Phase-step digital holography with speckled reference beams

Abstract

This paper investigates the use of speckled reference fields in phase-stepped digital holography. It considers both in the usual configuration with a smooth reference beam and where it is replaced by a speckled field that interferes with the object image. Phase stepping is applied to the reference beam and the images are digitally processed by a routine that would normally generate a true holographic image. It is shown that the field recorded is the product of the object and the reference fields, and this requires that the object image be in focus rather than be obtained by mathematical propagation of the field. Experimental results show reasonable quality images may be obtained and that interferometry can be performed with similar quality to that obtained with a smooth reference beam.