A theoretical model of a Thermochromic Liquid Crystal (TLC) imaging system was developed to aid in understanding the results of experiments on spectral effects and to investigate the various factors affecting the hue-temperature calibration of TLC’s. The factors in the model include the spectral distribution of the illumination source and UV filter, surface reflection of both the TLC and background, and the sensing device (camera) spectral characteristics and gain settings. It was found that typical hue-temperature calibration curves could not be entirely explained by a TLC reflectivity model with either a monochromatic spike or a narrow bandwidth reflectivity, which is often assumed. Experimental results could be explained, however, by a model that reflects over a relatively large band of wavelengths. The spectral characteristics of the five illumination sources (those for which experiments were performed) were considered. Background reflection, which commonly accounts for 30%–50% of the reflected light, was found to significantly attenuate the hue-temperature calibration curves toward the background hue value. The effect of the illumination source on the hue-temperature calibration curves is demonstrated and several experimentally observed phenomena are explained by the results of the theoretical calculations, specifically the spectral reflective properties of the liquid crystals and the transmissivity of the R, G, and B filters in the image capture camera.
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Research Papers
Thermochromic Liquid Crystal Thermography: Illumination Spectral Effects. Part 2: Theory
M. R. Anderson,
M. R. Anderson
Senior Performance Engineer
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J. W. Baughn
J. W. Baughn
Professor
Fellow ASME
Department of Mechanical and Aeronautical Engineering,
e-mail: jwbaughn@ucdavis.edu
University of California
, Davis, One Shields Avenue, Davis, CA 95616
Search for other works by this author on:
M. R. Anderson
Senior Performance Engineer
J. W. Baughn
Professor
Fellow ASME
Department of Mechanical and Aeronautical Engineering,
University of California
, Davis, One Shields Avenue, Davis, CA 95616e-mail: jwbaughn@ucdavis.edu
J. Heat Transfer. Jun 2005, 127(6): 588-597 (10 pages)
Published Online: January 12, 2005
Article history
Received:
June 27, 2004
Revised:
January 12, 2005
Citation
Anderson, M. R., and Baughn, J. W. (January 12, 2005). "Thermochromic Liquid Crystal Thermography: Illumination Spectral Effects. Part 2: Theory." ASME. J. Heat Transfer. June 2005; 127(6): 588–597. https://doi.org/10.1115/1.1915388
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