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- 2015
- Calibration process of OSL detectors
- Iodine-131
- OSL-BeO
- Dosimetry of staff and patients
- Optically Stimulated Luminescence (OSL)
- Akdeniz University
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[IEEE 2018 - 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON) - Helsinki (2018.6.3-2018.6.5)] 2018 - 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON) - ICP WITH DEPTH COMPENSATION FOR CALIBRATION OF MULTIPLE TOF SENSORS
摘要： We propose an iterative closest point (ICP) based calibration for time of flight (ToF) multiple depth sensors. For the multiple sensor calibrations, we usually use 2D patterns calibration with IR images. The depth sensor output depends on calibration parameters at a factory; thus, the re-calibration must include gaps from the calibration in the factory. Therefore, we use direct correspondences among depth values, and the calibrating extrinsic parameters by using ICP. Usually, simultaneous localization and mapping (SLAM) uses ICP, such as KinectFusion. The case of multiple sensor calibrations, however, is harder than the SLAM case. In this case, the distance between cameras is too far to apply ICP. Therefore, we modify the ICP based calibration for multiple sensors. The proposed method uses specific calibration objects to enforce the matching ability among sensors. Also, we proposed a compensation method for ToF depth map distortions.
关键词： Calibration,Multiple RGB-D camera,ToF,ICP,Multiple Kinect
更新于2025-09-04 15:30:14
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Calibration and instrumental line shape characterization of a set of portable FTIR spectrometers for detecting greenhouse gas emissions
摘要： A comprehensive calibration procedure for mobile, low-resolution, solar-absorption FTIR spectrometers, used for greenhouse gases observations, is developed. These instruments commend themselves for campaign use and deployment at remote sites. The instrumental line shape (ILS) of each spectrometer has been thoroughly characterized by analyzing the shape of H2O signatures in open path spectra. A setup for the external source is suggested and the invariance of derived ILS parameters with regard to chosen path length is demonstrated. The instrumental line shape characteristics of all spectrometers were found to be close to nominal. Side-by-side solar observations before and after a campaign, which involved shipping of all spectrometers to a selected target site and back, are applied for verifying the temporal invariability of instrumental characteristics and for deriving intercalibration factors for XCO2 and XCH4, which take into account residual differences of instrumental characteristics. An excellent level of agreement and stability was found between the different spectrometers: the uncorrected biases in XCO2 and XCH4 are smaller than 0.01 and 0.15 %, respectively, and the drifts are smaller than 0.005 and 0.035 %. As an additional sensitive demonstration of the instrumental performance we show the excellent agreement of ground pressure values obtained from the total column measurements of O2 and barometric records. We find a calibration factor of 0.9700 for the spectroscopic measurements in comparison to the barometric records and a very small scatter between the individual spectrometers (0.02 %). As a final calibration step, using a co-located TCCON (Total Carbon Column Observation Network) spectrometer as a reference, a common scaling factor has been derived for the XCO2 and XCH4 products, which ensures that the records are traceable to the WMO in situ scale.
关键词： calibration,XCO2,XCH4,FTIR spectrometers,instrumental line shape,greenhouse gas emissions
更新于2025-09-04 15:30:14
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A Low-Complexity I/Q Imbalance Calibration Method for Quadrature Modulator
摘要： This brief presents a low-complexity I/Q (in-phase and quadrature components) imbalance calibration method for the transmitter using quadrature modulation. Impairments in analog quadrature modulator have a deleterious effect on the signal ?delity. Among the critical impairments, I/Q imbalance (gain and phase mismatches) deteriorates the residual sideband performance of the analog quadrature modulator degrading the error vector magnitude. Based on the theoretical mismatch analysis of the quadrature modulator, we propose a low-complexity I/Q imbalance extraction algorithm. After the parameter extraction, the transmitter is calibrated by imposing the counter imbalanced mismatch of the transmitter through the digital baseband. In comparison with existing I/Q imbalance calibration methods, the novelty of the proposed method lies in that: 1) only three spectrum measurements of the device-under-test are needed for extraction and calibration of gain and phase mismatches; 2) due to the blind nature of the calibration algorithm, the proposed approach can be readily applicable to an existing I/Q transmitter; 3) no extra hardware that degrades the calibration accuracy is required; and 4) due to the noniterative nature, the proposed method is faster and computationally more ef?cient than previously published methods.
