Abstract

We describe a new method of imaging phase objects using real-time dynamic holography. In the first step of this process, a volume hologram is produced in a single crystal of barium titanate by a coherent light beam being directed through a thin phase-distortion plate and then into the crystal. After the volume hologram forms, a second beam of short duration is sent into the crystal where it scatters off the hologram, producing a back-scattered beam. This beam, which is the phase conjugate of the original beam that produced the hologram, then passes through the phase-distortion plate after the plate has been shifted a small distance in a direction normal to the optical axis. This shift results in an imperfect removal of the phase aberration [1,2,3] in the back-propagating beam and hence, produces intensity variations in the optical field beyond the plate. These are images which show gradients in the phase object’s optical path length which occur along the direction of the shift. Although in principle these images can be obtained using the methods of off-axis holography, the process we use has no equivalent in conventional holography. In particular, by employing the self-phase-conjugating phenomenon in barium titanate [4,5,6] we are able to use a single beam and the rather simple arrangement shown in figure 1 to generate gradient images of different phase objects.

© 1986 Optical Society of America