On Thursday, the US Patent & Trademark Office published a patent application from Apple that relates to improving sensitivity, functionality, accuracy, speed of sensor operations and reliability of  using health sensors in all manner of wearable devices (Apple Watch, Smartglasses, HMD) as well as future iPhones, iPad and a host of other devices including a vehicle, home appliances and door locks, robots and more.

Embodiments described in this patent filing are directed to wearable devices, systems, and methods of determining a health parameter of a user, using sensors in the wearable devices. In some embodiments, one or more optical sensors are positioned on devices such as a watch, smartphone, cuff, earbud, smartglasses, XR headset or other device can be used to measure health metrics of a user.

For example, heart rate and peripheral oxygen saturation (SpO2) can be measured using infrared (IR), red, and green light-emitting diodes (LEDs). In other embodiments, non-optical sensors, such as piezoelectric or acoustic sensors, can also be used to measure health metrics, and can enable continuous or on-demand health metric measuring or monitoring.

Non-optical sensors are interesting because of their potential to reduce power consumption requirements beyond what is possible with optical sensors. This can be advantageous in that consumer products typically face challenges in terms of size, battery life, and so on. Any reduction in a device's power consumption requirements can be beneficial in terms of extending the device's use between battery charges, and/or enabling the device to operate with a battery having a reduced size or weight.

Further, two or more piezoelectric polyvinylidene fluoride (PVDF) sensors and/or acoustic sensors may be integrated into a wearable device and used to obtain relevant signals for health sensing. The wearable device may be watches, phones, earbuds, glasses, tablet computers, sleep products (e.g., in-bed sensor mats), cuffs (e.g., blood pressure cuffs), chest straps, and the like.

This arrangement works by measuring physiological health parameters and rejecting unrelated external noises that affect the signals associated with the physiological health parameters. This enables external noise interferences to be attenuated, thus improving signal to noise ratio (SNR) and enabling localized micro vibration sensing at low power consumption compared to optical sensors. Health metrics information can be extracted from sensed signals after subtracting out external aggressors (e.g., noise), and in some embodiments, applying filtering to an acquired signal, to determine a user's heart rate (HR), respiration rate, the presence of micro vibrations, and so on. In some embodiments, multiple types of sensors may be included in a device to improve SNR and/or reduce power consumption.

Relevant sensors to improve signal quality include microphones, piezoelectric PVDF sensors, capacitive gap sensors, strain gauges, accelophones, and accelerometers. Such sensors may increase a sensing bandwidth, sensitivity, SNR, or dynamic range or linearity of the measured physiological health parameters. Such sensors may be used to acquire a user's HR, ballistocardiogram (BCG)/seismocardiogram (SCG), respiratory motion, lung sounds, and so on. A user's respiration rate may be measured using seismocardiography. Such sensors can be less susceptible to body perspiration, environmental acoustic noise, motion artifacts, and so on. In some embodiments, such sensors may be a companion to optical sensing and may be switched ON or OFF depending on an optical SNR. 

In Apple's patent FIGS. 1B and 1C below the sensor system in the wearable device (#100: Apple Watch) may include multi-pixel PVDF, strain, or capacitive gap sensors 130, 132, 134, and 136 embedded in or around the back cover 114 (e.g., around the second back cover portion 114-2) to measure alternating current (AC) lung and heart signals.

This arrangement can be used to measure partial thromboplastin time (PTT), respiration rate (RR), or heart rate (HR), by measuring and rejecting external noises through the multi-location sensor arrangement. This multi-pixel arrangement can also be used to detect whether Apple Watch is being worn and/or a tightness of the watch while worn, or to detect a quality of contact between the skin of the user and the watch, or to detect any rotation, skew, or an orientation of the watch.

Apple's patent FIG. 1C above illustrates a new multi-pixel sensor being added to a future Apple Watch band.  

Apple's patent FIG. 2 below illustrates a perspective front view of an iPhone having sensors for determining a health parameter of the user and alternative bio-authentication sensors. According to Apple, these sensors could also be applied to a home door lock, thermostat, refrigerator or other home appliance, vehicle navigation system, a robot navigation system, an iPad and more.

In some embodiments, such as FIG. 3 below, a user may wear a pair of the wearable devices #300, in the form of separate earbuds, or different earphone housings of a headset, and so on. In these embodiments, environmental and/or physiological signals specific to each side of a user's head (e.g., each ear) can be measured.

In such embodiments, an accurate and precise clock/crystal embedded within each wearable device 300 or housing 308 can be used to synchronize and align time-stamped and/or time series measurements obtained from the sensors #314 of different wearable devices or housings.

For example, timings of changes in the signals produced by the sensors #314 can indicate air movement (e.g., pressure changes or acoustic propagation). As another example, this can enable measurement of temperature between the two ears by measuring the heat flux between the two ears using temperature sensors (e.g., sensors 3#14) in contact with the user (e.g., flexible thermopile sensors embedded inside or on the surface of the housing #308 on each of a user's ears or on each side of the user's head), and extrapolation of the core body temperature of the user.

Apple's patent FIG. 4 below illustrates a perspective front view of yet another example wearable device 400 having sensors for determining a health parameter of the user of the wearable device 400. The wearable device 400 may be a pair of glasses, smartglasses, and the like.

Further to Apple's patent FIG. 4, a multi-pixel sensor system #416 may include a first sensor #422 and a second sensor #424 mounted to the wearable device #400. In non-limiting embodiments, the first sensor is configured to detect a change in vibration, motion, or radiation associated with a physiological measurement of the user and generate a first signal based on the physiological measurement.

The second sensor is configured to sense a mechanical wave in an ambient environment of the wearable device and generate a second signal that may be used as a reference to measure and reject external noise aggressors. Both the 1st and 2nd sensors may, in some embodiments, be connected to controller #426 that monitors a user's activity or health.

For more details, review Apple's patent application # US 20230064273 A1. The lead inventor on the patent is listed as Meagan Spencer: Manager, Health Product Design.