All three IXPE observation of Crab pulsar and the best fitted polarimetric model (subtracting 90% of DC component to the Stokes parameters in the optical band). The first (second), third (fourth) and fifth (sixth) panels correspond to the polarization degree (polarization angle) for the first, second, and third observation of crab pulsar, respectively. The green line corresponds to MDP₉₉. The gray solid lines correspond to the best-fitted model without phase shift. The orange and gray arrows in the fourth panel highlight the polarization angle swing, at the interpulse, with and without a phase shift, respectively.