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  1. 1. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 5, July 2012 Study and Development of Iris Segmentation and Normalisation Techniques Anshu Parashar,Yogita Gulati this challenge. Examples include automatic retinalAbstract - There have been several implementations of vasculature scan, iris recognition, fingerprints matching,security systems using biometric, especially for hand shape identification, handwritten signature verification,identification and verification cases. The term and voice recognition systems. Since 1987, when L. Flom"biometrics" is derived from the Greek words bio (life) and A. Safir [12] concluded about the stability of irisand metric (to measure). In other words, bio means morphology and estimated the probability for the existence ofliving creature and metrics means the ability to measure two similar irises at 1 in 1072, the use of iris based biometrican object quantitatively. An example of pattern used in systems has been increasing. Iris is commonly recognized asbiometric is the iris pattern in human eye. The iris one of the most reliable, unique and noninvasive biometricpattern has been proved unique for each person. The iris measures: it has a random morphogenesis and, apparently, norecognition system consists of an automatic segmentation genetic penetrance. A biometric system provides automaticsystem that is based on the Hough transform, and is able identification of a human being based on some uniqueto localize the circular iris and pupil region, occluding physical or behavioral feature of the individual. Iriseyelids and eyelashes, and reflections. The extracted irisregion was then normalized into a rectangular block with recognition is regarded as the most reliable and accurateconstant dimensions to account for imaging biometric identification system being used in modern era.inconsistencies. Finally, the phase data from 1D Most commercial iris recognition systems use patentedLog-Gabor filters were extracted and quantized to four algorithms developed by Daugman [1, 2], and theselevels to encode the unique pattern of the iris into a algorithms are able to produce perfect recognition rates.bit-wise biometric template using Daugman’s However, published results have usually been producedrubber-sheet model. The Hamming distance was under favourable conditions, and there have been noemployed for classification of iris templates, and two independent trials of the technology.templates were found to match if a test of statisticalindependence was failed. II. OVERVIEW The system, as shown in Figure 1, is implemented inIndex Terms - Segmentation, Histogram equalization, HoughTransform, Normalization. MATLAB. I. INTRODUCTION The rapid developments in the field of InformationTechnology & WWW, causing human beings frequentlyconfront with various kinds of unauthorized access. Alsowith the enlargement of mankinds activity range, thesignificance for person’s status identity is becoming moreand more important. So many different techniques forperson’s status identity have been proposed for this practicaltask. Conventional methods for status identity check like Fig.1. Typical stages of iris recognition.password and identification card are not always reliable,because these methods can be easily forgotten, stolen or A general iris recognition system is composed of fourforged. A wide variety of biometrics have been developed for steps. Firstly an image containing the eye is captured then the original image containing iris is preprocessed to extract the iris. Thirdly iris features are extracted from the segmented Anshu Parashar,Associate Professor, Department of Computer Science image and is encoded in the form of an iris template and& Engineering, H.C.T.M, Kaithal, Haryana(India),Mobile No.9896262553 finally decision regarding acceptance or rejection of the(e-mail:parashar_anshul@yahoo.com). subject is made by means of matching. Yogita Gulati, M.Tech Student, Department of Computer Science &Engineering, H.C.T.M, Kaithal, Haryana(India),Mobile No.9215653212(e-mail:yogitagulati1111@yahoo.com). 237 All Rights Reserved © 2012 IJARCET
