Multiple-Beam Interferometry by Wavefront Reconstruction

A method is presented for producing multiple-beam interferograms by using holographic techniques. A conventional image hologram of the object under test is processed in such a way that nonlinearities are introduced. Then, in the reconstruction process, several reconstructed images of the object with successively amplified phase will arise from the consecutive diffraction orders. These images are made to superpose and form the multiple-beam interferogram by illuminating the hologram with an appropriate set of illuminating beams. The method is useful for testing optical surfaces and systems as well as in studies of refractive-index variations in transparent objects. One of the advantages of the method is that multiple-beam Fizeau fringes can be obtained from a non-reflecting object with a single light passage through the object.