Studies on Continuously Distributed Directional Imagein Automated Fingerprint Identification System
自动指纹识别系统中连续分布方向图的研究

Fingerprint directional image/field is a key technique of automated fingerprint identification system (AFIS). In order to improve the accuracy of fingerprint directional image further, combining the advantage of the continuity of the point directional image with the advantage of the robustness of the block directional image to the noises in the fingerprint image, a novel concept on the continuously distributed directional image/field (CDDF) and the method to compute it in the fingerprint images are developed, which transits smoothly and exhibits not only good continuity, well gradualness and excellent robustness to the noises, but very high precision, also. Therefore, it can effectively overcome the defect of low robustness to the noises of the point directional image and the weakness of low precision of the block directional image of the fingerprint image. The experimental results prove that the continuously distributed directional image can not only filter the noises in point directional image, but also represent the basic structural feature of fingerprint more precisely. Furthermore, it can solve the key problem of the continuity, the precision and the performance of robustness of fingerprint directional fields effectively, and lays the base for high precision of fingerprint image enhancement, binarization, global feature extraction, automatic classification, template matching and image encoding in AFIS.