Today the US Patent & Trademark Office published a patent application from Apple that relates to wearable self-mixing interferometry (SMI) ring used to sense physiological conditions of a user, such as a heart rate, blood oxygen saturation, blood pressure and more. In some embodiments, the ring could support an OLED display with indicator lights. The ring could be a health device that's an alternative to Apple Watch to some degree. And while we're on the topic of health devices, Apple was also granted a patent for the ECG feature for Apple Watch. 

Apple describes the ring as possibly providing input structures such as switches, buttons, touch screen inputs, voice inputs, and so on. For example, the wearable device (ring #102) including touch sensors and/or force sensors (e.g., integrated into one or more displays of these devices).

Further, the input structures of ring may detect force and/or touch inputs, whether static or motions, speed, direction, force, displacement, or other parameters of gestures applied to the input regions, including taps, swipes, multi-finger inputs, single- or multi-finger touch gestures, presses, and the like. Such user inputs may be used to control or modify the operation of the ring.

The core of the patent covers the self-mixing interferometry sensor(s) (SMI). The sensor may include an emitter positioned within the housing and configured to output coherent light toward a skin of the user when the housing is worn by the user. The sensor may also include a detector configured to detect a portion of coherent light reflected towards the sensor and generate electrical signals that indicate displacements of the skin based on the portion of coherent light. The electronic device may further include a transmitter operatively coupled with the sensor and configured to transmit physiological data based on the electrical signals.

Apple's patent FIG. 1 below shows an example of a physiological monitoring system that includes a wearable device in the form of a ring and an iPhone; FIG. 3 shows an example of a wearable device that includes an SMI sensor and is positioned on a finger of a user.

Apple's patent FIG. 5A above illustrates a detailed view of the positioning and interaction of the SMI sensor relative to a finger of a user; and FIG. 9 illustrates an example processes flow for using an SMI sensor to detect one or more physiological parameters of a user.

Below are 20 Technical Points about Apple's Invention

• An electronic device, comprising: a housing configured to be worn by a user; a sensor contained within the housing and comprising: an emitter positioned in the housing and configured to output coherent light toward a skin of the user when the housing is worn by the user; a detector configured to detect a portion of the coherent light that is reflected towards the sensor, and further configured to generate electrical signals corresponding to displacements of the skin, the electrical signals at least partly based on the portion of coherent light; and a transmitter operatively coupled with the sensor and configured to transmit the data from the electrical signals.
• The electronic device's housing comprises a band configured to wrap around a body part of the user and maintain a gap between the emitter and a skin surface of the user when the housing is worn by the user; the emitter comprises a vertical cavity surface emitting laser (VCSEL); the transmitter is further configured to wirelessly transmit the data from the electronic device; and the data comprises a time indicator that associates a displacement of the skin with a relative time of an electrical signal of the electrical signals generated by the detector.
• The electronic device's processing unit is configured to determine a heart rate of the user from the electrical signals.
• The electronic device further comprises a display configured to output a visual representation of the heart rate.
• The electronic device's detector is configured to detect the portion of coherent light that is reflected from the skin of the user.
• The electronic device's  membrane is positioned between the emitter and the skin of the user; wherein: the detector is configured to detect the portion of coherent light that is reflected from the membrane.
• The electronic device's membrane contacts the skin of the user when the housing is worn by the user; and the membrane is configured to move in response to movement of the skin.
• The electronic device's membrane comprises a reflective surface configured to direct the coherent light towards the detector.
• The electronic device further comprises a lens coupled with the housing and configured to focus the coherent light on the skin when the housing contacts the skin of the user.
• The electronic device's housing comprises a skin support configured to contact the skin of the user; and the emitter is offset from the skin support.
• The electronic device's emitter and the detector comprise a same structure.
• The electronic device comprises the following: a sensor comprising: an emitter configured to output coherent light toward a skin of a user when the electronic device is worn by the user; and a detector configured to detect a portion of the coherent light reflected from the user and generate electrical signals based on the portion of the coherent light; a housing containing the sensor and configured to position the emitter at a first distance from the skin of the user, the housing comprising a user interface configured to contact the skin of the user; and a transmitter positioned within the housing and operatively coupled with the sensor, the transmitter configured to transmit physiological data based on the electrical signals.
• The electronic device's UI is positioned adjacent to the sensor and is configured to contact the skin of the user, thereby maintaining a gap between the skin and the emitter.
• The electronic device's housing further comprises a membrane configured to be positioned between the emitter and the skin when the housing contacts the user.
• The electronic device's membrane is configured to reflect the coherent light outputted by the emitter back to the detector.
• The electronic device's emitter is a vertical cavity surface emitting laser (VCSEL); the detector is the VCSEL; and the VCSEL is configured to output the electrical signals based on a difference between the outputted coherent light and the portion of coherent light reflected from the user.
• The electronic device's  detector comprises a resonant cavity photodetector; and the resonant cavity photodetector comprises a circular structure positioned around the emitter.
• A method for tracking movement of a skin of a user, the method comprising: transmitting coherent light from a self-mixing interferometer (SMI) and towards a skin surface of the user; detecting a portion of the coherent light reflected toward the SMI; generating, at the SMI, an electrical signal based on the detected portion of the coherent light; determining displacements of the skin based on the electrical signal; and outputting a heart rate for the user based on the displacements of the skin.
• The method also includes displacements of the skin are tracked for a first duration; and outputting the heart rate comprises identifying heartbeats of the user for the first duration.
• The method further comprises displaying a visual output of the heart rate to the user based on the outputting.

For more details, review Apple's patent application number US 20220386955 A1.

Apple's Inventors

Ahmet Faith Cihan: Senior Optical HW Engineer

Mengshu Huang: Laser Sensing HW Design

Yuhao (Roy) Pan: Product Design Engineer

Adrian Harb:  No LinkedIn Profile available