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- 2017
- spectral reconstruction
- interference
- polarization
- transform
- imaging spectrometer
- Optoelectronic Information Science and Engineering
- BITTT
- Zhejiang University
- Guilin University of Aerospace Technology
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Use of Hyperspectral Image Data Outperforms Vegetation Indices in Prediction of Maize Yield
摘要： Hyperspectral cameras can provide reflectance data at hundreds of wavelengths. This information can be used to derive vegetation indices (VIs) that are correlated with agronomic and physiological traits. However, the data generated by hyperspectral cameras are richer than what can be summarized in a VI. Therefore, in this study, we examined whether prediction equations using hyperspectral image data can lead to better predictive performance for grain yield than what can be achieved using VIs. For hyperspectral prediction equations, we considered three estimation methods: ordinary least squares, partial least squares (a dimension reduction method), and a Bayesian shrinkage and variable selection procedure. We also examined the benefits of combining reflectance data collected at different time points. Data were generated by CIMMYT in 11 maize (Zea mays L.) yield trials conducted in 2014 under heat and drought stress. Our results indicate that using data from 62 bands leads to higher prediction accuracy than what can be achieved using individual VIs. Overall, the shrinkage and variable selection method was the best-performing one. Among the models using data from a single time point, the one using reflectance collected at 28 d after flowering gave the highest prediction accuracy. Combining image data collected at multiple time points led to an increase in prediction accuracy compared with using single-time-point data.
关键词： maize yield,hyperspectral imaging,prediction accuracy,vegetation indices,Bayesian methods
更新于2025-09-23 15:23:52
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Single Flip-Chip Packaged Dielectric Resonator Antenna for CMOS Terahertz Antenna Array Gain Enhancement
摘要： A single dielectric resonator antenna (DRA) capable of enhancing the antenna gain of each element of a 2×2 THz antenna array realized in a 0.18-μm CMOS technology is proposed in this work. The DRA implemented in a low-cost integrated-passive-device (IPD) technology is flip-chip packaged onto the CMOS antenna array chip through low-loss gold bumps. By designing the DRA to work at the higher-order mode of TE3,δ,9, only single DRA instead of conventionally needing four DRAs is required to simultaneously improve the antenna gain of each element of the 2×2 antenna array. This not only simplifies the assembly process but it can also reduce the assembly cost. Moreover, the DRA can provide great antenna gain enhancement because of being made of high-resistivity silicon material and higher-order mode operation. The simulated antenna gain of each on-chip patch antenna of the 2×2 CMOS antenna array can be increased from 0.1 to 8.6 dBi at 339 GHz as the DRA is added. To characterize the proposed DRA, four identical power detectors (PDs) are designed and integrated with each element of the 2×2 THz antenna array, respectively. By measuring the voltage responsivity of each PD output, the characteristics of each antenna of the antenna array with the proposed DRA, including the gain enhancement level and radiation pattern, can be acquired. The measurement results follow well with the simulated ones, verifying the proposed DRA operation principle. The four PDs with the proposed DRA are also successfully employed to demonstrate a THz imaging system at 340 GHz. To the best of the authors’ knowledge, the proposed DRA is the one with the highest-order operation mode at THz frequencies reported thus far.
关键词： Silicon,Flip-chip packaging,Terahertz,CMOS,Terahertz imaging system,Antenna,Higher-order mode,Power detector,Dielectric resonator antenna
更新于2025-09-23 15:23:52
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Enhancement of objects in photoacoustic tomography using selective filtering
摘要： Here we developed a real-time photoacoustic tomography (PAT) imaging acquisition device based on the linear array transducer utilized on ultrasonic devices. Also, we produced a phantom including diverse contrast media and acquired PAT imaging as the light source wavelength was changing to see if the contrast media reacted. Indocyanine green showed the highest reaction around the 800-nm band, methylene blue demonstrated the same in the 750-nm band, and gold nanoparticle showed the same in the 700-nm band. However, in the case of superparamagnetic iron oxide, we observed not reaction within the wavelength bands used herein to obtain imaging. Moreover, we applied selective filtering to the acquired PAT imaging to remove noise from around and reinforce the object’s area. Consequentially, we could see the object area in the imaging was effectively detected and the image noise was removed.
