We demonstrate two versatile, flexible, and accurate frameworks based on numerical and Monte Carlo approaches to simulate the X-ray speckle-based (SBI) technique for lab-based systems. The established tools can reprod...
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We demonstrate two versatile, flexible, and accurate frameworks based on numerical and Monte Carlo approaches to simulate the X-ray speckle-based (SBI) technique for lab-based systems. The established tools can reproduce experimental setups in a cone-beam geometry and with polychromatic sources. Furthermore, they are computationally efficient to enable a fast virtual multi-modal tomography of digitized inhomogeneous phantoms. The proposed methods were evaluated and validated by analytical and experimental data for various samples. The Monte Carlo approach provides a realistic and accurate simulation, which is useful in diffuser design and dosimetry studies, while the numerical method is very efficient for parametric and tomographic studies. These approaches will be used for the optimization of lab-based X-ray SBI setups and generating sample images for enhancing phase retrieval algorithms. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License.
The TOMBO system (thin observation module by bound optics) is a multichannel subimaging system over a single electronic imaging device. Each subsystem provides a low-resolution (LR) image from a unique lateral point o...
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The TOMBO system (thin observation module by bound optics) is a multichannel subimaging system over a single electronic imaging device. Each subsystem provides a low-resolution (LR) image from a unique lateral point of view. By estimating the image's lateral position, a high-resolution (HR) image is restored from the series of the LR images. This paper proposes an multistage algorithm comprised of successive stages, improving difficulties in previous suggested schemes. First, the registration algorithm estimates the subchannel shift parameters and eliminates bias. Second, we introduce a fast image fusion, overcoming visual blockiness artifacts that characterized previously suggested schemes. The algorithm fuses the set of sampled subchannel images into a single image, providing the reconstruction initial estimate. Third, an edge-sensitive quadratic upper bound term to the total variation regulator is suggested. The complete algorithm allows the reconstruction of a clean, HR image, in linear computation time, by the use of the linear conjugate gradient optimization. Finally, we present a simulated comparison between the proposed method and a previously suggested image restoration method. The results show that the proposed method yields better reconstruction fidelity while eliminating spatial speckle artifacts associated with the previously suggested method. (c) 2013 Optical Society of America
A depth-dependent dispersion compensation algorithm for enhancing the image quality of the Fourier-domain optical coherence tomography (OCT) is presented. The dispersion related with depth in the sample is considered....
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A depth-dependent dispersion compensation algorithm for enhancing the image quality of the Fourier-domain optical coherence tomography (OCT) is presented. The dispersion related with depth in the sample is considered. Using the iterative method, an analytical formula for compensating the depth-dependent dispersion in the sample is obtained. We apply depth-dependent dispersion compensation algorithm to process the phantom images and in vivo images. Using sharpness metric based on variation coefficient to compare the results processed with different dispersion compensation algorithms, we find that the depth-dependent dispersion compensation algorithm can improve image quality at full depth. (C) 2017 Optical Society of America
We have developed a full-field high resolution quantitative phase imaging technique for observing dynamics of transparent biological samples. By using a harmonically matched diffraction grating pair (600 and 1200 line...
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We have developed a full-field high resolution quantitative phase imaging technique for observing dynamics of transparent biological samples. By using a harmonically matched diffraction grating pair (600 and 1200 lines/mm), we were able to obtain non-trivial phase difference (other than 0 degrees or 180 degrees) between the output ports of the gratings. Improving upon our previous design, our current system mitigates astigmatism artifacts and is capable of high resolution imaging. This system also employs an improved phase extraction algorithm. The system has a lateral resolution of 1.6 mu m and a phase sensitivity of 62 mrad. We employed the system to acquire high resolution phase images of onion skin cells and a phase movie of amoeba proteus in motion. (c) 2007 Optical Society of America.
Knowledge of the in situ temperature, size, velocity, and number density of a population of burning coal particles yields insight into the chemical and aerodynamic behavior of a pulverized-coal flame, e.g., through me...
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Knowledge of the in situ temperature, size, velocity, and number density of a population of burning coal particles yields insight into the chemical and aerodynamic behavior of a pulverized-coal flame, e.g., through means of combustion model validation. Sophisticated and reasonably accurate methods are available for the simultaneous measurement of particle velocity and temperature;however, these methods typically produce single particle measurements in small analyzed volumes and require extensive instrumentation. We present a simple and inexpensive method for the simultaneous, in situ, three- dimensional (3D) measurement of particle velocity, number density, size, and temperature. The proposed method utilizes a combination of stereo imaging, 3D reconstruction, multi-color pyrometry, and digital imageprocessing techniques. The details of theoretical and algorithmic backgrounds are presented, along with examples and validation experiments. By utilizing numerical simulations, rigorous uncertainty quantification is performed in order to estimate the accuracy of the method and explore how different parameters affect measurement uncertainty. The method is described in two parts. The first part, presented in this paper, describes particle velocity and population density mapping by stereo streaking velocimetry using overexposed emission images. (C) 2015 Optical Society of America
In this paper, we present a model that analyzes the influence of the temperature on the modulation transfer function (MTF) of an infrared membrane diffraction optical system. Based on the physical imaging mechanism of...
