Noise effect on the interpolation equation for near infrared thermography

Thierry Sentenac (1, 2) , Rémi Gilblas (2)

1 LAAS-RAP - Équipe Robotique, Action et Perception
2 ICA - Institut Clément Ader

This paper investigates the performance of interpolation equations for a near infrared thermal imager operating over wavelengths from 0.9 mu m to 1.7 mu m with various filter bandwidths and a broad temperature range from 300 degrees C to 1000 degrees C. The equations are based on a general formulation of the effective wavelength as a function of the temperature. The quality of the interpolation is assessed in relation to the order of the effective wavelength. However, the noise induced by the imperfections of the thermal imager significantly disturbs the signal, and this phenomenon is enhanced as the bandwidth of the filter increases (i.e. for low-temperature applications). The main purpose of this paper is to establish the right choice of the filter bandwidth and the expression and order of the interpolation equation in relation to the noise level on the thermal imager and the desired accuracy. This paper first outlines the background on interpolation equations and then tests them on synthetic data from signals delivered first by an ideal thermal imager (i.e. free from noise) and then from noisy signals. This simulation study provides a framework for users to select an interpolation equation with an adequate order for near infrared thermal imagers. The performances of the selected interpolation equations are finally demonstrated on real images performed by a near infrared thermal imager.

Domaines: Traitement du signal et de l'image [eess.SP]

Thierry Sentenac, Rémi Gilblas. Noise effect on the interpolation equation for near infrared thermography. Metrologia, 2013, 50 (3), pp.208-218. ⟨10.1088/0026-1394/50/3/208⟩. ⟨hal-01687307⟩