Calibration is vital to autostereoscopic 3D displays. This paper proposes a local calibration method that copes with any type of deformation in the optical layer. The proposed method is based on visual pattern analysis. Given the observations, we manage to localize the optical slits by matching the observations to the input pattern. In a principled optimization framework, we find an efficient calibration algorithm. Experimental validation follows. The local calibration shows significant improvement in 3D visual quality over the global calibration method. This paper also finds a new intuitive insight on the calibration in terms of the light field theory.