Spatial Phase-Shifting Digital Holography for Three-Dimensional Particle Tracking Velocimetry

This paper presents a holographic technique for three-dimensional particle tracking. The complex amplitude on an image sensor is measured with two pairs of spatially phase-shifted digital holograms captured in a short time interval using a phase-shifting technique. Pairs of digital holograms are used to track small tracer particles in three-dimensional space and the phase-adjusted complex amplitude is employed in numerical image reconstruction to accurately detect the particles. The performance of the method is evaluated by numerical simulation. In order to demonstrate the feasibility of the method for real flow measurement, it is applied to the velocity measurement of tracer particles in a small water channel along which a high voltage is applied. The resulting components of the velocity vector in three-dimensional space are compared to those obtained using a conventional single-shot phase-shifting technique.