Abstract

Ghost imaging provides coherent imaging with incoherent light by exploiting the spatial correlation between two incoherent beams created by, e.g., parametric down conversion (PDC). Each beam is sent through a distinct imaging system; the test and the reference arm. In the test arm an object is placed, while the reference arm contains only reference optics. Since the object is illuminated with spatially incoherent light no phase sensitive information about the object - such as its diffraction pattern - can be extracted by measuring only on the test arm. However, because of the mutual spatial correlation between the two beams, the diffraction pattern may be reconstructed by measuring the spatial cross-correlation between the beams. In other words, despite the beams being incoherent, the spatial coherence between them allows to perform coherent imaging: the ghost imaging scheme is therefore capable of doing coherent imaging with incoherent light. A particular case is when the object only alters the amplitude of the light, e.g., a Young's double slit: In this case, e.g., the Hanbury-Brown-Twiss (HBT) scheme can be used to measure the autocorrelation in the far zone of the test arm, and thereby extract the diffraction pattern even when using spatially incoherent light. However, for a general object, the HBT scheme cannot be used to extract information about the diffraction pattern when using incoherent light. It is therefore interesting to look beyond the case of an amplitude-only object. Here, we use a ghost imaging scheme to observe the diffraction pattern of a pure phase object (i.e., it only alters phase information).

© 2007 IEEE