Active Optical Metrology - a definition with examples

This paper deals with the discussion of several problems in optical metrology (HNDT, shape measurement) which can be solved better by an active approach - the so called active optical metrology. As an important difference in comparison to classic passive procedures the role of the model of the image formation/measuring process and its implementation into an active controlled feedback loop is analyzed. On example of phase reconstruction from 2D fringe patterns the necessity and the advantages of the active approach are explained first. Finally three examples are given where the solutions of complex measuring problems in HNDT and shape measurement are found by the implementation of active controlled feedback loops.