  2. 2. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 5, July 2012 III. EARLIER WORKS n Daugman [1, 2] proposed an integro-differential operator H ( xc , yc , r )   h( x j , y j , xc , yc , r ) (1) j 1for localizing iris regions along with removing the possibleeyelid noises. From the publications, we cannot judge wherewhether pupil and eyelash noises are considered in his 1 if g ( x j , y j , xc , yc , r )  0method. Wildes [4] processed iris segmentation through h( x j , y j , xc , yc , r )  simple filtering and histogram operations. Eyelid edges were 0 otherwisedetected when edge detectors were processed with horizontal (2)and then modeled as parabolas. No direction preferences lead The limbus and pupil are both modeled as circles and theto the pupil boundary. Eyelash and pupil noises were not parametric function g is defined as:considered in his method. Boles and Boashah [5], Lim et al. g ( x j , y j , xc , yc , r )  ( x j  xc ) 2  ( y j  yc ) 2  r 2[6] and Noh et al. [7] mainly focused on the iris imagerepresentation and feature matching, and did not introduce (3)the information about segmentation. Tisse et al. [8] proposed Assuming a circle with the center ( xc , yc ) and radius ra segmentation method based on integro-differential the edge points that are located over the circle result in a zerooperators with a Hough Transform. This reduced the value of the function. The value of g is then transformed tocomputation time and excluded potential centers outside ofthe eye image. Eyelashes and pupil noises were also not 1 by the h function, which represents the local pattern of theconsidered in his method. Ma et. al. [9] processed iris contour. The local patterns are then used in a votingsegmentation by simple filtering, edge detection and Hough procedure using the Hough transform, H , in order to locateTransform. In Maseks segmentation algorithm [11], the two the proper pupil and limbus boundaries. In order to detectcircular boundaries of the iris are localized in the same way. limbus, only vertical edge information is used. The upper andThe Canny edge detector is used to generate the edge map. lower parts, which have the horizontal edge information, areThen after doing a circular Hough transform, the maximum usually covered by the two eyelids. The horizontal edgevalue in the Hough space corresponds to the center and the information is used for detecting the upper and lower eyelids,radius of the circle. which are modeled as parabolic arcs. We implemented this method in MATLAB® by first employing canny edge IV. PROPOSED APPROACH detection to generate an edge map. For every iris recognition system, accuracy of the system is B. Normalizationhighly dependent on accurate iris segmentation. Better the The localized iris is then normalized to a rectangular blockiris is localized, better will be the performance of the system. with a fixed size radius being in correspondence to the widthOur basic experimentation of the Daugman’s mathematical of the block and angular displacement θ being inalgorithms for iris processing, is derived from the correspondence with the length of the block as shown in fig.information found in the open literature, led us to suggest a 2.few possible improvements. For justification of theseconcepts, we implemented in MATLAB. Afterwards we testedindividually the performances of the different processingblocks previously identified as follows: (1) locating iris in theimage, (2) Cartesian to polar reference transform, (3) localfeatures extraction, and encoding (4) matching. A. Segmentation Segmentation is a process of finding the most usefulportion of the iris image for further processing. It is done by Fig. 2: Daugman’s rubber sheet model.localizing pupil and iris boundaries, eyelashes and eyelids. Incase there is no proper segmentation, next stages of iris Formally, the rubber sheet is a linear model that assigns torecognition will suffer and false data will be generated as each pixel of the iris, regardless its size and pupillary dilation,template which in turn affects the recognition rates. To speed a pair of real coordinates (r, θ), where r is on the unit intervaliris segmentation, the iris has been roughly localized by a [0, 1] and θ is an angle in range [0, 2]. The remapping of thesimple combination of Gaussian filtering, canny edge iris image I(x, y) from raw Cartesian coordinates (x, y) to thedetection, and Hough transform. Hough Transform