434 research outputs found

    Side Information in Coded Aperture Compressive Spectral Imaging

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    Coded aperture compressive spectral imagers sense a three-dimensional cube by using two-dimensional projections of the coded and spectrally dispersed source. These imagers systems often rely on FPA detectors, SLMs, micromirror devices (DMDs), and dispersive elements. The use of the DMDs to implement the coded apertures facilitates the capture of multiple projections, each admitting a different coded aperture pattern. The DMD allows not only to collect the sufficient number of measurements for spectrally rich scenes or very detailed spatial scenes but to design the spatial structure of the coded apertures to maximize the information content on the compressive measurements. Although sparsity is the only signal characteristic usually assumed for reconstruction in compressing sensing, other forms of prior information such as side information have been included as a way to improve the quality of the reconstructions. This paper presents the coded aperture design in a compressive spectral imager with side information in the form of RGB images of the scene. The use of RGB images as side information of the compressive sensing architecture has two main advantages: the RGB is not only used to improve the reconstruction quality but to optimally design the coded apertures for the sensing process. The coded aperture design is based on the RGB scene and thus the coded aperture structure exploits key features such as scene edges. Real reconstructions of noisy compressed measurements demonstrate the benefit of the designed coded apertures in addition to the improvement in the reconstruction quality obtained by the use of side information

    Encoding complex valued fields using intensity

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    We present an approach enabling the representation of complex values using intensity only fields.  The method can be used for imaging with structured illumination and allows the study of new propagating physical quantities with the classical coherent or incoherent light field playing the role of hidden variable. This approach can further be generalized to encode higher order N-dimensional vectors and ensembles of N orthogonal fields. Different orthogonal, incoherent illumination patterns (Hadamard, sinusoidal, Laguerre-Gauss) have been experimentally tested in a single-pixel detection imaging scheme in order to compare their performances in terms of obtainable resolution.  We show experimentally that our encoding technique allows to reduce the required number of illuminations for a given, desired resolution.Publisher PDFPeer reviewe

    Multispectral Metamaterial Detectors for Smart Imaging

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    The ability to produce a high quality infrared image has significantly improved since its initial development in the 1950s. The first generation consisted of a single pixel that required a two-dimensional raster scan to produce an image. The second generation comprised of a linear array of pixels that required a mechanical sweep to produce an image. The third generation utilizes a two-dimensional array of pixels to eliminate the need for a mechanical sweep. Third generation imaging technology incorporates pixels with single color or broadband sensitivity, which results in \u27black and white\u27 images. The research presented in this dissertation focuses on the development of 4th generation infrared detectors for the realization of a new generation of infrared focal plane array. To achieve this goal, we investigate metamaterials to realize multicolor detectors with enhanced quantum efficiency for similar function to a human retina. The key idea is to engineer the pixel such that it not only has the ability to sense multimodal data such as color, polarization, dynamic range and phase but also the intelligence to transmit a reduced data set to the central processing unit (neurophotonics). In this dissertation, we utilize both a quantum well infrared photodetector (QWIP) and interband cascade detector (ICD) hybridized with a metamaterial absorber for enhanced multicolor sensitivity in the infrared regime. Through this work, along with some design lessons throughout this iterative process, we design, fabricate and demonstrate the first deep-subwavelength multispectral infrared detector using an ultra-thin type-II superlattice (T2-SL) detector coupled with a metamaterial absorber with 7X enhanced quantum efficiency. We also identify useful versus non-useful absorption through a combination of absolute absorption and quantum efficiency measurements. In addition to these research efforts, we also demonstrate a dynamic multicolor metamaterial in the terahertz regime with electronically tunable frequency and gain for the first time. Utilizing an electronically tunable metamaterial, one can design an imaging system that can take multiple spectral responses within one frame for the classification of objects based on their spectral fingerprint.\u2

    Una comparación cuantitativa y cualitativa de análisis de rendimiento de las cámaras espectrales compresiva

