scholarly journals The Operational Inflight Radiometric Uniform Calibration of a Directional Polarimetric Camera

2021 ◽  
Vol 13 (19) ◽  
pp. 3823
Author(s):  
Feinan Chen ◽  
Donggen Luo ◽  
Shuang Li ◽  
Benyong Yang ◽  
Liang Sun ◽  
...  
Keyword(s):  
Optical Sensors ◽  
Mean Squared Error ◽  
Radiation Detection ◽  
Calibration Method ◽  
Space Environment ◽  
Calibration Coefficient ◽  
Large Field ◽  
Observation Angle ◽  
Detection Accuracy ◽  
Calibration Samples

The directional polarimetric camera (DPC) on-board the GF-5A satellite is designed for atmospheric or water color detection, which requires high radiometric accuracy. Therefore, in-flight calibration is a prerequisite for its inversion application. For large field optical sensors, it is very challenging to ensure the consistency of radiation detection in the whole field of view in the space environment. Our work proposes a vicarious in-flight calibration method based on sea non-equipment sites (visible bands) and land non-equipment sites (all bands). Combined with environmental parameters and radiation transmission calculations, we evaluated the radiation detection accuracy of the 0° to 60° view zenith angle of the DPC in each band. Our calibration method is based on the single-day normalized radiance data measured by the DPC. Through data selection, enough calibration samples can be obtained in a single day (the number of desert samples is more than 5000, and the number of calibration samples of the ocean is more than 2.8×106). The measurements are compared with the simulation of 6SV VRT code or look-up tables. The massive amount of data averages the uncertainty of a single-point calculation. Although the uncertainty of a single sample is significant, the final fitting of the curve of the variation in the radiometric calibration coefficient with the observation angle can still keep the root mean squared error at approximately 2–3% or even lower, and for visible bands, the calibration results for both ocean sites and desert sites are in good agreement regarding the non-uniformity of the sensor.

scholarly journals A Novel Portable Gamma Radiation Sensor Based on a Monolithic Lutetium-Yttrium Oxyorthosilicate Ring

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3376
Author(s):  
Xi Zhang ◽  
Qiangqiang Xie ◽  
Siwei Xie ◽  
Xin Yu ◽  
Jianfeng Xu ◽  
...  
Keyword(s):  
Gamma Radiation ◽  
Gamma Rays ◽  
Detection Efficiency ◽  
Radiation Detection ◽  
Radiation Detectors ◽  
Large Field ◽  
Average Error ◽  
Detection Accuracy ◽  
Environmental Radiation ◽  
Radiation Sensor

Portable radiation detectors are widely used in environmental radiation detection and medical imaging due to their portability feature, high detection efficiency, and large field of view. Lutetium-yttrium oxyorthosilicate (LYSO) is a widely used scintillator in gamma radiation detection. However, the structure and the arrangement of scintillators limit the sensitivity and detection accuracy of these radiation detectors. In this study, a novel portable sensor based on a monolithic LYSO ring was developed for the detection of environmental radiation through simulation, followed by construction and assessments. Monte Carlo simulations were utilized to prove the detection of gamma rays at 511 keV by the developed sensor. The simulations data, including energy resolutions, decoding errors, and sensitivity, showed good potential for the detection of gamma rays by the as-obtained sensor. The experimental results using the VA method revealed decoding errors in the energy window width of 50 keV less than 2°. The average error was estimated at 0.67°, a sufficient value for the detection of gamma radiation. In sum, the proposed radiation sensor appears promising for the construction of high-performance radiation detectors and systems.

scholarly journals Gait Phase Detection Based on Muscle Deformation with Static Standing-Based Calibration

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1081
Author(s):  
Tamon Miyake ◽  
Shintaro Yamamoto ◽  
Satoshi Hosono ◽  
Satoshi Funabashi ◽  
Zhengxue Cheng ◽  
...  
Keyword(s):  
Learning Algorithm ◽  
Detection System ◽  
Calibration Method ◽  
Detection Algorithm ◽  
Video Data ◽  
Detection Accuracy ◽  
Phase Detection ◽  
Gait Phase ◽  
Logistic Regression Algorithm ◽  
Short Time

Gait phase detection, which detects foot-contact and foot-off states during walking, is important for various applications, such as synchronous robotic assistance and health monitoring. Gait phase detection systems have been proposed with various wearable devices, sensing inertial, electromyography, or force myography information. In this paper, we present a novel gait phase detection system with static standing-based calibration using muscle deformation information. The gait phase detection algorithm can be calibrated within a short time using muscle deformation data by standing in several postures; it is not necessary to collect data while walking for calibration. A logistic regression algorithm is used as the machine learning algorithm, and the probability output is adjusted based on the angular velocity of the sensor. An experiment is performed with 10 subjects, and the detection accuracy of foot-contact and foot-off states is evaluated using video data for each subject. The median accuracy is approximately 90% during walking based on calibration for 60 s, which shows the feasibility of the static standing-based calibration method using muscle deformation information for foot-contact and foot-off state detection.

