Improving spatio-temporal resolution of infrared images to detect thermal activity of defect at the surface of inorganic glass

G. Corvec (1) , Eric Robin (1) , Jean-Benoit Le Cam (1) , Jean-Christophe Sangleboeuf (1) , Philippe Lucas (2)

1 IPR - Institut de Physique de Rennes
2 Department of Materials Science and Engineering

This paper proposes a noise suppression methodology to improve the spatio-temporal resolution of infra-red images. The methodology is divided in two steps. The first one consists in removing the noise from the temporal signal at each pixel. Three basic temporal filters are considered for this purpose: average filter, cost function minimization (FIT) and short time Fast Fourier Transform approach (STFFT). But while this step effectively reduces the temporal signal noise at each pixel, the infrared images may still appear noisy. This is due to a random distribution of a residual offset value of pixels signal. Hence in the second step, the residual offset is identified by considering thermal images for which no mechanical loading is applied. In this case, the temperature variation field is homogeneous and the value of temperature variation at each pixel is theoretically equal to zero. The method is first tested on synthetic images built from infrared computer-generated images combined with experimental noise. The results demonstrate that this approach permits to keep the spatial resolution of infrared images equal to 1 pixel. The methodology is then applied to characterize thermal activity of a defect at the surface of inorganic glass submitted to cyclic mechanical loading. The three basic temporal filters are quantitatively compared and contrasted. Results obtained demonstrate that, contrarily to a basic spatio-temporal approach, the denoising method proposed is suitable to characterize low thermal activity combined to strong spatial gradients induced by cyclic heterogeneous deformations.

Keywords: Experimental mechanics; Cyclic mechanical loading; De-noising; Cost functions; Fast Fourier transforms; Infrared imaging; Indentation; Glass; Pixels; Spatio-temporal resolution; Spatio-temporal approach; Heterogeneous deformation; Soda Lime glass; Computer-generated images; Thermography (imaging); Temperature distribution; Temperature; Surface defects

Domains: Physics [physics]

G. Corvec, Eric Robin, Jean-Benoit Le Cam, Jean-Christophe Sangleboeuf, Philippe Lucas. Improving spatio-temporal resolution of infrared images to detect thermal activity of defect at the surface of inorganic glass. Infrared Physics and Technology, 2016, 77, pp.193--202. ⟨10.1016/j.infrared.2016.05.026⟩. ⟨hal-01372804⟩