1、Automated Iris Recognition Technology & Iris Biometric System,CS 790Q Biometrics,Instructor: Dr G. Bebis Presented by Chang Jia Dec 9th, 2005,2,Overview,The Iris as a Biometrics: The iris is an overt body that is available for remote assessment with the aid of a machine vision system to do automated
2、 iris recognition. Iris recognition technology combines computer vision, pattern recognition, statistical inference, and optics. The spatial patterns that are apparent in the human iris are highly distinctive to an individual. Clinical observations Developmental biology,3,The structure of the human
3、eye,The structure of the iris seen in a transverse section,The structure of the iris seen in a frontal section,Overview,4,Its suitability as an exceptionally accurate biometric derives from its extremely data-rich physical structure genetic independence no two eyes are the same patterns apparently s
4、table throughout life physical protection by a transparent window (the cornea), highly protected by internal organ of the eye externally visible, so noninvasive patterns imaged from a distance,Overview,5,The disadvantages to use iris as a biometric measurement are Small target (1 cm) to acquire from
5、 a distance (about 1 m) Moving target Located behind a curved, wet, reflecting surface Obscured by eyelashes, lenses, reflections Partially occluded by eyelids, often drooping Deforms non-elastically as pupil changes size Illumination should not be visible or bright,Overview,PART I: Iris Recognition
6、: An Emerging Biometric Technology,R. Wildes, “Iris Recognition: An Emerging Biometric Technology“, Proceedings of the IEEE, vol 85, no. 9, pp. 1348-1363, 1997.,CS 790Q Biometrics,7,Outline,Technical Issues * Image Acquisition Iris Localization Pattern Matching Systems and Performance* (Throughout t
7、he discussion in this paper, the iris-recognition systems of Daugman and Wildes et al. will be used to provide illustrations.),8,Technical Issues,Schematic diagram of iris recognition,9,I. Image Acquisition,Why important? One of the major challenges of automated iris recognition is to capture a high
8、-quality image of the iris while remaining noninvasive to the human operator. Concerns on the image acquisition rigs Obtained images with sufficient resolution and sharpness Good contrast in the interior iris pattern with proper illumination Well centered without unduly constraining the operator Art
9、ifacts eliminated as much as possible,10,The Daugman image-acquisition rig,I. Image Acquisition - Rigs,11,The Wildes et al. image-acquisition rig,I. Image Acquisition - Rigs,12,Result Image from Wildes et al. rig - capture the iris as part of a larger image that also contains data derived from the i
10、mmediately surrounding eye region,I. Image Acquisition - Results,13,In common: Easy for a human operator to master Use video rate capture Difference: Illumination The Daugmans system makes use of an LED-based point light source in conjunction with a standard video camera. The Wildes et al. system ma
11、kes use of a diffuse source and polarization in conjunction with a low-light level camera. Operator self-position The Daugmans system provides the operator with live video feedback The Wildes et al. system provides a reticle to aid the operator in positioning,Discussion,14,Purpose: to localize that
12、portion of the acquired image that corresponds to an iris In particular, it is necessary to localize that portion of the image derived from inside the limbus (the border between the sclera and the iris) and outside the pupil. Desired characteristics of iris localization: Sensitive to a wide range of
13、 edge contrast Robust to irregular borders Capable of dealing with variable occlusions,II. Iris Localization,15,The Daugman system fits the circular contours via gradient ascent on the parameters so as to maximize,Where is a radial Gaussian, and circular contours (for the limbic and pupillary bounda
14、ries) be parameterized by center location (xc,yc), and radius r (active contour fitting method),II. Iris Localization,16,The Wildes et al. system performs its contour fitting in two steps. (histogram-based approach) First, the image intensity information is converted into a binary edge-mapwhereand S
15、econd, the edge points vote to instantiate particular contour parameter values.,II. Iris Localization,17,The voting procedure of the Wildes et al. system is realized via Hough transforms on parametric definitions of the iris boundary contours.,II. Iris Localization,18,Illustrative Results of Iris Lo
16、calization,Obtained by using the Wildes et al. system,only that portion of the image below the upper eyelid and above the lower eyelid should be included,19,Both approaches are likely to encounter difficulties if required to deal with images that contain broader regions of the surrounding face than
17、the immediate eye region Difference: the active contour approach avoids the inevitable thresholding involved in generating a binary edge-map the histogram-based approach to model fitting should avoid problems with local minima that the active contour models gradient descent procedure might experienc
18、e,Discussion,20,Four steps: 1) bringing the newly acquired iris pattern into spatial alignment with a candidate data base entry; 2) choosing a representation of the aligned iris patterns that makes their distinctive patterns apparent; 3) evaluating the goodness of match between the newly acquired an
19、d data base representations; 4) deciding if the newly acquired data and the data base entry were derived from the same iris based on the goodness of match.,III. Pattern Matching,21,Purpose: to establish a precise correspondence between characteristic structures across the two images. Both of the sys
