Phaseless computational imaging with a radiating metasurface

Computational imaging modalities support a simplification of the active architectures required in an imaging system and these approaches have been validated across the electromagnetic spectrum. Recent implementations have utilized pseudo-orthogonal radiation patterns to illuminate an object of interest---notably, frequency-diverse metasurfaces have been exploited as fast and low-cost alternative to conventional coherent imaging systems. However, accurately measuring the complex-valued signals in the frequency domain can be burdensome, particularly for sub-centimeter wavelengths. Here, computational imaging is studied under the relaxed constraint of intensity-only measurements. A novel 3D imaging system is conceived based on 'phaseless' and compressed measurements, with benefits from recent advances in the field of phase retrieval. In this paper, the methodology associated with this novel principle is described, studied, and experimentally demonstrated in the microwave range. A comparison of the estimated images from both complex valued and phaseless measurements are presented, verifying the fidelity of phaseless computational imaging.Comment: 18 pages, 18 figures, articl

Structural Health Monitoring using Structured Lights and Infrared Thermography

Structural health monitoring (SHM) is a nondestructive data-driven process used to assess the conditions of structural systems using methods like acoustic emission, ultrasonic, thermal imaging etc. In recent years with advancement in computer vision, research into vision-based inspection methods using three dimensional (3D) optical imaging and point cloud data is a field of active research. Structured light technique is an active method in 3D optical imaging where patterns are projected on to the scene and the camera captures the distorted pattern caused by the scene. The method uses the pattern distortion information to recover the 3D geometry. Therefore, instead of relying on the scene optical properties, the structured light method uses a projector to project known structured patterns onto the scene and the correspondence is established using the captured projected pattern information. Infrared thermography ((IRT) technique is another widely used technique for contactless temperature measurement and stress analysis of materials based on thermo elastic effects. Furthermore, IRT can be used to estimate fatigue limit and fatigue life curve of structural materials. For both visible and thermal imaging pixels are the data acquisition points used for surface profiling. However, thermal cameras have lower resolutions in comparison to visible light due to larger sensor elements. To overcome the limitations of IRT and to better investigate temperature dependent structural deformations we propose the use of projective transformations to map thermal information on to 3D reconstructed surfaces using structural light technique.https://ecommons.udayton.edu/stander_posters/4054/thumbnail.jp

Are galaxies with AGN a transition population?

We present the results of an analysis of a well-selected sample of galaxies with active and inactive galactic nuclei from the Sloan Digital Sky Survey, in the range 0.01 < z < 0.16. The SDSS galaxy catalogue was split into two classes of active galaxies, Type~2 AGN and composites, and one set of inactive, star-forming/passive galaxies. For each active galaxy, two inactive control galaxies were selected by matching redshift, absolute magnitude, inclination, and radius. The sample of inactive galaxies naturally divides into a red and a blue sequence, while the vast majority of AGN hosts occur along the red sequence. In terms of H-alpha equivalent width, the population of composite galaxies peaks in the valley between the two modes, suggesting a transition population. However, this effect is not observed in other properties such as colour-magnitude space, or colour-concentration plane. Active galaxies are seen to be generally bulge-dominated systems, but with enhanced H-alpha emission compared to inactive red-sequence galaxies. AGN and composites also occur in less dense environments than inactive red-sequence galaxies, implying that the fuelling of AGN is more restricted in high-density environments. These results are therefore inconsistent with theories in which AGN host galaxies are a `transition' population. We also introduce a systematic 3D spectroscopic imaging survey, to quantify and compare the gaseous and stellar kinematics of a well-selected, distance-limited sample of up to 20 nearby Seyfert galaxies, and 20 inactive control galaxies with well-matched optical properties. The survey aims to search for dynamical triggers of nuclear activity and address outstanding controversies in optical/IR imaging surveys.Comment: 12 pages, 8 figures, accepted by MNRA

Computational Imaging Systems for High-speed, Adaptive Sensing Applications

Driven by the advances in signal processing and ubiquitous availability of high-speed low-cost computing resources over the past decade, computational imaging has seen the growing interest. Improvements on spatial, temporal, and spectral resolutions have been made with novel designs of imaging systems and optimization methods. However, there are two limitations in computational imaging. 1), Computational imaging requires full knowledge and representation of the imaging system called the forward model to reconstruct the object of interest. This limits the applications in the systems with a parameterized unknown forward model such as range imaging systems. 2), the regularization in the optimization process incorporates strong assumptions which may not accurately reflect the a priori distribution of the object. To overcome these limitations, we propose 1) novel optimization frameworks for applying computational imaging on active and passive range imaging systems and achieve 5-10 folds improvement on temporal resolution in various range imaging systems; 2) a data-driven method for estimating the distribution of high dimensional objects and a framework of adaptive sensing for maximum information gain. The adaptive strategy with our proposed method outperforms Gaussian process-based method consistently. The work would potentially benefit high-speed 3D imaging applications such as autonomous driving and adaptive sensing applications such as low-dose adaptive computed tomography(CT)

