Wide Field Of View Research Articles

The Application of Artificial Compound Eye in Precision Guided Munitions for Urban Combat

As an ideal visual perception system with miniaturization, multi-aperture, wide field of view, low aberration, infinite depth of field, high efficiency and real-time, bionic compound eye has obvious intelligent characteristics, which provides a new idea for the future intelligent development of precision guided weapons, and has also been highly concerned by the US military. Under the leadership of the military, the United States has carried out a series of studies and achieved a series of results. The strategic position of urban combat in the future is analyzed. The requirements of the U.S. Air Force for the next generation of precision-guided munitions, and also the strategic significance of developing urban combat weapons and equipment is described. The advantages and characteristics of artificial compound eye are briefly described. Mainly discussed a series of WFOV artificial compound eye seeker being studied and developed by the U.S. Air Force for urban warfare, as well as the research and development process. Finally, the development suggestion of the WFOV artificial compound eye seeker is given.

MP72-07 TIME EFFICIENCY AND PERFORMANCE OF DISPOSABLE VERSUS REUSABLE CYSTOSCOPES: A PROSPECTIVE, RANDOMIZED BENCHTOP COMPARISON

You have accessJournal of UrologyCME1 Apr 2023MP72-07 TIME EFFICIENCY AND PERFORMANCE OF DISPOSABLE VERSUS REUSABLE CYSTOSCOPES: A PROSPECTIVE, RANDOMIZED BENCHTOP COMPARISON Catalina Baas, Ricky Chen, Daniel R. Peverini, John Hartman, Akin S. Amasyali, Rose Leu, Aviram Assidon, Joshua D Belle, Elizabeth Baldwin, and D. Duane Baldwin Catalina BaasCatalina Baas More articles by this author , Ricky ChenRicky Chen More articles by this author , Daniel R. PeveriniDaniel R. Peverini More articles by this author , John HartmanJohn Hartman More articles by this author , Akin S. AmasyaliAkin S. Amasyali More articles by this author , Rose LeuRose Leu More articles by this author , Aviram AssidonAviram Assidon More articles by this author , Joshua D BelleJoshua D Belle More articles by this author , Elizabeth BaldwinElizabeth Baldwin More articles by this author , and D. Duane BaldwinD. Duane Baldwin More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003340.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: While reusable cystoscopes (RCs) are commonly used for urologic procedures, bulky equipment and lengthy sterilization times can impact efficiency. Disposable cystoscopes (DCs) may offer advantages including increased availability, greater portability, and faster setup times. The aim of this study is to compare procedure times, cystoscope specifications, and physician satisfaction between RCs and DCs. METHODS: Ten urologists performed simulated bedside cystoscopies using a prospective, randomized, crossover study design. A 3D-printed bladder model with 22 target letters was positioned within a female mannequin pelvis. Each subject used both a new disposable Ambu aScope 4 Cysto and a reusable Olympus CYF-5 flexible cystoscope to identify the targets. Afterward, participants completed a satisfaction survey. Times required for supply-gathering, setup, cystoscopy, and cleanup were compared. Image definition, field of view, deflection angle, force required for deflection, irrigation rate, weight, and working length were also compared. RESULTS: The DCs required less time for supply-gathering (187.5 vs 289.4 s, p<0.05), setup (203.3 vs 327.5 s, p<0.01), and cleanup (183.7 vs 356.2 s, p<0.05) while cystoscopy times were similar (230.4 vs 274.1 s, p=0.58). Optical testing showed higher image definition for the DCs (6.30 vs 2.00 line pairs/mm, p<0.01), but a smaller field of view (67° vs 108°, p<0.01) and no adjustable optical settings. The DCs had increased deflection (214° up/182° down vs 198° up/109° down, p<0.01) but required more force to deflect 180° up (6.86 vs 4.46 N, p<0.01) and 90° down (4.66 vs 3.55 N, p<0.01). The RC was heavier (325 vs 159 g), had a shorter working length (37.5 vs 39.0 cm), and a faster irrigation rate at 200 cm H2O (494.1 vs 387.4 mL/min, p<0.01). Post-testing, deflection was reduced for two DCs, but optical qualities remained unchanged. Survey results showed higher ratings in time-efficiency (9.5/10 vs 6.2/10, p<0.01) and overall satisfaction (9.3/10 vs 7.9/10, p<0.01) for the DCs. No subjective difference was found in maneuverability or image quality. CONCLUSIONS: While DCs had better image quality, greater deflection, and were faster to assemble and disassemble, RCs had greater durability, more optical settings, wider field of view, faster irrigation rates, and required less force for deflection. Knowledge of the strengths and weaknesses of each device could assist surgeons in optimizing cystoscope utilization in specific clinical scenarios. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e1026 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Catalina Baas More articles by this author Ricky Chen More articles by this author Daniel R. Peverini More articles by this author John Hartman More articles by this author Akin S. Amasyali More articles by this author Rose Leu More articles by this author Aviram Assidon More articles by this author Joshua D Belle More articles by this author Elizabeth Baldwin More articles by this author D. Duane Baldwin More articles by this author Expand All Advertisement PDF downloadLoading ...

