Quasi-Images

In the case of a binary image, we are dealing with a pixel array in two dimensions, which it is convenient to describe as a point set in ${\fam11\tenbbb R}^2$. There are many measurement processes which give point sets in higher dimensional spaces. For example, a standard method of sorting precious stones by colour is to place them on a tray and shine a light through the stone, as in Fig.2.13. The light is refracted to some extent by the stone, and the emergent beam is coloured. By placing a prism in the path of the emergent beam and an array of photocells across the spread out beam, the energy at different frequencies may be measured. If there are twelve such photoreceptors, the stone is transformed by the measuring process to a point in ${\fam11\tenbbb R}^{12}$. The usual methods of cluster analysis and recognition may then be applied.

 

Figure 2.13: Measuring coloured glass.