Slanted Edge Research Articles

Quality Analysis of Unmanned Aerial Vehicle Images Using a Resolution Target

Unmanned aerial vehicle (UAV) photogrammetry is an emerging means of acquiring high-precision rapid spatial information and data because it is cost-effective and highly efficient. However, securing uniform quality in the results of UAV photogrammetry is difficult due to the use of low-cost navigation devices, non-surveying cameras, and rapid changes in shooting locations depending on the aircraft’s behavior. In addition, no specific procedures or guidelines exist for performing quantitative quality tests or certification methods on UAV images. Additionally, test tools for UAV image quality assessment only use the ground sample distance (GSD), often resulting in a reduced image quality compared with that of manned aircraft images. In this study, we performed a modulation transfer function (MTF) analysis using a slanted edge target and a GSD analysis to confirm the necessity of MTF analysis in UAV image quality assessments. In this study, we aimed to address this issue by conducting a modulation transfer function (MTF) analysis using a slanted edge target and a ground sample distance (GSD) analysis. This was carried out to confirm the necessity of MTF analysis in evaluating UAV image quality. Furthermore, we analyzed the impact of flight height and mounted sensors on image quality at different study sites.

Integrated-mode proton radiography with 2D lateral projections

Integrated-mode proton radiography leading to water equivalent thickness (WET) maps is an avenue of interest for motion management, patient positioning, and in vivo range verification. Radiographs can be obtained using a pencil beam scanning setup with a large 3D monolithic scintillator coupled with optical cameras. Established reconstruction methods either (1) involve a camera at the distal end of the scintillator, or (2) use a lateral view camera as a range telescope. Both approaches lead to limited image quality. The purpose of this work is to propose a third, novel reconstruction framework that exploits the 2D information provided by two lateral view cameras, to improve image quality achievable using lateral views. The three methods are first compared in a simulated Geant4 Monte Carlo framework using an extended cardiac torso (XCAT) phantom and a slanted edge. The proposed method with 2D lateral views is also compared with the range telescope approach using experimental data acquired with a plastic volumetric scintillator. Scanned phantoms include a Las Vegas (contrast), 9 tissue-substitute inserts (WET accuracy), and a paediatric head phantom. Resolution increases from 0.24 (distal) to 0.33 lp mm−1 (proposed method) on the simulated slanted edge phantom, and the mean absolute error on WET maps of the XCAT phantom is reduced from 3.4 to 2.7 mm with the same methods. Experimental data from the proposed 2D lateral views indicate a 36% increase in contrast relative to the range telescope method. High WET accuracy is obtained, with a mean absolute error of 0.4 mm over 9 inserts. Results are presented for various pencil beam spacing ranging from 2 to 6 mm. This work illustrates that high quality proton radiographs can be obtained with clinical beam settings and the proposed reconstruction framework with 2D lateral views, with potential applications in adaptive proton therapy.

Numerical analysis of concentric jet impingement heat transfer to the concave surface of the cone

This work includes numerical investigation of concentric jet impingement heat transfer to the concave surface of 30° apex angle conical surface. Heat transfer results are represented in terms of nondimensional heat transfer coefficient Nusselt number along the slant edge of the cone. Turbulence intensity, static pressure distribution along slant edge of the cone, and velocity contours in the domain are also presented for a detail understanding of the flow behavior. Different geometrical parameters like diameter of pipe (10 mm, 14 mm, and 20 mm) and L/D (4.25, 6.25, and 10.25) are considered for heat transfer analysis. Jet Reynolds number is varied between 25000 and 82000 for each diameter and L/D case. It is observed that Nusselt number value is minimum close to the apex of the cone due to stagnation region, then increases with increase in the distance from the apex of the cone and becomes maximum due to maxima in the turbulence intensity and decreases with increases in the distance. Nusselt number value decreases with increase in the L/D. Nusselt number increases with increase in the jet Reynolds number. There is an insignificant influence of the diameter of pipe on Nusselt number for identical jet Reynolds number and L/D.

