Large Field Of View Research Articles

Control method of active optical telescope with multiple mirrors and large field of view

Control method of active optical telescope with multiple mirrors and large field of view

Large field-of-view pine wilt disease tree detection based on improved YOLO v4 model with UAV images.

Pine wilt disease spreads rapidly, leading to the death of a large number of pine trees. Exploring the corresponding prevention and control measures for different stages of pine wilt disease is of great significance for its prevention and control. To address the issue of rapid detection of pine wilt in a large field of view, we used a drone to collect multiple sets of diseased tree samples at different times of the year, which made the model trained by deep learning more generalizable. This research improved the YOLO v4(You Only Look Once version 4) network for detecting pine wilt disease, and the channel attention mechanism module was used to improve the learning ability of the neural network. The ablation experiment found that adding the attention mechanism SENet module combined with the self-designed feature enhancement module based on the feature pyramid had the best improvement effect, and the mAP of the improved model was 79.91%. Comparing the improved YOLO v4 model with SSD, Faster RCNN, YOLO v3, and YOLO v5, it was found that the mAP of the improved YOLO v4 model was significantly higher than the other four models, which provided an efficient solution for intelligent diagnosis of pine wood nematode disease. The improved YOLO v4 model enables precise location and identification of pine wilt trees under changing light conditions. Deployment of the model on a UAV enables large-scale detection of pine wilt disease and helps to solve the challenges of rapid detection and prevention of pine wilt disease.

Design and Fabrication of 2D Exit Pupil Expansion Holographic Grating Waveguide with Large Field of View

Design and Fabrication of 2D Exit Pupil Expansion Holographic Grating Waveguide with Large Field of View

Fourier-Based Fast 3-D Ultrasound Imaging Using Row-Column-Addressed 2-D Arrays.

A Fourier-based fast 3-D ultrasound imaging method using row-column-addressed (RCA) 2-D arrays is presented. The row elements in an RCA array are activated sequentially, and all the column elements are used to receive. The obtained dataset is adapted to approximate to that obtained using a fully sampled array after a plane wave at a given incident angle is transmitted. In this way, the fast algorithm in plane-wave Fourier imaging (PWFI) can be applied to the adapted dataset. In addition, synthesizing multiple datasets based on multiple incident angles enables angular compounding, which improves the image quality. The proposed method was validated using computer simulations and physical-phantom experiments. The results show that the spatial resolution and contrast of the proposed method are comparable with those of its PWFI counterpart without requiring a fully sampled (FS) array. Compared with the delay-and-sum (DAS) method using the RCA array, the proposed method provides comparable spatial resolution but lower contrast; however, the computational complexity is significantly reduced from O(N4Nz) to O(WN2Nz log2(N2Nz)) , where N is the number of elements on each side of the RCA array, Nz is the number of voxels in the axial direction in the output image, and W is the number of compounding angles. For example, in the simulated results when the maximum compounding angle M is 5°, at a given point the lateral - 6-dB width provided by the proposed method is 0.241 mm (0.267 mm for DAS), the contrast ratio of a hyperechoic cyst is 8.87 dB (9.10 dB for DAS), the number of real number operations is reduced by a factor of 20.62, and the number of memory accesses is reduced by a factor of 47.21, both compared with DAS. This novel fast algorithm could facilitate the development of compact real-time 3-D imaging systems, especially when the channel count is high and a large field of view (FOV) is required.

Advances in Microsphere-based Super-resolution Imaging.

Techniques to resolve images beyond the diffraction limit of light with a large field of view (FOV) are necessary to foster progress in various fields such as cell and molecular biology, biophysics, and nanotechnology, where nanoscale resolution is crucial for understanding the intricate details of large-scale molecular interactions. Although several means of achieving super-resolutions exist, they are often hindered by factors such as high costs, significant complexity, lengthy processing times, and the classical tradeoff between image resolution and FOV. Microsphere-based super-resolution imaging has emerged as a promising approach to address these limitations. In this review, we delve into the theoretical underpinnings of microsphere-based imaging and the associated photonic nanojet. This is followed by a comprehensive exploration of various microsphere-based imaging techniques, encompassing static imaging, mechanical scanning, optical scanning, and acoustofluidic scanning methodologies. This review concludes with a forward-looking perspective on the potential applications and future scientific directions of this innovative technology.