关键词： Photoacoustic image,real-time,back projection algorithm,selective filtering,ultrasonic imaging
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A CubeSat Train for Radar Sounding and Imaging of Antarctic Ice Sheet
摘要： In spite of more than 50 years of airborne radar soundings of Antarctic ice by the international community, there are still large gaps in ice thickness data. We propose a CubeSat satellite mission for complete sounding and imaging of Antarctica with 50 CubeSats integrated with a VHF radar system to sound the ice and image the ice-bed. One of the major challenges in orbital sounding of ice is off-vertical surface clutter that masks weak ice-bed echoes. We must obtain fine resolution both in the along track and cross track directions to reduce surface clutter. We can obtain fine resolution in the along track direction by synthesizing a large aperture by taking advantage of the forward motion of a satellite. However, we need a large antenna-array to obtain fine resolution in the cross track direction. We propose a train of 50 CubeSats with optimized offset position to obtain a 500-m long aperture and also coherently combine data from multiple passes of the train to obtain a very large aperture of 1-2 km in the cross track direction. Our initial analysis shows that we can obtain measurements with horizontal resolution of about 200 m and vertical resolution of about 20 m. The CubeSat will carry a transmitter and receiver with peak transmit power of about 50 W. We will synchronize all transmitters and receivers with a Ka-band system that serves as a communication link between the earth and Cubesats to downlink data and as command and control for the CubeSats.
关键词： cryosphere,imaging,CubeSat,Satellite formation,Antarctica,sounding
更新于2025-09-23 15:23:52
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Two-Dimensional Imaging Based on Near-Field Focused Array Antenna
摘要： In this letter, a near-field focused array antenna is applied to two-dimensional (2-D) microwave imaging, which steers its focus on the designed focal plane by changing the operating frequency and by phase control in two directions, respectively. The imaging system is composed of this array and two microstrip antennas, as receiver and transmitters, respectively. Simulations and measurements have proved the feasibility of the image reconstruction approach. The proposed method has a high imaging speed due to fast electrical beam scan, and thanks to the frequency scan performance of the array in one dimension, it also shows low-cost property against the fully phased method.
关键词： near-field focused beams,Microwave imaging,phased arrays,reconstruction algorithm
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE 10th Sensor Array and Multichannel Signal Processing Workshop (SAM) - Sheffield (2018.7.8-2018.7.11)] 2018 IEEE 10th Sensor Array and Multichannel Signal Processing Workshop (SAM) - Subspace-Based Imaging Using Only Power Measurements
摘要： In this paper, we are interested in the high-resolution imaging of an unknown area based on only power measurements of a small number of wireless transceivers located on one side of the unknown area. In order to do so, we propose a framework that achieves a polynomial order reduction in the number of antennas required for high-resolution imaging. More specifically, we show that by spacing the antennas at multiples of the wavelength and applying subspace-based analysis, we can image M targets using only 2M +1 transmit/receive antennas (as compared to the state-of-the-art value of M 2 + 1 antennas). We then validate our framework using simulations in both noise-free and noisy environments.
关键词： Super-resolution imaging,Time Reversal MUSIC,Rytov Model
更新于2025-09-23 15:23:52
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Prospective feasibility study for single-tracer sentinel node mapping by ICG (indocyanine green) fluorescence and OSNA (one-step nucleic acid amplification) assay in laparoscopic gastric cancer surgery
摘要： Background The double-tracer method has been established for sentinel node (SN) mapping in gastric cancer surgery. However, there remain several unresolved issues that prevent its widespread use in clinical practice. In this study, we aimed to demonstrate the feasibility of single-tracer SN mapping in laparoscopic surgery for gastric cancer, using indocyanine green (ICG) fluorescence imaging with a one-step nucleic acid amplification (OSNA) assay intraoperatively. Methods Patients with clinical T1N0M0 gastric adenocarcinoma preoperatively were considered for inclusion if they had a single primary lesion 4 cm or less in maximal diameter. Immunohistochemical staining with the anti-cytokeratin 19 antibody was performed on preoperative biopsy specimens, and patients with faint positive reactions were excluded. Intraoperatively, single-tracer SN biopsy with ICG fluorescence imaging was performed, followed by laparoscopic gastrectomy with modified D1+ or D2 lymph node dissection. Results Twenty eligible patients underwent SN biopsy and laparoscopic gastrectomy. SNs were identified in 17 cases (85%), with a median number of three SNs per patient. The median times for SN mapping and OSNA assay were 19 and 35 min, respectively. OSNA assay detected one metastatic lymph node, but all other nodes were negative. No adverse effects were observed in relation to SN mapping. Conclusions Single-tracer SN mapping by ICG fluorescence imaging with intraoperative diagnosis by OSNA assay is feasible and safe. SNs can be identified in most patients, without producing false-negative results. Further clinical trial to demonstrate the sensitivity is ongoing.
