(Digital Holographic PIV)
In the common optical flow measurement technique Particle Image Velocimetry (PIV) the investigated fluid flow is seeded with small particles. A laser light sheet is created and two images of the illuminated particle field are recorded in rapid succession. These images are correlated numerically which yields a two-dimensional vector field of the flow in the region of the light sheet.
By means of holography this method is exceeded to the third dimension (Holographic PIV). By recording a volume in a hologram and subsequent reconstruction the whole three-dimensional particle field in the flow can be captured.
In Digital Holographic PIV (DHPIV) holograms are not recorded on photographic film but with a digital camera. Its advantage is that recording and reconstruction can be carried out directly by the computer and no chemical processing followed by an additional digitalization is necessary. Furthermore, the behavior of fluids can be resolved in time considerably better.
By means of a holographic inline setup it is possible to reconstruct physically sensible three-dimensional trajectories from hologram series. Subject of current research is in particular the reduction of measurement uncertainties of the component in the direction of the beam.
Fig.1:Basic setup of an inline DHPIV system