External Measurement System for Aircraft Structural Parts Based on Digital Image Correlation in Signal-limited Spaces

An experimental study was performed on the application of the digital image correlation (DIC) technique to characterize aircraft components for which accurate time information is required. This study builds an aircraft external measurement system based on Stereo DIC. This system obtains real-time satellite time information from a GPS clock source and transmits it to a trigger unit. A camera acquires this information and displays it on the image. This solves the problem that some closed laboratories can use only computer time and cannot obtain accurate satellite time when using camera measurements. Moreover, we verify the reliability and accuracy of this approach, finding an average angular accuracy of better than 0.02 degrees and a relative error of less than 1%. Using the binocular Stereo DIC system, the accuracy of the measurements is clarified for specific conditions. Furthermore, we use this system to measure simulated aircraft landing gear, which moves at an angular velocity of 52.4 °/ s over a distance of 5 m with a wide field of view of 16.8°. The satellite time information acquired by the camera and the time information of the captured time targets are highly stable. The system’s reliability is demonstrated for use in practical engineering, contributing to the engineering application of Stereo DIC for external aircraft measurements.

Optical characterization of lithium fluoride thin-film imaging detectors for monochromatic hard X-rays

Lithium fluoride (LiF) crystals and thin films have been successfully investigated as X-ray imaging detectors based on optical reading of visible photoluminescence emitted by stable radiation-induced F2 and F+ 3 colour centres. In this work, the visible photoluminescence response of optically-transparent LiF film detectors of three different thicknesses, grown by thermal evaporation on Si(100) substrates and irradiated with monochromatic 7 keV X-rays at several doses in the range between 13 and 4.5 × 103 Gy, was carefully investigated by fluorescence optical microscopy. For all the film thicknesses, the photoluminescence response linearly depends on the irradiation dose in the investigated dose range. The lowest detected dose, delivered to the thinnest LiF film, only 0.5 μm thick, is estimated 13 Gy. Edge-enhancement imaging experiments, conducted by irradiating LiF film detectors at the same energy placing an Au mesh in front of them at a distance of 15 mm, allowed estimating a spatial resolution of (0.38 ± 0.05) μm, which is comparable to the microscope one. This very high spatial resolution in LiF film radiation detectors based on colour centres photoluminescence is combined with the availability of a wide field of view on large areas.

