WO2006081505A1 - Systeme de tetereconnaissance d'un iris - Google Patents

Systeme de tetereconnaissance d'un iris Download PDF

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Publication number
WO2006081505A1
WO2006081505A1 PCT/US2006/003104 US2006003104W WO2006081505A1 WO 2006081505 A1 WO2006081505 A1 WO 2006081505A1 US 2006003104 W US2006003104 W US 2006003104W WO 2006081505 A1 WO2006081505 A1 WO 2006081505A1
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iris
affected
map
regions
areas
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PCT/US2006/003104
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English (en)
Inventor
Rida Hamza
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Honeywell International Inc.
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Priority to KR1020077019289A priority Critical patent/KR101224408B1/ko
Priority to JP2007553302A priority patent/JP4767971B2/ja
Priority to EP06734016A priority patent/EP1842152B1/fr
Publication of WO2006081505A1 publication Critical patent/WO2006081505A1/fr

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
    • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
    • G06V40/18—Eye characteristics, e.g. of the iris

Definitions

  • the present invention pertains to recognition systems and particularly to biometric recognition systems . More particularly, the invention pertains to iris recognition systems .
  • the invention is a system that incorporates certain improvements which support biometrics technology for person recognition from afar.
  • Figure 1 shows a basis for iris center localization
  • Figure 2 shows iris references for image polar mapping
  • Figure 3 shows one dimensional polar segmentation
  • Figure 4 shows image segmentation omitting normalization for illustrative purposes ;
  • Figure 5 shows normalization and treating eyelid occlusions
  • Figure 6 shows segmentation and normalization conducted simultaneously;
  • Figure 7a shows examples of side effects of closures, eyelashes , and slanted oriented irises ;
  • Figure 7b shows examples of the results of an enhanced feature extraction
  • Figure 8 shows a perspective plane orientation in image acquisitions
  • Figure 9 shows an outline of segmentation of the iris into various regions and classifying the regions as unaffected and affected
  • Figure 10 shows the symmetric portion of the iris representing the non-occluded areas where the borders of the iris and sclera are visible ;
  • Figure 11 shows a determination of the center of the ellipse with an intersection of circles and an elliptic fitting scheme,-
  • Figure 12 relates to an adjustment/calibration of an iris radial longitude
  • Figure 13 is associated with a program for regenerating circles form ellipses ;
  • Figure 14 may show a visualization of the mixture modeling approach as applied to iris segmentation
  • Figures 15a, 15b and 15c show a mixture modeling based analysis
  • Figures 16a, 16b and 16c show another mixture modeling based analysis .
  • Figure 17 illustrates an example computer system usable in conjunction with certain illustrative instances of the present system.
  • the invention may provide people identification and verification, using an "iris-at-a-distanceTM” or " Iris@aDistanceTM” (Honeywell International Inc . ) system.
  • Iris recognition has been recently recognized and has gained a lot of attention due to its high reliability in identifying humans . Its suitability as an exceptionally accurate biometric derives from its extremely data-rich physical structure, genetic independence (no two eyes are the same even for twins) , stability over time , and non- contact means (a feature important for non-cooperative subjects) .
  • the present invention may help provide reliable calibration and an efficient segmentation (i . e . , localization) of the iris-at-a-distance, resulting in better extraction of the iris features that are eventually converted into a numeric code .
  • the iris codes may be compared with previously generated iris codes for verification and/or identification purposes .
  • iris features are a reliable/accurate biometric measure .
  • this accuracy lies heavily on how best the iris and pupil are segmented and extracted.
  • the segmentation approach is a relatively straightforward process of edge detection and circular fitting.
  • this is often not the case for iris-at-a-distance systems , which often do not enjoy the cooperation of the subj ect .
  • iris-at-a-distance system only a portion of the iris is captured due to, for example, closure effect and/or eyelash and eyelid occlusions .
  • a tilted head or a rotated iris typically must also be considered.
  • the present invention addresses these challenges , and in some cases , extracts accurate segments of the iris borders , among other things , in an iris-at-a-distance environment .
  • the process may include : 1) using a POSETM (i . e . , polar segmentation) technique to move virtually immediately the analysis to a polar domain and execute a 1-D segmentation of the iris borders ; 2) using one or more symmetry properties to detect one or more non-occluded areas of the iris - - non- symmetric regions can correspond to areas partially covered by eyelashes , eyelids , and so forth (thus asymmetric) - - and, in some cases , can limit the analysis to only those reliable segments where the iris and the sclera are detected (as noted in this description relative to symmetry) ; 3) once orientation is detected, identifying the nominal angles with the least likelihood of distortions (i .
  • POSETM i e e . , polar segmentation
  • the sclera is the tough white fibrous outer envelope of tissue covering the entire eyeball except the cornea.
  • the present invention is well suited for high- security access control or "at-a-distance biometrics" applications where less control is exercised on subj ect positioning and/or orientations .
  • Such operations may include, for example, subj ects captured at variant ranges from the acquisition device, and/or may not have the subjects eye (s) directly aligned with the imaging equipment .
  • it is difficult to implement the level of control required by most of the existing art to enable reliable iris recognition.
  • the present invention may help cope with asymmetry in acquired iris images , and may further help under uncontrolled environments as long as some of the iris annular is visible .
  • iris recognition may provide a reliable solution by offering a much more discriminating biometric than other types of biometrics including face and fingerprint recognition techniques .
  • iris recognition technology as a potential reliable personal identification tool .
  • this technology may have the following noted characteristics .
  • the iris is considered an internal and unique organ, yet is externally visible and can be measured at a distance .
  • iris recognition suitable for highly reliable personal identification then other notable biometrics such as facial recognition. It has been demonstrated that, unlike facial recognition, the phase structure and local features extracted from irises is purely epigenetic, so performance of iris recognition is not limited with application to identical twins or by the existence of partial genetic relationships .
