A Geometric Model for Polarization Imaging on Projective Cameras

The vast majority of Shape-from-Polarization (SfP) methods work under the oversimplified assumption of using orthographic cameras. Indeed, it is still unclear how Stokes vector projection behaves when the incoming rays are not orthogonal to the image plane. In this paper, we try to answer this question with a new geometric model describing how a general projective camera captures the light polarization state. Based on the optical properties of a tilted polarizer, our model is implemented as a pre-processing operation acting on raw images, and a scene-independent rotation of the reconstructed normal field. Moreover, our model is consistent with state-of-the-art forward and inverse renderers (as Mitsuba3 and ART), intrinsically enforces physical constraints among the captured channels, and handles the demosaicing of DoFP sensors. Experiments on existing and new datasets demonstrate the accuracy of the model when applied to commercially available polarimetric cameras.