Browsing by Author "Holloway, Jason"

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    Increasing temporal, structural, and spectral resolution in images using exemplar-based priors
    (2013-09-16) Holloway, Jason; Veeraraghavan, Ashok; Baraniuk, Richard G.; Kelly, Kevin F.
    In the past decade, camera manufacturers have offered smaller form factors, smaller pixel sizes (leading to higher resolution images), and faster processing chips to increase the performance of consumer cameras. However, these conventional approaches have failed to capitalize on the spatio-temporal redundancy inherent in images, nor have they adequately provided a solution for finding $3$D point correspondences for cameras sampling different bands of the visible spectrum. In this thesis, we pose the following question---given the repetitious nature of image patches, and appropriate camera architectures, can statistical models be used to increase temporal, structural, or spectral resolution? While many techniques have been suggested to tackle individual aspects of this question, the proposed solutions either require prohibitively expensive hardware modifications and/or require overly simplistic assumptions about the geometry of the scene. We propose a two-stage solution to facilitate image reconstruction; 1) design a linear camera system that optically encodes scene information and 2) recover full scene information using prior models learned from statistics of natural images. By leveraging the tendency of small regions to repeat throughout an image or video, we are able to learn prior models from patches pulled from exemplar images. The quality of this approach will be demonstrated for two application domains, using low-speed video cameras for high-speed video acquisition and multi-spectral fusion using an array of cameras. We also investigate a conventional approach for finding 3D correspondence that enables a generalized assorted array of cameras to operate in multiple modalities, including multi-spectral, high dynamic range, and polarization imaging of dynamic scenes.
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    SAVI: Synthetic apertures for long-range, subdiffraction-limited visible imaging using Fourier ptychography
    (AAAS, 2017) Holloway, Jason; Wu, Yicheng; Sharma, Manoj K.; Cossairt, Oliver; Veeraraghavan, Ashok
    Synthetic aperture radar is a well-known technique for improving resolution in radio imaging. Extending these synthetic aperture techniques to the visible light domain is not straightforward because optical receivers cannot measure phase information. We propose to use macroscopic Fourier ptychography (FP) as a practical means of creating a synthetic aperture for visible imaging to achieve subdiffraction-limited resolution. We demonstrate the first working prototype for macroscopic FP in a reflection imaging geometry that is capable of imaging optically rough objects. In addition, a novel image space denoising regularization is introduced during phase retrieval to reduce the effects of speckle and improve perceptual quality of the recovered high-resolution image. Our approach is validated experimentally where the resolution of various diffuse objects is improved sixfold.
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    Synthetic apertures for long-range, sub-diffraction limited visible imaging using fourier ptychography
    (2020-06-23) Cossairt, Oliver Strider; Holloway, Jason; Veeraraghavan, Ashok; Sharma, Manoj Kumar; Wu, Yicheng; Rice University; Northwestern University; United States Patent and Trademark Office
    A method for imaging objects includes illuminating an object with a light source of an imaging device, and receiving an illumination field reflected by the object. An aperture field that intercepts a pupil of the imaging device is an optical propagation of the illumination field at an aperture plane. The method includes receiving a portion of the aperture field onto a camera sensor, and receiving a sensor field of optical intensity. The method also includes iteratively centering the camera focus along the Fourier plane at different locations to produce a series of sensor fields and stitching together the sensor fields in the Fourier domain to generate an image. The method also includes determining a plurality of phase information for each sensor field in the series of sensor fields, applying the plurality of phase information to the image, receiving a plurality of illumination fields reflected by the object, and denoising the intensity of plurality of illumination fields using Fourier ptychography.
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    Synthetic Apertures for Visible Imaging Using Fourier Ptychography
    (2016-09-20) Holloway, Jason; Veeraraghavan, Ashok N
    In long-range imaging, spatial resolution is predominantly limited by diffraction blur. Diffraction blur is a fundamental limit that is determined by the diameter of the lens used in the imaging system. In principle, the diameter of a lens can be increased to circumvent diffraction. In reality, cost and manufacturing limitations place a limit on the maximum diameter that can be achieved. Therefore, computational methods are required to super-resolve the observed, blurry image and recover spatial resolution lost to diffraction. Macroscopic Fourier ptychography is proposed as a practical means to create a synthetic aperture for visible imaging to achieve sub-diffraction limit spatial resolution. In this thesis, two principle barriers to implementing Fourier ptychography are addressed and resolved. First, a prototype imaging system is introduced to recover high-resolution long distance images in a reflection imaging geometry. Second, an image space regularization technique is developed to reconstruct optically rough surfaces that exhibit speckle. Experimental results demonstrate, for the first time, a macroscopic Fourier ptychography imaging system to achieve sub-diffraction resolution of optically rough objects in a reflection geometry. Spatial resolution is increased six-fold over any single captured image.