is used to dimensionless non concentric polar coordinate system (r, θ)deduce the radius and center of the pupil and iris circles. can be represented as:Canny edge detection operator [15] is used to detect theedges in the iris image which is the best edge detection I(x(r, θ), y(r, θ)) → I(r, θ) (4)operator available in MATLAB. Hough Transform where x(r, θ) and y(r, θ) are defined as linear combinations of Considering the obtained edge points both the set of pupillary boundary points (xp(θ), yp(θ)) and theas ( x j , y j ), j  1, 2,3,...., n , a Hough transform can be set of limbus boundary points along the outer perimeter of the iris (xs(θ), ys(θ)) bordering the sclera:written as: 238 All Rights Reserved © 2012 IJARCET
  3. 3. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 5, July 2012 extraction was accomplished through the use of twox  r ,    1  r  * x p    r * xs   (5) dimensional Gabor filters followed by a binarization process.y  r ,    1  r  * y p    r * ys   Finally, feature comparison was made through the Hamming distance. A data set of grayscale iris digital images provided where I(x, y) is the iris region image, (x, y) are the original by he Chinese Academy of Sciences (CASIA) is used forcartesian coordinates, (r,θ) are the corresponding normalized testing. The CASIA [14] version 1 database consists of 756polar coordinates, and (xp, yp) and (xi,yi) are the coordinates gray scale images coming out of 108 distinct classes and 7of the pupil and iris boundaries along the θ direction. images of each eye. We carried out our experiments in C. Feature Extraction and Encoding MATLAB 7.8 (R2009a). Elapsed time for the iris Feature Extraction is a process to extract the information preprocessing (segmentation and normalization) followed by feature extraction and encoding and hamming distancefrom the iris image. These features can not be used for matching is 133.7 seconds with an average hamming distancereconstruction of images. But these values are used in 0.3486. Results of segmentation and normalization processclassification. Gabor filters are used for the purpose. Gabor are shown in fig. 3.filters give rotation – invariant system for feature extraction.In our experiments, we employed a Gabor filter withisotropic 2D Gaussian for rotation invariant classification.Gabor filter’s frequency domain equation is as follows:G ( x, y )  g ( x, y ) exp( 2 j (u.x  v. y )) (6)g ( x, y )   exp( x 2  y 2 / 2 2 ). j  1 The complex function G(x, y) can be spilt into two parts, (a) (b)even and odd filters. Ge(x, y) and Go(x, y), which are also (a) (b)known as symmetric and anti-symmetric filters respectively.The spatial Gabor filter is given in eq. 4.Ge ( x, y )  g ( x, y ) cos(2 f ( x cos   y sin  )) (7)Go ( x, y )  g ( x, y)sin(2 f ( x cos   y sin  )) (c) where G(x,y) is Gabor filter’s kernel and g(x,y) is anisotropic 2D Gaussian function. Fig. 3. (a) Original Iris Image, (b) Segmented Iris Image, (c) Normalized Iris Image D. Matching Matching is performed using Hamming distance measure Results in the form of graph between frequency anddefined in eq. 5. Hamming distance are shown for both genuine and imposters 1 N separately as well as combined. Curve between FAR and HD   X j  Yj N j 1 (8) FRR is also shown. Example results are here shown which are performed on a subset of 105 images of CASIA databaseThe result is the no. of bits that are different between the from 15 different subjects.binary codes Xj and Yj. If the hamming distance between twoimages is 0, provided that there have not been any noisepatterns in the image while it was segmented and normalized,the two images are from same subject and same eye.However, it is the ideal case and even in most perfectconditions, it is not the case. Hamming distance in practicalconditions, i.e. considering some amount of noise is alsoavailable while acquiring the image, varies in the range (0,1].It is measured against a pre defined threshold value whichsays if the calculated hamming distance is greater than thethreshold this means the two images are not from the samesubject else the images are from the same subject. V. EXPERIMENTS AND RESULTSIn the experiments, we implemented the method described byDaugman[13] which is composed of four main stages. In thesegmentation we implemented the integro-differentialoperator that searches for both iris and pupil borders. Feature 239 All Rights Reserved © 2012 IJARCET
