Contrast manipulation and controllable spatial filtering via photorefractive two-beam coupling

Abstract A scheme is presented that achieves passive controllable spatial filtering via two-beam coupling in BaTiO 3 , between a reference beam and the optical Fourier transform of an input image. The nature of thespatial filtering is determined by the intensity dependent gain seen by each component of the Fourier transform. By appropriate choice of intensity ratio, the operations of contrast enhancement, feature extraction, and defect enhancement are possible, and representative examples of these are given.