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

Multi-Color Luminescence Transition of Upconversion Nanocrystals via Crystal Phase Control with SiO2 for High Temperature Thermal Labels

Upconversion nanocrystals (UCNs)-embedded microarchitectures with luminescence color transition capability and enhanced luminescence intensity under extreme conditions are suitable for developing a robust labeling system in a high-temperature thermal industrial process. However, most UCNs based labeling systems are limited by the loss of luminescence owing to the destruction of the crystalline phase or by a predetermined luminescence color without color transition capability. Herein, an unusual crystal phase transition of UCNs to a hexagonal apatite phase in the presence of SiO2 nanoparticles is reported with the enhancements of 130-fold green luminescence and 52-fold luminance as compared to that of the SiO2-free counterpart. By rationally combining this strategy with an additive color mixing method using a mask-less flow lithography technique, single to multiple luminescence color transition, scalable labeling systems with hidden letters-, and multi-luminescence colored microparticles are demonstrated for a UCNs luminescence color change-based high temperature labeling system

"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

Triple-Mode Switched-Inductor-Capacitor DC-DC Buck Converter with Reusable Flying Capacitor and Bang-Bang Zero-Current Detector for Wide Load Current Range

Although the capacity of a battery with a small form factor is extremely low, demand for long usage time of Internet of Things (IoT) products is increasing. Owing to this limitation of the battery, power management integrated circuits (PMICs) are used for extending the battery usage time with high efficiency. In particular, since IoT devices are mostly in the sleep mode in the idle state, PMICs should achieve high efficiency for ultralight loads in the sleep mode as well as for heavy loads in the active mode. In this paper, an accurate bang-bang zero-current detector (to prevent a reverse inductor current) and a triple-mode switched inductor-capacitor dc-dc buck converter with a reusable flying capacitor are presented; these techniques can maintain high efficiency over a wide load current range. The proposed buck converter was fabricated in a 0.18-mu m 1P4M CMOS process. A power conversion efficiency exceeding 85% was achieved in the load range of 100 mu A to 300 mA

A case of malignant hyperthermia during anesthesia induction with sevoflurane -A case report-

We experienced a case of malignant hyperthermia (MH) in 6-year-old boy during anesthesia induction for strabismus surgery. It has been generally reported that sevoflurane can induce the delayed onset of MH in the absence of succinylcholine. Our case of MH was elicited after about 2-3 min of sevoflurane administration with N2O, O2 and rocuronium. However, we successfully treated the patient by early recognition of his condition and administering symptomatic treatment and dantrolene