An improved three-dimensional characterization of defocusing digital particle image velocimetry (DDPIV) based on a new imaging volume definition

摘要

The full development of the equations for defocused digital particle image velocimetry as proposed by Kajitani and Dabiri (2005 Meas. Sci. Technol. 16 790-804) predefined a finite area at the focal plane to be imaged onto the CCDs. This resulted in bounded overlapping viewing cones of the lenses, i.e. the observable domain, within which a tetrahedral imaging volume was defined. The resulting ray tracing suggested that the observable domain would not be fully imaged onto the CCDs. Furthermore, the tetrahedral imaging volume, which was also a definition used to develop the characteristic three-dimensional DDPIV equations, only represented a limited portion of the observable domain. It is shown that by avoiding these incorrect definitions, a more accurate description of the three-dimensional DDPIV measurement system can be developed by introducing a new measurement volume based on the CCD dimensions, which replaces the tetrahedral volume, as well as introducing a new system optical axis. Lastly, a geometric uncertainty analysis is conducted and compared to the results found by Kajitani and Dabiri.