  • iris annular image Conversion of an iris annular image into a numeric code that can be easily manipulated may be essential to iris recognition.
  • Computing iris features may use a good-quality segmentation process that focuses on the subject' s iris and properly extracts its borders .
  • POSETM Honeywell International Inc .
  • a 1-D Polar based "segmentation approach” POSE differs from the usual state-of-the art techniques in that it may conduct a one-dimensional segmentation process in the polar domain, replace the exhaustive search for geometric models (such as circles) and avoid the use of costly edge detections and curve fitting by simply executing a straightforward peak search on ID signatures .
  • the present approach may map immediately into the polar domain right from the start .
  • POSE may map the analysis at an earlier stage then previously done into the polar domain . By conducting the segmentation in polar domain, this may lead to a more efficient and faster process to execute not only the segmentation, but also calibration, and noise removal , all in one single step to generate a feature map for the encoding step .
  • the technique may be suited for the iris-at-a- distance applications , i . e . , in cases where subj ects are unaware that they are under surveillance, or in a crowded area, or even in cases where subj ect is aware of iris control but are non-cooperative .
  • Such operations may include subjects captured at variant ranges from the acquisition device or may not have their eye directly aligned with the imaging equipment .
  • the present system may solve the asymmetry problem associated with image acquisition without the collaboration of the subj ects and that it can operate under uncontrolled operations as long as some of the iris annular is visible .
  • iris inner and outer boundaries of iris may be approximated by ellipses than circles of irregular shapes using snake delineation.
  • the two ellipses are usually not concentric .
  • One may characterize the shape and texture of the structure of the iris having a large number of interlacing blocks such as freckles , coronas , furrows , crypts , and stripes .
  • a change in the camera-to-eye distance may result in variations in the size of the same iris .
  • Preprocessing to reduce the side effects of non-uniform lighting or illumination reflections may be needed before one executes feature extractions procedures .
  • Specular (mirror-like) reflections and the treatment of soft specular reflected dots may affect the segmentation analysis .
  • the outer boundaries of the iris may be captured with irregular edges due to presence of eyelids and eyelashes . Taken in tandem, these observations suggest that iris localization may be sensitive to a wide range of edge contrasts .
  • the orientation of head and eyes may result into different perspective of views of the iris circular shape .
  • the captured shapes of the iris are usually far from circles or ellipses due to the orientation, tilt and slant angles .
  • Iridian i . e . , pertaining to an iris
  • the Iridian technology algorithms may limit the extensibility of the iris recognition into real-time non-controlled environment . While certain operations are consistent with the preconditions , it is difficult to implement these existing technologies without the level of control required by the algorithms .
  • Hough transforms Some issues with a Hough method may include requiring threshold values to be chosen for edge detection, which may result into critical information (e .g. , edge points) being removed/missed, and thus resulting into failure to detect the iris or pupil regions .
  • the Haugh transform is computationally intensive due to its brute-force approach, and then may not be suitable for real-time applications .
  • the method may fail where the image is subj ect to local noise in the eye image since it works on local spatial features .
  • a Daugman integro-differential operator may be seen as a variation of Haugh transform, since it appears to make use of derivatives of the image and perform a search to find geometric information that determines spatial parameters identifying the circles of the iris and pupil .
  • the advantage the Daugman operator has over Haugh may be that it does not require threshold values as it is based on raw derivatives . However, it may fail when the image suffers from local spatial noise (e .g . , specular reflections along the eye image , speckles due to digitization, and so forth) .
  • one approach in dealing with the eyelid occlusions masks portions of the image may use linear fitting.
  • the eyelid boundaries may be irregular due to the presence of eyelashes as well .
  • Another approach in dealing with variable occlusions may be modeling the eyelids with parabolic curvatures and using the extracted configuration of model components to fine tune the image intensity derivative information. The alternative may cost a lot of computation given that is based on edge detection and non-linear curve fitting.
  • Another iris recognition technique may be based on a ID process ; but it is mostly tailored to improve the encoding scheme for better representation of the iris features rather than simplifying the segmentation process .
  • some methods construct a set of ID intensity signals decomposed from the 2D constructed iris map .
  • Gaussian moments applied on ID representation of feature vectors may have been advocated by some as the best representation of local features that indirectly quantify the variations in textures due to coronas , stripes, furrows , and so forth.
  • Such technique may still be based on 2D segmentation process to construct a 2D normalized polar map of the iris .
  • a new ID encoding scheme that may generate a ID iris signature includes translation, rotation, illumination, and scale invariant .
  • the merit of this method is that may allow users to enroll at lower level of iris image quality. This implies that the technique may not be as reliable as the 2D encoding scheme . However, that technique may support the concept of having a search mode before passing the limited potential subj ects to a 2D encoding for final identifications .
  • the present approach may implement a complete ID segmentation and encoding iris technique .
  • Iris segmentation may be a factor to note .
  • the first stage of iris recognition may be to isolate the actual iris region in a digital image of the eye . Often, for others , the iris region may be approximated by geometric models , i . e . , two circles , to simplify the image processing segmentation of the iris and pupil .
  • the dimensional inconsistencies among the captured iris images may be primarily due to many reasons such as a stretching of the iris caused by the pupil dilation from varying levels of illumination and lighting .
  • the varying distance of image capture and imager orientation may be due to camera or head tilting and slanting. There may be local rotation of the eye within the eye socket .
  • the subj ect or the subject ' s face might not be directly aligned with the acquisition device .
  • Image enhancement may be applied to minimize illumination artifacts , i . e . , non-uniform brightness that illuminates areas more than others within the iris annular region. Reducing the illumination artifacts may improve subsequent encoding and feature extraction steps .
