Ridge distance is an intrinsic texture property of fingerprints and it has important application in automatic fingerprint identification system. However

up to now

only several literatures touch ridge distance estimation deeply. Ridge distance estimation is developed in this paper and a method based on statistical window for ridge distance estimation in fingerprint images is brought out. A fingerprint image is divided into non-overlap blocks and a statistical window and a base line is defined for each block image. A statistical method is used to acquire the distribution of ridge in the statistical window and the ridge distance of a block image is estimated. Even to block images in which ridge directions vary acutely only if the dominant direction is existent or to block images in which noises are comparatively serious

such as much ridge breaks

the method still can estimate ridge distance reliably. Tests with some typical images show the good performance of the method presented in this paper.