A method for biometric processing of images of part of the human body having papillary ridges for fraud detection aimed at determining that the imaged part of the human body is authentic, said biometric processing method being performed by a sensor comprising: - an automated data-processing system, - an emissive screen comprising an array of individually controllable pixels, the state of the pixels defining a display pattern of the emissive screen, - a substrate on which are disposed elements sensitive to light constituting an imager and sharing the orientation of the emissive screen, said sensor comprising a surface adapted to receive in contact a part of the human body to be imaged, said emissive screen being configured to light said part of the human body to be imaged when said part of the human body is in contact with the surface, said method comprising the steps according to which, to acquire images of part of the human body having papillary ridges on contact with the surface: - the emissive screen displays at least one first display pattern to light said part of the human body and the imager acquires at least one first image of said part of the human body, - from this first image, the automated data-processing system determines at least one second display pattern different to the first display pattern, the determination of the second pattern comprising analysis of the first image to locate a representation (32, 33) of the part of the human body in said first image, and determination of the second pattern comprises positioning lighting zones (42, 43, 62, 72) in the second pattern corresponding to the location of the representation of the part of the human body in the first image, said lighting zones of the second pattern comprising luminous geometric figures (62, 72) which are distinct and separate, - the emissive screen displays at least the second pattern to light said part of the human body so that said part of the human body in contact with the surface is illuminated by said lighting zones when the emissive screen displays the second pattern, and the imager acquires at least one second image of said part of the human body, - biometric processing is performed on a final image constructed from at least the second image, said biometric processing comprising performing a method for fraud detection aimed at determining that the imaged part of the human body is authentic by means of representations in the second image of projections of the luminous geometric figures of the second pattern. - an automated data-processing system, - an emissive screen comprising an array of individually controllable pixels, the state of the pixels defining a display pattern of the emissive screen, - a substrate on which are disposed elements sensitive to light constituting an imager and sharing the orientation of the emissive screen, - the emissive screen displays at least one first display pattern to light said part of the human body and the imager acquires at least one first image of said part of the human body, - from this first image, the automated data-processing system determines at least one second display pattern different to the first display pattern, the determination of the second pattern comprising analysis of the first image to locate a representation (32, 33) of the part of the human body in said first image, and determination of the second pattern comprises positioning lighting zones (42, 43, 62, 72) in the second pattern corresponding to the location of the representation of the part of the human body in the first image, said lighting zones of the second pattern comprising luminous geometric figures (62, 72) which are distinct and separate, - the emissive screen displays at least the second pattern to light said part of the human body so that said part of the human body in contact with the surface is illuminated by said lighting zones when the emissive screen displays the second pattern, and the imager acquires at least one second image of said part of the human body, - biometric processing is performed on a final image constructed from at least the second image, said biometric processing comprising performing a method for fraud detection aimed at determining that the imaged part of the human body is authentic by means of representations in the second image of projections of the luminous geometric figures of the second pattern.