Optical diffraction tomography (ODT) solves an inverse scattering problem to obtain label-free, 3... more Optical diffraction tomography (ODT) solves an inverse scattering problem to obtain label-free, 3D refractive index (RI) estimation of biological specimens. This work demonstrates 3D RI retrieval methods suitable for partially-coherent ODT systems supported by intensity-only measurements consisting of axial and angular illumination scanning. This framework allows for access to 3D quantitative RI contrast using a simplified non-interferometric technique. We consider a traditional iterative tomographic solver based on a multiple in-plane representation of the optical scattering process and gradient descent optimization adapted for focus-scanning systems, as well as an approach that relies solely on 3D convolutional neural networks (CNNs) to invert the scattering process. The approaches are validated using simulations of the 3D scattering potential for weak phase 3D biological samples.
Polarized reflectance maps of bovine articular cartilage are rich in texture content. Image textu... more Polarized reflectance maps of bovine articular cartilage are rich in texture content. Image texture analysis extracts quantitative parameters useful to assess intact cartilage versus cartilage with mechanical surface damage or enzymatic degradation.
Coherent optical frequency-domain reflectometry (C-OFDR) is a distance measurement technique with... more Coherent optical frequency-domain reflectometry (C-OFDR) is a distance measurement technique with significant sensitivity and detector bandwidth advantages over normal time-of-flight methods. Although several swept-wavelength laser sources exist, many exhibit short coherence lengths, or require precision mechanical tuning components. Semiconductor distributed feedback lasers (DFBs) are advantageous as a mid-to-long range OFDR source because they exhibit a narrow linewidth and can be rapidly tuned simply via injection current. However, the sweep range of an individual DFB is thermally limited. Here, we present a novel high-resolution OFDR system that uses a compact, monolithic 12-element DFB array to create a continuous, gap-free sweep over a wide wavelength range. Wavelength registration is provided by the incorporation of a HCN gas cell and reference interferometer. The wavelength-swept spectra of the 12 DFBs are combined in post-processing to achieve a continuous total wavelength sweep of more than 40 nm (5.4 THz) in the telecommunications C-Band range.
Fresnel transform implementation methods are explored which dramatically reduce the minimum recon... more Fresnel transform implementation methods are explored which dramatically reduce the minimum reconstruction distance requirements and allow maximal signal recovery with numerically improved resolution scaling at any distance. Methods are illustrated using experimental results.
Compressive holography with multiple projection tomography is applied to solve the inverse ill-po... more Compressive holography with multiple projection tomography is applied to solve the inverse ill-posed problem of reconstruction of 3D objects with high axial accuracy. To visualize the 3D shape, we propose Digital Tomographic Compressive Holography (DiTCH), where projections from more than one direction as in tomographic imaging systems can be employed, so that a 3D shape with better axial resolution can be reconstructed. We compare DiTCH with single-beam holographic tomography (SHOT) which is based on Fresnel back-propagation. A brief theory of DiTCH is presented, and experimental results of 3D shape reconstruction of objects using DITCH and SHOT are compared.
The nonlinearity inherent in four-wave mixing in photorefractive (PR) materials is used for adapt... more The nonlinearity inherent in four-wave mixing in photorefractive (PR) materials is used for adaptive filtering. Examples include script enhancement on a periodic pattern, scratch and defect cluster enhancement, periodic pattern dislocation enhancement, etc. through intensity filtering image manipulation. Organic PR materials have large space-bandwidth product, which makes them useful in adaptive filtering techniques in quality control systems. For instance, in the case of edge enhancement, phase conjugation via four-wave mixing suppresses the low spatial frequencies of the Fourier spectrum of an aperiodic image and consequently leads to image edge enhancement. In this work, we model, numerically verify, and simulate the performance of a four wave mixing setup used for edge, defect and pattern detection in periodic amplitude and phase structures. The results show that this technique successfully detects the slightest defects clearly even with no enhancement. This technique should facilitate improvements in applications such as image display sharpness utilizing edge enhancement, production line defect inspection of fabrics, textiles, e-beam lithography masks, surface inspection, and materials characterization.
