Assessment of black rot development on apple surface using laser biospeckle technique

Abstract

In our present study, the laser biospeckle technique has been applied to monitor the spread of black rot fungal disease and evaluate the infected area on apple surface for the first time to the best of our knowledge. Image processing algorithms such as inertia moment (IM), absolute value of differences (AVD) and spatial-temporal speckle correlation show the reduction of biospeckle activity of the black rot infected apples in comparison to that of the healthy apples with increase in time, once the visible symptom of the disease sets in. Spectral activity maps obtained using Fujii, inverse Fujii and parameterized Fujii show the spread of this infection with the progression of day. Under exposition test and histogram plot have been used to evaluate the increase of darkness of the infected apple with the progression of day and the results have come out as a replica of the change of colour of the region of interest. % biospeckle activity loss on the final day of the experiment has been found to be 17.83% and 11.91% for healthy apples & 92.42% and 78.63% for infected apples using IM and AVD respectively. An increase in the infected area and % increase in infected area of the region of interest on the image plane has been determined to be 0.33 mm2 and 58.57% respectively on the final day of the experiment.