Análise de resposta em freqüência do biospeckle laser

Abstract

This work presents a study of the interaction of the laser light with tissue of beans seeds (Phaseolus Vulgaris L.). It is a contribution for the development of biospeckle technique applied to recognition of alive tissues of beans seeds contaminated with fungi and its differentiation by the frequency specter. Biospeckle is an interference optic phenomenon that occurs when the laser light reaches a surface where some dynamic process occurs, due to biological activities or purely physic changes. The technique involves image treatment and do distinguish the contribution of each activity material in the seeds, the technique of Inertial Moment and frequency analysis were used. For frequency analysis, the Fourier Transform preceded of the convolution was applied. A great challenge in this area is to identify the elements that contribute to increase the activity of biospeckle, such as water, microorganisms, among others. In this direction, this research work had given one more step aiming to characterize the interaction of the laser with the biological material. Three groups of bean seeds were used, one of healthy seed and two groups of seeds contaminated with Aspergillus and Fusarium fungi, and the biospeckle were analyzed considering its activity and its frequency spectra. The seeds were illuminated each-by-each in a randomly order. The results had shown differences in the average values of IM of the three groups of seeds in all the illuminations. Also, it was observed the presence of some different harmonic in the biospeckle of the groups and differences between the harmonic for seeds of the same group. This work allow to confirm that it is possible to differentiate contaminated seeds from noncontaminated seeds using frequency analysis of the biospeckle laser.