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geometrical calibration

Huijie Zhao, Ziye Wang, Guorui Jia, Xudong Li, Ying Zhang
The hyperspectral data and 3D structural data are highly useful in botanical research. But, the two types of information are often acquired separately and hard to be combined. In this work, a novel dual-path configuration based on acousto-optical tunable filter (AOTF) is proposed to acquire an image, structural and hyperspectral information within one acquisition process by a combination of laser triangulation. Under the configuration, the hyperspectral data and the 3D structure can be matched to subpixel level after geometrical calibration...
June 25, 2018: Optics Express
Yubin Huang, Kuang-Chao Fan, Wei Sun, Shujie Liu
In this paper, a compact four-degree-of-freedom (4-DOF) measurement system is presented. With a special optical configuration, the pitch error, yaw error, and two straightness errors of the moving target are able to be detected by only a single laser beam from a collimated laser diode. A 2D hybrid mirror angle steering mount is designed to perform the large angle turning for the axis alignment and very fine angle tuning by PZT actuators for real-time beam drift compensation. A series of calibration and comparison experiments have been carried out to verify the performance of the proposed system...
June 25, 2018: Optics Express
Xia Liu, Zhenyu Liu, Guifang Duan, Jin Cheng, Xuetao Jiang, Jianrong Tan
Precise calibration of a binocular vision system is the foundation of binocular vision measurement. In this paper, we propose a highly precise and robust binocular camera calibration method, which is devoted to minimize the error between the geometric relation of 3D reconstructed feature points and the ground truth, such as adjacent distance error, collinear error, and right-angle error. In addition, the reprojection error and epipolar are introduced to satisfy the homography relation and epipolar geometry theory better...
June 20, 2018: Applied Optics
R Usamentiaga, C Ibarra-Castanedo, X Maldague
Geometric information from infrared images can complement the information about the measured infrared radiation. However, this requires geometric camera calibration. In this work, three calibration methods for infrared cameras are compared: a direct and an iterative estimation of the transformation between image and world coordinates and a complete camera calibration method using a specifically designed calibration target. The three methods are compared and the obtained performance for metric measurements on a plane is evaluated...
June 20, 2018: Applied Optics
Marcin Kozłowski, Chiara Bedon, Dániel Honfi
Glass is largely used in architectural and engineering applications (i.e., buildings and vehicles) as a structural material, especially in the form of laminated glass (LG) sections. To achieve adequate and controlled safety levels in these applications, the well-known temperature-dependent behavior of viscoelastic interlayers for LG sections should be properly accounted for during the design process. Furthermore, the materials' thermomechanical degradation with increases of temperature could severely affect the load-bearing performance of glass assemblies...
August 16, 2018: Materials
Jayaraj Joseph, Nabeel P M, Malay Ilesh Shah, Mohanasankar Sivaprakasam
OBJECTIVE: Assessment of local arterial properties has become increasingly important in cardiovascular research as well as in clinical domains. Vascular wall stiffness indices are related to local pulse pressure (ΔP) level, mechanical and geometrical characteristics of the arterial vessel. Non-invasive evaluation of local ΔP from the central arteries (aorta and carotid) is not straightforward in a non-specialist clinical setting. In this work, we present a method and system for real-time and beat-by-beat evaluation of local ΔP from superficial arteries-a non-invasive, cuffless and calibration-free technique...
2018: PloS One
Q Tong, M Chen, Z Xin, D Wei, X Zhang, J Liao, H Wang, C Xie
When all the parts of the wavefront imaging system are kept static after wavefront measuring, the target's images are blurry, because the depth of field (DOF) of the system affects the imaging quality. In this paper, the method for extending the DOF of the wavefront imaging system through an integrated architecture of a liquid-crystal microlens array (LCMLA) powered by electricity and a common photosensitive array, is presented. The DOF can be extended remarkably only by stitching together several sub-images of the LCMLA...
