US-12616386-B1 - Integrated circuit for photoplethysmography (PPG)

Abstract

In some embodiments, an apparatus comprises: a first die comprising one or more image sensors; a second die comprising one or more light emitters; one or more through package vias (TPVs), wherein a TPV of the one or more TPVs is configured to allow light emitted from at least one light emitter of the one or more light emitters to pass through the first die; and a controller. The controller may be configured to: cause the at least one light emitter to emit light, through the TPV of the one or more TPVs, toward a tissue of a user; determine one or more characteristics of reflected light captured by at least one image sensor of the one or more image sensors; and determine photoplethysmography (PPG) data for the user based on the determined one or more characteristics of the reflected light.

Inventors

• Manoj Bikumandla
• Andrew Matthew Bardagjy
• Ajay Bikumandla

Assignees

• META PLATFORMS TECHNOLOGIES, LLC

Dates

Publication Date

20260505

Application Date

20220204

Claims (20)

1. 1 . An apparatus, comprising: a first die comprising one or more image sensors; a second die comprising one or more light emitters; one or more through package vias (TPVs), wherein a TPV of the one or more TPVs is configured to allow light emitted from at least one light emitter of the one or more light emitters to pass through the first die; and a controller configured to: cause the at least one light emitter to emit light, through the TPV of the one or more TPVs, toward a tissue of a user; determine one or more characteristics of reflected light captured by at least one image sensor of the one or more image sensors; and determine photoplethysmography (PPG) data for the user based on the determined one or more characteristics of the reflected light.
2. 2 . The apparatus of claim 1 , wherein the TPV of the one or more TPVs is filled with a high-index light guide material such that the TPV couples light from the at least one light emitter.
3. 3 . The apparatus of claim 1 , further comprising a wire grid polarizer above the first die.
4. 4 . The apparatus of claim 3 , wherein the wire grid polarizer comprises a plurality of orientations.
5. 5 . The apparatus of claim 4 , wherein the plurality of orientations are each arranged on a different portion of the wire grid polarizer.
6. 6 . The apparatus of claim 1 , where the one or more light emitters comprise one or more vertical cavity surface-emitting lasers (VCSELs).
7. 7 . The apparatus of claim 1 , wherein at least a subset of the one or more light emitters emit light in an infrared wavelength.
8. 8 . The apparatus of claim 7 , wherein the infrared wavelength is within a range of about 870 nanometers-970 nanometers.
9. 9 . The apparatus of claim 1 , wherein at least a subset of the one or more light emitters emit light in a red wavelength.
10. 10 . The apparatus of claim 9 , wherein the red wavelength is within a range of about 630 nanometers to 680 nanometers.
11. 11 . The apparatus of claim 1 , wherein the one or more image sensors comprise one or more CMOS image sensors.
12. 12 . The apparatus of claim 11 , wherein a CMOS image sensor of the one or more CMOS image sensors comprises two transfer gates.
13. 13 . The apparatus of claim 1 , wherein the controller is further configured to: receive a first set of samples by activating and deactivating a first image sensor of the one or more image sensors with a first waveform having a predetermined frequency and in phase with a pulsed waveform; and receive a second set of samples by activating and deactivating the first image sensor with a second waveform having the predetermined frequency and out of phase with the pulsed waveform.
14. 14 . The apparatus of claim 13 , wherein the controller is further configured to determine a DC offset of the PPG data based on an average of two samples of the first set of samples.
15. 15 . The apparatus of claim 13 , wherein the controller is further configured to determine a phase of the PPG data based on a ratio of a sample of the first set of samples to a sample of the second set of samples.
16. 16 . The apparatus of claim 11 , wherein a CMOS image sensor of the one or more CMOS image sensors is a 4T CMOS image sensor.
17. 17 . A method, comprising: causing at least one light emitter to emit light toward a tissue of a user, wherein a first die comprises the at least one light emitter, and wherein light emitted from the at least one light emitter passes through one or more through package vias (TPVs) and through a second die that comprises one or more image sensors; determining one or more characteristics of reflected light captured by at least one image sensor of the one or more image sensors; and determining photoplethysmography (PPG) data for the user based on the determined one or more characteristics of the reflected light.
18. 18 . The method of claim 17 , wherein causing the one or more light emitters to emit light towards the tissue of the user comprises causing the one or more light emitters to emit light as a pulsed waveform having a predetermined frequency, and wherein the method further comprises: receiving a first set of samples associated with a first transfer gate of the two transfer gates by activating and deactivating the first transfer gate of the two transfer gates with a first waveform having the predetermined frequency and in phase with the pulsed waveform; and receiving a second set of samples associated with a second transfer gate of the two transfer gates by activating and deactivating the second transfer gate of the two transfer gates with a second waveform having the predetermined frequency and 90 degrees out of phase with the pulsed waveform.
