Fingerprint enhancement using STFT analysis

Contrary to popular belief, despite decades of research in fingerprints, reliable fingerprint recognition is still an open problem. Extracting features out of poor quality prints is the most challenging problem faced in this area. This paper introduces a new approach for fingerprint enhancement based on short time Fourier transform (STFT) Analysis. STFT is a well-known technique in signal processing to analyze non-stationary signals. Here we extend its application to 2D fingerprint images. The algorithm simultaneously estimates all the intrinsic properties of the fingerprints such as the foreground region mask, local ridge orientation and local ridge frequency. Furthermore we propose a probabilistic approach of robustly estimating these parameters. We experimentally compare the proposed approach to other filtering approaches in literature and show that our technique performs favorably.     

Latent fingerprint matching

Latent fingerprint identification is of critical importance to law enforcement agencies in identifying suspects: Latent fingerprints are inadvertent impressions left by fingers on surfaces of objects. While tremendous progress has been made in plain and rolled fingerprint matching, latent fingerprint matching continues to be a difficult problem. Poor quality of ridge impressions, small finger area, and large nonlinear distortion are the main difficulties in latent fingerprint matching compared to plain or rolled fingerprint matching. We propose a system for matching latent fingerprints found at crime scenes to rolled fingerprints enrolled in law enforcement databases. In addition to minutiae, we also use extended features, including singularity, ridge quality map, ridge flow map, ridge wavelength map, and skeleton. We tested our system by matching 258 latents in the NIST SD27 database against a background database of 29,257 rolled fingerprints obtained by combining the NIST SD4, SD14, and SD27 databases. The minutiae-based baseline rank-1 identification rate of 34.9 percent was improved to 74 percent when extended features were used. In order to evaluate the relative importance of each extended feature, these features were incrementally used in the order of their cost in marking by latent experts. The experimental results indicate that singularity, ridge quality map, and ridge flow map are the most effective features in improving the matching accuracy.     

A minutia-based partial fingerprint recognition system

Matching incomplete or partial fingerprints continues to be an important challenge today, despite the advances made in fingerprint identification techniques. While the introduction of compact silicon chip-based sensors that capture only part of the fingerprint has made this problem important from a commercial perspective, there is also considerable interest in processing partial and latent fingerprints obtained at crime scenes. When the partial print does not include structures such as core and delta, common matching methods based on alignment of singular structures fail. We present an approach that uses localized secondary features derived from relative minutiae information. A flow network-based matching technique is introduced to obtain one-to-one correspondence of secondary features. Our method balances the tradeoffs between maximizing the number of matches and minimizing total feature distance between query and reference fingerprints. A two-hidden-layer fully connected neural network is trained to generate the final similarity score based on minutiae matched in the overlapping areas. Since the minutia-based fingerprint representation is an ANSI-NIST standard [American National Standards Institute, New York, 1993], our approach has the advantage of being directly applicable to existing databases. We present results of testing on FVC2002's DB1 and DB2 databases.     

一种结合节点和方向场的指纹匹配算法

指纹匹配是指纹识别中的一个重要问题,直接影响着系统的正确率。目前普遍使用的匹配算法主要是基于节点的匹配算法。Ross提出了结合节点和纹理特征的指纹匹配方法,但Ross方法时间代价大。本文提出了结合节点和方向场的匹配算法,在用节点进行旋转和平移对齐的基础上,计算两个指纹方向场的一致性。实验结果表明：该算法可以比现现有的基于节点的匹配算法更准确地区分两个指纹,同时比Ross方法更快。     

Fingerprint warping using ridge curve correspondences

The performance of a fingerprint matching system is affected by the nonlinear deformation introduced in the fingerprint impression during image acquisition. This nonlinear deformation causes fingerprint features such as minutiae points and ridge curves to be distorted in a complex manner. A technique is presented to estimate the nonlinear distortion in fingerprint pairs based on ridge curve correspondences. The nonlinear distortion, represented using the thin-plate spline (TPS) function, aids in the estimation of an "average" deformation model for a specific finger when several impressions of that finger are available. The estimated average deformation is then utilized to distort the template fingerprint prior to matching it with an input fingerprint. The proposed deformation model based on ridge curves leads to a better alignment of two fingerprint images compared to a deformation model based on minutiae patterns. An index of deformation is proposed for selecting the "optimal" deformation model arising from multiple impressions associated with a finger. Results based on experimental data consisting of 1,600 fingerprints corresponding to 50 different fingers collected over a period of two weeks show that incorporating the proposed deformation model results in an improvement in the matching performance.     