The purpose of this paper is to construct a robust modeling framework for imaging systems in orde... more The purpose of this paper is to construct a robust modeling framework for imaging systems in order to predict the performance of detecting small targets such as Unmanned Aerial Vehicles (UAVs). The underlying principle is to track the flow of scene information and statistics, such as the energy spectra of the target and power spectra of the background, through any number of imaging components. This information is then used to calculate a detectivity metric. Each imaging component is treated as a single linear shift invariant (LSI) component with specified input and output parameters. A component based approach enables the inclusion of existing component-level models and makes it directly compatible with image modeling software such as the Night Vision Integrated Performance Model (NV-IPM). The modeling framework also includes a parallel implementation of Monte Carlo simulations designed to verify the analytic approach. However, the Monte Carlo simulations may also be used independently to accurately model nonlinear processes where the analytic approach fails, allowing for even greater extensibility. A simple trade study is conducted comparing the modeling framework to the simulation.
We propose tunable single-layer and multi-layer (periodic and with defect) structures comprising ... more We propose tunable single-layer and multi-layer (periodic and with defect) structures comprising nanoparticle dispersed metamaterials in suitable hosts, including adaptive coded aperture constructs, for possible Adaptive Coded Aperture Imaging (ACAI) applications such as in microbolometry, pressure/temperature sensors, and directed energy transfer, over a wide frequency range, from visible to terahertz. These structures are easy to fabricate, are low-cost and tunable,
The performance of a novel joint transform correlator (JTC) based on photorefractive (PR) two-bea... more The performance of a novel joint transform correlator (JTC) based on photorefractive (PR) two-beam coupling (TBC) is analyzed by determining the dependence of relevant figures of merit such as the discrimination ratio, the peak-to-correlation plane energy ratio, and the peak-to-noise ratio on the PR gain coefficient and pump-probe beam ratio for a variety of reference and signal images. In this scheme, spatially separated reference and signal images constitute the pump, which transfers energy to a weak probe in a novel image processing setup where the PR polymer serves as the spatial filter in the Fourier plane.
Fluorescence microscopy (FM) is costly, time consuming, and requires considerable sample preparat... more Fluorescence microscopy (FM) is costly, time consuming, and requires considerable sample preparation. Here we present a virtual fluorescence staining method based on DL to transform fluorescence images of molecular labels into other molecular fluorescence labels.
Optical diffraction tomography (ODT) solves an inverse scattering problem to obtain label-free, 3... more Optical diffraction tomography (ODT) solves an inverse scattering problem to obtain label-free, 3D refractive index (RI) estimation of biological specimens. This work demonstrates 3D RI retrieval methods suitable for partially-coherent ODT systems supported by intensity-only measurements consisting of axial and angular illumination scanning. This framework allows for access to 3D quantitative RI contrast using a simplified non-interferometric technique. We consider a traditional iterative tomographic solver based on a multiple in-plane representation of the optical scattering process and gradient descent optimization adapted for focus-scanning systems, as well as an approach that relies solely on 3D convolutional neural networks (CNNs) to invert the scattering process. The approaches are validated using simulations of the 3D scattering potential for weak phase 3D biological samples.
Polarized reflectance maps of bovine articular cartilage are rich in texture content. Image textu... more Polarized reflectance maps of bovine articular cartilage are rich in texture content. Image texture analysis extracts quantitative parameters useful to assess intact cartilage versus cartilage with mechanical surface damage or enzymatic degradation.
Coherent optical frequency-domain reflectometry (C-OFDR) is a distance measurement technique with... more Coherent optical frequency-domain reflectometry (C-OFDR) is a distance measurement technique with significant sensitivity and detector bandwidth advantages over normal time-of-flight methods. Although several swept-wavelength laser sources exist, many exhibit short coherence lengths, or require precision mechanical tuning components. Semiconductor distributed feedback lasers (DFBs) are advantageous as a mid-to-long range OFDR source because they exhibit a narrow linewidth and can be rapidly tuned simply via injection current. However, the sweep range of an individual DFB is thermally limited. Here, we present a novel high-resolution OFDR system that uses a compact, monolithic 12-element DFB array to create a continuous, gap-free sweep over a wide wavelength range. Wavelength registration is provided by the incorporation of a HCN gas cell and reference interferometer. The wavelength-swept spectra of the 12 DFBs are combined in post-processing to achieve a continuous total wavelength sweep of more than 40 nm (5.4 THz) in the telecommunications C-Band range.
