Minimization of the influence of passive-light contribution in active imaging of the degree of polarization

Active imaging systems that measure the degree of polarization (DOP) are often perturbed by passive light owing to ambient illumination. Passive light introduces a shot noise that combines with the noise due to the active signal to perturb estimation of the DOP. We quantitatively study its influence and show that the polarization state of active illumination can be adjusted to minimize the influence of passive light. It is thus an additional degree of freedom for optimization.