high accuracy, good linearity, and fast focus speed for the actual requirements of industrial inspection processes. This method has been applied to the circuit board component defect detection in our laboratory.

The article deals with assessment of the suitability of using a laser triangulation sensor to measure the displacement in vertical axis of a measuring microscope. Data obtained from sensor calibration are used for determination of measuring range in which the smallest measurement error occurs. Linear approximation of the inverse calibration function is applied to correct systematic errors in reduced measuring range of the sensor. Residual measurement errors of corrected sensor output can be applied in uncertainty calculation for sensor future measurements. [ABSTRACT FROM AUTHOR]

In this paper, a flexible laser beam profiler is proposed to easily measure the profile of a train wheel for railway inspection. It only requires two laser beams (together and in parallel) to obtain two three-dimensional point-clouds based on the laser triangulation principle. Either the laser beam profiler or the wheel can be freely moved. The motion need not be known. The wheel profile will be obtained in two steps. First, the wheel axis position and orientation are obtained by minimizing the distance between one of the point-clouds and the other translated point-cloud, and translation is defined as a rotation of any point on the point-cloud around the wheel axis until it lies on the other point-cloud's laser plane. In the second step, the wheel profile is extracted by selecting one of the point-clouds and rotating it about the wheel axis and by finding the intersection of rotating points and a perpendicular plane, the perpendicular plane is defined as any arbitrary plane which passes through the wheel axis. This method is useful particularly for obtaining geometrical parameters of a wheel such as flange height, flange slope and flange thickness. In order to commission the proposed method, a prototype system was designed and manufactured. The performance of the system, evaluated in different circumstances, shows a measurement error of up to 2%. Compared with classical methods utilizing a caliper or those which use expensive equipment or additional parts such as reference guides, the proposed method is easy to use and flexible. Also, a novel calibration method is utilized to calibrate the system accurately and freely. [ABSTRACT FROM AUTHOR]

In this paper we use linear vibration approach to make a model of a horizontal vibration screen, which can be applied at gravel pit in order to perform separation operation of the wet gravel particles. The model can produce the natural frequencies of the system, which are useful in the adjustment of the angular velocity of the vibration exciter. A laser triangulation unit is well applicable to measure peak-to-peak amplitude of the working vibration screen. Comparison has been performed between the results of the simulation and the measurements.

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A measuring system based on laser triangulation for ranging a turbulent water surface in a laboratory environment is presented in this paper. The system is composed of a light detection and ranging (LIDAR) device, serving as a light source, and a high-speed camera. Single-point illumination was chosen to facilitate the introduction of the epipolar line in the image-processing step and thus improve the distinction between primary and other reflections, which increase the uncertainty of the measurement and introduce noise. The system was used to measure the water surface in an open channel confluence, which is composed of main and tributary channels, which join at a 90° angle. The surface was measured for 2.01 s, resulting in 54,682 points measured in 543 profiles. The influence of image process parameters (height and width of filtering kernel and width of area surrounding the epipolar line) on smooth and rough water surface was studied. The results show that the parameters' influence is at least an order of magnitude smaller than the amplitude of water surface fluctuation. [ABSTRACT FROM AUTHOR]

The present work demonstrates a multi-parameter control for constant track geometry and consistent layer height in laser metal deposition process. A two-channel pyrometric camera is used to maintain a constant melt pool size by a laser power control, whereby a constant bead geometry can be provided. In addition, laser triangulation sensors are used to observe the layer shape and maintain an optimum overlap by the lateral movement of the processing head. Without prior parameter studies a net shape geometry with a machining allowance of only 2% can be achieved. [ABSTRACT FROM AUTHOR]

Underwater 3-D measurement has many applications, for example, in the oil and gas industry, archeology, and biology. Systems with laser triangulation sensors (LTSs) are being currently used underwater, even though they face some strong environment influences. Among these challenging influences are poor image quality and refraction, due to optical window interfaces between water and air inside the camera chamber. The refraction effect can be modeled knowing the distance from the camera pinhole center to the surface of refraction, the axis of refraction, the refractive index of the mediums, and the thickness of the optical window. This paper analyses a method for underwater LTS measurement using real experiments. The proposed method is based on the pinhole camera model, a refraction modeling, and a fitted mathematical plane for the projected laser light plane. After the in-air calibration, a step standard is measured underwater and the window distance from the camera is optimized. The method is evaluated according to guidelines for optical systems evaluation (VDI/VDE 2634). [ABSTRACT FROM AUTHOR]

When automatically generating programs for flatbed laser cutting machines, it is advantageous to know the position of the supporting tips of the raw material. This allows the nesting layout and tool path to be adapted in an intelligent way. The problem of measuring the supporting tips of a laser cutting machine has not been considered in published literature before. We introduce possible methods first and choose a laser triangulation system. A novel setup, where none of the components is at a right angle to the measured surface, is proposed to account for the circumstances in a laser cutting machine. Its performance is investigated thoroughly with special regard to robustness and accuracy. In order to achieve very high accuracies, the setup is extrinsically calibrated on the measured object and different line extraction algorithms are tested for their effect on the measurement result. It is shown that the measurement setup is robust for different changes in the environment, such as different slat materials, bent supporting tips, and slagging. The measurement accuracy of the setup is calculated to be within ± 0.8 mm. [ABSTRACT FROM AUTHOR]