Comparison of Sub-pixel Estimation of PIV Using Frequency Response Analysis

Article type: Research Article

Authors: Okamoto, K.

Affiliations: Nuclear Engineering Research Laboratory, The University of Tokyo, Tokai-mura, Ibaraki 319-1188, Japan. e-mail: [email protected]

Abstract: The frequency responses on sub-pixel evaluation techniques have been investigated using the Monte-Carlo technique. The frequency response by the FFT based cross-correlation gives very good results although some gain loss does exist for small displacement (less than 0.5 pixel). Few gain losses are observed in the Direct Cross-Correlation, but the sub-pixel accuracy is limited to be about 0.1 pixel which implies that it could not detect a small displacement. To detect sub-pixel displacement with higher accuracy, the gradient technique with iterative correlation is the best. For a small interrogation area (e.g., 4 × 4), only the gradient technique can detect small displacement accurately.

Keywords: PIV, sub-pixel estimation, cross-correlation, FFT, gradient technique

Journal: Journal of Visualization, vol. 5, no. 4, pp. 355-361, 2002