A RING SENSOR SYSTEM USING A MODIFIED POLAR COORDINATE SYSTEM TO DESCRIBE THE SHAPE OF IRREGULAR OBJECTS

For agricultural produce such as potatoes, size and shape determinatio n is very important in grading lines. If electronic sensor systems are installed, weighing cells and optical sensors such as cameras or simp le shadow solutions are predominantly used. These systems are limited with regard to the numbers of 'views' of the object, which determines the accuracy for the determination of geometrical parameters. A ring s ensor system is described consisting of a large number of optical tran smitters and receivers which are arranged alternately. The emitters st robe infrared light in sequence round the ring, creating a large numbe r of 'viewpoints'. Optical connections to each receiver are made. As a n object passes through the ring, a shadow zone of each transmitter be am is created. As a result, the tangential chords can be found. A modi fied polar coordinate system, an algorithm and trigonometrical functio ns are described which allows the contour of the convex hull of three- dimensional objects to be formed. One advantage of this system is that the data from the ring is in the form of components of vectors and ca n be used to describe the whole object. As a result an enveloping spir al of the object is created.