An improved electrical and thermal model of a microbolometer for electronic circuit simulation
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Published:2012-09-18
Issue:
Volume:10
Page:183-186
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ISSN:1684-9973
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Container-title:Advances in Radio Science
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language:en
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Short-container-title:Adv. Radio Sci.
Author:
Würfel D.,Vogt H.
Abstract
Abstract. The need for uncooled infrared focal plane arrays (IRFPA) for imaging systems has increased since the beginning of the nineties. Examples for the application of IRFPAs are thermography, pedestrian detection for automotives, fire fighting, and infrared spectroscopy. It is very important to have a correct electro-optical model for the simulation of the microbolometer during the development of the readout integrated circuit (ROIC) used for IRFPAs. The microbolometer as the sensing element absorbs infrared radiation which leads to a change of its temperature due to a very good thermal insulation. In conjunction with a high temperature coefficient of resistance (TCR) of the sensing material (typical vanadium oxide or amorphous silicon) this temperature change results in a change of the electrical resistance. During readout, electrical power is dissipated in the microbolometer, which increases the temperature continuously. The standard model for the electro-optical simulation of a microbolometer includes the radiation emitted by an observed blackbody, radiation emitted by the substrate, radiation emitted by the microbolometer itself to the surrounding, a heat loss through the legs which connect the microbolometer electrically and mechanically to the substrate, and the electrical power dissipation during readout of the microbolometer (Wood, 1997). The improved model presented in this paper takes a closer look on additional radiation effects in a real IR camera system, for example the radiation emitted by the casing and the lens. The proposed model will consider that some parts of the radiation that is reflected from the casing and the substrate is also absorbed by the microbolometer. Finally, the proposed model will include that some fraction of the radiation is transmitted through the microbolometer at first and then absorbed after the reflection at the surface of the substrate. Compared to the standard model temperature and resistance of the microbolometer can be modelled more realistically when these higher order effects are taken into account. A Verilog-A model for electronic circuit simulations is developed based on the improved thermal model of the microbolometer. Finally, a simulation result of a simple circuit is presented.
Publisher
Copernicus GmbH
Reference4 articles.
1. Weiler, D., Ruß, M., Würfel, D., Lerch, R., Yang, P., Bauer, J., Kropelnicki, P., Heß, J., and Vogt, H.: Improvements of a Digital 25$\\mu $m Pixel-Pitch Uncooled Amorphous Silicon TEC-less VGA IRFPA with Massively Parallel Sigma-Delta-ADC Readout; Proc. of SPIE, Vol. 8012, 80121F-1-7, 2011. 2. Wood, R. A.: Monolithic Silicon Microbolometer Arrays; Uncooled Infrared Imaging Arrays and Systems, edited by: Kruse, P. and Skatrud, D., Semiconductors and Semimetals, 47, 45–121, Academic Press, 1997. 3. ~Würfel, D.,Ruß, M.,~Lerch, R.,~Weiler, D.,~Yang, P., and~Vogt, H.: An Uncooled VGA-IRFPA with Novel Readout Architecture; Adv. Radio Sci., 9, 107-110, 2011. 4. Würfel, D.: Rauscharme Ausleseschaltungen für die Infrarot-Sensorik; Dissertation, Universität Duisburg-Essen, 2010.
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