Fig. 4
From: Adaptive particle image velocimetry based on sharpness metrics
Zernike mode amplitude scan of PIV images with introduced defocus by the deformable mirror. a The Z4 scan reveals the correct Z4 RMS value for a sharp image, namely + 2.7 μm. b Z5 scan. c Z6 scan. Except S4 (steepness) all other metrics exhibit a double-peak behavior whose maxima metric values do not correspond to sharp images