Single speckle image analysis for monitoring the hardening kinetics of glass ionomer cements

Abstract

In this paper, we monitor the setting reaction of commercial glass ionomer cements using a laser speckle technique and adopting a spatial approach in the analysis of recorded speckle images. Experimental results showed that spatial contrast and speckle grain size increased as two studied cements underwent their setting reactions. After combining two geometrical configurations to measure the intensities of backscattered and transmitted light, we concluded that the increase in speckle grain size was caused by an increase in size of the scattering centers, since cement components aggregate and hence transition from a Rayleigh to a Mie scattering regime. Finally, two main phases were distinguished in the hardening process, as reported in the literature; however, the technique we propose has the advantage of easily identifying these two phases. The analysis of a single speckle image offers multiple advantages over the temporal analysis of a series of speckle images, in particular due to the low number of images recorded and a far shorter image processing time.

Polarized laser speckle images produced by calibrated polystyrene microspheres suspensions: comparison between backscattering and transmission experimental configurations

“…The two statistical properties of speckle images using power spectral densities (PSDs) and autocorrelation functions [3,4], several applications of this phenomenon have been developed and tested in different fields, such as agriculture, medicine, and industry [5][6][7][8]. From a more fundamental point of view, calibrated phantoms have been used to study the separate effects of changes in the medium properties such as scatterers size [9], refractive index [10], anisotropy factor [11], concentration [12], or their combined effects [13] on polarized light scattering behavior by considering either forward scattered photons [13] or backscattered ones [14].…”