The previous page shows an optical prism, known as a porro prism, evolved by the system. This type of prism is sometimes used within binoculars to allow the distance between the lenses to be compressed into a smaller space. This design was evolved from an initial population of randomly positioned, previously evolved right-angle prisms (i.e., the system evolved the large porro prism from smaller components).
The desired function of a porro prism was defined by three reusable 'evaluation modules'. These specified that the prism should be a certain size, should be unfragmented (i.e., no part should be unconnected and 'float free' of the design), and that it should have a number of specified optical characteristics. These were defined by specifying the initial position and direction of five light rays, and the desired final position and direction of these rays after passing through the design. The ability of designs to direct the light from source to required destination was then judged by raytracing software. In this way the desired optical function of the prism was defined without indirectly defining the shape of the prism.
The evolved design shows an almost perfect porro prism, evolved by the system. This was a difficult problem with only one acceptable solution, making the task of designing the prism more of a challenge to the system. Nevertheless, once the desired optical characteristics were properly defined, the system was able to consistently evolve good solutions for a number of different types of optical prism, such as the one shown.