The feasibility of an opto-electronic inspection system for the sorting and grading
of apples with respect to ripeness and quality is studied. This study comprises a
detailed spectral analysis of the healthy skin as well as a variety of visual
defects. Three different apple species were studied: Cox orange, Golden delicious
and Golden rennet. Spectral wavebands of interest appear to be the chlorophyll peak
around 570nm, the ripeness peak around 64Onrrt and the near infra-red beyond 75Onxn.
Stem and calix of apples pose a separate problem because their spectral reflection
cannot be distinguished from that of most visual defects. A solution for this
problem is given.