Research progress on liquid crystal polarization converter with a large field of view and broadband

Research progress on liquid crystal polarization converter with a large field of view and broadband

Experimental astronomical observation using a lobster eye optics

AbstractA lobster eye (LE) is a wide‐field type of X‐ray optics, which provides a large field of view at the expense of angular resolution. The optics presented in this paper are the LE optics in Schmidt arrangement made from glass sheets with golden reflective coatings. It was used as a scientific payload on the WRXR rocket experiment. Before the mission itself, the optics was tested on ground to obtain more information about its behavior. Part of these tests were several nights of observation at the Ondrejov observatory. We used the optics in combination with a CMOS camera to acquire images in visible light of various bright sources in the sky. In order to enable long‐time exposures, the robotic mount of the BART telescope was used. The goal of this experiment was to confirm the focal length of the optics using a source at infinity, and to show how the optics, designed for X‐ray observations, performs in visible light. This brief article describes the methods used for evaluation and presents and discusses the results obtained within the night observation experiment.

System design and validation of Central Redundant Array Mega-tile (CRAM)

Abstract Exploration of the 21cm signal during the Cosmic Dawn and the Epoch of Reionisation (EoR) can unravel the mysteries of the early Universe when the first stars and galaxies were born and ionised, respectively. However, the 21 cm signal is exceptionally weak, and thus, the detection amidst the bright foregrounds is extremely challenging. The Murchison Widefield Array (MWA) aims to measure the brightness temperature fluctuations of neutral hydrogen from the early Universe. The MWA telescope observes the radio sky with a large field of view (FoV) that causes the bright galaxies, especially near the horizon, to contaminate the measurements. These foregrounds contaminating the EoR datasets must be meticulously removed or treated to detect the signal successfully. The Central Redundant Array Mega-tile (CRAM) is a zenith-pointing new instrument, installed at the centre of the MWA Phase II southern hexagonal configuration, comprising of 64 dipoles in an $8 \times 8$ configuration with a FoV half the width of the MWA’s at every frequency under consideration. The primary objective of this new instrument is to mitigate the impact of bright radio sources near the field centre in accordance with the reduced primary beamshape and to reduce the contamination of foreground sources near the horizon with the reduced sidelobe response of the larger array configuration. In this paper, we introduce the new instrument to the community and present the system architecture and characteristics of the instrument. Using the first light observations, we determine the CRAM system temperature and system performance.

Adaptive multiscale microscope with fast zooming, extended working distance, and large field of view

Adaptive multiscale microscope with fast zooming, extended working distance, and large field of view

Characterization of a new fluorescence lifetime imaging ophthalmoscope

Aims/Purpose: Fluorescence lifetime imaging ophthalmoscopy (FLIO) allows in vivo measurement of autofluorescence intensity decays of endogenous fluorophores in the ocular fundus. So far, only devices from Heidelberg Engineering based on the Spectralis system have been used in FLIO research. Here, we present and characterize a new FLIO device based on the RETImap system from Roland Consult.Methods: The device is based on a confocal scanning laser ophthalmoscope (35° field, 512 × 512 px). A ps diode laser (BDL‐SMN 473 nm, Becker & Hickl GmbH, Berlin, Germany) excites autofluorescence. The fluorescence photons are split into a short (498–560 nm, SSC) and a long (560–720 nm, LSC) spectral channel (one HPM‐100‐40 detector [Becker & Hickl GmbH] each) and are detected by time‐correlated single photon counting (SPC‐160, Becker & Hickl GmbH). We determined the maximum laser power (ILT2400, International Light Technologies, Inc. Peabody, MA, USA) and analysed the instrument's behaviour at three different laser power levels (150 μW, 200 μW and max.) in terms of laser spectrum (CAS140CT, Instrument Systems GmbH, Munich, Germany) and instrument response function (IRF). The IRF was determined using a 25 μM Eosin Y solution, mixed with a 5 M solution of potassium iodide, placed in a flat cuvette (110‐OS, Hellma GmbH & Co. KG, Müllheim, Germany) in front of the objective lens of the FLIO device. Fluorescence measurements of approximately 1‐min duration were performed three times for all three laser powers. The IRF and the full width at half maximum (FWHM) were calculated using FLIMX software (www.flimx.de).Results: The max. laser power was 280 μW. The peak wavelengths of the laser spectra were 467.6 (150 μW), 467.9 (200 μW) and 468.0 nm (280 μW). IRF FWHM in SSC were 298.6 ± 1.1 ps (150 μW), 341.0 ± 2.5 ps (200 μW) and 347.5 ± 6.0 ps (280 μW). In LSC, the IRF FWHM were 290.4 ± 3.8 ps (150 μW), 344.0 ± 3.4 ps (200 μW) and 358.8 ± 1.3 ps (280 μW). Results are mean ± standard deviation.Conclusions: A new fluorescence lifetime imaging ophthalmoscope has been characterized. The device offers a high laser power for fluorescence excitation, a large field of view, a high spatial resolution, and a sufficiently high time resolution. Thus, it is suitable for fluorescence lifetime studies.

