# US 12,112,568 B2 · Biometric optical antispoofing based on imaging through a transmission angular dependent optical filter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,112,568 B2 - Document ID: US12112568B2 - Status: Granted - Kind: B2 - Application number: 18/030,399 - Filed: 2021-10-14 - Published: 2023-11-23 - Granted: 2024-10-08 - Earliest claimed: 2020-10-23 - Assignees: Fingerprint Cards Anacatum IP AB - Applicants: Fingerprint Cards Anacatum IP AB - Inventors: Petter Östlund - Web page: https://patentgrep.com/patent/US12112568B2 ## CPC - G06V 40/1394: {using acquisition arrangements} - G02B 5/281: {designed for the infrared light} - G06V 10/143: Sensing or illuminating at different wavelengths - G06V 40/13: Sensors therefor - G06V 40/1318: {using electro-optical elements or layers, e.g. electroluminescent sensing} - G06V 40/1324: {by using geometrical optics, e.g. using prisms (G06V40/1312 takes precedence)} - G06V 40/1382: {Detecting the live character of the finger, i.e. distinguishing from a fake or cadaver finger} - G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A biometric imaging arrangement configured to acquire an image of an object 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, the optical filter assembly further having at least a first 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. ## Claims ### Claim 1 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, 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 optical filter is adapted to have a second cut-off wavelength in the visible range of wavelengths, wherein the second cut-off wavelength depends on the angle of incidence of the received light on the optical filter assembly. ### Claim 2 (depends on 1) The biometric imaging arrangement according to claim 1, wherein the optical filter assembly is adapted to at least partly block light within a blocking subrange of the visible wavelength range, wherein the blocking subrange cut-off wavelengths depends on the angle of incidence of the received light on the optical filter assembly. ### Claim 3 (depends on 1) The biometric imaging arrangement according to claim 1, wherein the first cut-off wavelength is in the red range of visible light and the second cut-off wavelength is in the blue range of visible light. ### Claim 4 (depends on 1) The biometric imaging arrangement according to claim 1, wherein the optical filter assembly is adapted to block infrared light for all incident angles. ### Claim 5 (depends on 1) The biometric imaging arrangement according to claim 1, wherein the optical filter assembly comprises an absorptive filter for blocking infrared light. ### Claim 6 (depends on 1) The biometric imaging arrangement according to claim 1, wherein the optical filter assembly covers the entire photodetector pixel array of the image sensor. ### Claim 7 (depends on 1) The biometric imaging arrangement according to claim 1, configured to perform biometric authentication based on a radial distribution of wavelengths in an acquired image, or, based on a radial distribution of intensities in an acquired image. ### Claim 8 (depends on 1) The biometric imaging arrangement according to claim 1, configured to be arranged under an at least partly transparent display panel and to acquire an image of an object located on the opposite side of the least partly transparent panel. ### Claim 9 (depends on 1) An electronic device comprising: an at least partly transparent display panel; the biometric imaging arrangement according to claim 1, and processing circuitry configured to: receive a signal from the biometric imaging arrangement indicative of a biometric object touching the at least partly transparent display panel, perform a biometric authentication procedure based on the detected biometric object. ### Claim 10 (depends on 9) The electronic device according to claim 9, wherein the electronic device is a mobile device. ### Claim 11 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. ### Claim 12 (depends on 11) The method according to claim 11, wherein the biometric authentication is based on an intensity of red light detected by one of a first set of photodetector pixels and a second set of photodetector pixels compared to the intensity of light detected by the other one of the first set of photodetector pixels and the second set of photodetector pixels. ### Claim 13 (depends on 12) The method according to claim 12, wherein biometric authentication is based on a relation between the intensity of the detected red light compared to an intensity of blue and/or green light detected by the other one of the first and second set of photodetector pixels. ### Claim 14 (depends on 11) The method according to claim 11, wherein the first set of pixels are inner photodetector pixels and the second set of pixels are outer photodetector pixels, where the inner photodetector pixels are closer to the center of the photodetector pixel array than the outer photodetector pixels. ### Claim 15 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. ### Claim 16 (depends on 15) The biometric imaging arrangement according to claim 15, wherein the optical filter assembly is adapted to at least partly block light within a blocking subrange of the visible wavelength range, wherein the blocking subrange cut-off wavelengths depends on the angle of incidence of the received light on the optical filter assembly. ### Claim 17 (depends on 15) The biometric imaging arrangement according to claim 15, wherein the optical filter assembly is adapted to block infrared light for all incident angles. ### Claim 18 (depends on 15) The biometric imaging arrangement according to claim 15, wherein the optical filter assembly comprises an absorptive filter for blocking infrared light. ### Claim 19 (depends on 15) The biometric imaging arrangement according to claim 15, wherein the optical filter assembly covers the entire photodetector pixel array of the image sensor. ### Claim 20 (depends on 15) An electronic device comprising: an at least partly transparent display panel; the biometric imaging arrangement according to claim 15, and processing circuitry configured to: receive a signal from the biometric imaging arrangement indicative of a biometric object touching the at least partly transparent display panel, and perform a biometric authentication procedure based on the detected biometric object.