Project

Vision system for inspection of the exterior quality of potatoes

This project involves the development and realisation of a vision system for quality inspection of washed table potatoes.

Description of problem

Potatoes are inspected manually based on various quality aspects. A differentiation is made bewteen geometrical features (size and shape) and external malformations based on colour and texture (decay, greening, damages, scab,  growth lesions, etc.).
Various potato cultivars and recognisable diseases and defects

Aim

The aim of the project is to develop an automatic read and grade station for table potatoes. These have washed before grading and are mostly free of adhering soil particles.

Results

In this project, Pro-Pak International BV has been responsible for the mechanical aspects of the grading line. This involved transportation, stabilisation, feeding into the inspection system, the actual sorting of the potatoes and the operation of the machine. GreenVision is responsible for the development of the inspection unit, which consists of cameras, lighting, dedicated hardware for data-processing and the machine-user interface. A total view of the entire machine is shown below..

The potatoes are held firmly and speeded along to be inspected at 1.5 m/sec by a 3CC line-scan camera. The potatoes are being inspected "in-flight" to avoid disturbances from conveyor belts; as such, the entire potato surface is in view
The potatoes are held firmly and speeded along to be inspected at 1.5 m/sec by a 3CC line-scan camera. The potatoes are being inspected "in-flight" to avoid disturbances from conveyor belts; as such, the entire potato surface is in view
The 3-CCD line-scan camera set-up to obtain a 360-degree image. One camera inspects 3 rows simultaneously
The 3-CCD line-scan camera set-up to obtain a 360-degree image. One camera inspects 3 rows simultaneously

The computer analyses and sorts the potatoes into one of the pre-determined quality classes. The limits of the quality classes and the sort-sizes can be adjusted via the user interface. The potatoes leave the inspection line when they are dropped at the respective rejection stations.

Adjusting classification limits per defect (top left); sort size limits (top right); the combination of quality cum length towards the exit points (below left); an image captured by the 3-CCD line-scan camera
Adjusting classification limits per defect (top left); sort size limits (top right); the combination of quality cum length towards the exit points (below left); an image captured by the 3-CCD line-scan camera