Biometric optical antispoofing based on imaging through a transmission angular dependent optical filter

A method for biometric authentication of a biometric object using a biometric imaging arrangement comprising:

• an image sensor comprising a photodetector pixel array configured to detect light transmitted from the object for capturing an image, and
• an optical filter assembly comprising at least an interference filter arranged to cover the photodetector pixel array and being adapted to at least partly block infrared light from reaching the photodetector pixel array,
• the optical filter assembly further being adapted to have at least a first variable cut-off wavelength in the visible range of wavelengths, wherein the first variable cut-off wavelength depends on the angle of incidence of the received light on the optical filter assembly and is tailored for liveness detection,
• wherein the method comprises:
• acquiring an image of the object;
• and
• performing biometric authentication based on an evaluation of the radial distribution of wavelengths in the acquired image, or, based on a radial distribution of intensities in the acquired image.

A biometric imaging arrangement configured to acquire an image of an object, the biometric imaging arrangement comprising:

• an image sensor comprising a photodetector pixel array configured to detect light transmitted from the object for capturing an image;
• an optical filter assembly comprising at least an optical interference filter, the optical filter assembly being arranged to cover the photodetector pixel array, and the optical filter assembly having an infrared cut-off wavelength to at least partly block infrared light from reaching the photodetector pixel array;
• and
• the optical filter assembly further having at least a first variable cut-off wavelength in the visible range of wavelengths, wherein the first cut-off wavelength depends on the angle of incidence of the received light on the optical filter assembly and is tailored for liveness detection,
• wherein the biometric imaging arrangement is configured to perform biometric authentication based on:
• (i) a radial distribution of wavelengths in an acquired image, or (ii) a radial distribution of intensities in an acquired image.