A segmentation algorithm for the automatic recognition of Fuji apples at harvest

An algorithm for the automatic recognition of Fuji apples on the tree was developed for a robotic harvesting system. The machine vision system was composed of a colour charge coupled device camera to capture apple images, and a personal computer to process images for recognising and locating the fruit. The fruit image was enhanced using the red colour difference because results showed that the fruit had the highest red colour difference among the objects in the image. The intensity histogram of the enhanced image had a bimodal distribution for the fruit portion and the background portion. The maximum grey level variance of the red colour difference between the fruit and the background determined the optimal threshold. The optimal threshold had the minimum probability between the peaks of the two distributions. Results of the segmentation using the optimal threshold showed a success rate of over 88%. However, the error rate was over 18% for images with the back lighting condition.