Relay Imaging Research Articles

Methods of protecting uav radio channels against unauthorized Access

The adoption and widespread use of unmanned aerial vehicles (UAVs) is constantly increasing in many areas. This is due to the ability of drones to record and relay real-time video and images along with the ability to fly and carry cargo. However, when using drones, a number of problems arise, because outsiders can gain access to information transmission channels to meet their own needs. Information attacks on UAVs lead to significant consequences, including commercial and non-commercial losses. The purpose of this work is to study UAVs and their vulnerability and protection during flight. To achieve the goal, the methods of searching scientific and technical literature, analysis, classification, systematization and generalization of available data on UAVs were used. On the basis of the found key industry publications, a comprehensive analysis of methods of protecting UAV radio channels against hacker attacks was carried out. The interception process is described as one of the options for UAV access threats, namely: signal interception, control interception, physical interception. The following methods of UAV radio channel protection are substantiated: signal encryption; use of spectral methods; authentication and authorization; use of physical barriers; creation of unique software for UAVs; Closing all radio communication channels on the UAV itself; returning it using a recorded route. The actual scientific and practical task, which consists in the theoretical and methodological substantiation of the approaches and principles of UAV radio channel protection in real time, has been solved. The variant of the mutual position in space of the UAV, the control panel (PU) and the radio electronic suppression station is presented, as well as the method of decentralized wireless interaction of these components. Prospects and advantages of using artificial intelligence are revealed.

The effect of transport apertures on relay-imaged, sharp-edged laser profiles in photoinjectors and the impact on electron beam properties

In a photoinjector electron source, the initial transverse electron bunch properties are determined by the spatial properties of the laser beam on the photocathode. Spatial shaping of the laser is commonly achieved by relay imaging an illuminated circular mask onto the photocathode. However, the Gibbs phenomenon shows that recreating the sharp edge and discontinuity of the cut profile at the mask on the cathode is not possible with an optical relay of finite aperture. Furthermore, the practical injection of the laser into the photoinjector results in the beam passing through small or asymmetrically positioned apertures. This work uses wavefront propagation to show how the transport apertures cause ripple structures to appear in the transverse laser profile even when effectively the full laser power is transmitted. The impact of these structures on the propagated electron bunch has also been studied with electron bunches of high and low charge density. With high charge density, the ripples in the initial charge distribution rapidly wash-out through space charge effects. However, for bunches with low charge density, the ripples can persist through the bunch transport. Although statistical properties of the electron bunch in the cases studied are not greatly affected, there is the potential for the distorted electron bunch to negatively impact machine performance. Therefore, these effects should be considered in the design phase of accelerators using photoinjectors.

Inverse design of metasurface based off-axis image relay

The rapid advancement of portable electronics has created enormous demand for compact optical imaging systems. Such systems often require folded optical systems with beam steering and shaping components to reduce sizes and minimize image aberration at the same time. In this study, we present a solution that utilizes an inverse-designed dielectric metasurface for arbitrary-angle image-relay with aberration correction. The metasurface phase response is optimized by a series of artificial neural networks to compensate for the severe aberrations in the deflected images and meet the requirements for device fabrication at the same time. We compare our results to the solutions found by the global optimization tool in Zemax OpticStudio and show that the proposed method can predict better point-spread functions and images with less distortion. Finally, we designed a metasurface to achieve the optimized phase profile.

Simultaneous visualization of density and pressure in hydrogen leakage based on self-imaging via dual-channel interference

