Optimum design and error analysis of a monocular stereoscopic sensor used in three-dimensional particle image velocimetry

摘要

Particle image velocimetry (PIV) is the newest entrant to the field of fluid flow measurement and provides instantaneous velocity fields over global domains. A monocular stereoscopic sensor is designed according to the characteristics of a 3D-PIV system. It includes only one CCD camera and two groups of symmetry mirrors. A measured particle in the flow field is mapped to the CCD image surface from two angular directions and each directed-picture occupies half the image surface. Imaging procedure is decomposed to illustrate the principle of the monocular stereoscopic sensor. It is proved that folding optical path enables the possibility of miniaturized sensor design. A perspective transformation model and a geometric error model are presented for analysis and design of stereoscopic PIV system. The relationship between sensor performance and its geometric parameters is discussed in detail. These parameters contain the angle between two mirrors in the same group, the angle and distance between mirrors in each group, the distance between mirrors and camera and so on. Enough theoretical research is made for the optimum design of the stereovision system. In addition, measuring accuracy is also related to the position of the particle, especially in both x and z direction. Simulation results indicate that out-of-plane errors are higher than in-plane errors in most area.