Analysis of the Slanted-Edge Measurement Method for the Modulation Transfer Function of Remote Sensing Cameras

The modulation transfer function (MTF) serves as a crucial technical index for assessing the imaging quality of remote sensing cameras, which is integral throughout their entire operational cycle. Currently, the MTF evaluation of remote sensing cameras primarily relies on the slanted-edge method. The factors influencing the slanted-edge method’s effectiveness are broadly classified into two categories: algorithmic factors and image factors. This paper innovatively comprehensively analyzes the influencing factors of the slanted-edge method and proposes an improved slanted-edge method to calculate the MTF testing method of remote sensing cameras, which is applied to the MTF testing of remote sensing cameras. Since the traditional algorithm can only be applied in the small angle situation, this paper proposes a new method of slanted-edge method test calculation based on the optimal oversampling rate (OSR) adaptive model of the slanted edge and uses simulation experiments to verify the reliability of the algorithm model through the deviation of the slanted-edge angle calculation and MTF measurement, and the results show that the algorithm improves the accuracy of the MTF measurement compared with the ISO-cos and OMINI-sine methods. Then, the effects of the slanted-edge angle, image region of interest (ROI), as well as image contrast and signal-to-noise ratio (SNR) on the accuracy of the MTF calculation by the slanted-edge method were quantitatively analyzed as the constraints of the slanted-edge method test. Based on the laboratory target experiment, the algorithm flow and various influencing factors obtained in the simulation stage are verified, and the experimental results are more consistent with the various test results obtained in the simulation stage. Consequently, the slanted-edge method introduced in this paper is applicable for future remote sensing camera MTF testing. This approach offers a valuable reference for on-orbit focusing, satellite operational condition monitoring, lifespan estimation, and image restoration.

A Novel Approach to Design Multiplexer Using Magnetic Quantum-Dot Cellular Automata

Magnetic quantum-dot cellular automata (MQCA) is a recent technology in computation based on closely coupled ferromagnetic and antiferromagnetic dots; it is favorable as the fabrication issues arise day by day at the nanometer scale in CMOS technology. In this letter, first, we propose MQCA-based 2:1 Multiplexer using conventional horizontal and vertical approaches. In the next step, we propose a novel area efficient compact design approach with the help of the explicit interaction, coupling concept & dominant nature of slant edge nanomagnets. The proposed compact design methodology leads to 71%-97% reduction in the total number of nanodots and 22%-99% reduction in area occupancy compared to the horizontal, vertical, nanomagnetic QCA, and existing QCA-based 2:1 Mux. To showcase the scalability of our proposed structure, we also implement an 8:1 Multiplexer. The design layouts and simulation results are verified using the MuMax3 micromagnetic simulator.

Spatial-numeric method application to the movable wedge problem for Physics First pedagogy

The objective is to solve the college physics problem of a block sliding down a movable smooth wedge without friction anywhere using a spatial-numeric perspective. The drawing method used the sum of the normal force and weight of the block to find the wedge acceleration. The drawing method results are equivalent to the algebra method results within drawing accuracy. The result of a geometric construction with regular drawing uncertainly was shown for the case without any horizontal applied force. For the case of a given horizontal applied force, an additional numeric graphing method was shown with additional drawing uncertainty in the result. The geometric construction without graphing resuted in solving the horizontal applied force case via scaling in the concept of modified gravity experienced by the block on the wedge’s slant edge, assuming a pre-requisite knowledge of algebra and trigonometry. The presented spatial numeric method and results imply a Physics First pedagogy of using the spatial numeric abilities, with the inclusion of the pre-projectile problem, pre-traffic-light problem, and post-collision problem in a one-semester syllabus.

Research on the Modulation Transfer Function Detection Method of a Bayer Filter Color Camera.

Bayer filter color cameras are more and more widely used in the field of aerospace remote sensing, but the Bayer filter causes great degradation in image quality; therefore, obtaining a means of achieving the high-precision measurement of the modulation transfer function (MTF) of Bayer filter color cameras is an urgent problem. In order to solve this problem, this paper develops a slanted-edge method via three steps: the detection of the slanted edge, the acquisition and processing of the edge spread function (ESF), and the acquisition and processing of the line spread function (LSF). A combination of the Canny operator and Hough transform is proposed for the detection of the slanted edge, which improves the fitting accuracy and anti-interference ability of the algorithm. Further, the Canny operator is improved by constructing an adaptive filter function and introducing the Otsu method, which can more effectively smooth the image and remove its false edges. A method of processing ESF data by combining cubic spline interpolation and Savitzky-Golay (SG) filtering is proposed, which reduces the effects of noise and the non-uniform sampling of ESF on MTF. A method of LSF processing using Gaussian function fitting is proposed to further reduce the effect of noise on MTF. The improved algorithm is verified by the MTF measurement test applied to a specific type of Bayer filter color space camera. The simulation and test results show that the improved slanted-edge method discussed in this paper has greater precision and a better anti-interference ability, and it can effectively solve the difficult problem associated with MTF detection in Bayer filter color space cameras.