Risk assessment of hydrogen energy technologies is a necessary condition for the arrival of a hydrogen energy economy society. Currently, most methods for detecting hydrogen leaks use a single concentration or pressure sensor. Structural visualization and parametric diagnosis of complex flow fields cannot be solved simultaneously by a single detection method. The main objective of this work is to propose an advanced optical detection method to simultaneously monitor the outlet pressure and density field distribution during hydrogen leakage. For the detection of the density field distribution, we use double propagation of the laser beam in the hydrogen jet to improve the phase sensitivity and relay imaging of the object between each pass to maintain spatial resolution. Error analysis shows that the error of our proposed method is 2.47 %, which is within the error tolerance. The sensitivity analysis shows that our detection sensitivity is twice that of the conventional Mach-Zehnder interferometer. For the detection of outlet pressure, we propose a mathematical model in which the half-length axis of the laser spot is linearly related to the outlet pressure and use the deformation of the laser beam in the hydrogen jet to detect the outlet pressure. The results show that the hydrogen jet can be regarded as a gas-phase lens when detecting the outlet pressure, and the deformation of the laser beam profile in the horizontal direction increases linearly with the increase of the jet pressure. The results of the study can provide a reference for the detection of accidental hydrogen leakage and the improvement of hydrogen safety regulations.

Defect detection and response non-uniformity correction of a monocentric camera based on fiber optic relay imaging.

The monocentric camera based on fiber relay imaging offers benefits of light weight, compact size envelope, vast field of view, and high resolution, which can fully fulfill the index requirements of space-based surveillance systems. However, the fiber optic plate's (FOP) defects will result in the loss of imaging data, and the FOP's discrete structural features will exacerbate the imaging's non-uniformity. A global defect detection approach based on manual threshold segmentation of saturated frames is suggested to detect FOP defect features. The suggested method's efficacy and accuracy are confirmed when compared to the classical Otsu algorithm. Additionally, through tests, the relative imaging response coefficients of each pixel are identified, the response non-uniformity of the pixels is corrected, and the whole image non-uniformity drops from 10.01% to 0.78%. The study in this paper expedites the use of fiber relay imaging-based monocentric cameras in the field of space-based surveillance, and the technique described in this paper is also appropriate for large-array optical fiber coupled relay image transmission systems.

Image-plane coherent diffractive imaging using variable-ratio lateral-shearing interferometry

Coherent diffractive imaging (CDI) is an imaging technique that directly recovers the amplitude and phase information of the test object from the recorded diffraction patterns with an iterative algorithm. Different from the traditional CDI, here an image-plane CDI is proposed based on the variable-ratio lateral-shearing interferometry. Variable-ratio operation can realize three optical functions, the first is the array imaging, the second is the image relay, and the third is variable-ratio shear. In experiment, a frame of array diffraction patterns is recorded in one single exposure. Then, each sub-diffraction pattern is extracted through the image features and is sequentially used to recover the test object by phase retrieval. The experimental results of phase-only and amplitude-only object verify the effectiveness and robustness of our proposed method. This method not only circumvents the calibration problem of gratings but also strengthens the convergence conditions required for phase retrieval, which has broad applications in fields such as optical imaging and wavefront sensing.

Design of a dual scattering angle multi-pass Thomson scattering system with signal separation function on Heliotron J.

This paper proposes a design of dual scattering angles multi-path Thomson scattering system with a signal separation function to solve the overlapping phenomenon of scattered light signals and to increase the measurement accuracy for the investigation of anisotropic electron velocity distribution. Furthermore, an optical path design is proposed to demonstrate how overlapping scattered light signals can be separated by setting the optical path in a limited room with a compact layout, which makes the incident interval between two overlapping scattered light signals 1.7 times longer than that of our current system. The specific position of each optical component existing in the system is determined via a Gaussian beam analysis to avoid damage caused by overexpansion of spot size with the application of two cooperating image relay systems. Conversely, a polychromator is optimized by resetting the pass waveband of the interference filter combination to achieve high accuracy in electron temperature (Te) measurement corresponding to two scattering angles simultaneously.

