Experimental study of the effects of the ratio of intensities of the reference and object waves on the performance of off-axis digital holography

In this paper we present an experimental study of the effects of the ratio of the intensities of the reference and object waves on the performance off-axis digital holography operating in tight diffraction-limited regimen. The analysis is focused on the comparison of the information contained in the hologram before and after performing the spatial filtering of the zero diffraction order and the twin image. We show that in the Fourier transform of the recorded hologram the information of the object is preserved regardless the ratio of intensities of the object and reference waves. This fact allows the right spatial filtering of the +1 or −1 diffraction order leading to similar reconstructed images for holograms recorded with very different ratios of the intensities of the reference and object waves. The results show that the usual rule of thumb of 1:1 ratio for seeking maximum fringe contrast is not really required. Experimental results of a regular die are utilized for validating the claims.