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A new static method of calibration for low-cost laser triangulation systems
摘要： As a non-contact high-ef?ciency method, laser triangulation has long been studied by many scholars. Building such a system usually requires calibration where system parameters are found or amended to achieve the targeted precision. Traditional calibration methods require using either precise movement or high precision gauge object that are accompanied with extra manufacturing cost and auxiliary equipment/devices and hence increase the overall cost as well as prevent widespread applications, for instance, due to required environment conditions to be ful?lled. A new static method was, therefore, proposed to calibrate a system without need of a motion or a high precision gauge object to be deployed. The method relies on preparation of the data on a scalar compound target with a geometric estimator as quality indicator. Based on this method, three versions of a low-cost prototype were built, which achieved sub-millimeter precision. Although the precision is suf?cient for a measurement often used manufacturing large panels, higher precision is achievable with additional work which is to be undertaken in the future. The proposed method makes tradeoff between precision and cost. This was followed by testing on the measurement of a small panel part as application-case study. The proven feasibility of the method proposed suggested potential of developing low-cost, inline industrial system (large or small) for inspecting sheet parts during manufacturing, especially panel component manufacturing, including that from metal sheets and composite materials.
关键词： Calibration,Inspection,Panel manufacturing,Measurement,Modelling,Laser triangulation
更新于2025-09-23 15:21:01
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A Study on the Uncertainty of a Laser Triangulator Considering System Covariances
摘要： A laser triangulation system, which is composed of a camera and a laser, calculates distances between objects intersected by the laser plane. Even though there are commercial triangulation systems, developing a new system allows the design to be adapted to the needs, in addition to allowing dimensions or processing times to be optimized; however the disadvantage is that the real accuracy is not known. The aim of the research is to identify and discuss the relevance of the most significant error sources in laser triangulator systems, predicting their error contribution to the final joint measurement accuracy. Two main phases are considered in this study, namely the calibration and measurement processes. The main error sources are identified and characterized throughout both phases, and a synthetic error propagation methodology is proposed to study the measurement accuracy. As a novelty in uncertainty analysis, the present approach encompasses the covariances of correlated system variables, characterizing both phases for a laser triangulator. An experimental methodology is adopted to evaluate the measurement accuracy in a laser triangulator, comparing it with the values obtained with the synthetic error propagation methodology. The relevance of each error source is discussed, as well as the accuracy of the error propagation. A linearity value of 40 μm and maximum error of 0.6 mm are observed for a 100 mm measuring range, with the camera calibration phase being the main error contributor.
关键词： accuracy,camera calibration,laser triangulation,laser calibration,uncertainty,covariances
更新于2025-09-23 15:19:57
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Laser ranging measurements of turbulent water surfaces
摘要： Laser ranging is a measurement method, applied in a wide range of applications. In this study, laser ranging is used to measure the height of turbulent water flows. Measurements were performed in three cross sections of a confluence where a tributary flow meets the main flow. Both flows exhibited high Reynolds and Froude numbers where the free-water surface profiles were turbulent, non-stationary and non-homogeneous. Measurements were taken using a commercial LIDAR and a high-speed camera. The high-speed camera was operated on the principle of laser triangulation, using only the illumination from the LIDAR laser beam. Since, no other state-of-the-art method for measuring instantaneous water surface profiles exists, LIDAR and triangulation methods could only be compared with each other. The results show good agreement between both methods for the average turbulent water profile and fair agreement for instantaneous profiles. Presented herein is an explanation of these results.
关键词： Non-stationary surface,Free surface,Turbulence,High-speed camera,LIDAR,Laser triangulation
更新于2025-09-23 15:19:57
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Macrostickies measurement by an automated method using laser triangulation and near infrared spectroscopy
摘要： In recycled paper processes, stickies are at the origin of many production disturbances, such as machine breaks, defects in paper and converting problems. Typically, a macrostickies measurement involves separating them from the pulp by screening, then characterising by one of the available inspection and classification methods. The most recognized method in Europe is INGEDE#4. It gives useful information about stickies particles count and size. However the measurement is time-consuming, because of the manual preparation involving numerous steps. In this work, we present an automated macro-contaminant measurement method which allows to (i) determine the 3 dimensional morphology of screened particles (without any deformation) and (ii) classify the particles as stickies among contaminants. This is achieved by a combination of laser triangulation and local near-infrared (NIR) spectroscopy. Starting from the screened contaminants deposited on a filter paper, the stickies measurement is fully automated. The stickies count results from the proposed method are closely correlated with those from the INGEDE#4 method.
关键词： Contaminants,Stickies,Sensor,Recycled pulp,Near infrared spectroscopy,Laser triangulation
更新于2025-09-23 15:19:57
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A laser triangulation sensor for vibrational structural analysis and diagnostics
摘要： The industrial progress has reached a level in which it is necessary to understand the behavior of mechanical components and to monitor their conditions without disassembling them. Nowadays, a suitable methodology is based on vibrational analysis usually performed through acceleration signals measured directly on the system to be tested. However, in the last years, the industrial scenario has deeply changed due to the need for time reduction, in particular, for the control operations at the end of the productive line. The genuine methods based on acceleration measurements, for example, through piezoelectric accelerometers, came into conflict with the industrial need as the sensors used for the quality control have to be easily and fastly mounted and unmounted. A valid alternative is represented by the exploitation of laser triangulation sensors that are able to measure the dynamic displacement in a contactless way, strongly reducing the (un)mounting time. The target of this paper is to highlight pros and cons of the contactless displacement analysis through laser triangulation sensors with respect to the contact one through genuine accelerometers by means of a comparison between the results obtained both for experimental modal analysis and vibrational diagnostics of rotating machines.
关键词： displacement analysis,experimental modal analysis,laser triangulation sensor,Vibration,vibrational diagnostics
更新于2025-09-19 17:13:59
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Coaxial laser triangulation for height monitoring in laser metal deposition
摘要： The control of the height parameter plays a crucial role in the laser metal deposition (LMD) process. A mismatch between the deposition height increment and the process growth rate can generate geometrical inaccuracies as well as collisions. The paper presents a method based on triangulation for monitoring in-line the height on a LMD system composed of a coaxial deposition head, an anthropomorphic robot and a fiber laser. The measurement device is implemented within the deposition head, with a probe laser beam that is launched coaxially through the nozzle and focused directly on the melt pool at different positions depending on the standoff distance. The position of the probe spot is acquired through a coaxial camera and converted in relative height values. The system is demonstrated for the distance measurement over a range of some millimeters during the deposition of AISI 316L stainless steel. This method allows for high flexibility being independent on the deposition direction.
关键词： additive manufacturing,optical monitoring,directed energy deposition,laser triangulation
更新于2025-09-12 10:27:22