Anti-spoofing sensing for rejecting fake fingerprint patterns in under-screen optical sensor module for on-screen fingerprint sensing

1. An electronic device capable of detecting a fingerprint by optical sensing, comprising:

a screen that provides touch sensing operations and includes a display panel structure to display images;

a top transparent layer formed over the device screen as an interface for being touched by a user for the touch sensing operations and for transmitting the light from the display structure to display images to a user;

an optical sensor module located below the display panel structure to receive probe light that passes through the screen to detect a fingerprint; and

a capacitive sensor array coupled to the screen to measure capacitance signals as a capacitive anti-spoofing sensor for rejecting a fake fingerprint pattern,

wherein the optical sensor module includes:

an optical sensor array of optical detectors to convert the received light from the top transparent layer and display panel that carries a fingerprint pattern of the user into detector signals representing the fingerprint pattern,

a pinhole layer located between the display panel and the optical sensor array and structured to include a single pinhole that is structured to produce a large optical field of view in collecting the received light and to transmit the collected light towards the optical sensor array, and

a lens located between the pinhole layer and the optical sensor array to receive the transmitted light from the single pinhole and to focus the received light onto the optical sensor array for optical imaging at an enhanced spatial imaging resolution at the optical sensor array in comparison with a lower spatial imaging resolution when using the pinhole to project light onto the optical sensor array without the lens.

2. The device as in claim 1 , wherein

the optical sensor module includes one or more optical filtering layers to transmit probe light for optical sensing of fingerprints while blocking background day light at optical wavelengths longer than the probe light.

3. The device as in claim 1 , wherein the screen is a LCD screen.

4. The device as in claim 1 , wherein the screen is an OLED screen.

5. The device as in claim 1 , wherein

the capacitive sensor array is configured to measure an image contrast in the capacitance signals as a capacitive anti-spoofing sensor for rejecting a fake fingerprint pattern.

6. The device as in claim 1 , wherein

the capacitive sensor array is configured to measure an integrated signal strength in the capacitance signals as a capacitive anti-spoofing sensor for rejecting a fake fingerprint pattern.

7. An electronic device capable of detecting a fingerprint by optical sensing, comprising:

a screen that provides touch sensing operations and includes a display panel structure to display images;

a top transparent layer formed over the device screen as an interface for being touched by a user for the touch sensing operations and for transmitting the light from the display structure to display images to a user; and

an optical sensor module located below the display panel structure to receive probe light that passes through the screen and configured (1) to detect a fingerprint by detecting and extracting an image carried by the received probe light and (2) to measure optical absorption signals at different optical wavelengths associated with different optical absorption characteristics by human blood at the different optical wavelengths for rejecting a fake fingerprint pattern free of human blood, wherein the optical sensor module includes an optical sensor array of optical detectors to convert the received light from the top transparent layer and display panel that carries a fingerprint pattern of the user into detector signals representing the fingerprint pattern, a pinhole layer located between the display panel and the optical sensor array and structured to include a single pinhole that is structured to produce a large optical field of view in collecting the received light and to transmit the collected light towards the optical sensor array, and a lens located between the pinhole layer and the optical sensor array to receive the transmitted light from the single pinhole and to focus the received light onto the optical sensor array for optical imaging at an enhanced spatial imaging resolution at the optical sensor array in comparison with a lower spatial imaging resolution when using the pinhole to project light onto the optical sensor array without the lens.

8. The device as in claim 7 , wherein

the optical sensor module includes one or more optical filtering layers to transmit probe light for optical sensing of fingerprints while blocking background day light at optical wavelengths longer than the probe light.

9. The device as in claim 7 , wherein the screen is a LCD screen.

10. The device as in claim 7 , wherein the screen is an OLED screen.

11. A method for operating an electronic device that includes an optical sensor module for optically detecting a fingerprint and a capacitive fingerprint senor module for capacitively detecting the fingerprint, comprising:

operating a capacitive fingerprint sensor module having an array of capacitive sensors to obtain capacitive sensor signals representing an input fingerprint pattern of an object;

processing the obtained capacitive sensor signals to obtain a capacitive sensor signal parameter that includes a capacitive signal strength, an image constructed from the obtained capacitive sensor signals or an image contrast of the image constructed from the obtained capacitive sensor signals;

applying the capacitive sensor signal parameter to determine whether the object is a finger of a live user;

operating an optical fingerprint sensor module to optically sense whether the object is a finger of a live user and to obtain an optical image of fingerprint of the object;

combining measurements by both the optical fingerprint sensor module and the capacitive fingerprint sensor module to authenticate whether a measured fingerprint is from a finger of a live user and whether the fingerprint is from an authorized user,

operating the optical fingerprint sensor module to obtain an optical image of the object;

processing the obtained optical image of the object to determine whether the obtained optical image is a composition of two different images; and

denying access when the obtained optical image is a composition of two different images.

