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Airborne Laser Scanning (ALS) and Filtering Algorithms
Published in Ahmad Fikri Bin Abdullah, A Methodology for Processing Raw Lidar Data to Support Urban Flood Modelling Framework, 2020
LiDAR intensity values are a measure of the return signal strength. They are relative rather than absolute, and vary with altitude, atmospheric conditions, bi-directional reflectance properties, and the reflectivity of the target. In terms of laser scanning returns, it is possible to have multiple echoes due to obstructions. Reflectance varies with material characteristics as well as the light used, and different materials have different reflectance (Jeong HS et al., 2002). Consequently, intensities may give useful information in identifying certain objects in a LiDAR point cloud. From previous literature, 'asphalt' (often called bitumen in Asia) has an intensity value of 10-20%, 'grass' approximately 50%, 'tree' 30-60%, and 'house roof of 20-30%. Because each class has a different intensity, separation between objects can be established. Figure 4.5 shows the reflectivity of various wave lengths of Infra-red in LiDAR.
Testing the Workplace Environment
Published in Samuel G. Charlton, Thomas G. O’Brien, Handbook of Human Factors Testing and Evaluation, 2019
Reflectance is measured using a spot brightness probe and photometer. It should be measured on all control panel surfaces, workstation surfaces, and other surfaces where reflected light may cause discomfort or interfere with visibility. Reflectance is the amount of light reflected from a surface and is directly dependent on the amount of light falling on the surface. Thus, measurements of both illuminance and luminance must be made at each measurement point. The test specialist should establish measurement points in a grid pattern along the surface. Grids should be of 1 – and 2-ft increments. Measurements should be made under all potential lighting conditions. Luminance measurements should be taken using the spot brightness probe held perpendicular to the surface with the distance from the surface dependent on the field of view of the probe. Illuminance measurements should be taken using the photometer probe mounted flat on the surface. Reflectance is then calculated as follows: Reflectance = Luminance/Illuminance × 100.
Polygonal Scanners: Components, Performance, and Design
Published in Gerald F. Marshall, Glenn E. Stutz, Handbook of Optical and Laser Scanning, 2018
Several tools are available to measure the optical performance of the coating. Common measuring tools to determine reflectance are spectrophotometers and laser reflectometers. Spectrophotometers are used to provide information on the reflectance versus wavelength. The majority of spectrophotometers with a reflectance measuring attachment are limited to small sample sizes on the order of 1 to 2 in in diameter. This fact usually precludes measuring the polygon itself. A witness sample is coated at the same time as the polygon and can be used to represent the actual part performance. This can be a reliable method of ascertaining the performance of the polygon as long as the witness sample has a similar surface preparation and quality level to the polygon. This means that diamond turned witness samples should be used with diamond turned polygons and polished witness samples used with polished mirrors.
Study of silicone hydrogel contact lenses’ surface reflection characteristics using confocal microscopy
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Tomasz Suliński, Natalia Nowak, Jędrzej Szymański, Jacek Pniewski
In order to numerically demonstrate the differences in reflection from the inner surface of each lens material, calculations were made of the average value of reflection from raw images, using ImageJ software. Let us denote dimensionless reflectance and transmittance for the first (outer) contact lens surface as R1 and T1, and reflectance for the second (inner) surface as R2. The relation between reflectance and transmittance is R = 1–T. Therefore, assuming that R1 = R2, the calculated reflection signal RS for the inner surface is given by RS = (1–R)R, which is a reflected fraction of the light incident onto the outer CL surface. For each lens, the measured RS is calculated as an average value based on an analysis in a 5 µm × 50 µm (xz) window, that covers the inner CL surface with neighboring PBS and lens material. The results, normalized to 1 for the biggest value (for lotrafilcon A), are shown in Figure 4. The normalization was performed to eliminate arbitrary units of the reflection signal, measured for the same incident laser power.
Optimization problems involving matrix multiplication with applications in materials science and biology
Published in Engineering Optimization, 2022
The first example is from materials science and is called the multi-layer thin films problem. Reflectance is an important electromagnetic property of materials and, in many optics applications, materials with high reflectance are desired. When the reflectance of a metallic substrate is not satisfactory, dielectric coating materials can be used for enhancement. For instance, the reflectance of tungsten at 450 nm wavelength is approximately 47%, but it can be increased to 87% if one layer each of titanium dioxide and magnesium fluoride thin films with quarter wavelength optical thicknesses are coated on top. Given a material library and a budget on the number of layers, the multi-layer thin films problem seeks to find the optimal configuration of dielectric coating materials and their thicknesses to be coated in each layer so that the reflectance is maximized. This classical problem in optics is typically solved via heuristic and metaheuristic methods (Tikhonravov, Trubetskov, and DeBell 1996; Hobson and Baldwin 2004; Rabady and Ababneh 2014; Shi et al.2017; Keçebaş and Şendur 2018), and a rigorous treatment of the underlying optimization problem is lacking in the literature.
Effects of interior architecture for optimal use of natural light and electrical energy saving
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Ayat Mohammadi Tabar, Mohammad Moradi, Rima Fayaz
The previous research performed on the use of natural light have focused on determining the optimal window area, ceiling skylights and design of external sunshades. Based on the investigations performed, using DIALux software, the light distribution inside a real scale room was examined (Makaremi et al. 2018). This research aims to investigate the effects of applying different design strategies on lighting energy use and visual comfort level. Surface finishing reflectance, type, number and mounting height of luminaires are variables in the study. The findings indicate that the type of luminaire is the most decisive parameter in quantity and quality of light in an indoor environment. The results show the possibility of electrical energy savings up to 45% by increasing surface reflectance properties.