基于无基底焦平面阵列红外热像仪的理论模型分析

Analysis of theoretical model of thermal infrared imager based on the substrate-free focal plane array

基于双材料微悬臂梁热变形原理的光学读出非制冷红外探测阵列经历了从有基底结构向无基底结构的发展过渡,无基底阵列的红外成像结果和有限元模型分析均表明无基底阵列不满足恒温基底条件.本文结合电学比拟的方法,提出了一种新的基于无基底焦平面阵列(focalplaneArray,FPA)的热传递分析的理论模型.分析采用整体考虑的思路,避开了无基底FPA阵列各单元热传递互相影响所产生的复杂热分布分析,并考虑了框架对热量的吸收与传递.理论模型采用外边框与环境等温的边界条件,虽不及有限元方法对边界条件的处理灵活,但也已取得与实验一致的计算结果,可以用作为计算无基底FPA响应的近似公式.同时,该理论模型避免了有限元建模计算的繁琐,在大阵列下计算尤为便捷,而且还能根据响应要求计算无基底FPA应具备的像素尺寸,实现FPA反向设计与优化.

Based on thermal deformation of bi-material microcantilever,the focal plane array（FPA）of uncooled optical readout infrared（IR） imaging system has undergone a development from substrate array to substrate-free array.The experimental imaging result and finite element method（FEM） analysis indicated that the substrate-free focal plane array（FPA） did not accord with the condition of constant frame temperature.This paper proposed a new theoretical model on thermal transmission of substrate-free FPA with electrical analogy method.Considering the system as a whole,the analysis of complex thermal interaction of adjacent elements could be averted while the heat absorption and transmission of frame could be considered.The temperature of outer frame was set to be equal to the ambient temperature as a boundary condition.Although it was not so flexible compared with FEM analysis when dealing with the boundary condition,the theoretical model was proved to correspond with the experimental result,and could be used as an approximate formula in thermal response calculation of substrate-free FPA.The model avoids the complication of FEM analysis,especially for large arrays.Further more,the model can be used for substrate-free FPA dimensions design and optimization under certain response target.