  • the perspective orientation may be addressed before conducting feature extraction; however, this could add more computational burden on the system.
  • the present segmentation algorithm does not appear to require these preprocessing steps to extract accurate features of the iris .
  • Encoding may be noted. In order to provide accurate recognition or identification of individual irises , one may need to extract the most discriminating information present in the polar presentation of the extracted iris . Just the significant features of the iris patterns may need to be encoded so that comparisons between two subj ects can be made easy.
  • the encoding scheme may be to generate a simpler template of a few bits that captures the essence of iris patterns . The extracted numeric code may then be used to compare it to multiple stored codes .
  • Encoding the iris signature may include applying an encoding algorithm such as wavelet or Gabor filters or other techniques as listed below to extract textural information from images , such as the detailed patterns of the iris to produce a bitwise template containing a number of bits of information and excluding some of the corrupt areas using masking within the iris pattern .
  • the choice of the encoding filters may be made on the basis of achieving the best recognition rate and preserving the iris patterns in the limited generated bitwise template .
  • the merit of this scheme is that it may provide a quick way of matching subj ects and also provide way to generate the most probable match instead of the best match when facing with poor quality iris images and iris patterns . For instance, one may conduct average weighting on the numeric code when conducting matching using any of the information divergence measure .
  • Encoding may include the actual encoding of the extracted features having different means of filtering and processing.
  • the encoding mechanism may involve applying one or more selected filters to the segmented iris image (s) .
  • Some of the filters used by the state-of- the art techniques may include but are not limited to the following, such as wavelet / bank filters which may be also known as part of a multi-resolution technique .
  • the wavelet approach may have an advantage over traditional Fourier transform in that the frequency data is localized.
  • Gabor filters may also be capable of presenting a conjoint representation of the iris pattern in a spacial and frequency domain.
  • Log Gabor filtering may be more reliable than Gabor filtering .
  • Haar filters have been shown to possibly outperform Gabor filters .
  • Laplacian filters may involve pyramid based decomposition to obtain a simplified version of the signal .
  • This process may execute matching between a query and encoded signatures .
  • information measures including but not limited to, may include a hamming code, a Euclidian code, a Jeffery code, a Kullback code , or any other standard information divergence measure which can be used to provide the weighted distance .
  • the average weighted measure may be emphasized in the present approach. More weight may be distributed on the most significant bits versus lower bits . As a result, a phasor value may be represented by 8 or 16 segments (2 A N) rather than just 2 bits in other codes . The weights may be distributed based upon the significance of the bit position.
  • POSE may perform iris recognition under suboptimal image acquisition conditions .
  • the technique may be used for iris segmentation to detect all boundaries (inner, outer, eyelid and sclera and horizon) of the image iris .
  • This technique may be well suited for high-security access control or iris-at-a-distance applications with less control exercised on subject positioning or orientations .
  • Such operations may include subj ects captured at variant ranges from the acquisition device or may not have their eye directly aligned with the imaging equipment .
  • it may be difficult to implement the level of controls required by much of the existing art to enable reliable iris recognition operations .
  • the present approach of iris recognition may cope with asymmetry in acquired iris imaging and it may operate under any uncontrolled operations as long as some of the iris annular is visible .
  • Measurement of the center of the inner boundary may be of interest .
  • the segmentation analysis does not necessarily rely on exact measurements of centers of both boundaries . Additional steps to extract the exact center of the inner iris ellipse may be noted.
  • Iris center localization may be shown in Figure 1.
  • the blob analysis likely will not necessarily lead to an accurate center of the pupil 11. Hence, further processing may be required to come up with a more accurate measure to locate the pupil center .
  • the segmentation process may include the ID POSE technique, although other approaches may be used.
  • ID POSE the ID POSE technique
  • the analysis may be conducted only on a subsection of the image surrounding the iris 13. In many other techniques , extraction of polar representation occurs near the end of the analysis .
  • a rapid polar conversion from an approximate center may permit a fast ID segmentation in polar domain .
  • the POlar SEgmentation may yield rapid extraction of the apparent pupil and iris boundaries using one dimension signal processing .
  • the analysis may detect all kind of boundaries ; including non-elliptic boundaries (i . e . , geometrically and biologically distorted images) .
  • the approach may handle line-of-sight boundaries at the far side of a significantly rotated head, eye, and/or iris .
  • Detection of a starting point within the pupil may be sufficient to initiate the mapping to a polar domain. Further adjustment of the pupil center may be considered as part of the POSE technique in the polar domain.
  • the central point estimate may be based on any blob analysis , thresholding (presuming that the pupil resides at the darkest contrast of the eye image) , or other approaches .
  • the pupil center may be used as a basis of the analysis .
  • the iris region may be normalized further to be centric / centered with respect to the same pupil center .
  • the ROI may be mapped to the polar domain with respect to the estimated pupil center 12 , C (x o , y o ) :
  • iris 13 width Based upon the predefined/estimated center, one may proceed by estimating an approximate iris 13 width. Then one may use the predefined center and iris width to execute the mapping immediately before any actual segmentation is executed.
  • Figure 2 shows the referenced parameters that are used to map the image domain to the polar domain, that is , the Figure shows iris references for image polar mapping
  • the analytical ID function may be defined at each angle as a function of the radius variable, r:
  • Figure 3 shows ID polar segmentation .
  • the present approach may be further simplified to ID match filter to detect the exact edges of boundaries of the iris 13.
  • the segmentation may then be conducted at all desired predefined angles .
  • the peaks 15 and 16 from left to right represent the radii of the pupil 11 and the iris 13 , respectively.
  • Figure 4 shows image segmentation omitting normalization for illustrative purposes (note that normalization is normally conducted on ID signals extracted during the segmentation process) .
