Microscale Infrared Technologies for Spectral Filtering and Wireless Neural Dust

Pivotal technologies, such as optical computing, autonomous vehicles, and biomedical implantables, motivate microscale infrared (IR) components. Hyperspectral imagers (HSI), for example, require compact and narrowband filters to obtain high-spatial and -spectral resolution images. HSIs acquire continuous spectra at each pixel, enabling non-destructive analyses by resolving IR scattering/absorption signatures. Toward this end, dielectric subwavelength gratings (SWG) are intriguing filter candidates since they are low-loss, have no moving parts, and exhibit narrow spectral features. Wireless neural implantables are another apropos microscale IR technology. Wireless IR data and power transfer disposes of infection-prone percutaneous wires by leveraging the IR transparency window in biological tissue. This dissertation contains two related topics. The first details SWG IR filters, and the second studies progress toward wireless neural motes. This work extends the capabilities of SWG IR filters. Following a theoretical overview, mid-wave infrared (MWIR, 3-7 um) transmittance filters are experimentally demonstrated using the zero-contrast grating scheme. Via a facile silicon fabrication process, we realize narrowband polarization-dependent and polarization-independent MWIR transmittance filters with some of the highest Q observed in MWIR SWGs. An empirical study confirms the relationship between filter performance and grating size, an important trade-off for HSIs. We then demonstrate GaAs SWG filters for monolithic integration with active optoelectronic devices. The GaAs SWGs perform comparably to their silicon counterparts. To enable narrowband filtering at normal incidence, we investigate symmetry-breaking in geometrically asymmetric gratings. The presented SWG geometries access quasi-bound states in the continuum (BIC). Studies in Fano resonance and diffraction efficiency symmetry provide physical insight. Asymmetric 1D and 2D SWGs furnish polarization-dependent and -independent filtering, respectively. We experimentally demonstrate normal incidence long-wave IR (LWIR, 7-12 um) transmittance filtering in asymmetric SWGs and confirm symmetry-breaking implications. A reduced-symmetry hexagonal pattern presents an early design for truly polarization-independent quasi-BIC coupling in SWGs. Advancements in implantable neural devices promise great leaps in brain mapping and therapeutic intervention. To meet this challenge, we investigated a wireless neural mote system using near-infrared (NIR, 800 nm – 3 um) photovoltaics and LEDs to wirelessly harvest power and transmit data. The neural recorders consist of three subsystems: an epitaxial GaAs-based optoelectronic chip, a Si CMOS IC, and a carbon fiber probe. Though this work encompasses the efforts of many, this dissertation outlines contributions in a few critical areas. To overcome low-flux LED emission, we devise an optical setup with ≈0.1% photon detection efficiency. Monte Carlo techniques model NIR scattering in biological tissue. Another steep challenge is the heterogeneous integration of the three material systems in a compact (200x170x150 um^3) package. To relay data and power between the GaAs and CMOS chips, through-wafer vias are critical. Using a novel selective copper plating technique, we demonstrate through-wafer GaAs vias with <2 Ohm series resistance. Additionally, conductive blind vias are presented for carbon fiber probe insertion. A self-aligned parylene etch mask permits sub-kOhm connection to a buried metal contact while maintaining GOhm substrate isolation. Both via structures meet the requirements of being low-resistance, insulated from the substrate, and amendable to thinned wafer processing. Finally, we demonstrate extensive processing on thinned chips and advances toward full heterogeneous integration via flip-chip alignment and solder bump bonding.PHDElectrical and Computer EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/169986/1/barrowm_1.pd

Current research opportunities of image processing and computer vision

Image processing and computer vision is an important and essential area in today’s scenario. Several problems can be solved through computer vision techniques. There are a large number of challenges and opportunities which require skills in the field of computer vision to address them. Computer vision applications cover each band of the electromagnetic spectrum and there are numerous applications in every band. This article is targeted to the research students, scholars and researchers who are interested to solve the problems in the field of image processing and computer vision. It addresses the opportunities and current trends of computer vision applications in all emerging domains. The research needs are identified through available literature survey and classified in the corresponding domains. The possible exemplary images are collected from the different repositories available for research and shown in this paper. The opportunities mentioned in this paper are explained through the images so that a naive researcher can understand it well before proceeding to solve the corresponding problems. The databases mentioned in this article could be useful for researchers who are interested in further solving the problem. The motivation of the article is to expose the current opportunities in the field of image processing and computer vision along with corresponding repositories. Interested researchers who are working in the field can choose a problem through this article and can get the experimental images through the cited references for working further.

Experimentation and Simulation of Pulsed Eddy Current Thermography of Subsurface Aircraft Corrosive Defects

During the life cycle of aircraft, external structures are under constant attack from environmental degradation in the form of corrosion. Corrosive defects consist of multiple types of surface and subsurface damage that are often undetectable due to surface coatings or insulation leading to loss in structural integrity. Non-destructive techniques for corrosion detection typically require the removal of paint. Detection of corrosion under insulation (CUI) is highly valuable for cost and time effectiveness. Although techniques have been developed for detection of CUI, not many of these satisfy the criteria for portability and hangar operation. To address this, multiple techniques were investigated yielding Pulsed Eddy Current Thermography (PECT) as a promising technique to pursue a proof of concept. Through multiphysics simulation using COMSOL, case studies were developed to understand and predict the temperature responses of aircraft materials when altering the current, lift off, and defect size and to design the coil for optimal non-destructive detection capabilities. Initial studies were conducted on various samples including coated and uncoated Aluminum, Carbon steel, Zinc-galvanized carbon steel with different types of corrosion. A novel in-house MATLAB© code was developed for post-processing of the corroded samples. Initially, defect localizations through edge heating or from dissipation were captured through IR thermography. To address issues with non-uniformity of heating that decrease the accuracy and precision of this technique, the thermal change with respect to time was analyzed through each frame and decomposed using Fourier transform from the time domain to a frequency domain. Manufactured corroded defects made through salt fog and acid baths, such as pitting voids, were detected under insulation of 125 microns with diameters ranging from 0.5 - 1 mm for all material systems. These results show the high potential of PECT for aerospace on-field applications providing location and shape for defects under insulation

Imaging White Blood Cells using a Snapshot Hyper-Spectral Imaging System

Automated white blood cell (WBC) counting systems process an extracted whole blood sample and provide a cell count. A step that would not be ideal for onsite screening of individuals in triage or at a security gate. Snapshot Hyper-Spectral imaging systems are capable of capturing several spectral bands simultaneously, offering co-registered images of a target. With appropriate optics, these systems are potentially able to image blood cells in vivo as they flow through a vessel, eliminating the need for a blood draw and sample staining. Our group has evaluated the capability of a commercial Snapshot Hyper-Spectral imaging system, specifically the Arrow system from Rebellion Photonics, in differentiating between white and red blood cells on unstained and sealed blood smear slides. We evaluated the imaging capabilities of this hyperspectral camera as a platform to build an automated blood cell counting system. Hyperspectral data consisting of 25, 443x313 hyperspectral bands with ~3nm spacing were captured over the range of 419 to 494nm. Open-source hyperspectral datacube analysis tools, used primarily in Geographic Information Systems (GIS) applications, indicate that white blood cells\u27 features are most prominent in the 428-442nm band for blood samples viewed under 20x and 50x magnification over a varying range of illumination intensities. The system has shown to successfully segment blood cells based on their spectral-spatial information. These images could potentially be used in subsequent automated white blood cell segmentation and counting algorithms for performing in vivo white blood cell counting

Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

NASA Tech Briefs, October 1992

Topics covered include: Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication technology; Mathematics and Information Sciences; Life Sciences