A Machine Vision System for Continuous Field Measurement of Grape Fruit Diameter

It is necessary to measure dynamics of the fruit diameter to understand how plants respond to diurnal variation in water content and long-term growth conditions. Current techniques for measuring the fruit diameter are mostly touching measurements. The contact of the sensor places a stress on the grape fruit and may introduce erroneous results because of the touching of the grape fruit. We have presented a non-contact optical method for the accurate measurement of the fruit diameter in the grape field. The vision measuring system consists of a CMOS camera equipped with a telecentric lens, red back lighting board and PC. This system eliminates the fruit contact required by using the displacement transducers. Extensive experiments showed that the vision system is accurate and robust. This developed system achieves a repeatable accuracy of plusmn7 um for measuring the fruit diameter and provides an effective tool to better detect physiological disorders in plant.