In order to describe the NBP image, we proposed to use a decomposing architecture.First, the NBP image is decomposed into several blocks. The mean of each block is calculated. After that, the variations of the means are encoded. One block is encoded by 1 if its mean are greater than its rightneighbor’s mean, 0 otherwise. A binary matrix of the variation means are extracted and used as template of the iris(Fig5).