Digital Holographic Interferometry and Phase-Shifting Digital Holography

Abstract

If the holograms of the object are digitally recorded using a CCD camera and they are compared by computing the phase difference of the digitally reconstructed images, then the process is called digital holographic interferometry (DHI). In current technology, commercial CCD cameras have pixel sizes around 5 mm, which can sometimes limit the spatial resolution required for large off-axis angles (,2 deg), which, in practice, limits DH to inline or near-inline configurations. In DHI, the recorded holograms are individually reconstructed by numerical methods, and the experimental setup is simpler compared to AHI. Due to the numerical reconstruction process, the interference phase, which represents the deformation field, can be calculated by subtracting the reconstructed phases of the undeformed and deformed object waves. Thus, there is no need to generate a macroscopic interference pattern. Additionally, the interference phase in DHI can be determined without sign ambiguity.