LOW DIMENSIONAL REPRESENTATION OF VEIN PATTERNS TO PERFORM RECOGNITION Author(s): Maleika Mehr Nigar Mohamed Heenaye- Mamode Khan, University of Mauritius Biometric based security systems, which involve the identification of individuals using their distinct physical or behavioral characteristics, is becoming more popular. Human physiological features possess the properties such as universality, uniqueness, permanence, collectability and circumvention. The most popular biometrics are used are fingerprints, iris scans, faces and signatures Biometric features are harder to copy, forge and very rare for them to be lost. Thus, biometric offers a more secure and reliable performance [1]. Though many researches have been carried out on biometric techniques, there seems to be a lot of scope for further improvement of existing techniques in addition to finding more reliable and practical biometric and techniques for using them for security purposes. A practical biometric should meet the specified recognition accuracy, speed and resource requirement, be harmless to users, be accepted by intended population and be sufficiently robust against various fraudulent methods and attacks to the system [2]. Recently hand vein pattern biometrics has attracted increasing interest from both research communities and industries [1]. A vein pattern is the vast network of blood vessels underneath a person’s skin. The shape of vascular patterns in the same part of the body is believed to be distinct from each other and remains stable over a long period of time. Furthermore, the blood vessels are hidden underneath the skin and are mostly invisible to the human eyes and hence vein patterns are much harder to copy compared to other biometric features. Vein patterns are unique, stable and have strong immunity to forgery and thus they can become a potential good biometric which offers secure and reliable features for person identity verification [3]. As a kind of biometric feature authentication system, hand vein recognition has more merits than the others and thus it has a vast foreground [4]. A typical hand vein pattern biometric consists of five processing stages [1]: Hand Image Acquisition, image enhancement, vein pattern extraction, skeletonisation and vein pattern matching. Hand image acquisition consists of capturing the vein pattern of the dorsal hand. Since the veins are invisible to the naked eye and are found beneath the skin, we have to use infrared to capture the veins. During experimentation phase, some researchers found that it is necessary to irradiate the back of the hand using an IR cold source. In this way, the reduced haemoglobin in veinous blood absorbs more of the incident IR radiation than the surrounding tissue and thus appearing darker [5]. Image enhancement is the second phase where noises introduced when capturing images are filtered. In fact, to enhance the quality of the image, filters are used to reduce the possible imperfections in the image due to sensor noise and other effects. Different techniques like Gaussian Low Filter, normalization and nonlinear diffusion have been applied [6, 7] to enhance images. The next step is the vein pattern extraction where the vein patterns are separated from the image background. Thresholding is used to obtain the vein pattern. Among many other methods, Wang et al [3] have used the idea of fingerprint biometrics where a fingerprint pattern has been represented by a number of critical points known as the ridge endings and ridge bifurcations. In the same way, critical points called minutiae, which are branching and ending points, were extracted from the vein patter. As human being grows, the vein grows. However, the vein pattern which is the sole feature used to recognize an individual remains the same. Skeletonisation is then performed to obtain a thinned version of the vein pattern. The vein pattern is thinned using the thinning algorithms proposed by Zhang and Suen [8] and the skeleton is obtained. The final phase is vein pattern matching: This is where the image is compared with the one stored in the database. Correlation and Hausdorff Distance have been used to match vein patterns [1]. Vein pattern recognition has been so far, done by distinguishing vein patterns by comparing the properties and relation between pixel values [5, 6, 11]. Consequently, each pixel needs to be stored and processed, and this makes matching very slow. In this work, we have developed a method to create a low dimensional representation of vein patterns and then perform recognition. We have reduced the dimension of representation of veins by using PCA (Principal Component Analysis). The low dimensional representation of veins in the eigenveins approach is derived by applying Principal Component Analysis to the set of veins. So far, PCA has been applied to face recognition and to hand geometry [9, 10]. In the face recognition, the system functions by projecting face images onto a feature space known as eigenfaces that spans the significant variations among known face images [9]. We have applied the PCA method successfully to the dorsal vein patterns. The experimental results obtained are encouraging. The low dimensional representation has a direct effect on the speed of vein recognition. References [1] Wang Lingyu, Graham Leedham, “Near- and- Far- Infrared Imaging for Vein Pattern Biometrics”, Proceedings of the IEEE International Conference on Video and Signal Based Surveillance, 2006 [2] A.K. Jain, A.Ross and S.Prabhakar, “ An Introduction to biometric Recognition”, IEEE Transactions on circuits and systems for Video Technology, Vol 14, No 1, January 2004. [3] L.Wang, G. Leedham, and D.Cho “Minutiae feature analysis for infrared hand vein pattern biometrics, The Journal of the pattern recognition society, Volume 41 , Issue 3 (March 2008) Pages 920-929 Year of Publication: 2008 ISSN:0031-3203 [4] K.Wang, Y.Zhang, Z.Yuan and D.Zhuang, “Hand Vein Recognition Based on Multi- Classifier Fusion Decision”, In Proceedings of the 2006 International Conference on Mechatronics and Automation, June 25-28 2006, Luoyang, China [5] J.M.Cross, C.L.Smith, “Thermographic Imaging of Subcutaneous Vascular Network of the Back of the Hand for Biometric Identification”, IEEE 29th Annual 1995 International Carnahan Conference, (1995) 20- 35 [6] A.M. Badawi, “Hand Vein Biometric Verification Prototype: A Testing Performance and Patterns Similarity” In Proceedings of the 2006 International Conference on Image Processing, Computer Vision, and Pattern Recognition (IPCV'06: June 26-29, 2006, Las Vegas, USA [7] M. Shahin, A. Badawi, and M. Kamel, “Biometric Authentication Using Fast Correlation of Near Infrared Hand Vein Patterns”, International Journal of Biomedical Sciences Volume 2 Number 3 2007 [8] T. Y. Zhang and C. Y. Suen, "A fast parallel algorithm for thinning digital patterns," Commun. ACM, vol. 27, no. 3, pp. 236--239, 1984. [9] T.Chin and D.Suter, “A study of the Eigenface Approach for Face Recognition. Technical Report MECSE-6- 2004 [10] I.Dagher, W.Kobersy and W.Nader, “Human Hand Recognition using IPCA-ICA Algorithm”, EURASIP Journal on Advances in signal processing, vol .2007 [11] C.Lin. and k. Fan, 2004, Biometric Verification Using Thermal Images of Palm- Dorsa Vein Patterns, IEEE Transactions on circuit and systems for video technology, vol.14, No2, Pg 199-213, February 2004.