Purposive and qualitative active vision

Qualitative vision, which in the past has been wrongly called inexact, makes sense when it is coupled with purposive vision, which formulates questions for which qualitative solutions are possible. To demonstrate the usefulness of this approach, the author considers visual motion (or navigation) problems, and assumes that the observer is active. He describes the preliminary design of Medusa, a purposive and qualitative visual motion machine that can robustly solve many navigational problems without reconstructing the scene