关键词： Fluorescence imaging,Indocyanine green,Sentinel lymph node,Surgical pathology,Gastric cancer
更新于2025-09-23 15:23:52
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Fast Detection of Sclerotinia Sclerotiorum on Oilseed Rape Leaves Using Low-Altitude Remote Sensing Technology
摘要： Sclerotinia sclerotiorum, one of the major diseases infecting oilseed rape leaves, has seriously affected crop yield and quality. In this study, an indoor unmanned aerial vehicle (UAV) low-altitude remote sensing simulation platform was built for disease detection. Thermal, multispectral and RGB images were acquired before and after being artificially inoculated with Sclerotinia sclerotiorum on oilseed rape leaves. New image registration and fusion methods based on scale-invariant feature transform (SIFT) were presented to construct a fused database using multi-model images. The changes of temperature distribution in different sections of infected areas were analyzed by processing thermal images, the maximum temperature difference (MTD) on a single leaf reached 1.7 degrees Celsius 24 h after infection. Four machine learning models were established using thermal images and fused images respectively, including support vector machine (SVM), random forest (RF), K-nearest neighbor (KNN) and na?ve Bayes (NB). The results demonstrated that the classification accuracy was improved by 11.3% after image fusion, and the SVM model obtained a classification accuracy of 90.0% on the task of classifying disease severity. The overall results indicated the UAV low-altitude remote sensing simulation platform equipped with multi-sensors could be used to early detect Sclerotinia sclerotiorum on oilseed rape leaves.
关键词： machine learning,multispectral technology,oilseed rape,image fusion,thermal imaging technology,Sclerotinia sclerotiorum
更新于2025-09-23 15:23:52
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A Hyperspectral Imaging Instrumentation Architecture Based on Accessible Optical Disc Technology and Frequency-Domain Analyses
摘要： Hyperspectral imaging (HSI) is an emergent instrumentation technology with great potential in many applications, due to its ability to measure important spectral features. However, the widespread adoption of HSI requires the development of accessible (i.e., inexpensive and uncomplicated) HSI instrumentation architectures. In this paper, we present, design, develop, and evaluate an accessible HSI instrumentation architecture, with snapshot operation, based on the integration of readily available components and frequency multiplexing with Fourier analyses. In the experimental work, an incident image beam is divided into spatial image channels, each with an assigned dynamic binary code via a dynamic coded aperture. This dynamic coded aperture is constructed from repurposed diffractive optical disc technologies and is patterned with strategic opaque and transparent regions. When it is rotated by a motor, dynamic binary codes are used, along with Fourier analyses, to identify the diffraction of each spatial image channel. The spatially overlapped spectra from the diffraction are directed onto a charge-coupled device sensor, and each spatial image channel is distinguished through Fourier analyses. The resulting Fourier amplitude spectra are transformed into corresponding functions of wavelength, and this transformation is based on the experimental instrumentation geometry. The performance of the HSI instrumentation architecture is evaluated using a comparison with data from a commercial spectrometer. The presented HSI instrumentation architecture can be adapted for 2-D operation. Ultimately, the presented HSI instrumentation architecture can benefit regions of the world that have limited financial resources and a need for accessible HSI technologies.
关键词： Electromagnetic devices,optical diffraction,hyperspectral sensors,multispectral imaging
更新于2025-09-23 15:23:52
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Spectroscopic Compton imaging of prompt gamma emission at the MeV energy range
摘要： This work explores a novel tomographic approach to PGAA that is both quantitative and spatially resolved, adapted from a clinical "proton beam range finder" in which MeV gamma rays are imaged by coincidence measurements of Compton scattered gamma rays with multi-detector arrays. We performed preliminary measurements using a Compton camera made with CdZnTe detector arrays on a series of test samples with high-energy (> 1 MeV) gamma emission lines. 3D image reconstructions were performed on the 2.2 MeV peak from H. The image reconstruction methods were also evaluated using the emission data generated by Monte Carlo simulations under ideal conditions.
关键词： 3D elemental distribution,Compton imaging,Prompt gamma activation analysis
更新于2025-09-23 15:23:52