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Fourier Transform Techniques for Imaging Performance Evaluations of Thermal Imaging Cameras Used by the Fire Service

Published

Author(s)

Francine K. Amon, A Ducharme

Abstract

Infrared (IR) technology for fire fighting applications has matured to the point that most first responder organizations either have purchased or are considering the purchase of thermal imaging cameras. Thermal imagers can provide first responders with critical information to size up a fire incident, track fire growth, and to locate victims, other first responders, and egress routes. While these devices represent a significant investment, typically on the order of $10k per camera, first responders have little guidance on instrument performance beyond manufacturer literature and recommendations from other users. These issues are further complicated because the demands placed on thermal imagers are application dependent. Currently, there are no standardized performance guidelines available to aid end users in making purchasing decisions. We shall use Fourier transforms in two ways in this discussion: first, as an expedient way to assess a thermal imaging camera s spatial resolution; and second, as a way to extract vital spatial frequency information from realistic images in order to design bench-scale test targets for use in other proposed performance tests. The advantages of using these techniques for image analysis are twofold: first, inherent difficulties related to the exact position of the test target with respect to the imager detector array can be alleviated if the elements of the target are numerous enough and are randomly arranged; and second, realistic images such as that of a firefighter standing nearby can be replaced with a simple bar pattern having similar frequencies. Two image analysis techniques that exploit these advantages have been developed for evaluation of thermal imaging cameras and are described in this paper.The techniques developed in this work are useful in the design of test methods for evaluation of thermal imaging cameras used by first responders. In addition to reducing the measurement error associated with linear shift invariance, a connection is established between the bench-scale test facility targets used and realistic images that a first responder might expect to see at an emergency event. References[1] Amon, F. K.; Bryner, N. P.; Hamins, A., Thermal Imaging Research Needs for First Responders: Workshop Proceedings , NIST Special Publication 1040, June 2005.[2] NFPA 180X Proposed Standard on Thermal Imaging Cameras for Emergency Services, Draft 01 , National Fire Protection Association, November 2006.[3] Flannery, B. P., Teukolsky, S. A., Vetterling, W. T., Numerical Recipes: The Art of Scientific Computing , pp. 390-407, ISBN 0-521-30811-9, 1986.[4] Daniels, A., Boreman, G. D., Ducharme, A. D., Random transparency targets for modulation transfer function measurement in the visible and infrared regions, Opt. Eng., Vol 34, No. 3, March 1995.
Citation
Abstract and Applied Analysis
Volume
2

Keywords

firefighter technology, Fourier transform, infrared camera, modulation transfer function, random MTF target, thermal imaging camera

Citation

Amon, F. and Ducharme, A. (2007), Fourier Transform Techniques for Imaging Performance Evaluations of Thermal Imaging Cameras Used by the Fire Service, Abstract and Applied Analysis, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=861450 (Accessed March 3, 2024)
Created September 5, 2007, Updated February 17, 2017