Surveying of Nearshore Bathymetry Using UAVs Video Stitching

In this paper, we extended video stitching to nearshore bathymetry for videos that were captured for the same coastal field simultaneously by two unmanned aerial vehicles (UAVs). In practice, a video captured by a single UAV often shows a limited coastal zone with a lack of a wide field of view. To solve this problem, we proposed a framework in which video stitching and bathymetric mapping were performed in sequence. Specifically, our method listed the video acquisition strategy and took two overlapping videos captured by two UAVs as inputs. Then, we adopted a unified video stitching and stabilization optimization to compute the stitching and stabilization of one of the videos separately. In this way, we can obtain the best stitching result. At the same time, background feature points identification on the shore plays the role of short-time visual odometry. Through the obtained panoramic video in Shuang Yue Bay, China, we used the temporal cross-correlation analysis based on the linear dispersion relationship to estimate the water depth. We selected the region of interest (ROI) area from the panoramic video, performed an orthorectification transformation and extracted time-stack images from it. The wave celerity was then estimated from the correlation of the signal through filtering processes. Finally, the bathymetry results were compared with the cBathy. By applying this method to two UAVs, a wider FOV was created and the surveying area was expanded, which provided effective input data for the bathymetry algorithms.

DSM Extraction Based on Gaofen-6 Satellite High-Resolution Cross-Track Images with Wide Field of View.

Digital Surface Model (DSM) is a three-dimensional model presenting the elevation of the Earth's surface, which can be obtained by the along-track or cross-track stereo images of optical satellites. This paper investigates the DSM extraction method using Gaofen-6 (GF-6) high-resolution (HR) cross-track images with a wide field of view (WFV). To guarantee the elevation accuracy, the relationship between the intersection angle and the overlap of the cross-track images was analyzed. Cross-track images with 20-40% overlaps could be selected to conduct DSM extraction. First, the rational function model (RFM) based on error compensation was used to realize the accurate orientation of the image. Then, the disparity map was generated based on the semi-global block matching (SGBM) algorithm with epipolar constraint. Finally, the DSM was generated by forward intersection. The GF-6 HR cross-track images with about 30% overlap located in Taian, Shandong Province, China, were used for DSM extraction. The results show that the mountainous surface elevation features were retained completely, and the details, such as houses and roads, were presented in valleys and urban areas. The root mean square error (RMSE) of the extracted DSM could reach 6.303 m, 12.879 m, 14.929 m, and 19.043 m in valley, ridge, urban, and peak areas, respectively. The results indicate that the GF-6 HR cross-track images with a certain overlap can be used to extract a DSM to enhance its application in land cover monitoring.

Antenna Setup for Future Joint Radar-Communications – Characteristics and Mounting Positions

Abstract. The development of millimeter wave systems is driven by the strong trend toward new communications generations and especially by the emerging joint radar and communications design approach. Safety-critical applications like platooning or intersection assistance will significantly benefit from the combination of sensing and communications. While radar performs a channel measurement and thus, needs a wide field of view (especially in city/intersection scenarios), communications aims to minimize the interference for other not addressed receivers (e. g. in a platoon) by a focused antenna design. The proposed work extends the analysis of the influence of various antenna positioning for a typical automotive scene by taking also different characteristics (antenna gain, half power beamwidth, and sidelobe level) into account. Hereby, it is mandatory to investigate the communications and sensing performance simultaneously. The positions at the front bumper – typical for radar sensors – and especially at the left mirror convinced regarding the vehicular communications as well as the sensing behaviour. Applying focused antennas is promising, however, has also limits if the signals are not received out of the main beam but out of the sidelobes, resulting in a critical communications performance. Thus, beam steering is recommended to be applied in the future.

Light-curve modelling for the initial rising phase of rapidly evolving transients powered by continuous outflow

ABSTRACT A wind-driven model is a new framework to model observational properties of transients that are powered by continuous outflow from a central system. While it has been applied to fast blue optical transients (FBOTs), the applicability has been limited to post-peak behaviours due to the steady-state assumptions; non-steady-state physics, e.g. expanding outflow, is important to model the initial rising phase. In this paper, we construct a time-dependent wind-driven model, which can take into account the expanding outflow and the time evolution of the outflow rate. We apply the model to a sample of well-observed FBOTs. FBOTs require high outflow rates (∼30 M⊙ yr−1) and fast velocities (∼0.2–0.3c), with the typical ejecta mass and energy budget of ∼0.2 M⊙ and ∼1052 erg, respectively. The energetic outflow supports the idea that the central engine of FBOTs may be related to a relativistic object, e.g. a black hole. The initial photospheric temperature is 105 –106 K, which suggests that FBOTs will show ultraviolet (UV) or X-ray flash similar to supernova shock breakouts. We discuss future prospects of surveys and follow-up observations of FBOTs in the UV bands. FBOTs are brighter in the UV bands than in the optical bands, and the time-scale is a bit longer than that in optical wavelengths. We suggest that UV telescopes with a wide field of view can play a key role in discovering FBOTs and characterizing their natures.

