Fingerprint sensors having in-pixel optical sensors

• US 10,732,771 B2
• Filed: 12/24/2014
• Issued: 08/04/2020
• Est. Priority Date: 11/12/2014
• Status: Active Grant

• Current Assignee: Shenzhen Goodix Technology Co., Ltd.
• Original Assignee: Shenzhen Goodix Technology Co., Ltd.
• Inventors: Yang, Meng-Da, Pi, Bo
• Primary Examiner(s): Vaughn, Jr., William C
• Assistant Examiner(s): Baptiste, Jerry Jean
• Application Number:
  US14/583,048
• Publication Number:
  US 20160132712A1
• Time in Patent Office: 2,050 Days
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1318 using electro-optical elements or layers, e.g. electroluminescent sensing
• CPC Class Codes: G06V 40/15 Biometric patterns based on physiological signals, e.g. heartbeat, blood flow
• CPC Class Codes: G06V 40/70 Multimodal biometrics, e.g. combining information from different biometric modalities

Abstract

In one aspect, a fingerprint sensor device for fingerprint detection includes a light source configured to emit light at a wavelength. The fingerprint sensor device includes an array of sensor pixels to acquire an optical image indicative of a fingerprint. Each sensor pixel includes a photodetector to detect the emitted light reflected off of a target finger and output an optical signal based on the detected reflected light. Each sensor pixel includes a collimator disposed over the photodetector to direct the reflected light in a substantially vertical direction from above the photodetector toward the photodetector. Each sensor pixel includes sensor signal detection circuitry communicatively coupled to the photodetector to acquire the outputted optical signal.

Claims

1. A fingerprint sensor device for fingerprint detection, comprising:

a light source that emits light at a wavelength; and

an array of sensor pixels located to receive and detect light which includes emitted light from the light source to acquire an optical image indicative of a fingerprint and to reeive a capacitive image indicative of the fingerprint,

each sensor pixel including;

a photodetector configured to detect the emitted light reflected off of a target finger and output a photodetector signal based on the detected reflected light;

different collimators coupled to the photodetector, each collimator structured to include an optical transmission path with a small numerical aperture to collect and direct the reflected light from above the photodetector toward the photodetector in incident directions along the optical transmission path without an optical lens while blocking incident light in incident directions at large angles with respect to the optical transmission path, wherein the different collimators to allow the collimators to block light that directly comes from the light emitting diode from emitting each photodetector;

an electrically conductive electrode that can be capacitively coupled to a local part of the touched portion of the finger, forming a fingerprint associated capacitor that outputs a capacitive signal representing a respective capacitive value for the fingerprint that is separate from the photodetector signal from a photodetector within the same sensor pixel representing a portion of an optical image indicative of the fingerprint, wherein the array of sensor pixels is located to capacitively couple with a touched portion of a finger to form an array of fingerprint associated capacitors having capacitive values indicative of a fingerprint; and

sensor signal detection circuitry communicatively coupled to the photodetector to receive the photodetector signal and to receive the capacitive signal.

2. The fingerprint sensor device of claim 1, wherein the light source includes a light emitting diode located at a peripheral location outside an area of the different collimators to allow the collimators to collect only light from the above the photodetector in incident directions along optical transmission paths of the different collimators.

3. The fingerprint sensor device of claim 1, comprising metal electrodes that are patterned to form the collimators, wherein each metal electrode is structured to form a hole through the metal electrode as a collimator.

4. The fingerprint sensor device of claim 1, wherein the different collimators coupled to a corresponding photodetector include an optical fiber bundle.

5. The fingerprint sensor device of claim 1, including:

sensor switching circuitry coupled to the sensor signal detection circuitry and operable to switch between electrically connecting the sensor signal detection circuitry to the photodetector to receive the photodetector signal and to the electrically conductive electrode to receive the capacitive signal, within a sensor pixel.

6. The fingerprint sensor device of claim 5, wherein the sensor signal detection circuitry includes:

an integrator electrically coupled to the sensor switching circuitry to integrate electrical charges associated with the fingerprint associated capacitor responsive to a touch by a finger of a user or the photodetector signal from the photodetector.

7. The fingerprint sensor device of claim 6, wherein the integrator comprises:

a reference voltage generator configured to generate a reference voltage;

an amplifier, comprising;

a positive input terminal electrically coupled to the reference voltage generator to receive the reference voltage;

a negative input terminal electrically coupled to the sensor switching circuitry; and

an output terminal of the amplifier;

an integrating capacitor electrically coupled between the negative input terminal and the output terminal of the amplifier; and

a reset switch electrically coupled between the negative input terminal and the output terminal of the amplifier.

8. The fingerprint sensor device of claim 7, wherein the reference voltage generator is configured to vary the generated reference voltage.

9. The fingerprint sensor device of claim 8, wherein the reference voltage generator includes a digital to analog converter to vary the generated reference voltage.

10. The fingerprint sensor device of claim 1, wherein the capacitive signal associated with the fingerprint associated capacitor represents information on a ridge or a valley of a finger.

11. The fingerprint sensor device of claim 1, further comprising:

a sensor processor coupled to receive an output of the sensor signal detection circuitry based on photodetector signals generated from sensing collected light at the photodetectors carrying information on the heartbeat of a user and process the received output to measure the heart beat.

