An improved electrical and thermal model of a microbolometer for electronic circuit simulation
[摘要] The need for uncooled infrared focal plane arrays (IRFPA) for imagingsystems has increased since the beginning of the nineties. Examples for theapplication of IRFPAs are thermography, pedestrian detection forautomotives, fire fighting, and infrared spectroscopy. It is very importantto have a correct electro-optical model for the simulation of themicrobolometer during the development of the readout integrated circuit(ROIC) used for IRFPAs. The microbolometer as the sensing element absorbsinfrared radiation which leads to a change of its temperature due to a verygood thermal insulation. In conjunction with a high temperature coefficientof resistance (TCR) of the sensing material (typical vanadium oxide oramorphous silicon) this temperature change results in a change of theelectrical resistance. During readout, electrical power is dissipated in themicrobolometer, which increases the temperature continuously. The standardmodel for the electro-optical simulation of a microbolometer includes theradiation emitted by an observed blackbody, radiation emitted by thesubstrate, radiation emitted by the microbolometer itself to thesurrounding, a heat loss through the legs which connect the microbolometerelectrically and mechanically to the substrate, and the electrical powerdissipation during readout of the microbolometer (Wood, 1997). The improvedmodel presented in this paper takes a closer look on additional radiationeffects in a real IR camera system, for example the radiation emitted by thecasing and the lens. The proposed model will consider that some parts of theradiation that is reflected from the casing and the substrate is alsoabsorbed by the microbolometer. Finally, the proposed model will includethat some fraction of the radiation is transmitted through themicrobolometer at first and then absorbed after the reflection at thesurface of the substrate. Compared to the standard model temperature andresistance of the microbolometer can be modelled more realistically whenthese higher order effects are taken into account. A Verilog-A model forelectronic circuit simulations is developed based on the improved thermalmodel of the microbolometer. Finally, a simulation result of a simplecircuit is presented.
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[效力级别] [学科分类] 电子、光学、磁材料
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