Fast 3-D fingertip reconstruction using a single two-view structured light acquisition

Current contactless fingertip recognition systems based on three-dimensional finger models mostly use multiple views (N >; 2) or structured light illumination with multiple patterns projected over a period of time. In this paper, we present a novel methodology able to obtain a fast and accurate three-dimensional reconstruction of the fingertip by using a single two-view acquisition and a static projected pattern. The acquisition setup is less constrained than the ones proposed in the literature and requires only that the finger is placed according to the depth of focus of the cameras, and in the overlapping field of views. The obtained pairs of images are processed in order to extract the information related to the fingertip and the projected pattern. The projected pattern permits to extract a set of reference points in the two images, which are then matched by using a correlation approach. The information related to a previous calibration of the cameras is then used in order to estimate the finger model, and one input image is wrapped on the resulting three-dimensional model, obtaining a three-dimensional pattern with a limited distortion of the ridges. In order to obtain data that can be treated by traditional algorithms, the obtained three-dimensional models are then unwrapped into bidimensional images. The quality of the unwrapped images is evaluated by using a software designed for contact-based fingerprint images. The obtained results show that the methodology is feasible and a realistic three-dimensional reconstruction can be achieved with few constraints. These results also show that the fingertip models computed by using our approach can be processed by both specific three-dimensional matching algorithms and traditional matching approaches. We also compared the results with the ones obtained without using structured light techniques, showing that the use of a projector achieves a faster and more accurate fingertip reconstruction.