An optical Flow technique based on the use of Dynamic Programming has
been applied to Particle Image Velocimetry thus yielding a significant
increase in the accuracy and spatial resolution of the velocity field
. Results are presented for calibrated synthetic sequences of images a
nd for sequences of real images taken for a thermally driven flow of w
ater with a freezing front. The accuracy remains better than 0.5 pixel
/frame for tested two-image sequences and 0.2 pixel/frame for four-ima
ge sequences, even with a 10% added noise level and allowing 10% of pa
rticles of appear or disappear. A velocity vector is obtained for ever
y pixel of the image.