Cancellation of motion artifacts caused by a division-of-time polarimeter

For any kind of imaging polarimeter, at least four intensity images, named polarization state images, are needed to compute one full Stokes vector. When the polarimeter is designed according to the division-of-time principle, polarization state images are acquired sequentially. Consequently, the main issue is the systematic occurrence of artifacts as the scene is not static. Even though this is well known, little research has been done on this subject. Here a two-step motion-compensation-based method is proposed to fix it. The first step consists in estimating the motion between each image acquired according to the same polarization state. Then each image is warped according to a fraction of the previously estimated motion. Due to their dense and accurately estimated motion field we have shown optical-flow techniques to be the most efficient for motion-estimation in this case. Compensating the motion using optical flow to estimate it actually leads to a strong correlation criterion between corrected and reference polarization images. Our method allows the estimation of the polarization by post-processing the polarization state image sequence. It leads to a good estimation quality whether the scene is static or not, thus fixing the main issue of a divisionof- time polarimeter.