We propose a new iris presentation attack detection method using three-dimensional features of an observed iris region estimated by photometric stereo. Our implementation uses a pair of iris images acquired by a common commercial iris sensor (LG 4000). No hardware modifications of any kind are required. Our approach should be applicable to any iris sensor that can illuminate the eye from two different directions. Each iris image in the pair is captured under near-infrared illumination at a different angle relative to the eye. Photometric stereo is used to estimate surface normal vectors in the non-occluded portions of the iris region. The variability of the normal vectors is used as the presentation attack detection score. This score is larger for a texture that is irregularly opaque and printed on a convex contact lens, and is smaller for an authentic iris texture. Thus the problem is formulated as binary classification into (a) an eye wearing textured contact lens and (b) the texture of an actual iris surface (possibly seen through a clear contact lens). Experiments were carried out on a database of approx. 2,900 iris image pairs acquired from approx. 100 subjects. Our method was able to correctly classify over 95 of samples when tested on contact lens brands unseen in training, and over 98 of samples when the contact lens brand was seen during training. The source codes of the method are made available to other researchers.
An idea based on photometric stereo approach and illumination from different directions was proposed by Lee and Park @cite_14 . They use the fact that the surface of a live iris is not perfectly flat and so will cast shadows when illuminated from different directions. In turn, a flat iris printout does not cast shadows. Properties of the surface estimated by photometric stereo method are then used to distinguish between a live iris and a flat printout. The method proposed in this paper is different from the above method since it is designed for detection of textured contact lenses (not paper printouts) and it makes different assumptions on three-dimensional properties of the observed objects. In our method, and for image resolutions used in commercial systems, we assume that iris is more flat than the artifacts (textured contact lenses) we want to detect. This is an opposite assumption to the one made by Lee and Park, and the photometric stereo is applied in different ways in both methods.
@cite_14
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A new fake iris detection method based on 3D feature of iris pattern is proposed. In pervious researches, they did not consider 3D structure of iris pattern, but only used 2D features of iris image. However, in our method, by using four near infra-red (NIR) illuminators attached on the left and right sides of iris camera, we could obtain the iris image in which the 3D structure of iris pattern could be shown distinctively. Based on that, we could determine the live or fake iris by wavelet analysis of the 3D feature of iris pattern. Experimental result showed that the Equal Error Rate (EER) of determining the live or fake iris was 0.33p. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 162–166, 2010