Target Detection and Recognition for Traffic Congestion in Smart Cities Using Deep Learning-Enabled UAVs: A Review and Analysis

In smart cities, target detection is one of the major issues in order to avoid traffic congestion. It is also one of the key topics for military, traffic, civilian, sports, and numerous other applications. In daily life, target detection is one of the challenging and serious tasks in traffic congestion due to various factors such as background motion, small recipient size, unclear object characteristics, and drastic occlusion. For target examination, unmanned aerial vehicles (UAVs) are becoming an engaging solution due to their mobility, low cost, wide field of view, accessibility of trained manipulators, a low threat to people’s lives, and ease to use. Because of these benefits along with good tracking effectiveness and resolution, UAVs have received much attention in transportation technology for tracking and analyzing targets. However, objects in UAV images are usually small, so after a neural estimation, a large quantity of detailed knowledge about the objects may be missed, which results in a deficient performance of actual recognition models. To tackle these issues, many deep learning (DL)-based approaches have been proposed. In this review paper, we study an end-to-end target detection paradigm based on different DL approaches, which includes one-stage and two-stage detectors from UAV images to observe the target in traffic congestion under complex circumstances. Moreover, we also analyze the evaluation work to enhance the accuracy, reduce the computational cost, and optimize the design. Furthermore, we also provided the comparison and differences of various technologies for target detection followed by future research trends.

Fourier ptychographic topography.

Topography measurement is essential for surface characterization, semiconductor metrology, and inspection applications. To date, performing high-throughput and accurate topography remains challenging due to the trade-off between field-of-view (FOV) and spatial resolution. Here we demonstrate a novel topography technique based on the reflection-mode Fourier ptychographic microscopy, termed Fourier ptychograhpic topography (FPT). We show that FPT provides both a wide FOV and high resolution, and achieves nanoscale height reconstruction accuracy. Our FPT prototype is based on a custom-built computational microscope consisting of programmable brightfield and darkfield LED arrays. The topography reconstruction is performed by a sequential Gauss-Newton-based Fourier ptychographic phase retrieval algorithm augmented with total variation regularization. We achieve a synthetic numerical aperture (NA) of 0.84 and a diffraction-limited resolution of 750 nm, increasing the native objective NA (0.28) by 3×, across a 1.2 × 1.2 mm2 FOV. We experimentally demonstrate the FPT on a variety of reflective samples with different patterned structures. The reconstructed resolution is validated on both amplitude and phase resolution test features. The accuracy of the reconstructed surface profile is benchmarked against high-resolution optical profilometry measurements. In addition, we show that the FPT provides robust surface profile reconstructions even on complex patterns with fine features that cannot be reliably measured by the standard optical profilometer. The spatial and temporal noise of our FPT system is characterized to be 0.529 nm and 0.027 nm, respectively.

An improved method for retrieving aerosol optical depth over Ebinur Lake Basin from Gaofen-1