  • eyelids 17 and 18 , and/or eyelashes 19 may obscure some of the iris 13 annular region.
  • Related art techniques may treat these obscurations as noise and tend to isolate the obscured region by first detecting the edges of the eyelids/eyelashes by fitting multiple linear/nonlinear curvatures/lines to the upper and lower eyelids using, for example, a Hough transformation, in many cases , thus adding more computational burden to already complicated procedures .
  • the present isolation of affected areas of the iris 13 may be done by comparing the expected radius segment 20 (median value of estimated segments 20 , the expected length may be limited to only measurements taken at the nominal angles with least likelihood of distortions or noise) with the measured width. If there is a significant reduction in measured width, then the data may be treated as noisy and treated separately.
  • Figure 5 shows normalization and treating eyelid 17 , 18 occlusions 21.
  • First one may mask all the corresponding pixels 22 at the affected angles . Although, this approach is simpler than the following approach, it tends to exclude some pixels that may end up being crucial for discriminations .
  • the expected width value i . e . , median value of the measurements
  • Iris 13 normalization may be noted. For the purpose of achieving more accurate recognition results , it may be necessary to correct for the shape deformation and bring uniformity into the shape of the iris 13 before passing the polar data into the encoding scheme . Typical techniques conduct normalization towards the end. With the present technique, normalization may be conducted during the segmentation process .
  • iris 13 circular shape it is expected that at least four major artifacts may result into deformation of the iris 13 circular shape, thus making a normalization scheme necessary while mapping the iris pixels into the rubber polar presentation.
  • First there may be range differences . Irises of different people may be captured at different ranges of the camera even under constrained conditions .
  • the present normalization scheme may be able to preserve the discriminating features of deformed iris 13 into the new presentation.
  • there may be perspective orientations which may include any line-of- sight boundaries at the far side of a significantly rotated head, eye 10 , and/or iris 13.
  • the present normalization process may be conducted as the iris 13 segment is extracted from POSE technique . For instance, let
  • the normalized signal may be based on the interpolation/decimation of the signal .
  • the normalized output is stated as follows :
  • L may be the desired dimension (i . e . , number of rows) for the polar representation of the iris 13 texture .
  • the variable h may vary based upon the deformation type and amount of degradations .
  • Figure 6 shows segmentation and normalization of the iris 13 conducted simultaneously. A feature extraction technique may be noted.
  • the present approach addresses a number of challenges and may makes headway towards the commercialization of a reliable iris system without any constrains on the subj ect of interest .
  • Interest may be in particular interest in recognizing / identifying subjects in large open spaces like airport gates , plazas, potentially crossroads, and sensitive checkpoints .
  • These applications may constitute iris-at-a-distance with no constrains imposed in image acquisitions , and which may be referred to hereon as "iris-at-a-distance" (IAD) .
  • IAD iris-at-a-distance
  • a comprehensive iris-at-a-distance system may depend primarily on two different technologies- -optical design and a computer vision solution.
  • the computer vision solution may be stressed in this section.
  • the present system may be the only one that features a reliable segmentation stage for irregular acquired iris 13 images .
  • the practical aspects of fielding an iris-at- a-distance system may be noted.
  • the occlusion issues of eyelashes 19 and eyelids 17 , 18 may be some of the challenges .
  • the POSE segmentation technique may be used to solve some of the challenges .
  • POSE may have been proven to be a more reliable mechanism than such things as spatial thresholding or Hough space based techniques .
  • Spatial thresholding may do a questionable j ob of classifying all the relevant iris pixels of the eye image .
  • Edge detection and Hough transform may require an intensive computational load to execute all necessary- steps to extract the iris 13 segmentation.
  • fitting the iris into predefined shapes such as circles , ellipses or predefined curves (representing eyelashes) may be closest to reality only under constrained conditions where the subject iris is placed through guidelines to picture a perfect perspective of the iris 13. This scenario appears to be far from real in the iris-at-a-distance approach.
  • Figure 7a shows an example of side effects of closures, eyelashes 19 , and slanted oriented irises 13. Many of the related art algorithms fail when faced with closure, occlusions , and deformation in image acquisition .
  • the present system may use a feature extraction technique based on the POSE segmentation approach to handle such scenarios .
  • the present approach may cope well with asymmetry in acquired images and it may operate under uncontrolled operations .
  • Figure 7b shows the outcome of the present approach with enhanced feature extraction 24 results .
  • Perspective plane transformation may be noted.
  • a present preprocessing approach may be based upon perspective plane orientation that addresses some of the deformations in image acquisitions .
  • Such operations may include subj ects captured at variant angles from the acquisition device or the subjects may have their eye 10 or iris 13 not directly looking into the imaging equipment .
  • the present preprocessing approach for estimating the orientation in space of the face surface from an imaging angle may be based upon the fact that some of these orientation angles are provided by the face recognition tool .
  • One may derive an accurate model of the captured image and its respective projection in the imaging plane .
  • the perspective projection may have a dominant and fundamental role in the present preprocessing operations to detect iris 13 positions with respect to the face, and not with respect to the imaging plane . Segmentation of the iris 13 may be considerably simplified if the effects of the perspective proj ections are eliminated.
  • the POSE technique may be easily applied once on the recovered face image with aligned perspective .
  • the orientation estimation may be essential if the camera is situated at an angle of the normal axis of the eye gaze . For instance, the segmentation and feature extraction 24 procedures may be considerably simplified if the effects of the perspective proj ection are eliminated first, thus reducing the asymmetry in the captured frames and producing accurate segmentations .
  • Figure 8 shows a perspective plane orientation in image acquisitions .
  • the analysis may involve a high-order partial-differential equation .