Analysis of influence of imaging resolution of relay lens on image reconstruction quality in pixel-wise coded exposure imaging technology

Pixel-wise coded exposure (PCE) imaging based on digital micromirror device (DMD) is an advanced high-speed imaging technology, which can realize the high-speed imaging by using a low-frame-rate camera. During exposure time, the multi-frame image information of a dynamic object can be integrated into one encoded image, and then the multi-frame sub-exposure images can be extracted by the post-processing algorithm. Therefore, the accurate pixel-to-pixel alignment between the DMD and the camera is the key step to realize PCE imaging, which has drawn much attention from researchers. So their studies mainly focused on how to achieve accurate pixel matching. However, the resolution of the relay imaging lens, as another important influence factor of PCE imaging, also has a significant influence on the imaging results, but few people have studied and analyzed it. To solve this problem, in this work, we theoretically analyze the influence of the resolution of the relay imaging system on the reconstructed decoded images, and verifies the theoretical analysis through simulation and imaging experiments. On this basis, a PCE imaging system is built, and a point spread function (PSF) estimation method of relay lens based on the fringe phase is proposed. Furthermore, a Richard-Lucy deconvolution algorithm is introduced into the reconstruction process of coded image to effectively improve the quality of PCE imaging, which is of great significance in developing the PCE imaging technology.

Design of a Concentric Multi-Scale Zoom Optical System Based on Wide Object Distance and High-Precision Imaging.

To effectively balance the trade-off between a large field of view (FOV) and high resolution of an optical system, as well as to solve the problem of image stitching misalignment after focusing, firstly, this paper conducts a theoretical analysis of the design principle of the concentric multi-scale optical system and the causes of image stitching misalignment after focusing. Secondly, the design idea of using a combination structure of a two-layer front concentric imaging group and an image-space telecentric relay imaging array and then a joint full-motion zoom relay imaging system is proposed. Finally, an image-space telecentric two-step zoom concentric multi-scale optical system with a 7 × 7 relay imaging array is designed. The FOV of this optical system is 60° × 45°; the focal lengths are 50 mm and 100 mm for the center channel and 50 mm for the other channels. This concentric multi-scale zoom system has the advantages of both high-precision imaging stitching with a wide object distance and high-resolution imaging, which makes up for the defects of the conventional concentric multi-scale optical system, making it a promising application in the fields of aviation and security.

Tele‐Ultrasound: Virtual Hands‐on Medical Education for Novice Users Utilizing FAST & Carpal Tunnel Models, Pilot Study

Ultrasound (US) training is an emerging tool, utilized to enhance anatomy education in medical schools with preliminary incorporation into non‐medical anatomy courses. The need for distanced, virtual, education has always been present with an exponential increase in demand due to COVID‐19. Recent developments in point‐of‐care‐ultrasound (POCUS) have enabled relay of remote imaging and communication, Tele‐US. This pilot study aims to assess whether the integration of virtual self‐paced modules and virtually guided (VG) ultrasound sessions, utilizing the Butterfly iQ (BiQ) US device, is as effective as in‐person (IP) learning for novice users.Study sessions included three, 30‐minute modules: Introduction, Carpal Tunnel (CPL‐T), Focused assessment with sonography in trauma (FAST). Live hands‐on active learning sessions utilized CPL‐T and FAST modules where groups of 2‐3 participants performed peer‐peer scanning. Hands‐on guidance was given to IP groups, whereas VG groups received guidance through the BiQ Tele‐guidance software (TGS). The TGS provides remote video conferencing, real‐time imaging relay for simultaneous viewing by the operator and educator, educators ability to remotely change settings, and the integration of augmented reality to provide visual cues to the operator on screen. Seven first‐year medical students were invited to participate in the IRB‐exempt pilot study. Pre‐ and Post‐study online surveys were used to collect data on previous US training utilizing multiple choice questions and self‐perception of confidence levels US skill and usefulness of the BiQ US system. Perceptions were assessed utilizing a 5‐point Likert scale (1= strongly disagree/not useful/extremely difficult, 5= strongly agree/extremely useful/extremely easy). Additionally, a 20‐point assessment was administered IP by staff to participants in a random order on 4 key anatomical regions; median nerve, radial artery, hepatorenal recess, and thorax to assess participant US skill levels at the end of the live session. Feedback provided to participants after the assessment period was completed for all participants.Two‐way t‐tests were used to assess post‐study ratings and assessment scores. Pre‐ and post‐study survey response rates were 100% (3 IP, 4 VG) with roughly equal gender distribution. Comparison of post assessment survey did not show a significant difference (SD) in self confidence levels (P>0.05) between the groups across all 5 prompts: ease of CPL‐T/ FAST, usefulness of BiQ, confidence in displaying CPL‐T/FAST. Further, a SD in scores during the live session assessment was not observed (IP average= 15.5 ±0.71, VG average= 12.3 ±2.9; P=0.1). Detailed analysis was not performed due to the limited sample size of the pilot study.Perceived confidence and assessment scores do not differ when comparing traditional POCUS to Tele‐US using BiQ for novice users, suggesting that medical students can demonstrate equal competency levels when undergoing distanced US education as IP courses. Yet, further testing is required to expand the sample size and test in‐group variances.

