An Application of Wavefront Reconstruction to Interferometry

The method of wavefront reconstruction can be used in three ways to extend the usefulness of interferometry. First, a multiple fringe interferogram with a different fringe spacing, and/or a zero-order interferogram can be produced from a multiple fringe interferogram. Second, a multiple fringe interferogram can be used to produce a new interferogram which is focused on a particular plane of the object field. Third, a schlieren photograph and/or shadowgraph can be produced from an interferogram. The technique will be particularly useful for investigating transient phenomena, such as are encountered in wind-tunnel or shock-tube testing. The limitations of the technique are reviewed.