  • one may- assume a pinhole perspective proj ection model to provide an estimate of the geometric view of the actual face from the camera 25 perspective .
  • One may use the elevation angle of the face normal for representing the orientation of the face .
  • the elevation angle a.
  • ⁇ may be the angle between the upper eyelid 18 center and the back proj ection of the image tilt vector (cos ⁇ , sin ⁇ ) on the face plane 26.
  • the tilt vector may be associated with the elevation angle and indicate how much the surface of the face is tilted from the perspective of the imaging plane 27.
  • the coordinate transformation from the actual face to the imaging plane 27 may be given by
  • the purpose of this effort may be to explore that which will enhance current capabilities of the POSE technique in iris 13 recognition as applied to more unconstrained iris capture in more diverse environments where occlusions 21 and irregularities are expected.
  • the present approach may operate under any of these uncontrolled operations as long as some of the iris 13 annular is visible in the acquired image .
  • An overall view of the present approach is shown in Figure 9.
  • the approach may be initiated by a step 31 segmenting the iris 13 region using the POSE technique; then one may do a step 32 to classify the iris regions into unaffected versus affected regions .
  • a step 33 one may process the unaffected regions to fit regular or irregular, i . e . , elliptic , iris shapes . This may involve an elliptic fitting step 38 for normalization .
  • the present curvature fitting approach may be general enough to cover virtually all possible cases for irregular shapes using snake delineation via POSE .
  • one may then process the affected regions to cover any possible regions that can be calibrated using the parameters of the extracted shape, i . e . , calibration step 37 to reduce occlusion effects .
  • a step 35 one may cluster out the areas where iris 13 is completely covered with eyelashes 18 or eyelids 17 and 18 using the mixture modeling technique step 36.
  • steps 36 , 37 and 38 There may be inputs from steps 36 , 37 and 38 for an encoding step 39 , where the map of the iris 13 may be converted into a numeric bitwise code .
  • the first stage of iris recognition is to isolate the actual iris region in a digital eye image .
  • the POSE technique may be successfully applied to extract the iris region with least computation possible, i . e . , a ID based analysis .
  • the success of the present POSE segmentation may depend on the imaging quality of eye images . For instance, one may presume that images are passed through preprocessing stages to eliminate artifacts due to specula reflections or any other types of background noise .
  • POSE may localize the analysis around the pupil center and immediately map it to the polar domain, without a need to adjust for non-concentric to the iris center which is a process that may be required by the related art .
  • Figure 9 shows a feature extraction 24 approach using POSE 31.
  • Iris classification step 32 may use symmetry in POSE edges .
  • POSE may or the related art may segment the iris 31 as long as it is visible .
  • POSE may require only a portion not necessarily the entire iris be visible .
  • the eyelids 17 and 18 and eyelashes 19 may normally occlude the upper and lower parts of the iris 13 region.
  • the related art may make use of a Hough transform to solve the extraction of eyelashes 19 or eyelids 17 and 18 approximating the upper 18 and lower 17 eyelids with parabolic arcs .
  • the derivative of horizontal direction may be adjusted for detecting the eyelids 17 and 18.
  • the Hough transform method may require thresholding to be chosen for edge detection, and this may result in critical edge points being removed, resulting in a failure to detect arcs (or even circles for the iris borders) .
  • the Hough method may be computationally intensive due to its brute-force approach and thus may not -be practical for the iris-at-a-distance application .
  • An approach may be introduced for detecting the orientation of the eye 10 without having to add extra processes .
  • This approach may be based on detecting the symmetry of the POSE resulting edge points .
  • the symmetric portion 41 of the iris 13 may represent the non-occluded areas where the borders of the iris 13 and sclera are clearly visible .
  • the asymmetric regions represent the eyelids 17 and 18 and eyelashes 19 (obviously the asymmetry is due to occlusion of the sclera) .
  • There may be an iris image classification using asymmetry in detected POSE edges . This technique may provide a way to identify best visible iris areas from affected areas . The affected area may be either masked out or subj ected to further analysis to extract more texture patterns if deemed necessary.
  • the elliptic-fitting step 38 based normalization may be used, as noted in Figure 9 and introduced in Figure 11.
  • the edge map may be generated by radially POSE segmentation over all angles .
  • the symmetric points 43 of the edge map may then be selected for the normalization process . From these symmetric arc points 43 , votes may be cast in within POSE space (i . e . , ranges are predefined by POSE edge map) for the parameters of variable circles 42 passing through each edge point 43 of the symmetric arcs .
  • the ellipse 44 detection scheme may then be based on the overlapping of these variable circles 42.
  • These edge points 43 may be used as the center coordinates of these variable circles 42 which are able to define any circle according to the equation,
  • the circle radius may vary based upon how distant the center from the extreme edge point as shown in Figure 11.
  • the corresponding radius variation may be computed as dr , dy ⁇ y, and the resulting radius for each iteration may be defined as
  • a maximum point in the POSE space may correspond to the intersection of majority of constructed circles and thus to the corresponding radii and center 45 of the ellipse 44 as illustrated in Figure 11.
  • Calibration may be used to reduce occlusion effects .
  • An automatic POSE segmentation model may prove to be successful in detecting virtually all iris regions including area portions occluded by the eyelid 17 or 18.
  • an accurate normalization to bring the analysis into uniformity and make significantly accurate matching against templates in the database, one may need to resample the points detected along the radial axis based on the actual radius of the iris 13 and not on the detected one as it does not represent the complete radius .
  • measurements may be adjusted and rescaled accordingly based upon the best elliptic fitting to the edge map points detected in the nominal areas (i . e . , symmetric edges) .
  • the approach may be shown in the following steps .
  • ⁇ — ; given that r - Third, one may rescale the map based upon calibration factors .
