Michio Hamakoga

Digital image processing in polarized light for evaluation of foliar injury

Abstract Foliar injury simulated in cucumber leaves by using air pollutants of SO 2 and O 3 resulted in variation of the polarization of light reflected at the leaf surface. The injured area was visualized at earlier stages in vertically polarized light having electric field vibration parallel to the plane of incidence. The injured leaf image was taken by a vidicon camera in vertically polarized light and digitized for computation. This digitized image was denoted as a matrix of reflectances of the vertically polarized light. The injured area was disciminated in the matrix by setting a threshold level of the reflectance at 3%. The ratio of reflectances in the injured area to those in the normal area was found useful for representing the degree of the injury. These results suggest that this method of image processing can be applied to the evaluation of foliar injury using on-line measurement.