Determination of stem and calyx location on apples using automatic visual inspection

Automatic surface blemish detection systems for apples can be confused by the stem, calyx, and concavities. If the stem and calyx are incorrectly classified as blemishes, a false grade will be assigned to a fruit. A new method to determine the location of these concavities is described. The apples were illuminated by blue linear light sources and a standard colour video camera was employed to detect the reflection patterns. Blue lights were employed because they were outside the spectrum of interest for blemish detection. This enables the technique to be used simultaneously with blemish detection. The reflection patterns were in the form of light stripes, with a shape dependent on the shape and orientation of each apple. Analysis of these patterns made it possible to identify the location of stem and calyx regions. Details of a laboratory implementation of the acquisition system and an outline of the algorithms, are presented together with some preliminary results.