Field Performance of Machine Vision for the Selective Harvest of Asparagus

A machine vision system was developed to identify and locate harvestable spears of asparagus. An image acquisition vehicle was fabricated to videotape portions of asparagus rows from a commercial production field. Images were acquired using a monochrome CCD camera. The detection of reflectance properties of asparagus was enhanced by using optical bandpass filters for near-infrared radiation. Videotaped segments acquired in the field were analyzed. Image processing techniques based on geometrical characteristics of asparagus spears were used to identify and locate harvestable spears in the images. Harvestable spears measured in the field were compared to those found by machine vision. The vision system correctly identified from 86 to 97% of the harvestable spears in six 15 m row segments analyzed. The uncertainty in the location of spears was within a 2.97 by 5.39 cm window with 95% confidence.