Back-projection algorithm with misalignment corrections for 2D3C stereoscopic PIV

In stereoscopic PIV mapping and warping algorithms are used to back-project the image information on the object plane. The mapping algorithm back-projects each pixel, whereas the warping algorithm back-projects the 2D displacement vectors. In this paper, both algorithms and the misalignment of the laser sheet regarding the object plane are considered. Then, a new algorithm using both mapping and warping algorithms is described for a 2D3C angular stereoscopic PIV set-up with standard lenses and the so-called Scheimpflug condition. The accuracy of the new algorithm, that takes into account laser sheet misalignment, is compared to the previous algorithm on the same sets of images. These sets are recorded from a paper pattern mounted on a 3D translation and rotation stage and from a turbulent pipe flow. The tests show that the accuracy benefit is one order of magnitude on these sets. The accuracy gain depends on the laser sheet misalignment magnitude, which can be measured using the mapping algorithm.