# US 12,217,530 B2 · Under-display ultrasonic fingerprint sensors for foldable displays > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,217,530 B2 - Document ID: US12217530B2 - Status: Granted - Kind: B2 - Application number: 18/302,241 - Filed: 2023-04-18 - Published: 2023-08-10 - Granted: 2025-02-04 - Earliest claimed: 2021-08-30 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Shiang-Chi Lin; Hrishikesh Vijaykumar Panchawagh; Jessica Liu Strohmann; Yipeng Lu; Chin-Jen Tseng; Kostadin Dimitrov Djordjev; Min-Lun Yang; Chia-Wei Yang - Web page: https://patentgrep.com/patent/US12217530B2 ## CPC - G06V 40/1306: {non-optical, e.g. ultrasonic or capacitive sensing} - G01S 7/52079: {Constructional features (constructional features of transducers B06B; mounting transducers G10K11/00; constructional features of ultrasonic medical diagnostic devices A61B8/44)} - G06F 1/1637: {Details related to the display arrangement, including those related to the mounting of the display in the housing} - G06F 1/1684: {Constructional details or arrangements related to integrated I/O peripherals not covered by groups G06F1/1635 - G06F1/1675} - G06F 3/043: using propagating acoustic waves - G06F 21/32: using biometric data, e.g. fingerprints, iris scans or voiceprints - G06F 2203/04102: Flexible digitiser, i.e. constructional details for allowing the whole digitising part of a device to be flexed or rolled like a sheet of paper - G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract An apparatus may include an ultrasonic sensor stack, a foldable display stack and a transmission enhancement layer. The foldable display stack may include a display stiffener and display stack layers. The display stack layers may form one or more display stack resonators configured to enhance ultrasonic waves transmitted by the ultrasonic sensor stack in a first ultrasonic frequency range. In some implementations, a transmission enhancement resonator may include the display stiffener and the transmission enhancement layer. In some examples, the transmission enhancement resonator may include at least a portion of the ultrasonic sensor stack. The transmission enhancement resonator may be configured to enhance the ultrasonic waves transmitted by the ultrasonic sensor stack in the first ultrasonic frequency range. ## Claims ### Claim 1 An apparatus, comprising: an ultrasonic sensor stack; a display stack, comprising: a high-impedance layer having an acoustic impedance of 10 MRayls or more; and display stack layers configured to cause ultrasonic waves transmitted by the ultrasonic sensor stack to have one or more display stack-induced local amplitude maxima in a first ultrasonic frequency range; and a transmission enhancement layer, wherein the high-impedance layer and the transmission enhancement layer comprise a transmission enhancement resonator configured to cause the ultrasonic waves transmitted by the ultrasonic sensor stack to have a transmission enhancement resonator-induced local amplitude maximum in the first ultrasonic frequency range; wherein the transmission enhancement resonator-induced local amplitude maximum corresponds to a frequency in a range from 5 MHz to 15 MHz. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the transmission enhancement resonator has a thickness corresponding to a multiple of a half wavelength of a shear wave or a longitudinal wave having a frequency in the first ultrasonic frequency range. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the display stack layers include one or more display stack resonators and wherein the one or more display stack resonators are configured to cause the one or more display stack-induced local amplitude maxima. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein the one or more display stack resonators includes a first resonator bounded by the high-impedance layer and a glass layer of the display stack. ### Claim 5 (depends on 4) The apparatus of claim 4, wherein the first resonator includes a plurality of layers of an organic light-emitting diode display. ### Claim 6 (depends on 4) The apparatus of claim 4, wherein the one or more display stack resonators includes a second resonator bounded by the glass layer and an outer surface of the display stack. ### Claim 7 (depends on 1) The apparatus of claim 1, further comprising a control system configured to cause the ultrasonic sensor stack to transmit first ultrasonic waves in the first ultrasonic frequency range and to perform an authentication process based, at least in part, on ultrasonic sensor signals corresponding to reflections of the first ultrasonic waves. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the transmission enhancement layer resides between the ultrasonic sensor stack and the high-impedance layer. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the transmission enhancement layer has a thickness of less than a quarter wavelength of a shear wave or a longitudinal wave having a frequency in the first ultrasonic frequency range. ### Claim 10 (depends on 1) The apparatus of claim 1, wherein the transmission enhancement layer comprises an aluminum layer having an aluminum layer thickness in a range from 50 microns to 100 microns, a copper layer having a copper layer thickness in a range from 25 microns to 50 microns or a stainless steel layer having a stainless steel layer thickness in the range from 25 microns to 50 microns. ### Claim 11 (depends on 1) The apparatus of claim 1, further comprising a first adhesive layer residing between the transmission enhancement layer and the high-impedance layer and a second adhesive layer residing between the transmission enhancement layer and the ultrasonic sensor stack. