SPECTRAL ANALYSIS OF PEACH SURFACE DEFECTS

ABSTRACT The spectral reflectance of peach surface defects (bruise, cut, scar, scale, brown rot, wormhole) in the 350 to 1200 nm range was measured. Sorting criteria which were suitable for use with a machine vision system were developed and evaluated based on their potential for discriminating between defective and normal peach surface. Separability was calculated in terms of the Mahalanobis distance between the two classes. Sorting criteria which were based on ratios of wave-lengths had good separability for some defects, but multivariate sorting criteria with at least one unnormalized component were required for good class discrimination for all peach defect types at a fixed set of wavelengths. A three-wave-length criterion with spectral sensitivities centered at 650, 720, and 815 nm had the highest Mahalanobis distances for the types of peach defects tested.