Under-display ultrasonic fingerprint sensors for foldable displays

Patent metadata

Field	Value
Publication number	US-11798307-B2
Application number	US-202117446436-A
Country	US
Kind code	B2
Filing date	Aug 30, 2021
Priority date	Aug 30, 2021
Publication date	Oct 24, 2023
Grant date	Oct 24, 2023

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.

First claim

The invention claimed is:

1. An apparatus, comprising:
an ultrasonic sensor stack;
a foldable display stack, comprising:
a display stiffener; 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 display stiffener 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.

2. 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.

3. 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.

4. The apparatus of claim 3 , wherein the one or more display stack resonators includes a first resonator bounded by the display stiffener and a glass layer of the foldable display stack.

5. The apparatus of claim 4 , wherein the first resonator includes a plurality of layers of an organic light-emitting diode display.

6. 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 foldable display stack.

7. The apparatus of claim 1 , wherein the transmission enhancement resonator-induced local amplitude maximum corresponds to a frequency in a range from 5 MHz to 15 MHz.

8. 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.

9. The apparatus of claim 1 , wherein the transmission enhancement layer resides between the ultrasonic sensor stack and the display stiffener.

10. 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.

11. 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.

12. The apparatus of claim 1 , further comprising a first adhesive layer residing between the transmission enhancement layer and the display stiffener and a second adhesive layer residing between the transmission enhancement layer and the ultrasonic sensor stack.

13. The apparatus of claim 12 , 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.

14. 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.

15. The apparatus of claim 14 , 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.

16. The apparatus of claim 14 , wherein the TFT substrate has a thickness in a range from 50 microns to 200 microns.

17. The apparatus of claim 14 , wherein the TFT substrate comprises glass.

18. The apparatus of claim 14 , wherein:
the TFT substrate has a first acoustic impedance value;
the display stiffener 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.

19. The apparatus of claim 1 , wherein the display stiffener comprises one or more of a metal layer or a non-metal layer having an acoustic impedance of 10 MRayls or more.

20. The apparatus of claim 1 , wherein the display stiffener has a thickness in a range from 30 microns to 300 microns.

21. The apparatus of claim 1 , wherein the display stiffener 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.

22. The apparatus of claim 1 , wherein the apparatus is a mobile device that includes the ultrasonic sensor stack, the foldable display stack and the transmission enhancement layer.

23. The apparatus of claim 1 , wherein the transmission enhancement layer includes at least a portion of the ultrasonic sensor stack.

24. An apparatus, comprising:
ultrasonic sensor means;
a foldable display stack, comprising:
a display stiffener; 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 display stiffener, 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.

25. The apparatus of claim 24 , 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.

26. The apparatus of claim 24 , 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.

27. 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 display stiffener layer and a transmission enhancement layer, 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.

28. The method of claim 27 , wherein the local maximum of ultrasonic wave transmission corresponds to

Assignees

• Qualcomm Inc

Inventors

• Lin Shiang-Chi
• Panchawagh Hrishikesh Vijaykumar
• Strohmann Jessica Liu
• Lu Yipeng
• Tseng Chin-Jen
• Djordjev Kostadin Dimitrov
• Yang Min-Lun
• Yang Chia-Wei

Classifications

• G06V40/1306 Primary

  non-optical, e.g. ultrasonic or capacitive sensing · CPC title

• G01S7/52079

  Constructional features (constructional features of transducers B06B; mounting transducers G10K11/00; constructional features of ultrasonic medical diagnostic devices A61B8/44) · CPC title

• G06F21/32 Primary

  using biometric data, e.g. fingerprints, iris scans or voiceprints · CPC title

• G06F1/1637

  Details related to the display arrangement, including those related to the mounting of the display in the housing · CPC title

• G06F3/043

  using propagating acoustic waves · CPC title