  4. 4. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 5, July 2012Fig. 4. (a) Hamming Distance vs. Relative Frequency for [7] S. Noh, K. Pae, C. Lee, and J. Kim, “Multiresolutionimposter, for genuine, for both imposter and genuine independent component analysis for iris identification,” Incombined, and FAR vs. FRR Proceedings of ITC CSCC’02, 1674–1678, (2002). [8] C. Tisse, L.Martin, L. Torres, and M. Robert, “Person identification technique using human iris recognition,” In Proceedings of ICVI’02, 294–299, (2002). [9] L. Ma, Y. Wang, and T. Tan, “Iris recognition using circular symmetric filters,” Proceedings of the 25th International Conference on Pattern Recognition, vol. 2, pp. 414–417, (2002). [10] X. Yuan and P. Shi. A non-linear normalization model for iris recognition. In Proceedings of the International Workshop on Biometric Recognition Systems IWBRS 2005, pages 135–142, China, 2005. [11] Libor Masek and Peter Kovesi, MATLAB Source Code for a Biometric Identification System Based on Iris Patterns, The School of Computer Science and Software Engineering, The University of Western Australia, 2003, Fig. 4. (b) FAR vs. FRR (shown separately) http://www.csse.uwa.edu.au/pk/studentprojects/libor/source code.html. [12] Flom, L. and Safir, A., “Iris Recognition System”, US VI. CONCLUSION Patent 4,641,349, 3 Feb. 1987. Accuracy of the results depends upon how effective [13] J. G. Daugman, "How iris recognition works," Patternsegmentation and normalization is done in preprocessing Recognition, 36(2), 279-291 (2003).stage of iris recognition. Various researchers have [14] Institute of Automation, Chinese Academy of Sciences.contributed significant amount of research for developing a CASIA iris image database, 2004.constraint free iris recognition system and a lots of research is http://www.sinobiometrics.comcurrently going on this direction. Basic need of iris [15] J.Canny, “A computational approach to edge detection,”recognition is valid input iris image which can be IEEE Transactions on Pattern analysis and Machinepreprocessed accurately and efficiently so that normalization Intelligence, 8: 679-698, November 1986.and other later stage functionalities discussed above can beimplemented and handled with effectiveness. Eyelashes Anshu Parashar is pursuing his Ph.D. degree in theremoval and other noise diminishing methods are not area of Data minning in Software Engineering from Department of Computer Engineering, Nationalconsidered which shows there is some scope of development Institute of Technology (Deemed University),available in proposed approach too. Angular deflection also Kurukshetra 136 119, India. Presently, he is workingaffects the recognition performance of the system which is as Associate Professor & Head Of Department (HOD)not considered in the proposed work and can be taken as a in Department of Computer Science and Engineering ,H.C.T.M, Kaithal, Haryana.future scope of the work. Yogita Gulati is pursuing her M.Tech in ComputerScience and Engineering from Haryana REFERENCES College Of Technology & Management, Kaithal. She obtained her Bachelor of Technology degree in[1] J. G. Daugman, “High confidence visual recognition of computer science and engineering from N.C.C.E,person by a test of statistical independence,” IEEE Trans, Israna in 2010.PAMI 15(11), 1148-1161 (1993).[2] J. G. Daugman, "The importance of being random: Photostatistical principles of iris recognition," Pattern Recognition,36(2), 279-291 (2003).[3] Yong Zhu, Tieniu Tan and Yunhong Wang, “BiometricPersonal Identification Based on Iris Patterns,” NationalLaboratory of Pattern Recognition (NLPR), Institute ofAutomation, Chinese Academy of Sciences, P. R. China(2003).[4] R. Wildes, “Iris recognition: An emerging biometrictechnology,” Proceedings of the IEEE, 85(9):1348–1363(1997).[5] W. Boles and B. Boashash, “A human identificationtechnique using images of the iris and wavelet transform,”IEEE Trans. Signal Processing, 46(4):1185–1188 (1998).[6] S. Lim, K. Lee, O. Byeon, and T. Kim, “Efficient irisrecognition through improvement of feature vector andclassifier,” ETRI Journal, 23(2):61–70 (2001). 240 All Rights Reserved © 2012 IJARCET