July 9, 2018: Optics Express
Qi Zhang, Chunping Zhang, Jinbo Ling, Qing Wang, Jingyi Yu
Light field cameras can capture both spatial and angular information of light rays, enabling 3D reconstruction by a single exposure. The geometry of 3D reconstruction is affected by intrinsic parameters of a light field camera significantly. In the paper, we propose a multi-projection-center (MPC) model with 6 intrinsic parameters to characterize light field cameras based on traditional two-parallel-plane (TPP) representation. The MPC model can generally parameterize light field in different imaging formations, including conventional and focused light field cameras...
August 9, 2018: IEEE Transactions on Pattern Analysis and Machine Intelligence
Fujio Araki, Takeshi Ohno, Suzuna Umeno
The purpose of this study was to develop a new ionization chamber dosimetry formalism for diagnostic kilovoltage x-ray beams based on a 60Co absorbed dose-to-water calibration coefficient . To validate the new chamber dosimetry, 39 fluence spectra of kilovoltage x-rays were calculated, using a SpekCalc program, for Al half-value-layer (Al-HVL) values of 1.4 8.5 mm and tube voltages of 50 137.6 kVp. We used these spectra to calculate the beam quality conversion factor for kilovoltage x-ray beams Qx to a 60Co beam for a PTW 30013 Farmer ionization chamber in a reference geometrical setup (depth = 1 cm in water, field size = 20 × 20 cm2)...
August 13, 2018: Physics in Medicine and Biology
Felicitas J Detmer, Bong Jae Chung, Fernando Mut, Martin Slawski, Farid Hamzei-Sichani, Christopher Putman, Carlos Jiménez, Juan R Cebral
PURPOSE: Unruptured cerebral aneurysms pose a dilemma for physicians who need to weigh the risk of a devastating subarachnoid hemorrhage against the risk of surgery or endovascular treatment and their complications when deciding on a treatment strategy. A prediction model could potentially support such treatment decisions. The aim of this study was to develop and internally validate a model for aneurysm rupture based on hemodynamic and geometric parameters, aneurysm location, and patient gender and age...
August 9, 2018: International Journal of Computer Assisted Radiology and Surgery
Brian A Logue, Erica Manandhar
Linear models for calibration curves are overwhelmingly created based on minimization of least squares error, with their goodness-of-fit (GOF) quantified using the square of the correlation coefficient (R2 ). Yet, R2 has well-known disadvantages when used to quantify GOF of calibration curves stemming from its calculation based on the absolute error of the signal (i.e., calculated vs. experimental). These disadvantages are exacerbated when using a geometric series of concentrations for calibration standards (e...
November 1, 2018: Talanta
J H Madden, Lisa Kaltenegger
We present a catalog of spectra and geometric albedos, representative of the different types of solar system bodies, from 0.45 to 2.5 μm. We analyzed published calibrated, uncalibrated spectra, and albedos for solar system objects and derived a set of reference spectra and reference albedos for 19 objects that are representative of the diversity of bodies in our solar system. We also identified previously published data that appear contaminated. Our catalog provides a baseline for comparison of exoplanet observations to 19 bodies in our own solar system, which can assist in the prioritization of exoplanets for time intensive follow-up with next-generation extremely large telescopes and space-based direct observation missions...
July 31, 2018: Astrobiology
Ming Zhang, Maya R Sternberg, Christine M Pfeiffer
Background: Harmonizing critical reagents for the folate microbiological assay (MBA) may improve among-laboratory comparability. Objective: We assessed the comparability of the MBA for serum folate (S-FOL) and whole-blood folate (WB-FOL) in an international comparison study. Methods: Eight laboratories obtained a kit containing CDC microorganism inoculum (chloramphenicol-resistant Lactobacillus rhamnosus), CDC calibrator (5-methyltetrahydrofolate), and 23 serum and WB hemolysate samples each...
May 1, 2018: Journal of Nutrition
Damian Wierzbicki
In the last few years, it has been possible to observe a considerable increase in the use of unmanned aerial vehicles (UAV) equipped with compact digital cameras for environment mapping. The next stage in the development of photogrammetry from low altitudes was the development of the imagery data from UAV oblique images. Imagery data was obtained from side-facing directions. As in professional photogrammetric systems, it is possible to record footprints of tree crowns and other forms of the natural environment...
