Robust Iris-Localization Algorithm in Non-Cooperative Environments Based on the Improved YOLO v4 Model.

Iris localization in non-cooperative environments is challenging and essential for accurate iris recognition. Motivated by the traditional iris-localization algorithm and the robustness of the YOLO model, we propose a novel iris-localization algorithm. First, we design a novel iris detector with a modified you only look once v4 (YOLO v4) model. We can approximate the position of the pupil center. Then, we use a modified integro-differential operator to precisely locate the iris inner and outer boundaries. Experiment results show that iris-detection accuracy can reach 99.83% with this modified YOLO v4 model, which is higher than that of a traditional YOLO v4 model. The accuracy in locating the inner and outer boundary of the iris without glasses can reach 97.72% at a short distance and 98.32% at a long distance. The locating accuracy with glasses can obtained at 93.91% and 84%, respectively. It is much higher than the traditional Daugman's algorithm. Extensive experiments conducted on multiple datasets demonstrate the effectiveness and robustness of our method for iris localization in non-cooperative environments.

[Hardening correction model of energy spectrum for X-ray TICT in testing composites workpiece].

In the case of a polychromatic source in X-ray TICT, the variation of attenuation coefficient with energy leads to low energy radiation being absorbed preferentially. In other words, the higher the energy, the lower the attenuation coefficient. With the transmission thickness augmenting, it is easier for X-ray to transmit the matter. The phenomenon is energy spectrum hardening. Thus, hardening correction has to be done. In the present paper, not only is energy spectrum hardening analyzed by theory and the relation stated between attenuation coefficient and transmission thickness in testing composites workpiece, but also the precise accurate theory model for hardening correction of energy spectrum and theory method are reasoned out in testing composites workpiece, which results from Beer's law and the characteristics of X-ray interaction with composites. Then, the attenuation coefficient that has been corrected is used for product back-projection reconstruction. Thus, the effect caused by X-ray beam hardening is wipped out effectively in testing composites workpiece.