Computational Schlieren Photography with Light Field Probes

We introduce a new approach to capturing refraction in transparent media, which we call light field background oriented Schlieren photography. By optically coding the locations and directions of light rays emerging from a light field probe, we can capture changes of the refractive index field between the probe and a camera or an observer. Our prototype capture setup consists of inexpensive off-the-shelf hardware, including inkjet-printed transparencies, lenslet arrays, and a conventional camera. By carefully encoding the color and intensity variations of 4D light field probes, we show how to code both spatial and angular information of refractive phenomena. Such coding schemes are demonstrated to allow for a new, single image approach to reconstructing transparent surfaces, such as thin solids or surfaces of fluids. The captured visual information is used to reconstruct refractive surface normals and a sparse set of control points independently from a single photograph.Natural Sciences and Engineering Research Council of CanadaAlfred P. Sloan FoundationUnited States. Defense Advanced Research Projects Agency. Young Faculty Awar

Doctor of Philosophy

dissertationMicrowave/millimeter-wave imaging systems have become ubiquitous and have found applications in areas like astronomy, bio-medical diagnostics, remote sensing, and security surveillance. These areas have so far relied on conventional imaging devices (empl

HYPERSPECTRAL LINE-SCANNING MICROSCOPY FOR HIGH-SPEED MULTICOLOR QUANTUM DOT TRACKING

One of the challenges in studying protein interactions in live cells lies in the capacity to obtain both spatial and temporal information that is sufficient to extend existing knowledge of the dynamics and interactions, especially when tracking proteins at high density. Here we introduce a high-speed laser line-scanning hyperspectral microscope that is designed to track quantum dot labeled proteins at 27 frames/sec over an area of 28 um2 using 128 spectral channels spanning the range from 500 to 750 nm. This instrument simultaneously excites 8 species of quantum dots and employs a custom prism spectrometer and high speed EMCCD to obtain spectral information that is then used to distinguish and track individual probes at high density. These emitters are localized to within 10s of nm in each frame and reconstructed trajectories yield information of the protein dynamics and interactions. This manuscript describes the design, implementation, characterization, and application of a high-speed laser line-scanning hyperspectral microscope (HSM). The intended primary application is that of investigating the dynamics of transmembrane antibody receptors using quantum dot labeled immunoglobulin E (QD-IgE). Several additional examples demonstrate other advantages and applications of this method, including 3D hyperspectral imaging of live cells and hyperspectral superresolution imaging

Novel Approach to Ocular Photoscreening

Photoscreening is a technique that is typically applied in mass pediatric vision screening due to advantage of its objective, binocular, and cost-effective nature. Through the retinal reflex image, ocular alignment and refractive status are evaluated. In the USA, this method has screened millions of preschool children in the past years. Nevertheless, the efficiency of the screening has been contentious. In this dissertation, the technique is reviewed and reexamined. Revisions of photoscreening technique are developed to detect and quantify strabismus, refractive errors, and high-order ocular aberrations. These new optical designs overcome traditional design deficiencies in three areas: First, a Dynamic Hirschberg Test is conducted to detect strabismus. The test begins with both eyes following a moving fixation target under binocular viewing, and during the test each eye is designed to be unconscientiously occluded which forces refixation in strabismus subjects and reveals latent strabismus. Photoscreening images taken under monocular viewing are used to calculate deviations from the expected binocular eye movement path. A significant eye movement deviation from binocular to monocular viewing indicates the presence of strabismus. Second, a novel binocular adaptive photorefraction (APR) approach is developed to characterize the retinal reflex intensity profile according to the eye\u27s refractive state. This approach calculates the retinal reflex profile by integrating the retinal reflex intensity from a coaxial and several eccentric photorefraction images. Theoretical simulations evaluate the influence from several human factors. An experimental APR device is constructed with 21 light sources to increase the spherical refraction detection range. The additional light source angular meridians detect astigmatism. The experimentally measured distribution is characterized into relevant parameters to describe the ocular refraction state. Last, the APR design is further applied to detect vision problems that suffer from high-order aberrations (e.g. cataracts, dry eye, keratoconus). A monocular prototype APR device is constructed with coaxial and eccentric light sources to acquire 13 monocular photorefraction images. Light sources projected inside and along the camera aperture improve the detection sensitivity. The acquired reflex images are then decomposed into Zernike polynomials, and the complex reflex patterns are analyzed using the Zernike coefficient magnitudes

Live imaging of whole mouse embryos during gastrulation : migration analyses of epiblast and mesodermal cells

During gastrulation in the mouse embryo, dynamic cell movements including epiblast invagination and mesodermal layer expansion lead to the establishment of the three-layered body plan. The precise details of these movements, however, are sometimes elusive, because of the limitations in live imaging. To overcome this problem, we developed techniques to enable observation of living mouse embryos with digital scanned light sheet microscope (DSLM). The achieved deep and high time-resolution images of GFP-expressing nuclei and following 3D tracking analysis revealed the following findings: (i) Interkinetic nuclear migration (INM) occurs in the epiblast at embryonic day (E)6 and 6.5. (ii) INM-like migration occurs in the E5.5 embryo, when the epiblast is a monolayer and not yet pseudostratified. (iii) Primary driving force for INM at E6.5 is not pressure from neighboring nuclei. (iv) Mesodermal cells migrate not as a sheet but as individual cells without coordination