Convolutional Neural Network를 활용한 SEM 영상품질 향상 및 영상품질 평가를 위한 MTF 측정기법

As the size of semiconductor devices gradually decreases, it is important to measure and analyze semiconductor devices, to improve the image quality of semiconductors. We use VDSR, one of the Super-Resolution methods to improve the quality of semiconductor devices’ SEM images. VDSR is also a convolutional neural network that can be optimized with various parameters. In this study, a VDSR model for semiconductor devices’ SEM images was optimized using parameters such as depth of layers and amount of training data. Meanwhile, the quantitative evaluation and the qualitative evaluation did not match at the low scale factor. To solve this problem, we proposed an MTF measurement method using the slanted edge for better quantitative evaluation. This method was verified by comparing the results with the PSNR and SSIM index results, which are known as quality indicators. Based on the results, it was confirmed that using the MTF value could be a better approach for the evaluation of SEM images of the semiconductor device than using PSNR and SSIM.

The Aerodynamic Effects of a 3D Streamlined Tail on the Windsor Body

The aerodynamic drag reduction of road vehicles is of continuing interest. The drag arising from the rear surfaces is usually the dominant component, but this can be alleviated by the tapering of the rear body. The effects on the aerodynamic characteristics of a simple body from adding an elongated tapered tail have been investigated in a wind tunnel experiment. The streamlined tail consists of a constant rear body side taper added to a constant upper body taper. The results have been compared with an earlier study of the same body with upper body tapering only. The effects of truncating the long tail are explored. Adding the planform tapering reduces the impact of the slant edge vortices, and drag and lift are substantially reduced. The lateral aerodynamic characteristics are largely unaffected.

The influence of image capture and processing on MTF for end of line test and validation

Slanted edge MTF measurement as per ISO12233 is the defacto standard for measuring camera sharpness at manufacturing end of line. MTF measured by slanted edge has a number of advantages for measuring sharpness, being scale invariant, and relatively robust to geometric distortion. However, slanted edge MTF measurement is known to be affected by image processing algorithms, including demosaic, edge enhancement, and denoise algorithms. To avoid these confounding factors, it is increasingly common to measure MTF directly from the raw sensor image. This approach is logical if you are assessing the optomechanical lens-imager alignment and focus. However, end-of-line production testing has specific requirements, including speed of execution, repeatability and reproducibility. These requirements are typically not considered when configuring a camera for end-of-line MTF measurement. In this study, the execution time, repeatability and reproducibility of MTF measurement for multiple image capture and image processing combinations are examined.

Shape optimization of inlet header of micro-channel heat sink using surrogate model combined with genetic algorithm

A lot of work has documented the significance of fluid-flow uniformity on the thermal-hydraulic performance of the micro-channel heat sink. The purpose of this work is to optimize the shape of inlet/outlet headers of a micro-channel heat sink to improve the flow distribution characteristics using the back propagation neural networks combined with the genetic algorithm as the surrogate model. The slanted edge of the inlet header is defined as the quadratic parabola instead of straight line. Meanwhile, the shape of the parabola is optimally designed for different flow rates. The 40 training sample points and six testing sample points on different geometry structures of inlet header are designed by the Latin hypercube sampling method. The 3-D CFD calculation is performed for all models. The objective function is defined as the non-uniformity of the fluid-flow. It is found that the prediction of the genetic algorithm back propagation for the fluid-flow distribution is capable of obtaining objective function values within the designed space. Through the optimizations, the non-uniformity of the optimal inlet header structure can be reduced by 52.43% to 33.17% for the inlet velocity of 0.05 m/s to 0.1 m/s, respectively, compared to that of the original design. The results demonstrate that the parabolic treatment for the slanted edge of the inlet header as well as structural optimization can greatly improve the flow uniformity of the micro-channel heat sink.