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein at least one of the first adhesive layer or the second adhesive layer has a thickness in a range from 3 microns to 10 microns. ### Claim 13 (depends on 1) The apparatus of claim 1, wherein the ultrasonic sensor stack includes a thin-film transistor (TFT) substrate and wherein the transmission enhancement resonator includes the TFT substrate. ### Claim 14 (depends on 13) The apparatus of claim 13, wherein the TFT substrate has a thickness of less than a quarter wavelength of a shear wave or a longitudinal wave having a frequency in the first ultrasonic frequency range. ### Claim 15 (depends on 13) The apparatus of claim 13, wherein the TFT substrate has a thickness in a range from 50 microns to 200 microns. ### Claim 16 (depends on 13) The apparatus of claim 13, wherein the TFT substrate comprises glass. ### Claim 17 (depends on 13) The apparatus of claim 13, wherein: the TFT substrate has a first acoustic impedance value; the high-impedance layer has a second acoustic impedance value that is greater than the first acoustic impedance value; and the transmission enhancement layer has a third acoustic impedance value that is greater than the first acoustic impedance value. ### Claim 18 (depends on 1) The apparatus of claim 1, wherein the high-impedance layer comprises one or more of a metal layer or a non-metal layer having an acoustic impedance of 10 MRayls or more. ### Claim 19 (depends on 1) The apparatus of claim 1, wherein the high-impedance layer has a thickness in a range from 30 microns to 300 microns. ### Claim 20 (depends on 1) The apparatus of claim 1, wherein the high-impedance layer has a thickness corresponding to a multiple of a half wavelength of a shear wave or a longitudinal wave having a frequency in a second ultrasonic frequency range that is higher than the first ultrasonic frequency range. ### Claim 21 (depends on 1) The apparatus of claim 1, wherein the apparatus is a mobile device that includes the ultrasonic sensor stack, the display stack and the transmission enhancement layer. ### Claim 22 (depends on 1) The apparatus of claim 1, wherein the transmission enhancement layer includes at least a portion of the ultrasonic sensor stack. ### Claim 23 An apparatus, comprising: ultrasonic sensor means; a display stack, comprising: a high-impedance layer; and one or more display stack resonators configured to enhance ultrasonic waves transmitted by the ultrasonic sensor means in a first ultrasonic frequency range; and a transmission enhancement layer, the high-impedance layer, the transmission enhancement layer and at least a portion of the ultrasonic sensor means forming a transmission enhancement resonator configured to enhance the ultrasonic waves transmitted by the ultrasonic sensor means in the first ultrasonic frequency range. ### Claim 24 (depends on 23) The apparatus of claim 23, wherein the transmission enhancement resonator has a thickness corresponding to a multiple of a half wavelength of a shear wave or a longitudinal wave having a frequency in the first ultrasonic frequency range. ### Claim 25 (depends on 23) The apparatus of claim 23, wherein enhancing an ultrasonic wave in the first ultrasonic frequency range comprises causing a local maximum of the ultrasonic wave in the first ultrasonic frequency range. ### Claim 26 A method, comprising: controlling, via a control system, an ultrasonic transceiver layer of an ultrasonic sensor system to transmit ultrasonic waves through at least a first resonator configured for causing a first local maximum of ultrasonic wave transmission in a first ultrasonic frequency range and a second resonator configured for causing a second local maximum of ultrasonic wave transmission in the first ultrasonic frequency range, the first resonator including a high-impedance layer and a transmission enhancement layer, the high-impedance layer having an acoustic impedance of 10 MRayls or more, the second resonator including one or more display stack layers; receiving, by the control system and from the ultrasonic sensor system, ultrasonic sensor signals corresponding to reflections of transmitted ultrasonic waves from a portion of a target object positioned on an outer surface of an apparatus that includes the ultrasonic sensor system; and performing, by the control system, an authentication process based, at least in part, on the ultrasonic sensor signals. ### Claim 27 (depends on 26) The method of claim 26, wherein the local maximum of ultrasonic wave transmission corresponds to a frequency in a range from 5 MHz to 15 MHz. ### Claim 28 (depends on 26) The method of claim 26, wherein the authentication process involves extracting target object features from the ultrasonic sensor signals. ### Claim 29 (depends on 28) The method of claim 28, wherein the target object features include at least one of fingerprint features or sub-epidermal features. ### Claim 30 (depends on 26) The method of claim 26, further comprising controlling access to the apparatus based, at least in part, on the authentication process.