  • Figure 12 One may have an adjustment / calibration of the iris radial longitude .
  • Figure 12 and its notation may be observed.
  • the present technique is well suited for iris-at-a- distance .
  • Such operations may include subj ects captured at variant ranges from the acquisition device or may not have their eye directly aligned with the imaging equipment .
  • the present concept here may cope with asymmetry in acquired iris imaging and it may operate under much any uncontrolled operations as long as some of the iris annular is visible .
  • a purpose of the present system is to have capabilities in iris recognition as applied to more unconstrained iris capture in rather diverse environments .
  • the present analyses may detect many sorts of boundaries , including irregular and non-elliptic boundaries , i . e .
  • the present approach may handle most any line-of-sight boundaries at the far side of a significantly rotated head level iris .
  • the pupil 11 region is not necessarily concentric with the iris 13 region and may usually be slightly nasal .
  • Reliable iris recognition technology may be a reality.
  • computing iris features requires a good-quality segmentation process that focuses on the iris boundaries extraction.
  • the present system may improve the capabilities of POSE as to application to quite unconstrained iris 13 capture in more diverse environments where occlusions and irregularities are expected.
  • the preprocessing approach here may be based on perspective orientation that addresses these deformations in image acquisition.
  • One may assume a perspective proj ection model to provide an estimate of the geometric view of the actual face from the camera perspective .
  • POSE may map the analysis at an early stage into the polar domain .
  • segmentation in the polar domain, one may be led to a more efficient and faster process to execute not only segmentation plus calibration and noise removal in one single step to generate the feature amp for the encoding scheme .
  • a least squares solution may be used for the iris fitting step .
  • measurement k may be formulated as follows :
  • VA: 1 -» N measurements , for each measurement (X k , y k ) ,
  • %ellipse find_me_ellipse (edges, rmin, rmax) -- returns the coordinates % of ellipse in an image using a simplified version of Hough transform to detect overlapping circles at the center .
  • the image may be rescaled to transfer elliptic shapes into circular shapes so that existing technology of circular fitting can be applied to locate elliptic center and eventually elliptic parameters as illustrated herein .
  • % h hough_circle (edge__img, rmin, rmax)
  • % - takes an edge map image, and performs the Hough transform
  • XList round (colsList/scale) ;
  • Texture segmentation may be accomplished using a mixture modeling (MM) technique . Segmentation may have originated in the related art based on a mixture of normals representation at the pixel level . This method may feature a far better adaptability to scene understanding and may handle even bimodal backgrounds (i . e . , means to discarding moving obj ects of non-interest in a dynamic scene) . In an attempt to mediate the computational burden required by the just noted approach, an adaptive mixture modeling approach may be implemented at the block level instead of pixel level analysis and simplified divergence measures may be introduced between the normals of incoming pixels/blocks and existing model distributions . Both alternatives may feature a far better adaptability to changes in image content and handle complex scenes .
  • MM mixture modeling
  • the present approach may use a multi-normal representation at the pixel level .
  • one does not necessarily model the pixels/blocks over-time; instead, one may model a block of pixels spatially with initialization executed on a predefined region of interest part of the iris area .
  • EM expectation-maximization
  • the present histogram algorithm may provide more reliable initial statistical ' support that facilitates fast convergence and stable performance of the distribution classification.
  • the present divergence measure may be a simplified version of the SID measure used to match criterions between normals of scanned pixels and existing model normals .
  • the measure may be a far superior measure to the fixed value (2-standard deviations) , and much more reliable than the predefined STD.
  • the measure may be for dual use, as described below, for the segmentation of the iris texture as well as for measuring similarities between iris signatures .
  • the model update may be performed using the first-in-first-out (FIFO) method while updating the weights of the model mix.
  • the update may be performed in a way that guarantees the classification of the scanned distribution in the outer, set, associated with the eyelashes 19 or eyelid 17, 18 regions (non-iris region) .
  • the present mixture modeling based concept may allow one to identify the eyelashes 19 and eyelids 17 and 18 pixels in each iris image while updating the description of each class of the iris texture' s mixture model .
  • the matched pixels may then be assembled into a continuous texture using a generic connected component algorithm.
  • Initialization 51 may be performed.
  • a goal of the initialization phase is to set initial statistical parameters for the pixel clusters corresponding the iris 13 and non-iris 50 regions with reasonable values that represent their classes ' distributions . These initial values may be used as a starting point for the dynamic changes in the pixel values across the iris 13 region and non-iris 50 regions .
  • One may extract a predefined region 52 of the iris 13 based upon the symmetry based classifier with a sufficient number of pixels and then process them before expanding to the rest of the image .
  • Each pixel 54 of the selected sub-region X may be considered as a mixture of three spatial-varying normal distributions :
  • the notation N( ⁇ 5 E,.) may represent a normal distribution with mean ⁇ and covariance matrix ⁇ .
  • the covariance matrix may be simplified to a scalar multiple of the identity matrix, i . e . , N( ⁇ ,., ⁇ ; .) .
  • the initialization 51 in Figure 14 may reveal iris distributions N( ⁇ ,, ⁇ D > - ⁇ Xp ⁇ . ) • and N( ⁇ ⁇ ,ol) as designated by 61, 62 and 63 , respectively.
  • Incoming evidence 67 from scanned pixel 54 may contribute ⁇ i (J) , ⁇ 2 (J) and ⁇ 3 (J) to distributions 61 , 62 and 63 , respectively.
  • Incoming evidence 68 from scanned pixel 54 may contribute Vi ( t) , V 2 ( t) and V 3 ( t) to distributions 64, 65 and 66, respectively.
  • Related mixture modeling methods may initialize the pixel values either with random numbers , an approximation 'algorithm, or EM algorithm.