Lake Ebinur is the largest saltwater lake in Xinjiang. In recent years, the exposed dry lake bottom surface has become a remarkable source of salt and dust owing to the desiccation of the lake. Given the importance of the lake basin to human livelihoods, comprehensive monitoring of basin behavior is required. Remote sensing offers numerous novel approaches to monitoring the spatial and temporal distribution of aerosols. During this study, high spatial resolution aerosol optical depth (AOD) inversion at Lake Ebinur was still in the gap stage. The wide-field-of-view (WFV) data from four cameras on the GaoFen-1 (GF-1) satellite, launched by China in April 2013, offers high spatial and temporal resolution and excellent potential for AOD estimation. Owing to the shortwave infrared band (SWIR) deficiency and the complexity of surface reflectance, the coefficient of variation (CV) was proposed as a measure of surface reflectance to develop a surface reflectance database for land cover characteristics in the Ebinur Lake Basin. The significant improvements of the algorithm include (1) the design of an accurate and universal cloud detection algorithm through the blue and red bands. (2) The CV was used to assess the robustness of surface reflectance under long time series. After dividing the surface reflectance image pixels with low robustness, a reasonable value was assigned according to the surface reflectance variation characteristics of the image pixels. (3) Aerosol models were determined from the long-term measurements of the CIMEL solar photometer (CE318), and the validation of ground-based observations showed good correlation that WFV/GF-1 AOD was comparable to CE318 AOD (R = 0.705; root mean square error (RMSE) = 0.098; mean absolute error (MAE) = 0.078), and the smaller MAE and RMSE confirmed the feasibility of inversion of AOD by this method.

Extensive 3D mapping of dislocation structures in bulk aluminum

Thermomechanical processing such as annealing is one of the main methods to tailor the mechanical properties of materials, however, much is unknown about the reorganization of dislocation structures deep inside macroscopic crystals that give rise to those changes. Here, we demonstrate the self-organization of dislocation structures upon high-temperature annealing in a mm-sized single crystal of aluminum. We map a large embedded 3D volume (100times 300times 300upmum^3) of dislocation structures using dark field X-ray microscopy (DFXM), a diffraction-based imaging technique. Over the wide field of view, DFXM’s high angular resolution allows us to identify subgrains, separated by dislocation boundaries, which we identify and characterize down to the single-dislocation level using computer-vision methods. We demonstrate how even after long annealing times at high temperatures, the remaining low density of dislocations still pack into well-defined, straight dislocation boundaries (DBs) that lie on specific crystallographic planes. In contrast to conventional grain growth models, our results show that the dihedral angles at the triple junctions are not the predicted 120^{circ }, suggesting additional complexities in the boundary stabilization mechanisms. Mapping the local misorientation and lattice strain around these boundaries shows that the observed strain is shear, imparting an average misorientation around the DB of approx 0.003 to 0.006^{circ }.

The First Flight of the Marshall Grazing Incidence X-Ray Spectrometer (MaGIXS)

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) sounding rocket experiment launched on 2021 July 30 from the White Sands Missile Range in New Mexico. MaGIXS is a unique solar observing telescope developed to capture X-ray spectral images of coronal active regions in the 6–24 Å wavelength range. Its novel design takes advantage of recent technological advances related to fabricating and optimizing X-ray optical systems, as well as breakthroughs in inversion methodologies necessary to create spectrally pure maps from overlapping spectral images. MaGIXS is the first instrument of its kind to provide spatially resolved soft X-ray spectra across a wide field of view. The plasma diagnostics available in this spectral regime make this instrument a powerful tool for probing solar coronal heating. This paper presents details from the first MaGIXS flight, the captured observations, the data processing and inversion techniques, and the first science results.

Resistivity index mapping in Kidney based on ultrasensitive Pulsed-Wave Doppler and automatic spectrogram envelope detection.

In recent years, ultrasensitive Pulsed-Wave Doppler (uPWD) ultrasound (US) has emerged as an alternative imaging approach for microcirculation imaging and as a complementary tool to other imaging modalities, such as positron emission tomography (PET). uPWD is based on the acquisition of a large set of highly spatiotemporally coherent frames, which allows high-quality images of a wide field of view to be obtained. In addition, these acquired frames allow calculation of the resistivity index (RI) of the pulsatile flow detected over the entire field of view, which is of great interest to clinicians, for example, in monitoring the transplanted kidney course. This work aims to develop and evaluate a method to automatically obtain an RI map of the kidney based on the uPWD approach. The effect of time gain compensation (TGC) on the visualization of vascularization and aliasing on the blood flow frequency response, was also assessed. A pilot study conducted in patients referred for renal transplant Doppler examination showed that the proposed method provided relative errors of about 15% for RI measurements with respect to conventional pulsed-wave (PW) Doppler.