Spectral Beam Combining of Diode Lasers Based on Separated Reflection Relay Imaging

Spectral Beam Combining of Diode Lasers Based on Separated Reflection Relay Imaging

Design overview of ex-vessel components for the Wide Angle Viewing System diagnostic for ITER Equatorial Port 12

The ITER equatorial visible and infrared Wide Angle Viewing System (WAVS) provides surface temperature measurements of plasma facing components by infrared (IR) thermography being one of its main roles to protect them from damage. It also images the plasma emission in the visible range. The diagnostic, which comprises 15 lines of sight distributed in four equatorial ports (3, 9, 12 and 17), will contribute to Machine protection, Basic control and Physics analysis in ITER. The design of the diagnostic in the equatorial port 12 (EP12) - comprising three lines of sight - is currently being developed within a Framework Partnership Agreement through a Specific Grant granted by F4E to the Consortium formed by CEA, Ciemat and Bertin Technologies. EP12 has to be operative for the ITER first plasma. The overview of the WAVS opto-mechanical design for the ex-vessel components in EP12 will be presented in the paper. The ex-vessel optics are composed of mirrors and refractive elements which relay the exit image of the port plug at the vacuum window up to the cameras placed inside a shielded cabinet in the Port Cell. The image relay through the Interspace, Bioshield and Port Cell has to cover a length of almost 10 m in order to reach the detectors. The refractive elements are arranged in sub-assemblies (optical modules) mechanically mounted in barrels and next assembled on a support structure. The assembly of these modules on site will be also presented in the paper. Furthermore, the Optical Hinge which is the first component of the ex-vessel optical chain (formed by two folding mirrors) aims to compensate the differential motion between the vacuum vessel and the building, in normal operation and baking. The mechanical assembly and the operation of this component will be also described in the paper.

Dual GRIN lens two-photon endoscopy for high-speed volumetric and deep brain imaging.

Studying neural connections and activities in vivo is fundamental to understanding brain functions. Given the cm-size brain and three-dimensional neural circuit dynamics, deep-tissue, high-speed volumetric imaging is highly desirable for brain study. With sub-micrometer spatial resolution, intrinsic optical sectioning, and deep-tissue penetration capability, two-photon microscopy (2PM) has found a niche in neuroscience. However, the current 2PM typically relies on a slow axial scan for volumetric imaging, and the maximal penetration depth is only about 1 mm. Here, we demonstrate that by integrating a gradient-index (GRIN) lens and a tunable acoustic GRIN (TAG) lens into 2PM, both penetration depth and volume-imaging rate can be significantly improved. Specifically, an ∼ 1-cm long GRIN lens allows imaging relay from any target region of a mouse brain, while a TAG lens provides a sub-second volume rate via a 100 kHz ∼ 1 MHz axial scan. This technique enables the study of calcium dynamics in cm-deep brain regions with sub-cellular and sub-second spatiotemporal resolution, paving the way for interrogating deep-brain functional connectome.

