Optical image processing using symbolic substitution: median filtering and edge detection

Either a phase-only hologram or an optical content-addressable memory can be used for the optical implementation of these image processors. One-dimensional windows of size three and five pixels and two-dimensional windows of size five and nine are used to eliminate noise from two-dimensional input images. Prewitt, Roberts, and difference operators are used for edge detection. It is shown that an acceptable number of substitution rules (or reference patterns) are necessary for implementing the processors. It is found that the Roberts-operator-based scheme is not most hardware efficient and also yields a thinner edge