Method of lensless, no-aperture, one-step rainbow holography: theory, practice, and applications

Abstract

We introduce an innovative modification in the technique for making rainbow holograms based upon synthesization of a modulation equivalent to a slit in the object wave. Such a simulation of the slit function is achieved by imparting a suitable in-plane motion to the diffusing background of the object transparency. It is shown that the plane of localization of the synthesized aperture can be positioned anywhere with respect to the object by using a properly shaped illuminating wave. Thus, the object itself rather than its real image is directly responsible for the rainbow hologram formation making the imaging lens unnecessary. A converging or a diverging spherical wave is used to illuminate the object transparency backed by a ground glass. The image reconstruction takes place in accordance with the conventional rainbow holographic process, with the synthesized aperture occupying the plane of convergence or divergence of the object wave as the case may be. We present a theoretical analysis of this novel method of rainbow holography and give some supporting experimental results. This is followed by its application to the visualization of phase objects and a discussion of the quality of the reconstructed images.