Enhanced emotional and motor responses to live versus videotaped dynamic facial expressions

Facial expression is an integral aspect of non-verbal communication of affective information. Earlier psychological studies have reported that the presentation of prerecorded photographs or videos of emotional facial expressions automatically elicits divergent responses, such as emotions and facial mimicry. However, such highly controlled experimental procedures may lack the vividness of real-life social interactions. This study incorporated a live image relay system that delivered models’ real-time performance of positive (smiling) and negative (frowning) dynamic facial expressions or their prerecorded videos to participants. We measured subjective ratings of valence and arousal and facial electromyography (EMG) activity in the zygomaticus major and corrugator supercilii muscles. Subjective ratings showed that the live facial expressions were rated to elicit higher valence and more arousing than the corresponding videos for positive emotion conditions. Facial EMG data showed that compared with the video, live facial expressions more effectively elicited facial muscular activity congruent with the models’ positive facial expressions. The findings indicate that emotional facial expressions in live social interactions are more evocative of emotional reactions and facial mimicry than earlier experimental data have suggested.

Compact, unit magnification, reflective imaging relay using freeform surfaces

We present a design for a unit magnification imaging relay that is compact. The design uses two mirrors, and one is used by light twice for a three-reflection system. The mirrors are specified with freeform surfaces. There are several tradeoffs of performance depending on field of view, F / #, and wavelength range. One example provides a 30-mm circular field of view at F / 2.8, and another example provides a circular field of view of 40 mm in diameter at F / 4 for a length of ∼400 mm. Adding a third nearly flat mirror allows a system to provide a 50-mm field of view at F / 4 for a length of 420 mm. A last example includes a beam splitter cube to allow accessing the full field of view. These systems are diffraction limited at 550 nm.

Visible Light Communication System Employing Space Time Coded Relay Nodes and Imaging Receivers

In this paper, authors propose a VLC system, whose source of information is assumed to be a power line, and employs a combination of relaying and multiple-input multiple-output (MIMO) techniques. Precisely, the performance of a VLC system, with relay nodes equipped with a MIMO technique called space time block coding (STBC), is investigated. The bit error rate (BER) performance of the Alamouti coding (AC) scheme, which is a type of STBC, is specifically considered. In order to enhance the overall system reliability, we propose to use an imaging receiver (ImR), in conjunction with the relay-MIMO setup. In comparison to when a nonimaging receiver (NImR) is employed, an improved signal-to-noise ratio (SNR) of 7 dB is observed when an ImR with a specific number of pixels, is used, hence, improving the BER. We also investigate and show that the selected number of pixels and receiver location have an effect on the system BER. SNR values of 9 dB, 11 dB and 15 dB were required to maintain a BER of 10 −4 for imaging receivers with 70, 50 and 20 pixels, respectively.

Experimental study on two-lens slit filtering

ABSTRACTTwo-lens slit filtering has great prospects for high-power lasers due to the excellent properties of inhibition of pinhole closure and compactness of the laser facility. With analysis of the beam profile, power spectrum density and near-field parameters, two-lens slit filtering and its image relay characteristic are experimentally demonstrated, showing a great improvement in beam quality and a good image relay property.

Geometry parameter calibration for focused plenoptic cameras.

Due to the subtle structure, the exact geometry parameters of the focused plenoptic camera cannot be retrieved after packaging, which leads to inaccurate light field processing such as visible artifacts in the rendering images. This paper proposes a novel blind calibration method to calculate the geometry parameters for the focused plenoptic cameras with high precision. It translates the problem of deriving the value of the geometry parameters to be the problem of deriving the pixel patch-size of each micro-image used in subaperture image rendering based on the geometry projection of the relay imaging process in the focused plenoptic camera. Then, a dark image calibration algorithm is proposed to retrieve the position and the geometry parameters of the MLA for subaperture image rendering. A triple-level calibration board with random texture is designed to realize focus plane confirming blindly, to facilitate capturing light field images at different object distances via a single shot and to benefit intensity feature matching in determining the rendering patch size. The rendering patch-size is found by the proposed Gradient-SSIM-based fractional-pixel matching based on the geometry projection analysis. Experiments conducted on the simulated data and the real imaging system demonstrate that the proposed method can acquire the geometry parameters with high accuracy and is robust to different focused plenoptic cameras.

基于微场镜阵列的红外光场中继成像系统

基于微场镜阵列的红外光场中继成像系统

基于微场镜阵列的红外光场中继成像系统

基于微场镜阵列的红外光场中继成像系统