19. 19 . The method of claim 18 , further comprising determining a DC offset of the PPG data based on an average of two samples of the first set of samples.
20. 20 . The method of claim 18 , further comprising determining a phase of the PPG data based on a ratio of a sample of the first set of samples to a sample of the second set of samples.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 17/217,672, filed Mar. 30, 2021, titled “INTEGRATED CIRCUIT FOR PHOTOPLETHYSMOGRAPHY (PPG),” which is herein incorporated by reference in its entirety for all purposes. BACKGROUND Photoplethysmography (PPG) is a technique that is used to estimate various physiological characteristics of a user, such as heart rate, oxygen saturation, heart rate variability, etc. Conventional devices that perform PPG suffer from several drawbacks. For example, conventional devices may produce PPG data that is of poor quality due to being noisy or containing artifacts. For example, PPG data may be of poor quality due to ambient light incident on a light sensor used by a PPG device. Poor quality PPG data may produce inaccurate estimates of physiological characteristics. This may be problematic, because users of conventional PPG devices may rely on the PPG device to produce accurate estimates of physiological characteristics, for example, to monitor health conditions. SUMMARY This disclosure relates generally to an integrated circuit for photoplethysmography (PPG). According to certain embodiments, an apparatus may comprise: a first die comprising one or more image sensors; a second die comprising one or more light emitters; one or more through package vias (TPVs), wherein a TPV of the one or more TPVs is configured to allow light emitted from at least one light emitter of the one or more light emitters to pass through the first die; and a controller configured to: cause the at least one light emitter to emit light, through the TPV of the one or more TPVs, toward a tissue of a user; determine one or more characteristics of reflected light captured by at least one image sensor of the one or more image sensors; and determine photoplethysmography (PPG) data for the user based on the determined one or more characteristics of the reflected light. In some embodiments, the TPV of the one or more TPVs is filled with a high-index light guide material such that the TPV couples light from the at least one light emitter. In some embodiments, the apparatus may further comprise comprising a wire grid polarizer above the first die. In some embodiments, the wire grid polarizer comprises a plurality of orientations. In some embodiments, the wire grid polarizer is fabricated from a single mask, and wherein an orientation of the plurality of orientations is determined based on a portion of the single mask that has been etched away. In some embodiments, the one or more light emitters comprise one or more edge vertical cavity surface-emitting lasers (e-VCSELs). In some embodiments, at least a subset of the one or more light emitters emit light in an infrared wavelength. In some embodiments, the infrared wavelength is within a range of about 870 nanometers-970 nanometers. In some embodiments, at least a subset of the one or more light emitters emit light in a red wavelength. In some embodiments, the red wavelength is within a range of about 630 nanometers to 680 nanometers. In some embodiments, the one or more image sensors comprise one or more CMOS image sensors. In some embodiments, a CMOS image sensor of the one or more CMOS image sensors comprises two transfer gates. In some embodiments, causing the one or more light emitters to emit light towards the tissue of the user comprises causing the one or more light emitters to emit light as a pulsed waveform having a predetermined frequency, and the controller is further configured to: receive a first set of samples associated with a first transfer gate of the two transfer gates by activating and deactivating the first transfer gate of the two transfer gates with a first waveform having the predetermined frequency and in phase with the pulsed waveform; and receive a second set of samples associated with a second transfer gate of the two transfer gates by activating and deactivating the second transfer gate of the two transfer gates with a second waveform having the predetermined frequency and 90 degrees out of phase with the pulsed waveform. In some embodiments, the controller is further configured to determine a DC offset of the PPG data based on an average of two samples of the first set of samples. In some embodiments, the controller is further configured to determine a phase of the PPG data based on a ratio of a sample of the first set of samples to a sample of the second set of samples. In some embodiments, a CMOS image sensor of the one or more CMOS image sensors is a 4T CMOS image sensor. According to some embodiments, an apparatus may comprise: one or more image sensors; a wire grid polarizer associated with the one or more image sensors; one or more light emitters; a wire grid polarizer associated with the one or more light emitters; and a controller. The controller may be configured to: cause at least one light emitter of the one or more light emitters to emit light toward a tissue of a use