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In this paper, we present a model that analyzes the influence of the temperature on the modulation transfer function (MTF) of an infrared membrane diffraction optical system. Based on the physical imaging mechanism of diffractive optical systems, the imaging characteristics of the diffraction optical system are characterized by using diffraction efficiency. Then we establish the corresponding calculation model and MTF analysis model based on scalar diffraction theory. In particular, considering the material properties of flexible membrane optical elements and thermal environment effect, the Zernike polynomials are used to establish the thickness distribution model of the membrane diffractive optical components combined with the finite element analysis. After that, we modify the MTF calculation model of diffraction optical system and accordingly propose the model of the infrared membrane diffraction optical system. Finally, we present some experimental results for a 2-m infrared membrane diffraction optical system. The results show that when the temperature is -40 degrees C and wavelength band is 80 nm at the center field of view, the diffraction efficiency is reduced to 81%, and MTF at 751 p/mm is reduced to 0.12. And when the temperature is -40 degrees C at edge field of view, the efficiency at center wavelength is reduced to 71%, and MTF at 751 p/mm is reduced to 0.02. The established model and method can be used to estimate the imaging performance of a space infrared membrane diffractive telescope and provide theoretical guidance for the processing algorithm and imaging system design. (C) 2018 Optical Society of America
This paper presents a computationally efficient method for the measurement of a dense image correspondence vector field using supplementary data from an inertial navigation sensor (INS). The application is suited to a...
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This paper presents a computationally efficient method for the measurement of a dense image correspondence vector field using supplementary data from an inertial navigation sensor (INS). The application is suited to airborne imaging systems, such as an unmanned air vehicle, where size, weight, and power restrictions limit the amount of onboard processing available. The limited processing will typically exclude the use of traditional, but computationally expensive, optical flow and block matching algorithms, such as Lucas-Kanade, Horn-Schunck, or the adaptive rood pattern search. Alternatively, the measurements obtained from an INS, on board the platform, lead to a closed-form solution to the correspondence field. Airborne platforms are well suited to this application because they already possess INSs and global positioning systems as part of their existing avionics package. We derive the closed-form solution for the image correspondence vector field based on the INS data. We then show, through both simulations and real flight data, that the closed-form inertial sensor solution outperforms traditional optical flow and block matching methods. (C) 2012 Optical Society of America
The Durham adaptive optics (AO) real-time controller was initially a proof of concept design for a generic AO control system. It has since been developed into a modern and powerful central-processing-unit-based real-t...
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The Durham adaptive optics (AO) real-time controller was initially a proof of concept design for a generic AO control system. It has since been developed into a modern and powerful central-processing-unit-based real-time control system, capable of using hardware acceleration (including field programmable gate arrays and graphical processing units), based primarily around commercial off-the-shelf hardware. It is powerful enough to be used as the real-time controller for all currently planned 8m class telescope AO systems. Here we give details of this controller and the concepts behind it, and report on performance, including latency and jitter, which is less than 10 mu s for small AO systems. (C) 2010 Optical Society of America
Adaptive optics takes its servo feedback error cue from a wavefront sensor. The common Hartmann-Shack spot grid that represents the wavefront slopes is usually analyzed by finding the spot centroids. In a novel applic...
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Adaptive optics takes its servo feedback error cue from a wavefront sensor. The common Hartmann-Shack spot grid that represents the wavefront slopes is usually analyzed by finding the spot centroids. In a novel application, we used the Fourier decomposition of a spot pattern to find deviations from grid regularity. This decomposition was performed either in the Fourier domain or in the image domain, as a demodulation of the grid of spots. We analyzed the system, built a control loop for it, and tested it thoroughly. This allowed us to close the loop on wavefront errors caused by turbulence in the optical system.
If we completely understand how a phenomenon works, we should be able to produce it ourselves. However, the individual differences in color appearance observed with #theDress seem to be a peculiarity of that photo, an...
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If we completely understand how a phenomenon works, we should be able to produce it ourselves. However, the individual differences in color appearance observed with #theDress seem to be a peculiarity of that photo, and it remains unclear how the proposed mechanisms underlying #theDress can be generalized to other images. Here, we developed a simple algorithm that transforms any image with bicolored objects into an image with the properties of #theDress. We measured the colors perceived in such images and compared them to those perceived in #theDress. Color adjustments confirmed that observers strongly differ in how they perceive the colors of the new images in a similar way as for #theDress. Most importantly, these differences were not unsystematic, but correlated with how observers perceive #theDress. These results imply that the color distribution is sufficient to produce the striking individual differences in color perception originally observed with #theDress-at least as long as the image appears realistic and hence compels the viewer to make assumptions about illuminations and surfaces. The algorithm can be used for stimulus production beyond this study. (C) 2020 Optical Society of America
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