2D and 3D optical imaging of SERS nanotags intracellularly

Adoption of a multi-marker nanotag approach will led to better disease characterisation whilst simultaneously enabling targeting of multiple disease markers or organelles. The employed nanotag method controllably aggregated nanoparticles with 1,6-hexamethylene diamine (1,6-HMD), before polymer coating with polyvinylpyrrolidone (PVP) and labelling with small molecule reporters; 4-mercaptopyridine (MPY), 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), 4-nitrobenzenethiol (NBT) and 2-naphthalenethiol (2-NPT). Within a multiple component suspension reporters were identified by their unique peak and when present within single cells or populations they were additionally identified using component direct classical least squares (DCLS). Within a single cell three of the four components (MPY, DTNB and NBT) were positively identified. 2D SERS imaging can monitor nanotag uptake but it provides no conclusive evidence of cellular inclusion. The simultaneous determination of cellular uptake and nanotag identification was however achieved using combined 3D Raman and SERS imaging. Three of the four components were detected within a single cell and by combining 2D sections from the 3D images it was possible to determine their intracellular location. Determination of intracellular localisation was achieved using principal component analysis (PCA) since it resulted in the resolution of a subcellular compartment. However, the ultimate success of the system will only be realised when active targeting is demonstrated. Nanotags were functionalised with peptide sequences specific for the endoplasmic reticulum (ER) and trans-Golgi network (TGN). Both nanotag systems were found to locate within lipid rich regions of the cell but they could not be positively confirmed as the ER or TGN. To identify these structures and confirm localisation, further chemometric methods must be investigated including hierarchical cluster analysis (HCA). In conclusion, the SERS nanotags were suitable imaging agents for 2 and 3D cell interrogation. 3D imaging simultaneously permitted organelle resolution and the intracellular localisation of the SERS nanotags. Targeting systems were developed and in future work their localisation within organelles will be confirmed by the application of advanced chemometric methods.Adoption of a multi-marker nanotag approach will led to better disease characterisation whilst simultaneously enabling targeting of multiple disease markers or organelles. The employed nanotag method controllably aggregated nanoparticles with 1,6-hexamethylene diamine (1,6-HMD), before polymer coating with polyvinylpyrrolidone (PVP) and labelling with small molecule reporters; 4-mercaptopyridine (MPY), 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), 4-nitrobenzenethiol (NBT) and 2-naphthalenethiol (2-NPT). Within a multiple component suspension reporters were identified by their unique peak and when present within single cells or populations they were additionally identified using component direct classical least squares (DCLS). Within a single cell three of the four components (MPY, DTNB and NBT) were positively identified. 2D SERS imaging can monitor nanotag uptake but it provides no conclusive evidence of cellular inclusion. The simultaneous determination of cellular uptake and nanotag identification was however achieved using combined 3D Raman and SERS imaging. Three of the four components were detected within a single cell and by combining 2D sections from the 3D images it was possible to determine their intracellular location. Determination of intracellular localisation was achieved using principal component analysis (PCA) since it resulted in the resolution of a subcellular compartment. However, the ultimate success of the system will only be realised when active targeting is demonstrated. Nanotags were functionalised with peptide sequences specific for the endoplasmic reticulum (ER) and trans-Golgi network (TGN). Both nanotag systems were found to locate within lipid rich regions of the cell but they could not be positively confirmed as the ER or TGN. To identify these structures and confirm localisation, further chemometric methods must be investigated including hierarchical cluster analysis (HCA). In conclusion, the SERS nanotags were suitable imaging agents for 2 and 3D cell interrogation. 3D imaging simultaneously permitted organelle resolution and the intracellular localisation of the SERS nanotags. Targeting systems were developed and in future work their localisation within organelles will be confirmed by the application of advanced chemometric methods

Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery

One of the main challenges for computer-assisted surgery (CAS) is to determine the intra-opera- tive morphology and motion of soft-tissues. This information is prerequisite to the registration of multi-modal patient-specific data for enhancing the surgeon’s navigation capabilites by observ- ing beyond exposed tissue surfaces and for providing intelligent control of robotic-assisted in- struments. In minimally invasive surgery (MIS), optical techniques are an increasingly attractive approach for in vivo 3D reconstruction of the soft-tissue surface geometry. This paper reviews the state-of-the-art methods for optical intra-operative 3D reconstruction in laparoscopic surgery and discusses the technical challenges and future perspectives towards clinical translation. With the recent paradigm shift of surgical practice towards MIS and new developments in 3D opti- cal imaging, this is a timely discussion about technologies that could facilitate complex CAS procedures in dynamic and deformable anatomical regions