Volume holographic pupils in ray, wave, statistical optics, and Wigner space

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 131-140).This thesis explores various aspects of the volume holographic pupils to better understand and implement multi-dimensional imaging. A full description and applications of volume holographic pupils are presented in ray, wave, statistical optics, and Wigner space. Volume holograms have both a shift variant nature and multiplex capability, which can efficiently extract specific information of multi-dimensional objects by engineering imaging kernels with shift variant point spread functions and using post-processing. Based on the k-sphere formulation, an efficient computation method of analyzing volume diffraction is developed. It is integrated with the ray tracing software ZEMAXr whose built-in analysis and optimization features provide a great versatility for analysis, design, and optimization of novel volume holographic imaging systems. For a plane wave reference hologram, the shape of the Bragg diffraction image is analyzed in detail, where the shape is a distorted ellipse. The wave optics formulation of volume diffraction is revisited and further developed into statistical optics. The partially coherent response of a volume holographic imaging system is derived. Based on spatial coherence measurements, new passive binary depth detection is proposed, which is a special case of multi-dimensional imaging. Spatially incoherent two objects at two distinct depths are discriminated: focused objects in the foreground and defocused objects in the background. The passive detection is demonstrated for featureless uniform objects under quasi-monochromatic light by measuring mutual intensity with a volume holographic imager. By exploiting cross spectral density measurement, the passive binary depth detection is also demonstrated under white light illumination. Finally, the Wigner distribution function for volume holographic pupils is introduced.The space-spatial frequency characteristics of volume holograms are analyzed with linear systems approach. Wigner representations of two volume holograms are examined: plane and spherical wave reference holograms. Then, various axial imaging systems, which measure the depth of objects from intensity images, are explored by the Wigner analysis. Two important conditions for axial imaging are established: 1) shift variant objects and 2) properly designed integration kernels. Based on these conditions, a shift variant imaging kernel is shown to be necessary for axial imaging.by Se Baek Oh.Ph.D

Partially coherent ambiguity functions for depth-variant point spread function design

The ambiguity function (AF) provides a convenient way to model how a camera with a modified aperture responds to defocus. We use the AF to design an optimal aperture distribution, which creates a depth-variant point spread function (PSF) from a sparse set of desired intensity patterns at different focal depths. Prior knowledge of the coherence state of the light is used to constrain the optimization in the mutual intensity domain. We use an assumption of spatially coherent light to design a fixed-pattern aperture mask. The concept of a dynamic aperture mask that displays several aperture patterns during one image exposure is also suggested, which is modeled under an assumption of partially coherent light. Parallels are drawn between the optimal aperture functions for this dynamic mask and the eigenmodes of a coherent mode decomposition. We demonstrate how the space of design for a 3D intensity distribution of light using partially coherent assumptions is less constrained than under coherent light assumptions.United States. Air Force Office of Scientific Research (National Defense Science and Engineering Graduate (NDSEG) fellowship)United States. Defense Advanced Research Projects Agency (DARPA Young Faculty Award)Alfred P. Sloan Foundation (Research Fellowship

WBSDF for simulating wave effects of light and audio

Diffraction is a common phenomenon in nature when dealing with small scale occluders. It can be observed on biological surfaces, such as feathers and butterfly wings, and man-made objects like rainbow holograms. In acoustics, the effect of diffraction is even more significant due to the much longer wavelength of sound waves. In order to simulate effects such as interference and diffraction within a ray-based framework, the phase of light or sound waves needs to be integrated

"Direct" grafting of linear macromolecular "wedges" to the edge of pristine graphite to prepare edge-functionalized graphene-based polymer composites

The edges of pristine graphite were covalently grafted with para-poly(ether-ketone) (pPEK) in a mildly acidic polyphosphoric acid (PPA)/phosphorus pentoxide (P(2)O(5)) medium. The resulting pPEK grafted graphite (pPEK-g-graphite) showed that the pristine graphite had been exfoliated into a few layers of graphene platelets (graphene-like sheets), which were uniformly dispersed into a pPEK matrix. As a result, the tensile properties of pPEK-g-graphite films were greatly improved compared to those of controlled pPEK films. The origins of these enhanced mechanical properties were deduced from scanning electron microscope (SEM) images of fracture surfaces. Upon tracing wide-angle X-ray scattering (WAXS) patterns of the film under strain, the graphene-like sheets were further exfoliated by an applied shear force, suggesting that a toughening mechanism for the pPEK-g-graphite film occurred. This approach envisions that the "direct'' edge grafting of pristine graphite without pre-treatments such as corrosive oxidation and/or destructive sonication is a simple and efficient method to prepare graphene-based polymer composites with enhanced mechanical properties.close161

Grafting of 4-(2,4,6-Trimethylphenoxy)benzoyl onto Single-Walled Carbon Nanotubes in Poly(phosphoric acid) via Amide Function

Single-walled carbon nanotubes (SWCNTs), which were commercial grade containing 60–70 wt% impurity, were treated in a mild poly(phosphoric acid) (PPA). The purity of PPA treated SWCNTs was greatly improved with or without little damage to SWCNTs framework and stable crystalline carbon particles. An amide model compound, 4-(2,4,6-trimethylphenoxy)benzamide (TMPBA), was reacted with SWCNTs in PPA with additional phosphorous pentoxide as “direct” Friedel–Crafts acylation reaction to afford TMPBA functionalized SWCNTs. All evidences obtained from Fourier-transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, scanning electron microcopy, and transmission electron microscopy strongly supported that the functionalization of SWCNTs with benzamide was indeed feasible

Divergent ancestral lineages of newfound hantaviruses harbored by phylogenetically related crocidurine shrew species in Korea

AbstractSpurred by the recent isolation of a novel hantavirus, named Imjin virus (MJNV), from the Ussuri white-toothed shrew (Crocidura lasiura), targeted trapping was conducted for the phylogenetically related Asian lesser white-toothed shrew (Crocidura shantungensis). Pair-wise alignment and comparison of the S, M and L segments of a newfound hantavirus, designated Jeju virus (JJUV), indicated remarkably low nucleotide and amino acid sequence similarity with MJNV. Phylogenetic analyses, using maximum likelihood and Bayesian methods, showed divergent ancestral lineages for JJUV and MJNV, despite the close phylogenetic relationship of their reservoir soricid hosts. Also, no evidence of host switching was apparent in tanglegrams, generated by TreeMap 2.0β

Experimental compressive phase space tomography

Phase space tomography estimates correlation functions entirely from snapshots in the evolution of the wave function along a time or space variable. In contrast, traditional interferometric methods require measurement of multiple two-point correlations. However, as in every tomographic formulation, undersampling poses a severe limitation. Here we present the first, to our knowledge, experimental demonstration of compressive reconstruction of the classical optical correlation function, i.e. the mutual intensity function. Our compressive algorithm makes explicit use of the physically justifiable assumption of a low-entropy source (or state.) Since the source was directly accessible in our classical experiment, we were able to compare the compressive estimate of the mutual intensity to an independent ground-truth estimate from the van Cittert-Zernike theorem and verify substantial quantitative improvements in the reconstruction