We consider laser-illuminated active polarimetric imaging systems that measure the orthogonal state contrast (OSC), a frequently used surrogate to the degree of polarization, that can be used, for example, to discriminate manmade objects from natural backgrounds in remote sensing. We investigate the estimation precision of the OSC parameter in the presence of speckle, Poisson, and additive noise by using the Cramer-Rao lower bound (CRLB). Using Monte Carlo simulations and optical experiments, we show that the expression of the CRLB models the actual OSC estimation performance with excellent accuracy. This result is important for the design and sizing of active polarimetric imagers since the closed-form expression of the CRLB makes it handy for back-of-the-envelope calculations.