20、tems under discussion compensate for image shift, scaling, and rotation. For both systems, iris localization is charged with isolating an iris in a larger acquired image and thereby accomplishes alignment for image shift.,III. Pattern Matching -Alignment,22,The Daugmans system uses radial scaling to
21、 compensate for overall size as well as a simple model of pupil variation based on linear stretching.,III. Pattern Matching -Alignment,while being constrained to capture a similarity transformation of image coordinates (x, y) to (x, y),Map Cartesian image coordinates (x, y) to dimensionless polar (r
22、, ) image coordinates according to,The Wildes et al. system uses an image-registration technique to compensate for both scaling and rotation. The mapping function (u,v) is to minimize,23,The two methods for establishing correspondences between acquired and data base iris images seem to be adequate f
23、or controlled assessment scenarios Improvements: more sophisticated methods may prove to be necessary in more relaxed scenarios more complicated global geometric compensations will be necessary if full perspective distortions (e.g., foreshortening) become significant,III. Pattern Matching -Alignment
24、,24,The Daugmans system uses demodulation with complex-valued 2D Gabor wavelets to encode the phase sequence of the iris pattern to an “IrisCode”.,III. Pattern Matching - Representation,25,In implementation, the Gabor filtering is performed via a relaxation algorithm, with quantization of the recove
25、red phase information yielding the final representation.,III. Pattern Matching - Representation,Pictorial Examples of one IrisCode,26,The Wildes et al. system makes us of an isotropic bandpass decomposition derived from application of Laplacian of Gaussian filters to the image data.In practice, the
26、filtered image is realized as a Laplacian pyramid. This representation is defined procedurally in terms of a cascade of small Gaussian-like filters.,III. Pattern Matching - Representation,with the standard deviation of the Gaussian and the radial distance of a point from the filters center,27,Result
27、: Multiscale representation for iris pattern matching. Distinctive features of the iris are manifest across a range of spatial scales.,III. Pattern Matching - Representation,Obtained by using the Wildes et al. system,28,The Daugman system computes the normalized Hamming distance asThe result of this
28、 computation is then used as the goodness of match, with smaller values indicating better matches.,IV. Pattern Matching Goodness of Match,29,The Wildes et al. system employs normalized correlation between the acquired and data base representations.,IV. Pattern Matching - Decision,30,IV. Pattern Matc
29、hing - Decision,For the Daugman system, this amounts to choosing a separation point in the space of (normalized) Hamming distances between iris representations. In order to calculate the cross-over point, sample populations of imposters and authentics were each fit with parametrically defined distri
30、butions.,31,For the Wildes et al. system, the decision-making process must combine the four goodness-of-match measurements that are calculated by the previous stage of processing (i.e., one for each pass band in the Laplacian pyramid representation) into a single accept/reject judgment.,IV. Pattern
31、Matching - Decision,32,Both the enrollment and verification modes take under 1s to complete. Empirical test 1: 592 irises from 323 persons the system exhibited no false accepts and no false rejects Empirical test 2: Phase1: 199 irises from 122 persons, 878 attempts in identification mode over 8 days
32、 no false accepts and 89 false rejects (47 retry with still 16 rejected) Phase2: 96 irises (among 199) with 403 entries for identification no false accepts and no false rejects,Systems and Performance - The Daugman iris-recognition system,33,Both the enrollment and verification modes require approxi
33、mately 10s to complete. Only one empirical test: 60 different irises with 10 images each (5 at the beginning and 5 about one month later) from 40 persons no false accepts and no false rejects.,Systems and Performance - The Wildes et al. iris-recognition system,34,Questions?,PART II: An Iris Biometri
34、c System for Public and Personal Use,M. Negin et al., “An Iris Biometric System for Public and Personal Use“, IEEE Computer, pp. 70-75, February 2000.,CS 790Q Biometrics,36,Iris identification process,The system captures a digital image of one eye, encodes its iris pattern, then matches that file ag
35、ainst the file stored in the database for that individual.,37,The public-use system,The public-use multiple-camera system for correctly positioning and imaging a subjects iris.,Note: wide-field-of-view (WFOV) & narrow-field-of-view (NFOV) camera,38,The public-use optical platform,left and right illu
36、minator pods, gaze director, and optical filter,(b) a solid model of the platforms internal components.,39,The user manually positions the camera three to four inches in front of the eye. Make sure that the devices LED centers within the aperture that superimposes the users line of sight and the cam
37、eras optical axis.,The personal-use system,40,Identification Performance,Verification distributions of authentic results (in brown) and imposter results (in green).,41,Field Trial Experience,The first pilot programwith the Nationwide Building Society in Swindon, Englandran for six months and include
38、d more than 1,000 participants, before going into regular service during the fourth quarter of 1998. The field trial experience has been very positive: 91 percent prefer iris identification to a PIN (personal identification number) or signature, 94 percent would recommend iris identification to friends and family, 94 percent were comfortable or very comfortable using the system. The survey also found nearly 100 percent approval on three areas of crucial importance to consumers: reliability, security, and acceptability.,42,Thank You.,Questions?,
