Processing of Interference Fringe Patterns to obtain highly localized Strain

Abstract

Mechanical strain and displacement measurements are important in general material testing. Especially non-contacting methods like optical measurement are needed to analyze the behaviour of micro materials since no other standard method is otherwise available. In this paper a measurement method is introduced that fulfills these requirements. The device under test has to be prepared only with two Vickers micro hardness indentations. These two markers are illuminated by a collimated laser beam. The mechanical strain or displacement can be measured by scanning the diffracted light field using two CCD line scan cameras. The measurement system is able to resolve displacement of these indentations in the nm range.