关键词: 指纹图像, 指纹分类, 方向图, 奇异点

Abstract: After investigation existing approaches to fingerprint classification，this paper introduces an improved structural fingerprint classification method.Using the directional field information，Poincare index can detect the discontinuous point in the directional field——singularities.According to the number of singularities，their position and structural character of fingerprint’s ridge lines，the basic category of fingerprint is classified.It successfully provides the information of fingerprint category for the matching method，thus improves the matching speed and precision.Experiment results illustrate that the method can perform better.

Key words: fingerprint image, fingerprint classification, directional image, singularity