Spectral Multiplexing of Fluorescent Endoscopy for Simultaneous Imaging with Multiple Fluorophores and Multiple Fields of View

Complex clinical procedures and small-animal research procedures can benefit from dual-site imaging provided by multiple endoscopic devices. Here, an endoscopic system is proposed which enables multiple fluorescence microendoscopes to be spectrally multiplexed on a single microscope base, enabling light sources and optical relays to be shared between endoscopes. The presented system is characterized for resolution using USAF-1951 resolution test charts and for modulation transfer function using the slanted edge method. Imaging is demonstrated both directly and with microendoscopes attached. Imaging of phantoms was demonstrated by targeting USAF charts and fiber tissues dyed for FITC and Texas Red fluorescence. Afterwards, simultaneous liver and kidney imaging was demonstrated in mice expressing mitochondrial Dendra2 and injected with Texas Red-dextran. The results indicate that the system achieves high channel isolation and submicron and subcellular resolution, with resolution limited by the endoscopic probe and by physiological movement during endoscopic imaging. Multi-channel microendoscopy provides a potentially low-cost means of simultaneous multiple endoscopic imaging during biological experiments, resulting in reduced animal harm and potentially increasing insight into temporal connections between connected biological systems.

A customized syringe for separating ingrown toe nail from the gutter

Abstract Ingrown toenails is a painful foot problems seen in primary care among young men. To provide immediate pain relief, some types of splints are placed in the gutter to separate it from the ingrown lateral nail. There are time-consuming and effort-intensive procedures that use available nail separators and elevators to separate the nail plate. Here, the hub of the syringe is cut obliquely to create a bevelled or slant edge to create a custom nail separator which is a useful device for the easy and less painful separation of the ingrown nail plate from its gutter, which is an important stage of nail splinting.

Electron Imaging Reconstruction for Pixelated Semiconductor Tracking Detectors in Transmission Electron Microscopes Using the Approach of Convolutional Neural Networks

Energetic electrons of several hundred-kilo electron volts (keV) as used in transmission electron microscopy applications do not deposit their energy completely at their point of entry (PoE). Instead, in a detector with a thickness of 450 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>, they produce randomly 3-D tracks often extending over many pixels. The length and the shape of these tracks strongly depend on the primary energy of the electrons. Statistically, an electron deposits most of its energy at the end of its track. The output of a tracking detector system is the pixelated 2-D projection of the energy deposition. The proposed convolutional neural network (CNN) is capable of performing a frame-based event analysis and PoE reconstruction. The resulting modulation transfer function (MTF) is 0.77 at a Nyquist frequency of 0.5 obtained from a slanted edge. It is based on a U-net with a specially designed loss function using the confusion matrix. The input data to the CNN only need to be offset corrected. The output of the CNN is a PoE map containing the probability of a PoE of an electron for each pixel and frame. The architecture of the designed CNN also allows reconstructing different frame sizes without retraining the network.

Numerical Investigation of a Drag Reduction Device Applied to the Ahmed Body

In this paper, a new technique of drag reduction around a simplified car body called the Ahmed body is introduced. A conduit has been perforated in this body. The purpose of this conduit is bringing part of airflow from the body’s front to be injected in its rear end where the recirculation occurs. In this study, a numerical model of a turbulent flow around a two–dimensional then three–dimensional body has been developed. Numerical simulations have been performed using the computational fluid dynamics software ANSYS Fluent. For the 2D case, series of numerical simulations have been performed. In these simulations, the conduit position relative to the body’s lower slant edge has been modified. For the position with minimum drag, the effect of narrowing the conduit exit has been tested. Finally, the effect of narrowing the conduit exit has been studied. For the 3D case, the effect of changing dimensions of a rectangular conduit and its position from the body’s lower slant edge have been studied. For the position with lower drag, the effect of narrowing the conduit exit has been studied. The 2D and 3D results show that in some conduit configurations, drag could be reduced.