A novel and accurate calibration method for cameras with large field of view using combined small targets

Measurement ◽  
2015 ◽  
Vol 64 ◽  
pp. 1-16 ◽  
Author(s):  
Zhen Liu ◽  
Fengjiao Li ◽  
Xiaojing Li ◽  
Guangjun Zhang
Keyword(s):  
Calibration Method ◽  
Field Of View ◽  
Large Field ◽  
Small Targets

scholarly journals Detecting the normal-direction in automated aircraft manufacturing based on adaptive alignment

2020 ◽  
Vol 103 (4) ◽  
pp. 003685042098121
Author(s):  
Ying Zhang ◽  
Hongchang Ding ◽  
Changfu Zhao ◽  
Yigen Zhou ◽  
Guohua Cao
Keyword(s):  
Calibration Method ◽  
Adaptive Method ◽  
Normal Direction ◽  
Detection Accuracy ◽  
Average Deviation ◽  
Important Indicator ◽  
Aircraft Manufacturing ◽  
Direction Detection ◽  
Hole Making ◽  
Vertical Accuracy

In aircraft manufacturing, the vertical accuracy of connection holes is important indicator of the quality of holes making. Aircraft products have high requirements for the vertical accuracy of holes positions. When drilling and riveting are performed by an automatic robotic system, assembly errors, bumps, offsets and other adverse conditions, can affects the accuracy of manufacturing and detection, and in turn the fatigue performance of the entire structure. To solve this problem, we proposed a technology for detecting the normal-direction based on the adaptive alignment method, built a mathematical model for posture alignment, and studied the calibration method and mechanism of the detection device. Additionally, we investigated techniques for error compensation using an electronic theodolite and other devices when the adaptive method is used for detection. In verification experiments of the method, multiple sets of results demonstrated that the key technical indicators are as follows: normal accuracy <0.5°, average deviation after correction =0.0667°. This method can effectively compensate the errors affecting hole making work in automated manufacturing, and further improve the positioning accuracy and normal-direction detection accuracy of the robot.

Calibration Method for Large Field of View Image Matching Parameters Based on Non-Metric Correction

2018 ◽  
Vol 38 (8) ◽  
pp. 0815004
Author(s):  
张致远 Zhang Zhiyuan ◽  
刘巍 Liu Wei ◽  
张洋 Zhang Yang ◽  
逯永康 Lu Yongkang ◽  
邸宏图 Di Hongtu ◽  
...  
Keyword(s):  
Image Matching ◽  
Calibration Method ◽  
Field Of View ◽  
Large Field

scholarly journals Flexible method for accurate calibration of large-scale vision metrology system based on virtual 3-D targets and laser tracker

2019 ◽  
Vol 16 (6) ◽  
pp. 172988141989351
Author(s):  
Xi Zhang ◽  
Yuanzhi Xu ◽  
Haichao Li ◽  
Lijing Zhu ◽  
Xin Wang ◽  
...  
Keyword(s):  
High Precision ◽  
Stereo Vision ◽  
Large Scale ◽  
Vision System ◽  
Calibration Method ◽  
Field Of View ◽  
Large Field ◽  
Laser Tracker ◽  
Calibration Target ◽  
Pose Tracking

For the purpose of obtaining high-precision in stereo vision calibration, a large-size precise calibration target, which can cover more than half of the field of view is vital. However, large-scale calibration targets are very difficult to fabricate. Based on the idea of error tracing, a high-precision calibration method for vision system with large field of view by constructing a virtual 3-D calibration target with a laser tracker was proposed in this article. A virtual 3-D calibration target that covers the whole measurement space can be established flexibly and the measurement precision of the vision system can be traceable to the laser tracker. First, virtual 3-D targets by calculating rigid body transformation with unit quaternion method were constructed. Then, the high-order distortion camera model was taken into consideration. Besides, the calibration parameters were solved with Levenberg–Marquardt optimization algorithm. In the experiment, a binocular stereo vision system with the field of view of 4 × 3 × 2 m3 was built for verifying the validity and precision of the proposed calibration method. It is measured that the accuracy with the proposed method can be greatly improved comparing with traditional plane calibration method. The method can be widely used in industrial applications, such as in the field of calibrating large-scale vision-based coordinate metrology, and six-degrees of freedom pose tracking system for dimensional measurement of workpiece, as well as robotics geometrical accuracy detection and compensation.

Moisture Analysis in Forage by Near-Infrared Reflectance Spectroscopy: Collaborative Study of Calibration Methodology

1991 ◽  
Vol 74 (2) ◽  
pp. 324-331
Author(s):  
William R Windham ◽  
Franklin E Barton
Keyword(s):  
Near Infrared ◽  
Collaborative Study ◽  
Calibration Method ◽  
Reflectance Spectroscopy ◽  
Near Infrared Reflectance ◽  
Moisture Concentration ◽  
Moisture Analysis ◽  
Relative Standard ◽  
Calibration Samples ◽  
Standard Deviations

Abstract Fifteen collaborating laboratories analyzed 16 forage samples including 3 blind duplicate pairs for moisture by air-oven (AO) method 7.007 (14th Ed.; 930.15, 15th Ed.) and nearinfrared reflectance spectroscopy (NIRS). Laboratories performed method 7.007 on 50 calibration samples and applied the NIRS calibration method Independently. NIRS moisture equations were used to predict the 16 test samples, and the values were compared to those for method 7.007. Moisture concentration of the test samples ranged from approximately 6 to 16%. Within-laboratory repeatability (sr) ranged from 0.10 to 0.18% and 0.16 to 0.39% for NIRS and method 7.007, respectively. Between-laboratory reproducibility (sR) ranged from 0.22 to 0.57 and 0.29 to 0.57 for NIRS and method 7.007, respectively. Repeatability relative standard deviations (RSDr) for the NIRS and AO methods ranged from 1.18 to 1.50% and 1.84 to 3.68%, respectively. The range in the average reproducibility relative standard deviations (RSDR) for the NIRS and AO methods were 1.29-7.49% and 3.64-6.66%, respectively. The NIRS method demonstrated consistently lower wlthln-laboratory RSDr agreement and between-laboratory variabilities equal to method 7.007. Thereby, we demonstrated that NIRS can be used as a standard method for the determination of 6-16% moisture In forages. The method has been adopted official first action by A0AC.

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