Fresnel transform implementation methods are explored which dramatically reduce the minimum recon... more Fresnel transform implementation methods are explored which dramatically reduce the minimum reconstruction distance requirements and allow maximal signal recovery with numerically improved resolution scaling at any distance. Methods are illustrated using experimental results.
Compressive holography with multiple projection tomography is applied to solve the inverse ill-po... more Compressive holography with multiple projection tomography is applied to solve the inverse ill-posed problem of reconstruction of 3D objects with high axial accuracy. To visualize the 3D shape, we propose Digital Tomographic Compressive Holography (DiTCH), where projections from more than one direction as in tomographic imaging systems can be employed, so that a 3D shape with better axial resolution can be reconstructed. We compare DiTCH with single-beam holographic tomography (SHOT) which is based on Fresnel back-propagation. A brief theory of DiTCH is presented, and experimental results of 3D shape reconstruction of objects using DITCH and SHOT are compared.
The nonlinearity inherent in four-wave mixing in photorefractive (PR) materials is used for adapt... more The nonlinearity inherent in four-wave mixing in photorefractive (PR) materials is used for adaptive filtering. Examples include script enhancement on a periodic pattern, scratch and defect cluster enhancement, periodic pattern dislocation enhancement, etc. through intensity filtering image manipulation. Organic PR materials have large space-bandwidth product, which makes them useful in adaptive filtering techniques in quality control systems. For instance, in the case of edge enhancement, phase conjugation via four-wave mixing suppresses the low spatial frequencies of the Fourier spectrum of an aperiodic image and consequently leads to image edge enhancement. In this work, we model, numerically verify, and simulate the performance of a four wave mixing setup used for edge, defect and pattern detection in periodic amplitude and phase structures. The results show that this technique successfully detects the slightest defects clearly even with no enhancement. This technique should facilitate improvements in applications such as image display sharpness utilizing edge enhancement, production line defect inspection of fabrics, textiles, e-beam lithography masks, surface inspection, and materials characterization.
The purpose of this paper is to construct a robust modeling framework for imaging systems in orde... more The purpose of this paper is to construct a robust modeling framework for imaging systems in order to predict the performance of detecting small targets such as Unmanned Aerial Vehicles (UAVs). The underlying principle is to track the flow of scene information and statistics, such as the energy spectra of the target and power spectra of the background, through any number of imaging components. This information is then used to calculate a detectivity metric. Each imaging component is treated as a single linear shift invariant (LSI) component with specified input and output parameters. A component based approach enables the inclusion of existing component-level models and makes it directly compatible with image modeling software such as the Night Vision Integrated Performance Model (NV-IPM). The modeling framework also includes a parallel implementation of Monte Carlo simulations designed to verify the analytic approach. However, the Monte Carlo simulations may also be used independently to accurately model nonlinear processes where the analytic approach fails, allowing for even greater extensibility. A simple trade study is conducted comparing the modeling framework to the simulation.
We propose tunable single-layer and multi-layer (periodic and with defect) structures comprising ... more We propose tunable single-layer and multi-layer (periodic and with defect) structures comprising nanoparticle dispersed metamaterials in suitable hosts, including adaptive coded aperture constructs, for possible Adaptive Coded Aperture Imaging (ACAI) applications such as in microbolometry, pressure/temperature sensors, and directed energy transfer, over a wide frequency range, from visible to terahertz. These structures are easy to fabricate, are low-cost and tunable,
The performance of a novel joint transform correlator (JTC) based on photorefractive (PR) two-bea... more The performance of a novel joint transform correlator (JTC) based on photorefractive (PR) two-beam coupling (TBC) is analyzed by determining the dependence of relevant figures of merit such as the discrimination ratio, the peak-to-correlation plane energy ratio, and the peak-to-noise ratio on the PR gain coefficient and pump-probe beam ratio for a variety of reference and signal images. In this scheme, spatially separated reference and signal images constitute the pump, which transfers energy to a weak probe in a novel image processing setup where the PR polymer serves as the spatial filter in the Fourier plane.
Fluorescence microscopy (FM) is costly, time consuming, and requires considerable sample preparat... more Fluorescence microscopy (FM) is costly, time consuming, and requires considerable sample preparation. Here we present a virtual fluorescence staining method based on DL to transform fluorescence images of molecular labels into other molecular fluorescence labels.
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Papers by george nehmetallah