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Research Of Optical Readout Uncooled Infrared Imaging System Based On MEMS

Posted on:2011-10-23Degree:DoctorType:Dissertation
Country:ChinaCandidate:T ChengFull Text:PDF
GTID:1118360305966614Subject:Solid mechanics
Abstract/Summary:PDF Full Text Request
Currently, infrared imaging has been a key technology in variety of military, in-dustrial, and commercial applications, especially uncooled infrared imaging has drawn substantially increased attention for its small dimension, low cost and high performance. Based on past achievements, this dissertation primarily studied a novel MEMS based optical readout uncooled infrared imaging system. The chief contents include:the finite element analysis and structural design of substrate-free focal plane array (FPA), the optimization of optical readout method, the miniaturization and in-dustrialization of uncooled infrared imaging system. The main achievements of this dissertation are as follows:(1) Based on the finite element method, the three-dimensional (3-D) finite ele-ment models of substrate/substrate-free FPA with 80×80 pixels were developed, and then using the sequential approach of multiphysics analysis in ANSYS software, the thermal and mechanical characterizations of substrate/substrate-free FPA were inves-tigated and found that:(a) As compared with the substrate FPA, because of the large decrease in thermal conductance, the supporting frame is a temperature-variable one. This brings out a unique thermal characteristic:(i) the supporting frame functions as a'thermal isola-tion' frame which reduces the thermal conductance and therefore increases the tem-perature change; (ii) the supporting frame also functions as a'thermal diffusion'frame which certainly results in the temperature pre-change in the ones not absorbing radia-tion. The linear superposition of the temperature pre-change by the other ones thus will greatly increase the temperature change. This characteristic will significantly in-crease the energy conversion efficiency, even with a magnitude of one order.(b) Because the supporting frame is a temperature-variable structure, the temper-ature change in the bi-material microcantilevers is almost in the same level, therefore, a potential of 33% improvement in thermo-mechanical efficiency is envisionedBased on the finite element analysis, the theoreticl model which assumes that the substrate is a temperature constant structure was corrected, namely the calculation of total thermal conductance and thermo-mechanical efficiency of each microcantilever.(2) An enhanced supporting frame was developed for substrate-free FPA. This design would not only increase the structure performance of supporting frame but also maintain an excellent thermal performance, and therefore is much suitable for large scale substrtate-free FPA (≥1024×1024).(3) Based on the Fraunhofer diffraction pattern of each reflector in Fourier Op-tics, and the theoretical model of the optical readout sensitivity was established and found to be a function of reflector length, curvature radius and position of knife-edge filter. Using this theoretical model, an optical resolution to the reflector deformation was developed. This optical solution can efficiently maximize the optical readout sen-sitivity, and the sensitivity loss induced by the deformed micro-reflector can be re-duced to minimum level.(4) Using FPGA and DSP, the first generation image acquisition and processing system based on miniaturization design was developed, and the prototype machine of optical readout uncooled infrared imagings system was aslo established. This proto-type machine could obtaion thermal image at room temperature but with a decrease in performance, as compared with the experimental platform.
Keywords/Search Tags:Infrared Imaging, Uncooled, Focal Plane Array, Optical Readout, Bi-material Microcantilever
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