We report the results of a comparison analysis of the accuracy of two optical techniques which are based on ray
deflection, background-oriented schlieren (BOS) and fringe deflection (FD). In both techniques, a camera registers
images of a spatial pattern displayed on a screen: for BOS, spots randomly located; for FD, straight fringes. Two
images corresponding to two different states of a phase object are then compared: with and without the object. After
introducing the object, the corresponding spatial structures undergo displacements that are proportional to the change
of index of refraction. The displacements are calculated by digital correlation in BOS, and by phase retrieval in FD.
Therefore, by both techniques, displacement maps of numerically-simulated phase objects are obtained. Preliminary
results show for FD, higher accuracy and less numerical processing.