Image stitching is a crucial technique in various fields of imaging and photography, which allows for the creation of high-resolution images by combining multiple smaller images with overlapping regions. Here, we propose a simple and fast method, the Subtraction Method (SM), for pixel and subpixel image stitching using holographic data. The feasibility of the SM is verified at the pixel and subpixel level using two 2D images captured by a 4-f imaging system. Additionally, the application of the SM for holographic data is also explored. The effective aperture of an inline holographic imaging system is enlarged by stitching four in-line holograms, demonstrating enhanced resolution and image quality after reconstruction. The stitching accuracy and computational time of the SM is compared with the correlation method. With optimization, the result shows that the SM achieves high accuracy and requires less computational time for image stitching when compared to contemporary image stitching algorithms.

In recent years, many phase space distributions have been proposed, and one of the more independently interesting is the Bai distribution function (BDF). The BDF has been shown to interpolate between the instantaneous auto-correlation function and the Wigner distribution function, and be applied in linear frequency modulated signal parameter estimation and optical partial coherence areas. Currently, the BDF is only defined for continuous signals. However, for both simulation and experimental purposes, the signals must be discrete. This necessitates the development of a BDF analysis workflow for discrete signals. In this work, we analyze the sampling requirements imposed by the BDF and demonstrate their correctness by comparing the continuous BDFs of continuous test signals with their numerically approximated counterparts. Our results permit more accurate simulations using BDFs, which will be useful in applying them to problems such as partial coherence.

Abstract Gibbs ringing is an artifact that occurs physically in many signal and image acquisition modalities. Gegenbauer reconstruction is an approach to reducing Gibbs artifacts based on polynomial smoothing of continuous regions of the signal using Gegenbauer polynomials. In this work, we systematically explain Gegenbauer reconstruction in the signal processing context. We investigate how the parameters, lambda and m, impact the behavior of Gegenbauer reconstruction. We make a quantitative comparison between Gegenbauer reconstruction and other Gibbs suppression methods. Gegenbauer reconstruction assumes that the locations of the discontinuities are known, so we examined how faulty edge detection results could impact Gegenbauer reconstruction. Our results question the standing of Gegenbauer reconstruction in the literature as an exceptionally high performing method of Gibbs ringing reduction.

In recent years, many novel phase space distributions have been proposed and one of the more independently interesting is the Bai distribution function (BDF). The BDF has been shown to interpolate between the instantaneous auto-correlation function and the Wigner distribution function, and to link the geometrical and wave optical descriptions in the Fresnel domain. Currently, the BDF is only defined for continuous signals. However, for both simulation and experimental purposes, the signals must be discrete. This necessitates the development of a BDF analysis workflow for discrete signals. In this paper, we will analyse the sampling requirements imposed by the BDF, and demonstrate their correctness by comparing the continuous BDFs of continuous test signals with their numerically approximated counterparts. Our results will permit more accurate simulations using BDFs, which will be useful in applying them to problems in, e.g., partial coherence.

In this paper we investigate the use of photopolymer material as the sensor medium. This research will focus on the creation of self-written waveguides within the photopolymer and the interaction with the environment. This SWW can be used to measure direction of propagation and angle of incidence upon the polymer material. Under environmental force new SWWs can be measured and recorded within the PVA/AA on a 3D plane. These newly created SWWs, from numerical modelling, can represent the interaction with the surrounding environment. This can be used to measure force and direction of movement.

Powerful chatbots, based on intensively-trained large language models, have recently become available for consumer use. The ability of such chatbots to provide credible textual responses to sophisticated engineering problems has been demonstrated in various subfields. This paper seeks to gauge the extent to which such a chatbot can be prompted to complete a set of homework and project exercises for university-level courses in analog, digital, mixed -signal, and signal processing classes. The purpose of this paper is to delineate and clearly articulate the present capabilities of artificial intelligence tools to complete coursework taks across the field of circuit theory. Building on these research findings, this paper suggests practical ways to mitigate artifical intelligence chatbot tools' disription to academic integrity and genuine learning in universities.

This paper presents a novel comparative study between two prominent compressed sensing algorithms - Orthogonal Matching Pursuit (OMP) and Iterative Hard Thresholding (IHT) - within the context of digital holography, specifically focusing on their efficacy in handling phase discontinuities. Previous research has predominantly centered on Gibbs ringing artifacts in image reconstruction and their mitigation. However, the aspect of phase discontinuities, which are critical in holographic imaging, has not been extensively explored. Our study implement both OMP and IHT algorithms in a simulated digital holographic environment, where phase discontinuities are inherent due to the nature of holographic imaging. We analyze how these algorithms perform in the presence of phase discontinuities. We quantitatively analyze the performance of each algorithm in handling phase discontinuities. Additionally, our study delves into the computational efficiency of both algorithms, considering their practical applicability in real-time holographic imaging systems. The results of our comparative analysis provide insights into the advantages and limitations of OMP and IHT in the context of phase discontinuities. Our findings have significant implications for advancing digital holography, particularly in applications requiring precise phase information, such as medical imaging, microscopy, and non-destructive testing.

In this article, we introduce an innovative tunable selective antenna leveraging variable liquid metal (LM) coupling length. Frequency reconfiguration is achieved by manipulating the LM length. The tuning mechanism relies on the precise movement of LM within 3D-printed microfluidic channels, controlled by varying voltage. The proposed antenna boasts a straightforward configuration and compact size, operating within the frequency range of 1-3.6 GHz. It generates multiple frequency bands including WiMAX, WiFi, and WLAN. Through meticulous optimization of the physical length of the liquid metal, six distinct frequency bands at 0.9-1.2 GHz, 1.2-1.6 GHz, 1.6-2 GHz, 2-2.4, 2.4-2.9 GHz, and 2.9-3.6 GHz GHz without any overlap are generated. Our study demonstrates a strong agreement between simulation and measurement results, affirming the efficacy of our design.