22. The fingerprint sensor device of claim 1, comprising:

different metal layers that are stacked and patterned to form the collimators.

23. The fingerprint sensor device of claim 1, comprising:

different layers of metal grids with openings to form the collimators.

24. The fingerprint sensor device of claim 1, comprising:

a silicon-based on multilayer structure that includes (1) bottom layers patterned to form photodetectors of the sensor pixels and (2) one or more metal layers formed over the bottom layers as the collimators have vertical optical transparent passages to collect and direct light to the photodetectors.

25. The fingerprint sensor device of claim 1, wherein, in each sensor pixel, the electrically conductive electrode is located above a corresponding photodetector within the same sensor pixel and includes a hole to allow transmission of light from the electrically conductive electrode to the photodetector.

26. The fingerprint sensor device of claim 1, wherein, in each sensor pixel, the electrically conductive electrode is located side by side with a corresponding photodetector within the same sensor pixel.

12. A fingerprint sensor device for fingerprint identification, comprising:

an array of sensor pixel circuitry arranged to form groups of electrically connected sensor pixel circuitry operable to capture fingerprint pattern of a touched portion of a finger, each sensor pixel circuitry in the array including;

a light source that emits light at a wavelength;

a photodetector located to receive and to detect the emitted light reflected off of the touch portion of the finger to produce a photodetector signal indicating a portion of an optical image of fingerprint of the finger; and

an electrically conductive electrode located to be capable of being capacitively coupled to a local part of the touched portion of the finger to form a fingerprint associated capacitor to produce a capacitive signal representing a respective capacitive value at the local part of the finger as a separate representation of the fingerprint from the photodetector signal within the same sensor pixel circuitry, wherein the electrically conductive electrode is disposed above the photodetector and structured to form a hole through the electrically conductive electrode to collimate the reflected light in a vertical direction from above the electrically conductive electrode toward the photodetector; and

sensor signal detection circuitry coupled to the array of sensor pixel circuitry to receive capacitive signals and photodetector signals and operable to capture the fingerprint pattern based on the capacitive signals and photodetector signals.

13. The fingerprint sensor device of claim 12, further comprising:

sensor switching circuitry configured to switch between electrically connecting the sensor signal detection circuitry to the photodetector and to the electrically conductive electrode in each sensor pixel circuitry;

wherein the sensor signal detection circuitry is configured to acquire an optical signal form the photodetector when electrically connected to the photodetector through the sensor switching circuitry and to acquire a capacitive signal from the electrically conductive electrode when electrically connected to the electrically conductive electrode.

14. The fingerprint sensor device of claim 13, wherein the sensor signal detection circuitry includes:

an integrator to store electrical charges associated with the charged fingerprint associated capacitor responsive to a touch by a finger of a user.

15. The fingerprint sensor device of claim 14, wherein the integrator comprises:

a reference voltage generator configured to generate a reference voltage;

an amplifier, comprising;

a positive input terminal electrically coupled to the reference voltage generator to receive the reference voltage;

a negative input terminal electrically coupled to the sensor switching circuitry; and

an output terminal of the amplifier;

an integrating capacitor electrically coupled between the negative input terminal and the output terminal of the amplifier; and

a reset switch electrically coupled between the negative input terminal and the output terminal of the amplifier.

16. The fingerprint sensor device of claim 13, wherein:

the sensor switching circuitry is operable to generate a control signal to control each sensor pixel circuitry in the array to integrate the output signal in each sensor pixel circuitry in the array in parallel.

17. The fingerprint sensor device of claim 12, further comprising:

a sensor processor coupled to receive an output of the sensor signal detection circuitry based on an output of the photodetector of one or more sensor pixels and process the received output to measure a heart beat of a user from light reflected from a finger of the user that is detected by the photodetector in the one or more sensor pixels.

18. A method for operating a fingerprint sensor device to detect a fingerprint, the method comprising:

detecting, by an array of sensor pixel circuitry in the fingerprint sensor device in which each sensor pixel includes a capacitive sensor and an optical sensor, capacitance values detected by capacitor sensors in different sensor pixels at different locations associated with a touch from a finger indicative of a fingerprint;

detecting, by optical sensors in the array of sensor pixel circuitry in the fingerprint sensor device, optical signals at the different locations associated with light reflected from the finger, wherein the optical signals collectively represent an optical image of the fingerprint;

outputting, by the array of sensor pixel circuitry, output signals that represent the detected capacitance values and optical signals; and

processing output signals to perform fingerprint identification, wherein processing the output signals includes enhancing the capacitive image to provide more information on valleys and ridges of the fingerprint by interpolating or recovering based on high resolution spatial information in the optical image.

19. The method of claim 18, wherein processing the output signals includes processing the output signals to acquire an optical image of the fingerprint and a capacitive image of the fingerprint.

20. The method of claim 19, comprising:

storing the acquired optical image and capacitive image as two types of registered fingerprint images for comparing scanned fingerprints during fingerprint identification.

21. The method of claim 19, wherein processing the output signals includes using the optical image to recover information on the ridges of the fingerprint in the capacitive image.