Application of ImPASS to translated images produces image resolution below the optical diffraction resolution limit

The image resolution produced by a lens/camera system is limited by the digital sampling frequency of the sensor and the diffraction limit as imposed by the front aperture diameter of the optics. A previous study using Image Phase Alignment Super-Sampling (ImPASS) demonstrated that Fourier phase information from a sequence of slightly displaced images can be used to achieve image resolution beyond the digital sampling frequency. In continuation of that work, this study applies ImPASS to sequences of slightly displaced empirical images for a range of aperture settings. The frames are up-sampled, aligned, and combined into a single frame. Application of Self-Deconvolving Data Restoration Algorithm (SeDDaRA) deconvolution reveals features with higher resolution. The slanted edge technique is applied to the processed images to establish the angular resolution of the system as a function of the effective f-number. When compared to Abbe’s resolution criteria, the measurements reveal that this super-sampling method produces image resolution that subceeds the diffraction limit of the lens/camera system.

Improvements on sampling of point spread function in optical transfer function measurement.

Point spread function (PSF), which is the intensity distribution of optical system impulse response and usually acquired by imaging a single pinhole in experiment, can characterize the quality of optical imaging system. Faithful recording of the two-dimensional intensity distribution of PSF is key for accurate measurement of optical transfer function (OTF), however distortions in recorded PSF can be easily caused by a large sampling interval and the electronic noise of the detector. Under a given sampling interval, the position-phase difference between pixels and intensity signals can change the intensity distribution of acquired PSF remarkably, making the computed OTF or MTF (modulation transfer function) error prone. Aiming at problems existing in pinhole based MTF measurement methods, this paper developed a new method with underline physics similar to that of slanted edge method to realize sub-pixel sampling of PSF intensity by using accurate non-integer up-sampling matrix of separate binary pixels and applying random patterns shown on digital micro-mirror device (DMD) as target. Numerical simulations show that improvement on the discrete sampling of point spread function with this method is very helpful to improve anti-noise robustness and the accuracy of optical transfer function measurement.

Time-resolved particle image velocimetry and pressure sensitive paint measurements of afterbody flow dynamics

A pair of counter-rotating vortices is produced in the wake of typical cargo aircraft fuselages due to their ramp shape. With a fast polymer-ceramic pressure sensitive paint (PC-PSP), we measure the global pressure fluctuations at very low velocities (15 to 75 m/s) in a surrogate cylinder with a slanted edge model. Through spectral proper orthogonal decomposition, we observe a family of convective pressure waves with peak energy at frequencies matching the vortex wandering frequencies in this flow.

Modulation transfer function measurements of HgCdTe long wavelength infrared arrays for the Near-Earth Object Surveyor

The modulation transfer function (MTF) is a useful measure in image quality analysis and performance budget determination. Sensitive long wavelength infrared (LWIR) detectors for astronomical space telescopes require slight modifications to the existing MTF measurement methods due to the increased prevalence of high dark current pixels. Presented here are the specifics of a modified slanted edge method to determine the MTF in λc > 10 μm HgCdTe detectors to be used with the planned Near-Earth Object Surveyor Mission. The measured MTF at Nyquist using 6 μm light is 0.22 ± 0.02 and is 0.25 ± 0.02 using 10 μm light for both 250 and 350 mV of applied reverse bias. These measurements are from edge spread functions with median signal values around 50% of the well depth, as the MTF is expected to change with signal value due to two brighter-fatter type effects. The expected trends caused by the influences of these two effects and the expected trends with wavelength of absorbed photons are all observed.

Accuracy and precision of an edge-based modulation transfer function measurement method using a variable oversampling ratio

The edge-based method standardized in ISO 12233 approximates the modulation transfer function (MTF) as a function of horizontal or vertical spatial frequency by analyzing a supersampled edge profile obtained from the captured image of a slightly slanted bi-tonal edge. The method describes the slanted projection of pixels sampled in a square array into a linear array of subpixel-wide bins. An ad hoc correction is available to accommodate the diagonal MTF measurements. However, using a fixed oversampling ratio in the standard method degrades the accuracy and precision of the MTF estimates, owing to the periodic misalignment between the projection paths and the bin array. A new edge-based method using a variable oversampling ratio, OMNI-sine, has been proposed to remedy this misalignment. In this study, computer simulations were performed to demonstrate the accuracy and precision of the MTF estimates over a full range of finely sampled slant angles.