This communication introduces an innovative approach to achieving an ultrawideband (UWB) reconfigurable multinotch band antenna. The antenna's performance is dynamically tuned using a variable liquid metal (LM) coupling length, making it suitable for applications in cognitive radio systems. The tuning mechanism involves controlling the LM within 3-D-printed microfluidic channels through the application of variable dc voltage. The proposed mechanism generates four distinct notch bands without any overlap. With a straightforward configuration and compact size, the proposed antenna spans the UWB spectrum [(4.1 to 12.5) GHz] while effectively generating band rejection in various application frequency bands, including WiMAX, WiFi, and WLAN, which is valuable for minimizing interference from these commonly used communication standards. The prototype measurements closely align with simulations, validating the feasibility and practical advantages of this liquid metal-based reconfigurable antenna design for cognitive radio systems.

This paper presents an analysis of the feasibility of using Laser Excited Phosphor spotlights mounted on loitering unmanned aerial vehicles to provide on-demand illumination to a section of terrain at night. An extensive analysis of existing technology is conducted to select components for such a proposed system. Following this analysis, the deliverable illumination to the ground is determined based on environmental and technological limitations. It is found that a system built from ‘off-the-shelf’ components could plausibly deliver upwards of 50 lx of illuminance on-demand to a user on the ground anywhere within a wide service area of multiple square kilometres.

Since late 2022, the sudden growth in the availability and capabilities of generative artificial intelligence tools, such as Large Language Models, has raised concerns about the threat they pose to the integrity of assessment in educational institutions. Such models are constantly evolving and improving, making the task of understanding exactly what they can do more difficult. Recognising this challenge, this paper establishes a Large Language Model exposure framework to qualitatively and quantitatively examine the assessment strategies of university modules to provide a high-level estimated indication of the exposure of these modules to potential dishonest use of such models in the completion of their assessments and coursework. This framework may be used and adapted when planning and reviewing teaching and learning practices and policies.

Fast and simple methods for motion estimation with subpixel accuracy are of interest in a variety of applications. In this paper, we extend a recently proposed method for quantifying 1D displacements with subpixel accuracy, referred to as the subtraction method (SM) to 2D motion. Simulation and experimental results are presented. The results indicate that any general motion in 2D involving combinations of in-plane motions in x and y can be determined using SM after a 1D calibration. The errors between the actual motion and estimated are examined.

In this article, we present a novel reconfigurable antenna with circular polarization on dual WiMAX bands (3.5, 5.8 GHz) based on liquid metal switching capability. The circular polarization reconfiguration is achieved by connecting the rectangular parasitic element (Pc) with the feed line by the liquid metal switch. The mechanism of switching is based on controlling the liquid metal in microfluidic channels by applying a voltage to move and remove the high-conductivity liquid metal EGaIn on the microchannel. The proposed antenna has a simple configuration and compact size that generates dual WiMAX band with Circular polarization (CP) performance by changing the state of the liquid metal switch that is suitable for 5G wireless technology.

Gibbs ringing is an artefact that is inevitable in any imaging modality where the measurement is Fourier band-limited. It impacts the quality of the image by creating a ringing appearance around discontinuities. Many novel ways of suppressing the artefact have been proposed, including machine learning methods, but the quantitative comparisons of the results have frequently been lacking in rigour. In this paper, we examine image quality assessment metrics on three test images with different complexity. We determine six metrics which show promise for simultaneously assessing severity of Gibbs ringing and of other error such as blurring. We examined applying metrics to a region of interest around discontinuities in the image and use the metrics on the resulting region of interest. We demonstrate that the region of interest approach does not improve the performance of the metrics. Finally, we examine the effect of the error threshold parameter in two metrics. Our results will aid development of best practice in comparison of algorithms for the suppression of Gibbs ringing.

We create two separate self-written waveguides (SWW) within photopolymer material. The coupling of these two self-written waveguides into a self-written coupling waveguide (SWCW), which are produced through the convergence of two self-written waveguides SWWs.

The theory of partial coherence is a significant part of Fourier optics, which has been utilized in numerous areas and applications. Therefore, the simulation of partially coherent systems is important for the system analysis and design of optical signal processing and other applications. Therefore, it is useful to identify the differences and strengths of existing simulation methods. In this paper, we compared three partially coherent field simulation algorithms including the random screen, superposition, and coherent mode decomposition methods based on their simulation results. Finally, we identified the optimal usage scenarios for each algorithm.

Compressed sensing is a signal processing technique used for signal reconstruction with significantly smaller number of samples than the requirements of the Nyquist-Shannon theorem. In this work, we simulate a lensless digital holographic system. We investigate the ringing-like artefact introduced by truncation by the camera aperture. We present the results of using the orthogonal matching pursuit based compressed sensing algorithms to combat this ringing-like artefact. We demonstrate that compressed sensing achieves remarkable reconstructions and suppresses ringing well, but only up to a point in terms of the size of the aperture. This research could help the advancement of compressive digital holography.

The Wigner distribution function (WDF) is a significant time-frequency analysis tool in, e.g., the theory of optical coherence and signal processing. Recently, various generalizations of the WDF associated with linear canonical transforms have been proposed to improve and broaden its applications. It is useful to identify which of these novel distributions have independent significance for further investigation. We plot these distributions for a test signal using symbolic integration to find which distributions are linear coordinate transforms of the WDF or have unique features. Five distributions are determined to be linear coordinate transforms of the WDF. Two distributions show unique characteristics. We focus on the mathematical interpretation, properties, and possible applications of those two distributions. We demonstrate how one of them can be used in the analysis of partially coherent systems.