July 26, 2018: Sensors
Ömür Gülsüm Deniz, Gamze Altun, Arife Ahsen Kaplan, Kiymet Kübra Yurt, Christopher S von Bartheld, Suleyman Kaplan
Stereology is a collection of methods which makes it possible to produce interpretations about actual three-dimensional features of objects based on data obtained from their two-dimensional sections or images. Quantitative morphological studies of the central nervous system have undergone significant development. In particular, new approaches known as design-based methods have been successfully applied to neuromorphological research. The morphology of macroscopic and microscopic structures, numbers of cells in organs and structures, and geometrical features such as length, volume, surface area and volume components of the organ concerned can be estimated in an unbiased manner using stereological techniques...
July 23, 2018: Journal of Neuroscience Methods
XueJun Jin, Jinwoo Jung, Seong Young Ko, Eunpyo Choi, Jong-Oh Park, Chang-Sei Kim
A cable-driven parallel robot has benefits of wide workspace, high payload, and high dynamic response owing to its light cable actuator utilization. For wide workspace applications, in particular, the body frame becomes large to cover the wide workspace that causes robot kinematic errors resulting from geometric uncertainty. However, appropriate sensors as well as inexpensive and easy calibration methods to measure the actual robot kinematic parameters are not currently available. Hence, we present a calibration sensor device and an auto-calibration methodology for the over-constrained cable-driven parallel robots using one-dimension laser distance sensors attached to the robot end-effector, to overcome the robot geometric uncertainty and to implement precise robot control...
July 23, 2018: Sensors
David Llopis-Castelló, Francisco Javier Camacho-Torregrosa, Alfredo García
The most important factors for road crash occurrence are infrastructure, vehicle, and human factors. In fact, infrastructure and its interaction with human factor have been thoroughly studied in recent years through geometric design consistency, which can be defined as how drivers' expectations and road behavior relate. Global consistency models were calibrated in the last decade to assess road safety on an entire homogeneous road segment. However, none of them include the underlying consistency phenomenon in their formulation...
July 18, 2018: Accident; Analysis and Prevention
Haim Abramovich, Idan Har-Nes
The use of a single bimorph as a harmonic oscillator aimed at harvesting vibrational energy is not effective due to its inherent narrow frequency bandwidth stemming from the need to adjust the natural frequency of the harvester to the platform excitation frequencies. Therefore, the present research focuses on the development, manufacturing, and testing of an advanced system based on three bimorphs, capable of adjusting their natural frequencies using tip end masses, and interconnected by springs, thus enlarging the system's bandwidth...
July 19, 2018: Materials
Gabriel Okello, Graham Devereux, Sean Semple
Household Air Pollution (HAP) from burning biomass fuels is a major cause of mortality and morbidity in low-income settings worldwide. Little is known about the differences in objective personal HAP exposure by age and gender. We measured personal exposure to HAP across six groups defined by age and gender (young children, young males, young females, adult males, adult females, and elderly) in rural households in two sub-Saharan African countries. Data on 24-hour personal exposure to HAP were collected from 215 participants from 85 households in Uganda and Ethiopia...
July 17, 2018: Environment International
Ho-Gun Ha, Sangseo Jeon, Seongpung Lee, Hyunseok Choi, Jaesung Hong
PURPOSE: For augmented reality surgical navigation based on C-arm imaging, accuracy of the overlaid augmented reality onto the X-ray image is imperative. However, overlay displacement is generated when a conventional pinhole model describing a geometric relationship of a normal camera is adopted for C-arm calibration. Thus, a modified model for C-arm calibration is proposed to reduce this displacement, which is essential for accurate surgical navigation. METHOD: Based on the analysis of displacement pattern generated for three-dimensional objects, we assumed that displacement originated by moving the X-ray source position according to the depth...
July 16, 2018: International Journal of Computer Assisted Radiology and Surgery
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