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Process Monitoring and Control
Published in Linkan Bian, Nima Shamsaei, John M. Usher, Laser-Based Additive Manufacturing of Metal Parts, 2017
Layer morphology monitoring: involves assessing the shape and physical aspects of the deposited layer. Traditionally, a line laser is projected on a deposited layer, the reflection is captured using a camera, and subsequently analyzed using image processing techniques (to account for distortion). The output is the layer height (or clad height). Recently, laser spectroscopy has been investigated as a means to go beyond simple height measurement, toward measurement of the characteristics of a deposited road (hatch spacing) [132].
Raman Hyperspectral Imaging
Published in N.C. Basantia, Leo M.L. Nollet, Mohammed Kamruzzaman, Hyperspectral Imaging Analysis and Applications for Food Quality, 2018
Rajesh Kumar R. Singh, N.C. Basantia
Laser source: This system consists of two spatially combined 785-nm laser heads mounted on a water-cooled cold plate, a laser-diode power supply, a system chiller, a collimating lens, and a clean-up filter. The laser beams generated by the two spatially combined laser heads pass through the collimating lens, resulting in a line laser. In the study, the laser head is positioned along the horizontal direction.
Accuracy assessment of light detection and ranging system measurements for jointed concrete pavement surface geometry
Published in Road Materials and Pavement Design, 2023
Shuo Yang, Ahmad Alhasan, Halil Ceylan, Sunghwan Kim, Bo Yang
In addition to stationary LiDAR systems, there are also other laser-based high-speed 3D profilometers, such as Mobile Laser Scanning (MLS) systems, 3D line laser imaging systems, and Automated Laser Profile Systems (ALPS), capable of capturing 3D surface profiles. An MLS system is consisting of a mobile platform, LiDAR module, computer and data storage, photo/video recording, and positioning hardware, including the satellite navigation system, an inertial measurement unit (IMU), and a distance measurement instrument (DMI). Such components can collect laser-scanned 3D point cloud data directly from surrounding objects to create a map and then calculate their coordinates according to the positions and orientations of the vehicle's sensors from the positioning hardware. The LiDAR module mounted on the MLS system can acquire a high-resolution 3D point cloud at traffic speed for topographic surveying and asset inventory purposes, and recent research studies have investigated their feasibility for pavement roughness inspection (Kumar et al., 2015). However, compared to a stationary LiDAR system, an MLS system usually provides relatively low accuracy and encounters significant challenges in establishing survey control points. A 3D line-laser imaging system utilises the 3D line profile cameras to generate the line profile and then uses the principle of laser triangulation to compute the elevation of points from the line profile. It could be mounted on both sides at the back of a van to acquire 3D profile data that completely covers a single lane, while a stationary LiDAR system can capture the 3D profile data of multiple lanes simultaneously. Also this system is primarily used for distress identification and quantification (Tsai & Wang, 2015). ALPS is a mobile low-speed profilometer with a 4.6 m long ALPS aluminium beam mounted at the front of a lawn tractor (Worel et al., 2003). Evenly spaced lasers at the beam are utilised to measure the distance between the pavement surface and the beam to obtain the transverse profile of a PCC slab. It’s important to note that ALPS takes measurements with the vehicle stopped, so traffic control is required on-site to collect data, whereas stationary LiDAR systems do not require traffic control on-site at all. All things considered, LiDAR is relatively more accurate, wider scan range, and safer when measuring 3D geometric characteristics in a pavement section.