Opportunistic investigation of vascular calcification using 3-dimensional dental imaging.

Given the growing use of cone-beam computed tomography (CBCT) scans, this study assessed radiation exposure from these scans in the context of national guidelines and recommended dose limits. The current literature was reviewed to quantify the benefit of opportunistic diagnosis of carotid artery calcification relative to the potential risk of radiation-induced cancer. The average radiation from CBCT at its largest field of view and highest resolution possible amounts to a reasonable but still low ionizing radiation exposure. This exposure is comparable to 22 days of background radiation and is notably lower than the radiation exposure from medical CT scans. According to the risk assessment analysis, the risk of stroke events involving internal and external carotid artery calcification (CAC) was 202 and 67 per 100,000 individuals, respectively. In contrast, the estimated risk of radiation-induced cancer associated with CBCT was notably lower, at 0.6 per 100,000. The present study advocates for a comprehensive assessment of CBCT scans encompassing the areas of the internal and external carotid arteries by a knowledgeable professional, given the potential advantages of early detection of vascular abnormalities. Dental professionals who take scans involving these areas need to be mindful of reporting these findings and refer patients to their primary care physician for further investigation.

TomoCAM: fast model-based iterative reconstruction via GPU acceleration and non-uniform fast Fourier transforms.

X-ray-based computed tomography is a well established technique for determining the three-dimensional structure of an object from its two-dimensional projections. In the past few decades, there have been significant advancements in the brightness and detector technology of tomography instruments at synchrotron sources. These advancements have led to the emergence of new observations and discoveries, with improved capabilities such as faster frame rates, larger fields of view, higher resolution and higher dimensionality. These advancements have enabled the material science community to expand the scope of tomographic measurements towards increasingly in situ and in operando measurements. In these new experiments, samples can be rapidly evolving, have complex geometries and restrictions on the field of view, limiting the number of projections that can be collected. In such cases, standard filtered back-projection often results in poor quality reconstructions. Iterative reconstruction algorithms, such as model-based iterative reconstructions (MBIR), have demonstrated considerable success in producing high-quality reconstructions under such restrictions, but typically require high-performance computing resources with hundreds of compute nodes to solve the problem in a reasonable time. Here, tomoCAM, is introduced, a new GPU-accelerated implementation of model-based iterative reconstruction that leverages non-uniform fast Fourier transforms to efficiently compute Radon and back-projection operators and asynchronous memory transfers to maximize the throughput to the GPU memory. The resulting code is significantly faster than traditional MBIR codes and delivers the reconstructive improvement offered by MBIR with affordable computing time and resources. tomoCAM has a Python front-end, allowing access from Jupyter-based frameworks, providing straightforward integration into existing workflows at synchrotron facilities.

