CORRECTION OF PIV IMAGE BIASING USING TWO CO-ROTATING MIRRORS

The rotating mirror configuration in particle image velocimetry (PIV) is generally used to provide an artificial image shift to resolve the directional ambiguities for the recorded particle image pairs. However, the reflected image from the rotating mirror inevitably creates normal velocity components with respect to the image plane, and this normal component causes spatially distributed systematic image errors. A potential solution for the problem is proposed to replace the single rotating mirror with two co-rotating mirrors. The use of two co-rotating mirrors reduces the image biasing with desired amounts of the velocity shift available, and, at the same time, makes the image biasing uniform on the entire image field so that analytical corrections for the biasing are readily feasible. Detailed imaging kinematics of the suggested method are presented to improve the design of practical PIV systems. Also presented is experimental confirmation of the image correction using two co-rotating mirrors.