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    Context: Spectral images (SI) contain spatial-spectral information about a scene arranging in a data cube, which often comprises a significant amount of data. However, traditional (SI) systems acquire data ignoring the high correlation between the measurements and the samples are redundant. Compressive spectral imaging systems compress spectral data in the acquisition step, so it allows reducing redundancy and the data amount. Recently, several spectral imaging systems have become available, providing new functionality for users and opening up the field to a wide array of new applications. For instance, the CASSI, SCSI, SSCS, and HYCA systems are four of the most outstanding systems.Methods: Some review works have provided comprehensive surveys of the available technologies and have shown how the new capabilities of spectral imaging approaches can be utilized. However, selecting a specific architecture requires a quantitative and qualitative comparison of these systems in the same scenarios.Results: This paper analyzes the qualitative and quantitative performance of these four compressive spectral imaging systems to evaluate them in the same scenarios. For that, the architectures are modeled as a system of linear equations; then, image reconstructions are accomplished through the same optimization approach, transmittance, coded aperture, and shot numbers.Conclusion: Results show that the performance of the SSCSI system attains better quality reconstruction in terms of PSNR.Contexto: Las imágenes espectrales (SI) contienen información espacio-espectral acerca de una escena disponible en un cubo de datos que usualmente comprende una cantidad significativa de éstos. Los sistemas tradicionales de (SI) adquieren datos redundantes ignorando la alta correlación entre las mediciones y las muestras redundantes. Los sistemas de compresión de imágenes espectrales comprimen los datos espectrales en la etapa de adquisición, lo que permite reducir la cantidad de datos y la redundancia. Actualmente, existen varios sistemas de imágenes espectrales disponibles que proporcionan nuevas funciones para los usuarios y abren un amplio campo de nuevas aplicaciones. Por ejemplo, los sistemas de CASSI, SCSI, SSCS, y HYCA son cuatro de los más destacados.Método: La revisión de algunos trabajos provee amplios estudios de tecnologías disponibles y muestra cómo se pueden utilizar las nuevas capacidades de los enfoques de formación de imágenes espectrales. Sin embargo, para la selección de una arquitectura específica se requiere una comparación cuantitativa y cualitativa de estos sistemas en los mismos escenarios.Resultados: En este trabajo se analiza el rendimiento cualitativo y cuantitativo de estos cuatro sistemas de compresión de imágenes espectrales para evaluarlos en los mismos escenarios. Para ello, cada arquitectura se modela como un sistema de ecuaciones lineales y el proceso de reconstrucción de las imágenes se logra con el mismo enfoque de optimización transmitancia, código de apertura y número de proyecciones.Conclusión: Se muestra que el sistema SSCSI alcanza el mejor rendimiento en la reconstrucción con el valor más alto PSNR

    COMPRESSIVE IMAGING AND DUAL MOIRE´ LASER INTERFEROMETER AS METROLOGY TOOLS

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    Metrology is the science of measurement and deals with measuring different physical aspects of objects. In this research the focus has been on two basic problems that metrologists encounter. The first problem is the trade-off between the range of measurement and the corresponding resolution; measurement of physical parameters of a large object or scene accompanies by losing detailed information about small regions of the object. Indeed, instruments and techniques that perform coarse measurements are different from those that make fine measurements. This problem persists in the field of surface metrology, which deals with accurate measurement and detailed analysis of surfaces. For example, laser interferometry is used for fine measurement (in nanometer scale) while to measure the form of in object, which lies in the field of coarse measurement, a different technique like moire technique is used. We introduced a new technique to combine measurement from instruments with better resolution and smaller measurement range with those with coarser resolution and larger measurement range. We first measure the form of the object with coarse measurement techniques and then make some fine measurement for features in regions of interest. The second problem is the measurement conditions that lead to difficulties in measurement. These conditions include low light condition, large range of intensity variation, hyperspectral measurement, etc. Under low light condition there is not enough light for detector to detect light from object, which results in poor measurements. Large range of intensity variation results in a measurement with some saturated regions on the camera as well as some dark regions. We use compressive sampling based imaging systems to address these problems. Single pixel compressive imaging uses a single detector instead of array of detectors and reconstructs a complete image after several measurements. In this research we examined compressive imaging for different applications including low light imaging, high dynamic range imaging and hyperspectral imaging

    Metamaterials for Computational Imaging

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    <p>Metamaterials extend the design space, flexibility, and control of optical material systems and so yield fundamentally new computational imaging systems. A computational imaging system relies heavily on the design of measurement modes. Metamaterials provide a great deal of control over the generation of the measurement modes of an aperture. On the other side of the coin, computational imaging uses the data that that can be measured by an imaging system, which may limited, in an optimal way thereby producing the best possible image within the physical constraints of a system. The synergy of these two technologies - metamaterials and computational imaging - allows for entirely novel imaging systems. These contributions are realized in the concept of a frequency-diverse metamaterial imaging system that will be presented in this thesis. This 'metaimager' uses the same electromagnetic flexibility that metamaterials have shown in many other contexts to construct an imaging aperture suitable for single-pixel operation that can measure arbitrary measurement modes, constrained only by the size of the aperture and resonant elements. It has no lenses, no moving parts, a small form-factor, and is low-cost.</p><p>In this thesis we present an overview of work done by the author in the area of metamaterial imaging systems. We first discuss novel transformation-optical lenses enabled by metamaterials which demonstrate the electromagnetic flexibility of metamaterials. We then introduce the theory of computational and compressed imaging using the language of Fourier optics, and derive the forward model needed to apply computational imaging to the metaimager system. We describe the details of the metamaterials used to construct the metaimager and their application to metamaterial antennas. The experimental tools needed to characterize the metaimager, including far-field and near-field antenna characterization, are described. We then describe the design, operation, and characterization of a one-dimensional metaimager capable of collecting two-dimensional images, and then a two-dimensional metaimager capable of collecting two-dimensional images. The imaging results for the one-dimensional metaimager are presented including two-dimensional (azimuth and range) images of point scatters, and video-rate imaging. The imaging results for the two-dimensional metaimager are presented including analysis of the system's resolution, signal-to-noise sensitivity, acquisition rate, human targets, and integration of optical and structured-light sensors. Finally, we discuss explorations into methods of tuning metamaterial radiators which could be employed to significantly increase the capabilities of such a metaimaging system, and describe several systems that have been designed for the integration of tuning into metamaterial imaging systems.</p>Dissertatio