12. The method as in claim 11 , wherein the operation of the optical fingerprint sensor module to optically sense whether the object is a finger of a live user includes:

illuminating the object with light at two different optical wavelengths at which human blood exhibits different optical absorption characteristics; and

using optical measurements obtained at the two different optical wavelengths to determine whether the object is a finger of a live user based on the different optical absorption characteristics in the optical measurements at the two different optical wavelengths.

13. The method as in claim 11 , wherein the operation of the optical fingerprint sensor module to optically sense whether the object is a finger of a live user includes:

operating the optical fingerprint sensor module to capture different fingerprint patterns of the object at different times to monitor time-domain evolution of a pattern deformation that indicates time-domain evolution of a press force from the object to determine whether the object is a finger of a live user.

14. The method as in claim 11 , further comprising:

operating the capacitive fingerprint sensor module first before turning on the optical fingerprint sensor module to use the capacitive sensor signal parameter as a trigger for turning the optical fingerprint sensor module.

15. The method as in claim 11 , further comprising:

turning on the capacitive fingerprint sensor module for capacitive sensing without turning on the optical fingerprint sensor module; and

using a result of the capacitive sensing as trigger to determine whether or not to turn on the optical fingerprint sensor module for optical sensing.

16. The method as in claim 11 , further comprising:

turning on both the capacitive fingerprint sensor module for capacitive sensing and the optical fingerprint sensor module for optical sensing to perform the capacitive sensing and the optical sensing in parallel; and

using results of both the capacitive sensing and optical sensing to determine whether to grant access to the electronic device.

17. A method for operating an electronic device that includes an optical sensor module for optically detecting a fingerprint and a capacitive fingerprint senor module for capacitively detecting the fingerprint, comprising:

operating a capacitive fingerprint sensor module having an array of capacitive sensors to obtain capacitive sensor signals representing an input fingerprint pattern of an object;

processing the obtained capacitive sensor signals to obtain an image of the input fingerprint pattern;

operating an optical fingerprint sensor module to optically sense whether the object is a finger of a live user based on based on different optical absorption characteristics of human blood at different optical wavelengths and to obtain an optical image of the input fingerprint pattern of the object;

combining measurements by both the optical fingerprint sensor module and the capacitive fingerprint sensor module to authenticate whether a measured fingerprint is from a finger of a live user and whether the fingerprint is from an authorized user;

processing the obtained optical image of the object to determine whether the obtained optical image is a composition of two different images; and

denying access when the obtained optical image is a composition of two different images.

18. The method as in claim 17 , further comprising:

turning on the capacitive fingerprint sensor module for capacitive sensing without turning on the optical fingerprint sensor module; and

using a result of the capacitive sensing as trigger to determine whether or not to turn on the optical fingerprint sensor module for optical sensing.

19. The method as in claim 17 , further comprising:

turning on both the capacitive fingerprint sensor module for capacitive sensing and the optical fingerprint sensor module for optical sensing to perform the capacitive sensing and the optical sensing in parallel; and

using results of both the capacitive sensing and optical sensing to determine whether to grant access to the electronic device.

20. The method as in claim 17 , further comprising:

processing the obtained capacitive sensor signals to also obtain a capacitive sensor signal parameter that includes a capacitive signal strength, an image constructed from the obtained capacitive sensor signals or an image contrast of the image constructed from the obtained capacitive sensor signals; and

applying the capacitive sensor signal parameter to determine whether the object is a finger of a live user.

21. The method as in claim 17 , further comprising:

operating the optical fingerprint sensor module to capture different fingerprint patterns of the object at different times to monitor time-domain evolution of a pattern deformation that indicates time-domain evolution of a press force from the object.