Channel Estimation and Performance Analysis of a Wide-FOV Visible Light Communication System With Random Receiver Orientation and Location

A practical visible light communications (VLC) system accounting for the effect of the random orientation and the random location of the photo-detector receiver is considered in this paper. The characterizations of the random orientation of the receiver, modeled as the receiver employing wide field of view (FOV) for data detection, and the random location of the receiver are utilized to derive the statistics for the scenarios in which (i) only the orientation of the receiver is random, (ii) only the location of the receiver is random, and (iii) both the orientation and location of the receiver are random. Furthermore, the receiver structures for a fully coherent VLC system and a VLC system employing the least-squares technique for channel estimation are proposed. Employing the receiver structures, the closed/series-form expressions for the symbol error probabilities are derived for all three scenarios of practical VLC channel models. The numerical results particularly show the crucial role of the ratio of the distance of the location of the receiver from the center of the receiving plane to the distance from the light-emitting diode (LED) to the center of the receiving plane in the performance of all the considered VLC systems.

Vesicoscopic ureteral reimplantation with a modified Glenn-Anderson technique for vesicoureteral reflux

Vesicoureteral reflux (VUR), commonly referred to as urinary reflux, is one of the most common congenital urological anomaly to occur during childhood. Historically, open vesicoureteral reimplantation has been the gold standard in the surgical treatment of VUR. Currently, vesicoscopic ureteral reimplantation is used as a minimally invasive alternative to open ureteral reimplantation. Most vesicoscopic procedures are performed using the transtrigonal Cohen technique. As a non-transtrigonal technique, the vesicoscopic Politano-Leadbetter technique is also performed, but requires dissection outside the bladder under a narrow surgical field, and in boy carries a risk of vas deferens injury. This study evaluated surgical outcomes and perioperative findings for vesicoscopic ureteral reimplantation using a modified Glenn-Anderson technique in children with VUR. Eighteen consecutive children who underwent vesicoureteral ureteral reimplantation using a modified Glenn-Anderson technique were included in this study. The surgical procedure was explained and surgical outcomes and perioperative findings were evaluated. Patients comprised 9 boys and 9 girls with 29 cases of ureteral reflux (7 unilateral cases, 11 bilateral cases). All procedures were performed laparoscopically, with no cases requiring conversion to open surgery. Median operative time was 143min for unilateral VUR and 194min for bilateral VUR. Only one case showed a complication (Clavien-Dindo grade 1). The remaining 17 cases showed no complications, with removal of the urethral catheter and discharge 2 days postoperatively. Seventeen of the 18 cases underwent postoperative voiding cystourethrography, showing no VUR in all cases. Vesicoscopic ureteral reimplantation is a minimally invasive alternative to open surgery, with most procedures performed using a transtrigonal Cohen technique. Regardless of whether the surgery is open or laparoscopic, a disadvantage of the Cohen technique is that postoperative transureteral treatment may not be possible. The Politano-Leadbetter technique has been reported as a non-transtrigonal technique. However, this requires dissection outside the bladder under a narrow surgical field, and carries a risk of vas deferens injury in boys. In this study, vesicoscopic ureteral reimplantation using a modified Glenn-Anderson technique provided good surgical outcomes with minimal perioperative complications and easy manipulation under a wide field of view. Although many minimally invasive treatments are available, vesicoscopic ureteral reimplantation using a modified Glenn-Anderson technique is safe and effective for patients with VUR 4 years old. To demonstrate the further utility of this procedure, long-term outcomes and safety evaluations are needed in a larger number of cases.