ESTUDIO COMPARATIVO TERMOGRÁFICO MEDIANTE SMARTPHONE Y CÁMARA EN EDIFICIOS

The cost of thermographic cameras has significantly decreased in recent years, making it an accessible and cost-effective solution for building and infrastructure inspection. With advancements in technology, low-cost thermographic devices have now become readily available in the market. These cost-effective devices offer a more convenient and accessible option for individuals and businesses to perform onsite temperature measurements. In this paper, we examine the capabilities and limitations of a thermal-equipped smartphone and the potential impact on the thermography industry by comparison with a dedicated thermographic camera. The advantages of thermography still hold true for recent low-cost devices: non-invasive inspections, quick and efficient measurements, and hidden defects easily detected. The low-cost thermal-equipped smartphone proved to be a highly maneuverable system, easy to use and with option of overlapping with real color image, what facilitates the interpretation. The low-cost system is also characterized by a larger field of view but also by a lower resolution, what makes it impracticable for measuring small objects. In any case, integration of non-destructive technologies in smartphones opens up a whole new world of possibilities for spreading the inspection of as-built buildings and infrastructures and democratizing the technology. Keywords: Low-Cost; inspection; thermal bridges; energy sustainability; energy efficiency; digital twins.

Diverging Polymer Acoustic Lens Design for High-Resolution Row-Column Array Ultrasound Transducers.

Spherical diverging acoustic lenses mounted on flat 2-D row-column-addressed (RCA) ultrasound transducers have shown the potential to extend the field of view (FOV) from a rectilinear to a curvilinear volume region and, thereby, enable 3-D imaging of large organs. Such lenses are usually designed for small aperture low-frequency transducers, which have limited resolution. Moreover, they are made of off-the-shelf pieces of materials, which leaves no room for optimization. We hypothesize that acoustic lenses can be designed to fit high-resolution transducers, and they can be fabricated in a fast, cost-effective, and flexible manner using a combination of 3-D printing and casting or computer numerical control (CNC) machining techniques. These lenses should increase the FOV of the array while preserving the image quality. In this work, such lenses are made in concave, convex, and compound spherical shapes and from thermoplastics and thermosetting polymers. Polymethylpentene (TPX), polystyrene (PS), polypropylene (PP), polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), and room-temperature-vulcanizing (RTV) silicone diverging lenses have been fabricated and mounted on a 128 + 128 6-MHz RCA transducer. The performances of the lenses have been assessed and compared in terms of FOV, signal-to-noise ratio (SNR), bandwidth, and potential artifacts. The largest FOV (24.0.) is obtained with a 42.64-mm radius PMMA-RTV compound lens, which maintains a decent fractional bandwidth (53%) and SNR at 6 MHz (.9.1-dB amplitude drop compared with the unlensed transducer). The simple PMMA TPX, PS, PP, PDMS, and RTV lenses provide an FOV of 12.2°, 6.3°, 8.1°, 11.7°, 0.6°, and 10.4°; a fractional bandwidth of 97%, 46%, 103%, 46%, 97%, 53%, and 49%; and an amplitude drop of -5.2, -4.4, -2.8, -15.4, -6.0, and -1.8 dB, respectively. This work demonstrates that thermoplastics are suitable materials for fabricating low-attenuation convex diverging lenses for large-aperture, high-frequency 2-D transducers. This is highly desired to achieve high-resolution volumetric imaging of large organs.

A large field-of-view angled panel detector for the development of a plant PET system

In plant research, positron emission tomography (PET) is sometimes employed for physiological studies of plants. However, due to the generally high cost of PET systems, their application in plant research centers can be challenging. Furthermore, the configurations of commercial PET systems might not always align well with the requirements of plant research. To address these issues, we have taken the initial steps towards a solution by developing a large field-of-view (LFOV) angled panel detector intended for the development of a plant PET system. This panel detector is composed of two gadolinium orthosilicate (GSO) scintillator blocks, an angled light guide, and four flat panel photomultiplier tubes (FP-PMTs). The GSO pixel size used in the scintillator block measures 2.65 mm (radial)× 2.85 mm (axial)× 15.0 mm, arranged in a configuration of 16 (radial)× 32 (axial) to form a scintillator block with overall dimensions of 44.0 mm (radial)× 94.4 mm (axial)× 15 mm (depth). By implementing an angled light guide, the two scintillator blocks were positioned at a 22.5-degree angle, resulting in the creation of a LFOV angled panel detector. This specific angle allowed for the arrangement of 16 scintillator blocks in a hexadecagonal shape using 8 panel detectors when arranged in a circular configuration. We successfully constructed a panel detector with an approximate field-of-view of 10 cm× 10 cm and conducted a comprehensive performance evaluation. Upon irradiating the panel detector with 511 keV gamma photons, nearly all 1024 GSO pixels were accurately resolved in the position histogram, displaying minimal distortion, and exhibiting an average peak-to-valley ratio of 5.0. Additionally, the energy resolution achieved was 14% full width at half maximum (FWHM). The resulting LFOV angled panel detector holds considerable promise for the use within a cost-effective, user-friendly as well as high performance plant PET system.