    Development of Plasmonic and X-Ray Luminescence Nanoparticles for Bioimaging and Sensing Applications

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    This dissertation discusses the development of plasmonic and X-ray luminescence nanoparticles (~100 nm) to use in bioimaging and sensing applications. The nanoparticles have interesting optical properties compared to their atomic levels and bulk materials. The optical properties of nanomaterials can be controlled by changing size, shape, crystal structure, etc. Also, they have a large surface area that can be functionalized with biomolecules. Therefore, the optical properties and biofunctionalized nanomaterials are useful in biomedical applications such as targeted drug delivery, bioimaging, and sensing. The overall theme is to use nanoparticles with interesting optical properties compared to their atomic levels and bulk materials to understand and control size/shape-dependent optical properties and crystallinity. Here, we discuss nanomaterials\u27 optical properties and biofunctionalization in three sections, 1) size/shape-dependent optical properties of plasmonic nanoparticles, which we develop a simple and robust mechanical approach to prepare plasmonic nanoparticle arrays, 2) X-ray optical luminescence of X-ray luminescence nanoparticles which depends on crystal defects and amount of dopants by synthesizing them and enhancing their intensity to use them in high-resolution imaging, 3) biofunctionalization of gold and X-ray luminescence nanoparticles to develop immunoassays. Chapter two describes the development of a simple, mechanical approach to preparing plasmonic nanoparticle arrays and transferring them onto a thin film. Plasmonic nanoparticles can absorb and scatter visible range light depending on their size, shape, and environment, and unlike fluorescence dyes, they do not photo-bleach. Plasmonic nanoparticles and array of nanoparticles have many applications including in bioimaging and sensing. The current methods to develop nanoparticle arrays and transfer them onto thin films are complex, time-consuming, and expensive. Here, we report a simple technique to generate patterns of gold and silver nanoparticles with controlled shape and shape-dependent optical properties. The pressure was applied to nanoparticles on a glass slide to convert nanospheres (diameter ~ 90 nm) to nanodiscs (diameter ~180 nm). Metal stamps and glucose deposits were placed on nanoparticles before applying pressure to generate patterns. The change in nanoparticle shape causes their localized surface plasmon resonance wavelength to red-shift. Also, we developed a method to remove undeformed nanoparticles using scotch tape and transform nanoparticle patterns into a flexible polymer film. Like plasmonic nanoparticles, X-ray luminescence nanophosphors can be used as an optical contrast agent in biomedical imaging and optical biosensors. They generate visible light through tissue when irradiated with X-rays. However, the sensitivity of these applications depends on the intensity of emitted visible light, and it is important to investigate methods to enhance its intensity. Herein, we describe the synthesis of X-ray scintillating NaGdF4:Eu and Tb nanophosphors via co-precipitate and hydrothermal methods, enhancing X-ray excited optical luminescence. The brightest particles were obtained using hydrothermal synthesis, and thermal annealing enhanced X-ray luminescence intensity. However, annealing above 600 °C changes the chemical structure to NaGd9Si6O26:Eu, which results in a shift in the X-ray luminescence spectra. Further, we demonstrated that the particles generate light through tissue and can be selectively excited using a focused X-ray source for imaging and spectroscopy. The fourth chapter brings plasmonic and X-ray luminescence particles together to develop immunoassays. Here, we describe a design and development of a gold nanoparticles-based lateral flow assay (LFA) to detect SARS-CoV-2 antibodies in human saliva and a proof of concept to develop an immunoassay using gold nanoparticles and X-ray luminescence nanoparticles. Gold and X-ray luminescence particles were functionalized with receptor binding domain protein and human anti-spike IgG, respectively. Our preliminary studies show the ability to develop the LFA to detect SARS-CoV-2 antibodies in human saliva, an immunoassay using RBD functionalized gold nanoparticles, and anti-spike IgG functionalized Gadolinium oxysulfide microparticles. The X-ray luminescence decreases by a factor of 1.8 due to light absorption when attaching gold nanoparticles to Gadolinium oxysulfide microparticles. This can be developed as an implantable immunoassay to quantify biomarkers in vivo locally and continuously. Chapter five includes a separate study that is not based on nanoparticles-based bioimaging and sensing. However, it discusses a behavioral analysis to discover and understand the X-ray stimulated behavior of Caenorhabditis elegans. Chapter six provides a conclusion and discusses possible future work for each chapter
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