Wide field of view and full Stokes polarization imaging using metasurfaces inspired by the stomatopod eye

Abstract Wide field of view and polarization imaging capabilities are crucial for implementation of advanced imaging devices. However, there are still great challenges in the integration of such optical systems. Here, we report a bionic compound eye metasurface that can realize full Stokes polarization imaging in a wide field of view. The bionic compound eye metasurface consists of a bifocal metalens array in which every three bifocal metalenses form a subeye. The phase of the bifocal metalens is composed of gradient phase and hyperbolic phase. Numerical simulations show that the bifocal metalens can not only improve the focusing efficiency in the oblique light but also correct the aberration caused by the oblique incident light. And the field of view of the bionic compound eye metasurface can reach 120° × 120°. We fabricated a bionic compound eye metasurface which consists of three subeyes. Experiments show that the bionic compound eye metasurface can perform near diffraction-limited polarization focusing and imaging in a large field of view. The design method is generic and can be used to design metasurfaces with different materials and wavelengths. It has great potential in the field of robot polarization vision and polarization detection.

Eyebox enlargement in holographic AR glasses.

Despite the high output characteristics of holographic optical elements (HOEs), there are still no affordable holographic AR glasses that combine qualities such as a wide field of view (FOV) and a large eyebox (EB). In this study, we propose an architecture for holographic augmented reality glasses that covers both needs. Our solution is based on the combination of an axial HOE with a directional holographic diffuser (DHD) illuminated by a projector. A transparent-type DHD redirects the light from the projector, increasing the angular aperture of the image beams and providing a large EB. A reflection-type axial HOE redirects the light, transforming the spherical beams into parallel ones and providing a wide FOV for the system. The main feature of our system is the coincidence of the DHD position with the planar intermediate image of the axial HOE. This unique condition makes the system free of off-axial aberrations and ensures high output characteristics. The proposed system has a horizontal FOV of 60deg and an EB width of 10mm. We used modeling and a prototype to prove our investigations.

Investigation of single-shot high-speed photography based on spatial frequency multiplexing.

The frequency recognition algorithm for multiple exposures (FRAME) is a spatial frequency multiplexing method that enables high-speed videography with high spatial resolution across a wide field of view and high temporal resolution up to femtoseconds. The criterion to design encoded illumination pulses is an essential factor that affects the sequence depth and reconstruction accuracy of FRAME but was not previously discussed. When the spatial frequency is exceeded, the fringes on digital imaging sensors can become distorted. To exploit the Fourier domain for FRAME with deep sequences and avoid fringe distortion, the maximum Fourier map for sequence arrangement was determined to be a diamond shape. The maximum axial frequency should be a quarter of the sampling frequency of digital imaging sensors. Based on this criterion, the performances of reconstructed frames were theoretically investigated by considering arrangement and filtering methods. To ensure optimal and uniform interframe quality, the frames near the zero frequency should be removed and optimized super-Gaussian filters should be employed. Experiments were conducted flexibly with a digital mirror device to generate illumination fringes. Following these suggestions, the movement of a water drip dropping on a water surface was captured with 20 and 38 frames with uniform interframe quality. The results prove the effectiveness of the proposed methods to improve the reconstruction accuracy and promote the development of FRAME with deep sequences.

Large numerical aperture off-axis reflective telescope design with a freeform mirror based on aperture expansion strategy.

Currently, the emission of greenhouse gases is one of humanity's leading threats. To accurately and efficiently measure greenhouse gas levels in the atmosphere, we must develop imaging spectrometer systems with larger numerical apertures (NAs). However, designing a telescope with a large NA is difficult in this system. This paper presents a design strategy for aperture expansion to create a freeform telescope with a large NA. We compared different off-axis reflective telescopes and chose the Korsch structure, which has obvious advantages because of its wide field of view (FoV), large NA, and low stray light. Moreover, based on the influence of the position of the freeform surface in the aberration correction, we propose to use a single freeform surface to reduce the cost and increase manufacturability. A freeform telescope with an effective focal length of 84mm, a large NA of 0.25, and a wide FoV of 20° is successfully designed. The modulation transfer function of the system is better than 0.62, the maximum distortion is controlled to be less than 0.486%, and the incident angle of the beam on the image plane is less than 10°. The design result shows that the instrument has wide FoV, large NA, low stray light, and high performance. At the same time, the design strategy in this paper provides an effective method for the telescope design of the imaging spectrometer with a large NA.