  • the related art initialization methods appeared to be applied to time- varying distribution and even then did not appear to prove practical in most scenarios as they all appear to result in slow learning (approximation) and crude estimates (EM algorithm--a very computationally intensive technique) which usually may result, into very biased results . unless a large number of pixels is considered to bring the initialization phase under control .
  • the weights may be linearly scaled based upon the fraction of pixels of each individual class with respect the overall accumulated pixels .
  • the result may be a mixture model for three normal distributions per iris pixel with initial weights . These normal distributions may represent three potential different states for each iris pixel .
  • each iris pixel component of a pixel may be represented as a mixture of a predefined number (e . g. , three may be used throughout the experiments) of normal distributions .
  • a predefined number e . g. , three may be used throughout the experiments.
  • K 3
  • other system arrangements may require larger number of classes to cover the dynamic changes within the iris texture contrast variations . From various experiments, it appears that three normals per iris may be a sufficiently rich representation scheme to capture natural texture variation. Adding more normals appears to simply increase the computational load without improving the quality of segmentation.
  • One may have mixture model based iris segmentation.
  • the initial mixture model may be updated dynamically thereafter while scanning the entire image .
  • the update mechanism may be based on new evidence (new scanned pixels) . None of the existing iris distributions may be dropped or replaced. However, distributions' parameters may change as it is dynamically updated. As for the non- iris distributions 64, 65 and 66, one of the existing distributions may be dropped and replaced with a new distribution if there is no match. While scanning throughout the image, at every point in space the distribution with the strongest evidence may be considered to represent the pixel' s most probable iris state .
  • Figure 14 may present a visualization of the mixture of normals model . The Figure may also reveal the mixture 'modeling approach as applied to iris segmentation.
  • the present procedure may be used to update the mixing proportions weights of the mixture models with no thresholds or learning parameters .
  • the model update may be performed and weights may be updated using adaptive weighting .
  • the update may be performed in a way that guarantees the inclusion of the incoming distributions in the non-iris distribution set . Once the minimum number of occurrence is reached, the least weighted distribution of non-iris may be replaced with the new most frequent distribution.
  • the algorithm may work as follows .
  • First, the existing distributions of the predefined region of the iris may be initialized and weights may be determined based upon the fraction of the population set .
  • Second, the algorithm may select the first K 0 distributions that account for eyelash 19 , eyelids 17 and 18 , limbic and other possible items .
  • Third, the algorithm may then check for any scanned pixel value to be ascribed to any of the existing normal distributions .
  • the matching criterion that one may use is an information divergence measure which may be a key contribution of the present approach from other similar methods . A divergence measure may be described herein.
  • the algorithm may update the mixture of distributions and their parameters .
  • the nature of the update may depend on the outcome of the matching operation . If a match is found within the iris or non- iris distributions , then the matched distribution may be updated using the method of moments . If a match is not found and the minimum number is reached, then the weakest distribution of the non-iris may be replaced with a new distribution. If the minimum required number is not reached, a counter may be incremented without replacing any distributions .
  • the update performed in this case may preserve the nature of the iris distribution mixture while guaranteeing the inclusion of the new distribution in the non-iris set , which may be an aspect of the present method.
  • the matching and model updates operations may be quite involved and are described in detail in the following . There may be- the information . divergence measure .
  • the SID measure may be the symmetric measure of the relative entropy measure .
  • the SID measure may be combined with the spectral angle mapper (SAM) .
  • SAM spectral angle mapper
  • the relative entropy which is usually a logical choice in most of divergence measurements does not appear to satisfy this property and thus is not necessarily used in the present approach. With little manipulation, one may show that
  • new scanned pixels data points may be modeled with fixed predefined distributions regardless of the application and operation conditions .
  • the distribution may have had been assumed constant where these constants were based on some experimental observations .
  • Present estimates may be based on the fact that the incoming distribution is modeled as follows :
  • H(f o ,g) mm ⁇ H(f iig ) ⁇ and one may have a match between f o and g if and only if H(f j ,g) ⁇ ⁇ , where K is predefined cutoff value . This may apply for just the iris region matching . No thresholds are used if the match is in the non-iris region.
  • the weights may be updated as follows :
  • K opt may be inversely driving the selection of the learning parameter without formulating the relationship between the two variables .
  • the actual driver of the learning parameter is the resulting divergence measure and how similar the incoming distribution is to the matched class .
  • the constant K opt should not be varying so as not to bias the overall measurement .
  • ⁇ i (t) ⁇ l (t- ⁇ ) + (l- ⁇ ) ⁇ g
  • Figures 15a, 15b and 15c show a mixture modeling based analysis .
  • Figure 15a may here be regarded as a resulting rubber sheet map with respect to the. pupil 11.
  • Figure 15b shows a mixture modeling based segmentation.
  • the iris 13 may be presented in red, the eyelid 17 , 18 in green, and the eyelash 19 in blue .
  • Figure 15b may be regarded as revealing a segmentation of iris 13 versus eyelashes 19 and eyelids 17 and 18.
  • Figure 15c shows a deduced (binary) mask 71 representing the eyelashes 19 and eyelids 17 and 18.
  • Figures 16a, 16b and 16c also show a mixture modeling based analysis .
  • Figure 16a shows an iris 13 normalized rubber sheet map .
  • Figure 16b shows a segmentation, of iris 13 versus eyelashes 19 and eyelids 17 and 18.
  • Figure 16c shows a binary mask 72 representing the eyelashes 19 and eyelids 17 and 18.
  • an acquiring an image of an eye an estimating a center of the pupil, an identifying a border of the pupil , an adjusting the center of the pupil, and a segmenting an iris from the border of the pupil to at least an outside border of the iris .
  • One may further estimate a shape of the iris .
