ASABE Technical Library - Abstract

Abstract. In this research, a novel method of fresh bruise detection was developed using a structured illumination reflectance imaging (SIRI) system. The SIRI system projects sinusoidal patterns of illumination onto samples, and image demodulation is then used to recover depth-specific information through varying the spatial frequency of the illumination pattern. The capability of SIRI was demonstrated through the detection of bruises on ‘Golden Delicious‘ and ‘Delicious‘ apples with varying levels of bruising. It was hypothesized that by confining the light penetration depth near the surface of each fruit, subsurface defects such as bruising should be more apparent under SIRI than conventional planar illumination imaging. Three 120^o phase-shifted reflectance images were acquired from 60 fruit each of ‘Golden Delicious‘ and ‘Delicious‘ variety at each of the four spatial frequencies (i.e., 0, 0.10, 0.15 and 0.25 cycles/mm). The reflectance images acquired by the system were then demodulated into an alternating component (AC) and direct component (DC), where the AC contained depth-specific information and the DC image represented the average reflectance from the apple sample. A bruise detection algorithm was applied to the demodulated AC images and the performance of the system was determined. Detection rates under structured illumination were consistently higher than those obtained under planar illumination. Bruises were successfully detected by the SIRI system at rates ranging from 70-100%, while detection rates under conventional planar illumination ranged from 0-50%. SIRI is promising as a new imaging modality for detecting depth-specific defects in agricultural products.