An energy resolved neutron imaging detector based on boron doped nMCP coupled with a time stamping optical camera

Energy resolved neutron imaging has developed rapidly due to its advantage on testing the inner structure of crystal samples. Neutron detector is one of the key components to determine the imaging results quality. The neutron sensitive microchannel plate (nMCP) has been widely used in energy resolved neutron imaging experiments because of the high spatial and timing resolution. However, the ability to adjust field-of-view (FOV) and spatial resolution has not been realized in the nMCP detector, which is an attractive capability in energy resolved neutron imaging experiments. In this paper, an energy resolved neutron imaging detector was developed by coupling nMCP with a time stamping camera. The neutrons were absorbed by nMCP and converted into light through a phosphor screen. Then the light was focused on the camera by optical lens. A data algorithm was designed to improve the data quality. By changing the magnification of the optical lens, large FOV (46mm diameter) and high spatial resolution (26 μm) were realized in the experiments at CSNS beamline 20. The energy resolved ability was demonstrated by a Bragg-edge transmission imaging experiment for aluminum and stainless-steel samples. The performance of this detector makes it a promising candidate used in energy resolved neutron imaging.

BOS and Hot-Film Analysis of a CH-53G Helicopter Wake in Ground Effect

Constant temperature anemometry and background-oriented schlieren (BOS) measurements on a CH-53G helicopter (takeoff mass ≈ 14t) are used to investigate the rotor wake including the vortex breakdown to statistical turbulence. Hovering flights at a range of hub heights 0.50 < h < 0.83 were investigated. The position of the rotorcraft was optically tracked using markers affixed to the fuselage. A complete breakdown of the tip vortices was noted within 0.3R of the rotor plane, in stark qualitative contrast to small-scale experiments which show the tip vortices persisting to the ground plane. The large (37 m2) BOS field of view showed a small effect of vortex pairing and blade vortex interaction, which was overshadowed by the rapid wake breakdown. Vortex pairing was found to result from varying vortex convection velocities rather than from initial differences in the vortex spacing due to the blade track.

A large field of view infrared staring imaging system based on liquid crystal grating

A large field of view infrared staring imaging system based on liquid crystal grating

Design of large field of view and high-resolution compound eye optical system

Design of large field of view and high-resolution compound eye optical system

Towards human-scale magnetic particle imaging: development of the first system with superconductor-based selection coils.

Magnetic Particle Imaging (MPI) is an emerging tomographic modality that allows for precise three-dimensional (3D) mapping of magnetic nanoparticles (MNPs) concentration and distribution. Although significant progress has been made towards improving MPI since its introduction, scaling it up for human applications has proven challenging. High-quality images have been obtained in animal-scale MPI scanners with gradients up to 7 T/m/μ0, however, for MPI systems with bore diameters around 200 mm the gradients generated by electromagnets drop significantly to below 0.5 T/m/μ0. Given the current technological limitations in image reconstruction and the properties of available MNPs, these low gradients inherently impose limitations on improving MPI resolution for higher precision medical imaging. Utilizing superconductors stands out as a promising approach for developing a human-scale MPI system. In this study, we introduce, for the first time, a human-scale amplitude-modulated (AM) MPI system with superconductor-based selection coils. The system achieves an unprecedented magnetic field gradient of up to 2.5 T/m/μ0 within a 200 mm bore diameter, enabling large fields of view of 100 × 130 × 98 mm3 at 2.5 T/m/μ0 for 3D imaging. While obtained spatial resolution is in the order of previous animal-scale AM MPIs, incorporating superconductors for achieving such high gradients in a 200 mm bore diameter marks a major step toward clinical MPI.