Fingerprint matching using OrientationCodes and PolyLines

Effectively incorporating various features with minutiae in fingerprint matching is a challenging task. This paper presents an algorithm to extract two novel discriminative features that describe three kinds of information: macro orientation patterns, micro ridge representation, and minutiae of fingerprints. These features, namely OrientationCodes and PolyLines, are fixed-length, easy to be measured in similarity, and effective in various stages of fingerprint matching, such as alignment, minutiae pairing, matching score computation, and matching rates fusion. In addition, the scheme of the proposed method has advantages of programming implementation, manipulating fingerprint matching much simpler and smoother at a high level. Experimental results on six data sets of FVC2002 and FVC2004 indicate the proposed algorithm not only achieves remarkably lower EERs, but also consumes significantly less computational times.     

Consensus fingerprint matching with genetically optimised approach

Fingerprint matching has been approached using various criteria based on different extracted features. However, robust and accurate fingerprint matching is still a challenging problem. In this paper, we propose an improved integrated method which operates by first suggesting a consensus matching function, which combines different matching criteria based on heterogeneous features. We then devise a genetically guided approach to optimise the consensus matching function for simultaneous fingerprint alignment and verification. Since different features usually offer complementary information about the matching task, the consensus function is expected to improve the reliability of fingerprint matching. A related motivation for proposing such a function is to build a robust criterion that can perform well over a variety of different fingerprint matching instances. Additionally, by employing the global search functionality of a genetic algorithm along with a local matching operation for population initialisation, we aim to identify the optimal or near optimal global alignment between two fingerprints. The proposed algorithm is evaluated by means of a series of experiments conducted on public domain collections of fingerprint images and compared with previous work. Experimental results show that the consensus function can lead to a substantial improvement in performance while the local matching operation helps to identify promising initial alignment configurations, thereby speeding up the verification process. The resulting algorithm is more accurate than several other proposed methods which have been implemented for comparison.     

一种采用脊线特征的指纹模糊匹配方法

针对目前指纹识别系统主要采用手指上细节点的分布来表征和匹配指纹,提出了一种采用指纹脊线特征的匹配算法,以提高细节点数量较少情况下的匹配精度.在特征提取阶段,通过脊线采样,只存储脊线采样点集以降低存储量;在匹配时,对欲匹配的两指纹利用细节特征配准脊线集,在重合区域内对两指纹脊线统一进行编码,通过编码的比较确定相似脊线;以相似脊线的相同位置编码为论域,以相同位置编码的相似程度为隶属度,建立衡量脊线相似程度的模糊集,采用加权平均法对多个相似脊线模糊集进行综合评判得到两指纹脊线总体相似度.最后将脊线匹配相似度与细节点匹配相似度进行加权融合得到两指纹最终的相似度.在FVC2004指纹库上的实验表明该算法能够有效提高指纹匹配的准确性.     

Fingerprint matching using ridges

Traditionally, fingerprint matching is minutia-based, which establishes the minutiae correspondences between two fingerprints. In this paper, a novel fingerprint matching algorithm is presented, which establishes both the ridge correspondences and the minutia correspondences between two fingerprints. First N initial substructure (including a minutia and adjacent ridges) pairs are found by a novel alignment method. Based on each of these substructure pairs, ridge matching is performed by incrementally matching ridges and minutiae, and then a matching score is computed. The maximum one of the N scores is used as the final matching score of two fingerprints. Preliminary results on FVC2002 databases show that ridge matching approach performs comparably with the minutia-based one.     

Modelling fingerprint ridge orientation using Legendre polynomials

The estimation of fingerprint ridge orientation is an essential step in every automatic fingerprint verification system. The importance of ridge orientation can be deflected from the fact that it is inevitably used for detecting, describing and matching fingerprint features such as minutiae and singular points. In this paper we propose a novel method for fingerprint ridge orientation modelling using Legendre polynomials. One of the main problems it addresses is smoothing orientation data while preserving details in high curvature areas, especially singular points. We show that singular points, which result in a discontinuous orientation field, can be modelled by the zero-poles of Legendre polynomials. The models parameters are obtained in a two staged optimization procedure. Another advantage of the proposed method is a very compact representation of the orientation field, using only 56 coefficients. We have carried out extensive experiments using a state-of-the-art fingerprint matcher and a singular point detector. Moreover, we compared the proposed method with other state-of-the-art fingerprint orientation estimation algorithms. We can report significant improvements in both singular point detection and matching rates.     

An effective algorithm for fingerprint image enhancement based on wavelet transform

Among all the fingerprint identification/verification systems, such as minutiae-based or filterbank-based fingerprint matching, the performance relies heavily on the quality of the input fingerprint images. In this paper, we propose an effective algorithm of fingerprint image enhancement, which can much improve the clarity and continuity of ridge structures based on the multiresolution analysis of global texture and local orientation by the wavelet transform. Experimental results show that the enhanced image quality by using the wavelet-based enhancement algorithm is much better than the other existing methods for improving the minutiae detection.     