  • there may be an adjustment an eye image orientation perspective based on availability of face orientation angles . It may be noted that the terms "region” and "area” may be used interchangeably. These terms may be used interchangeably with “segment” .
  • the border, of the pupil may be. an inside border of the iris .
  • the shape of the iris may be estimated as a regular shape while extracting the irregular actual shape of the inside border and the outside border of the iris .
  • the snake delineation may be performed with one dimensional segmentation.
  • the one dimensional segmentation may be performed in a polar domain originating at about the center of the pupil .
  • the border of the pupil and the outside border of the iris may be irregular shapes .
  • the irregular shapes may be normalized in a polar map .
  • the shape of the iris may be classified into unaffected regions and affected regions which can be normalized.
  • the scaling for the normalizing of the affected regions may vary based on an obscuration by extraneous objects of the affected regions .
  • One may identify symmetric segments of the unaffected regions .
  • the affected regions may have obscured affected regions and non-obscured affected regions .
  • There may be clustering to divide the affected regions into obscured affected regions and non-obscured affected regions .
  • the clustering may be texture clustering using mixture modeling.
  • the obscured affected regions may be masked.
  • the non-obscured affected regions may be a part of a fitting mechanism.
  • An irregular actual shape may be estimated from unaffected regions and non-obscured affected regions as a regular shape .
  • the irregular actual shape may be estimated from unaffected regions and non-obscured affected regions as a regular shape with a least square fitting approach applied to an elliptic quadratic curve .
  • the least square fitting approach may include scaling the regular shape from ellipses to circles, performing a transform to determine at least one •parameter, and scaling the circles back to ellipses .
  • An irregular actual shape may be estimated from unaffected regions and non-obscured affected regions as a regular shape with elliptic fitting using overlapping variable circles .
  • An irregular actual shape may be estimated from unaffected regions and non-obscured, affected regions as a regular shape with a scaling mechanism to transfer an elliptic fitting approach into a circular fitting approach.
  • Hamming distance may be one of several approaches that may be used.
  • the affected regions and the unaffected regions may be encoded into symmetric bins and asymmetric bins , respectively. There may be matching of the symmetric bins and asymmetric bins with symmetric bins and asymmetric bins of other irises .
  • a weighting accorded a match of the symmetric bins may be significantly greater than a weighting accorded a match of the asymmetric bins .
  • a weighting accorded a match of the symmetric bins with non-symmetric bins or vice versa may be less than a weighting accorded a match of symmetric bins with symmetric bins or vice versa, and may be greater than a weighting accorded a match of the non- symmetric bins with non-symmetric bins .
  • FIG 17 illustrates an example computer system usable in conjunction with certain illustrative instances of the invention.
  • Computer system 100 may have processor (s) 102.
  • the computer system 100 may also include a memory unit 130 , processor bus 122 , and input/output controller hub (ICH) 124.
  • the processor (s) 102 , memory unit 130 , and ICH 124 may be coupled to the processor bus 122.
  • the processor (s) 102 may have a suitable processor architecture .
  • the computer system 100 may have one, two, three, or more processors, any of which may execute a set of instructions in accordance with illustrative examples of the present invention .
  • the memory unit 130 may include an operating system 140 , which includes an I/O scheduling policy manager 132 and I/O schedulers 134.
  • the memory unit 130 may store data and/or instructions , and may comprise any suitable memory, such as a dynamic random access memory (DRAM) , for example .
  • the computer system 100 may also include IDE drive (s) 108 and/or other suitable storage devices .
  • a graphics controller 104 may control the display of information on a display device 106 , according to the illustrative examples of the invention.
  • the input/output controller hub (ICH) 124 may provide an interface to I/O devices or peripheral components for the computer system 100.
  • the ICH 124 may comprise any suitable interface controller to provide for any suitable communication link to the processor (s) 102 , memory unit 130 and/or to any suitable device or component in communication with the ICH 124.
  • the ICH 124 may provide suitable arbitration and buffering for each interface .
  • the ICH 124 may provide an interface to one or more suitable integrated drive electronics (IDE) drives 108 , such as a hard disk drive (HDD) or compact disc read-only memory (CD ROM) drive, or to suitable universal serial bus (USB) devices through one or more USB ports 110.
  • IDE integrated drive electronics
  • the ICH 124 may also provide an interface to a keyboard 112 , a mouse 114 , a CD-ROM drive 118 , and one or more suitable devices through one or more firewire ports 116.
  • the ICH : 124 may also provide a network interface 120 though which the computer system 100 can communicate with other computers and/or devices .
  • the computer system 100 may include a machine-readable medium that stores a set of instructions (e .g . , software) embodying any one, or all , of the methodologies for dynamically loading obj ect modules described herein.
  • software may reside, completely or at least partially, within memory unit 130 and/or within the processor (s) 102.

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Abstract

L'invention concerne un système de segmentation unidimensionnelle de l'iris d'un oeil dans une carte de l'iris et de classification de cette carte en zones non affectées et en zones affectées. Ce système comprend éventuellement le cadre adapté de forme régulière des zones destiné à la normalisation et à l'identification des zones non affectées comme des segments symétriques. En outre, ce système peut affecter des pondérations aux zones non affectées et aux zones affectées de la carte de l'iris et une carte déroulée de l'iris et leurs cases correspondant aux objectifs de mise en correspondance.
PCT/US2006/003104 2005-01-26 2006-01-26 Systeme de tetereconnaissance d'un iris WO2006081505A1 (fr)

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JP2007553302A JP4767971B2 (ja) 2005-01-26 2006-01-26 距離虹彩認識システム
EP06734016A EP1842152B1 (fr) 2005-01-26 2006-01-26 Systeme de tetereconnaissance d'un iris

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