Cross-Optical Property Image Translation for Face Anti-Spoofing: From Visible to Polarization

Despite the development of spectral sensors and spectral data-driven learning methods which have led to significant advances in face anti-spoofing (FAS), the singular dimensionality of spectral information often results in poor robustness and weak generalization. Polarization, another fundamental property of light, can reveal intrinsic differences between genuine and fake faces with advantaged performance in precision, robustness, and generalizability. In this paper, we propose a facial image translation method from visible light (VIS) to polarization (VPT), capable of generating valuable polarimetric optical characteristics for facial presentation attack detection using VIS spectrum information input only. Specifically, the VPT method adopts a multi-stream network structure, comprising a main network and two branch networks, to translate VIS images into degree of polarization (DoP) images and Stokes polarization parameters S₁ and S₂. To further improve image translation quality, we introduce a frequency-domain consistency loss as a complement to the existing spatial losses to narrow the gap in the frequency domain. The physical mapping relations for the DoP and Stokes parameters are employed, and the Stokes loss is designed to ensure that the generated polarization modalities conform to objective physical laws. Extensive experiments on the CASIA-Polar and CASIA-SURF datasets demonstrate the superiority of VPT over other baseline methods in terms of polarization image quality and its remarkable performance in the FAS task. This work leverages the inherent physical advantages of polarization information in material discrimination tasks while addressing hardware limitations in polarization image collection, proposing a novel solution for face recognition system security control.