基于稳定区域的形变指纹匹配算法

针对指纹匹配中的非线性形变问题,首次提出了稳定区域的概念,并给出了一种新颖的基于指纹稳定区域的形变指纹匹配算法。通过稳定区域这一概念,巧妙地把指纹匹配问题转化为寻找两幅指纹中对应稳定区域的问题。该算法通过稳定区域的构造、确认和扩张3个步骤,实现了从点到面再到更大区域,从线性形变区域到非线性形变区域的匹配策略。该算法在国际指纹识别竞赛FVC2004的数据库上进行了测试,实验结果表明,该算法有着良好的匹配性能,并有较强的处理非线性形变的能力。     

基于隐马尔可夫模型的指纹分类研究

指纹分类是针对大型指纹库的一个重要的索引方式，可以有效地提高指纹匹配的效率．指纹类型的不同表现为指纹纹理结构的差异，而指纹的方向场则可以有效地描述纹理结构的差异．同一类型指纹不同区域上方向角结构的差异以及相邻区域间方向角结构的联系可以视作一个马尔可夫随机场．本文利用嵌入式隐马尔可夫模型对指纹方向场进行建模分析，通过合理地抽取指纹的类型特征，构造观察向量、进行建模训练，然后利用训练好的马尔可夫模型进行匹配，最终提出并实现了一种新的鲁棒性强且精度较高的指纹分类方法．     

Partial fingerprint identification for large databases

Nowadays, most fingerprint sensors capture partial fingerprint images. Incomplete, fragmentary, or partial fingerprint identification in large databases is an attractive research topic and is remained as an important and challenging problem. Accordingly, conventional fingerprint identification systems are not capable of providing convincing results. To overcome this problem, we need a fast and accurate identification strategy. In this context, fingerprint indexing is commonly used to speed up the identification process. This paper proposes a robust and fast identification system that combines two indexing algorithms. One of the indexing algorithms uses minutiae triplets, and the other uses orientation field (OF) to index and retrieve fingerprints. Furthermore, the proposal uses some partial fingerprint matching methods on final candidate list obtained from the indexing stage. The proposal is evaluated over two national institutes of standards and technology (NIST) datasets and four fingerprint verification competition (FVC) datasets leading to low identification times with no accuracy loss.     

Live-scanned fingerprint classification with Markov models modified by GA

Live-scanning devices are widely used in many fields. An important difference between fingerprint images acquired by ink and paper and fingerprints acquired by live-scanning devices is completeness. Since the sensor sizes of live-scanning devices are usually smaller than an average fingerprint and users may not align their fingers properly on the sensors, only a part of a fingerprint may be scanned, resulting in the omission of some singular points. In this paper, we propose a novel approach which increases the classification performance for fingerprint images obtained by live-scanning devices. We extract ridge directional values and create Markov models. However, Markov models in each class share most transitions because fingerprints are basically circular in shape. In order to enhance the specific transitions of each class and to suppress the common transitions in the Markov models, we apply genetic algorithms. The performance of the optimized classification model using genetic algorithms was shown to be superior to the pre-optimization model. The proposed method effectively classifies live-scanned fingerprint images because this approach is based on the global feature of ridge direction, and is independent of the existence of singular points.     

Intelligent fingerprint quality analysis using online sequential extreme learning machine

Because the quality of fingerprints can be degraded by diverse factors, recognizing the quality of fingerprints in advance can be beneficial for improving the performance of fingerprint authentication systems. This paper proposes an effective fingerprint quality analysis approach based on the online sequential extreme learning machine (OS-ELM). The proposed method is based not only on basic fingerprint properties, but also on the physical properties of the various sensors. Instead of splitting a fingerprint image into traditional small blocks, direction-based segmentation using the Gabor filter is used. From the segmented image, a feature set which consists of four selected independent local or global features: orientation certainty, local orientation quality, consistency, and ridge distance, is extracted. The selected feature set is robust against various factors responsible for quality degradation and can satisfy the requirements of different types of capture sensors. With the contribution of the OS-ELM classifier, the extracted feature set is used to determine whether or not a fingerprint image should be accepted as an input to the recognition system. Experimental results show that the proposed method performs better in terms of accuracy and time consumed than BPNN-based and SVM-based methods. An obvious improvement to the fingerprint recognition system is achieved by adding a quality analysis system. Other comparisons to traditional methods also show that the proposed method outperforms others.     

Fingerprint Retrieval for Identification

This paper presents a front-end filtering algorithm for fingerprint identification, which uses orientation field and dominant ridge distance as retrieval features. We propose a new distance measure that better quantifies the similarity evaluation between two orientation fields than the conventional Euclidean and Manhattan distance measures. Furthermore, fingerprints in the data base are clustered to facilitate a fast retrieval process that avoids exhaustive comparisons of an input fingerprint with all fingerprints in the data base. This makes the proposed approach applicable to large databases. Experimental results on the National Institute of Standards and Technology data base-4 show consistent better retrieval performance of the proposed approach compared to other continuous and exclusive fingerprint classification methods as well as minutia-based indexing schemes