An optical scanning system (1500) includes a cover plate layer (1510), an illumination subsystem (1520), an optical sensor (1530), and a processor (1550). The optical scanning system (1500) is configured such that, in a bright and dark pattern corresponding to a pattern of contact between the object (1540) and the contact surface (1515), direct illumination light incident on the defined sensing area is diverted onto the optical sensor (1530) by internal specular reflection of the contact surface (1515). Covering of direct illumination light in a region of the contact surface (1515) suppressesspecular reflection in the region such that optical information is directed from the region to the optical sensor (1530) only by non-specular reflection. Three-dimensional (real) and two-dimensional (spoofing) objects typically exhibit different optical responses to lack of specular reflections in the obscured area, which can be used to detect such spoofing.
Anti-spoofing performed on two-dimensional false object in optical sensing module by using light and shade inversion imaging