Multiplexed two in-line holographic recordings for flow characterization in a flexible vessel

The simultaneous presence of the real and virtual images in the hologram reconstruction is inherent in the in-line holography. This drawback can be overcome with a shifted knife-edge aperture at the focal plane of the imaging lens. The shifted aperture DIH produces holograms where the real and virtual images are completely separated. In this paper we propose a modification of the shifted aperture DIH that allows recording two holograms simultaneously using one camera, while retaining the simplicity of the in-line configuration and the advantage of the shifted-aperture strategy. As in typical stereoscopy, the advantage of this configuration is limited by the angle between the two illuminating beams, and therefore the aperture size. Some improvement on the out-of-plane resolution can be expected from a combined analysis of the multiplexed holograms. In order to compare this technique with other in-line holographic configurations, several experiments have been performed to study the spatial resolution along the optical axis. The capabilities of the different techniques for characterizing the flow in a flexible and transparent model of a carotid bifurcation are also investigated.