Development of 3D Shape Measuring Method for Strawberry Fruits

Strawberry fruit shape is classified into several categories such as triangular pyramid, globosity and heart, and the classification has been done by grading system in breeding. However, the reliability is often lower because it is subjectively assessed by an estimator. In order to evaluate fruit shape more preciously, we have developed 3D measuring system based on photogrammetry. 3D modeling in fruits is difficult especially in the process of stereo-image matching. By tuning the system for fruit 3D modeling, we have established a user-friendly 3D modeling pipeline. The developed pipeline consists of automated image capturing module, image preprocessing module and 3D modeling module. Image capturing module is for system control of automatic 360° image capture with connected a rotation motorized stage and multiple cameras. Image preprocessing module is distinct fruit and background areas and masked background areas to enhance 3D modeling accuracy (detect feature points, reduce noise, and so on). 3D modeling module is performed 3D shape reconstruction by SfM (Structure from Motion) approach. The developed system is used for evaluation of strawberry fruit size and shape which is difficult to measure by 2D image analysis, and expected to apply other plant species.