关键词： Calibration,residual sideband (RSB),quadrature mismatch,transmitter,quadrature modulation,image rejection,single sideband
更新于2025-09-04 15:30:14
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[IEEE 2018 Ubiquitous Positioning, Indoor Navigation and Location-Based Services (UPINLBS) - Wuhan, China (2018.3.22-2018.3.23)] 2018 Ubiquitous Positioning, Indoor Navigation and Location-Based Services (UPINLBS) - Monocular Visual-Inertial State Estimation With Online Temporal Calibration
摘要： In most of visual-inertial state estimation frameworks, camera is usually assumed synchronized with inertial measurement unit (IMU). However, in practice, the timestamps of camera and IMU are typically affected by a time-varying delay, especially for low-cost IMU-camera integrated system (e.g. android phone). Tracking failures could occur easily then. In this paper, we discuss the effect of the temporal offset on map points triangulation and nonlinear optimization during visual-inertial simultaneous localization and mapping (SLAM) process, and propose two feasible solutions for compensating the offset between camera and IMU. We choose the simpler solution and propose a computationally tractable approach which can estimate the offset with all other variables of interest (the IMU pose, the camera-IMU calibration, etc.). Our simulation results demonstrate that the proposed approach is effective in scenarios involving both constant and time-varying offsets.
关键词： visual-inertial state estimation,camera,temporal calibration,SLAM,IMU
更新于2025-09-04 15:30:14
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[ACM Press the 9th ACM Multimedia Systems Conference - Amsterdam, Netherlands (2018.06.12-2018.06.15)] Proceedings of the 9th ACM Multimedia Systems Conference on - MMSys '18 - Skeleton-based continuous extrinsic calibration of multiple RGB-D kinect cameras
摘要： Applications involving 3D scanning and reconstruction & 3D Tele-immersion provide an immersive experience by capturing a scene using multiple RGB-D cameras, such as Kinect. Prior knowledge of intrinsic calibration of each of the cameras, and extrinsic calibration between cameras, is essential to reconstruct the captured data. The intrinsic calibration for a given camera rarely ever changes, so only needs to be estimated once. However, the extrinsic calibration between cameras can change, even with a small nudge to the camera. Calibration accuracy depends on sensor noise, features used, sampling method, etc., resulting in the need for iterative calibration to achieve good calibration. In this paper, we introduce a skeleton based approach to calibrate multiple RGB-D Kinect cameras in a closed setup, automatically without any intervention, within a few seconds. The method uses only the person present in the scene to calibrate, removing the need for manually inserting, detecting and extracting other objects like plane, checker-board, sphere, etc. 3D joints of the extracted skeleton are used as correspondence points between cameras, after undergoing accuracy and orientation checks. Temporal, spatial, and motion constraints are applied during the point selection strategy. Our calibration error checking is inexpensive in terms of computational cost and time and hence is continuously run in the background. Automatic re-calibration of the cameras can be performed when the calibration error goes beyond a threshold due to any possible camera movement. Evaluations show that the method can provide fast, accurate and continuous calibration, as long as a human is moving around in the captured scene.
关键词： 3D Skeleton,Interactive 3D Tele-Immersion,Point-Cloud,3D Calibration,Real-time
更新于2025-09-04 15:30:14
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Sea Ice Albedo from MISR and MODIS: Production, Validation, and Trend Analysis
摘要： The Multi-angle Imaging SpectroRadiometer (MISR) sensor onboard the Terra satellite provides high accuracy albedo products. MISR deploys nine cameras each at different view angles, which allow a near-simultaneous angular sampling of the surface anisotropy. This is particularly important to measure the near-instantaneous albedo of dynamic surface features such as clouds or sea ice. However, MISR’s cloud mask over snow or sea ice is not yet sufficiently robust because MISR’s spectral bands are only located in the visible and the near infrared. To overcome this obstacle, we performed data fusion using a specially processed MISR sea ice albedo product (that was generated at Langley Research Center using Rayleigh correction) combining this with a cloud mask of a sea ice mask product, MOD29, which is derived from the MODerate Resolution Imaging Spectroradiometer (MODIS), which is also, like MISR, onboard the Terra satellite. The accuracy of the MOD29 cloud mask has been assessed as >90% due to the fact that MODIS has a much larger number of spectral bands and covers a much wider range of the solar spectrum. Four daily sea ice products have been created, each with a different averaging time window (24 h, 7 days, 15 days, 31 days). For each time window, the number of samples, mean and standard deviation of MISR cloud-free sea ice albedo is calculated. These products are publicly available on a predefined polar stereographic grid at three spatial resolutions (1 km, 5 km, 25 km). The time span of the generated sea ice albedo covers the months between March and September of each year from 2000 to 2016 inclusive. In addition to data production, an evaluation of the accuracy of sea ice albedo was performed through a comparison with a dataset generated from a tower based albedometer from NOAA/ESRL/GMD/GRAD. This comparison confirms the high accuracy and stability of MISR’s sea ice albedo since its launch in February 2000. We also performed an evaluation of the day-of-year trend of sea ice albedo between 2000 and 2016, which confirm the reduction of sea ice shortwave albedo with an order of 0.4–1%, depending on the day of year and the length of observed time window.
关键词： calibration,MODIS,Sea ice,albedo,climate change,MISR
更新于2025-09-04 15:30:14