Mary M. Ledet

Date of Award

3-1-2009

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering

Department

Department of Electrical and Computer Engineering

First Advisor

LaVern A. Starman, PhD

Abstract

The Air Force has long relied on surveillance for intelligence and strategic purposes. Most surveillance systems rely on a lensing system to acquire their images, most of which are in either the visible or infrared wavelengths. Because lensing systems can be expensive, obtrusive, or hard to maintain, researchers have designed adaptive coded aperture imaging (ACAI) as a replacement system. Coded aperture imaging (CAI) has been used in both the astronomical and medical communities for years due to its ability to image light at short wavelengths and thus replacing conventional lenses. Where CAI is limited, researchers have discovered that adaptive coded aperture imaging can recover what is lost. ACAI uses a reconfigurable coding mask and digital signal processing to recover the original scene from the detector. In this effort, a prototype of MEMS microshutters has been designed and fabricated onto a 3 mm x 3 mm square of silicon substrate using the PolyMUMPS™ process. This prototype is a line-drivable array using thin flaps of polysilicon to cover and uncover an 8 x 8 array of 20 µm apertures and is the first known microshutter array to incorporate a line-drivable array driven by physical actuation. A characterization of the micro-shutters to include mechanical, electrical and optical properties is provided. This prototype, its actuation scheme, and other designs for individual microshutters have been modeled and studied for feasibility purposes, and this revealed that the actuation scheme failed in its design due to oversights in the design process and lack of space for each gear actuator. Because of conformality in the PolyMUMPS™ process, none of the microshutters could physically move, but optical analysis with a 632 nm HeNe laser revealed that they will not undergo upward deflection when exposed to irradiance sources of less than 0.5 W. The microshutters were also designed to transmit less than 20% of irradiated light and initial testing confirmed that fact. In addition, microshutters fabricated from an Al-Au alloy on a quartz wafer were characterized and showed that wedge-style shutters are functional, if not ideal for an ACAI array.

AFIT Designator

AFIT-GEO-ENG-09-03

DTIC Accession Number

ADA497537

Download

Share

COinS