Self-mixing interferometry-based head-mounted respiration sensing

A method for determining a respiration characteristic, comprising:

• operating an optical sensor subsystem to cause a set of one or more non-contact self-mixing interferometry (SMI) sensors in the optical sensor subsystem to emit a set of one or more beams of light toward a skin surface of a user;
• receiving a set of one or more SMI signals from the set of one or more non-contact SMI sensors;
• performing at least one integration of each of the received set of one or more SMI signals to generate a set of one or more integrated SMI signals;
• and
• determining the respiration characteristic based on a subset of one or more integrated SMI signals of the set of one or more integrated SMI signals.

A device, comprising:

• a head-mountable frame;
• an optical sensor subsystem mounted to the head-mountable frame and including,
• a set of one or more self-mixing interferometry (SMI) sensors, each SMI sensor of the set of one or more SMI sensors positioned on the head-mountable frame to be spaced a respective distance from a skin surface of a user when the head-mountable frame is worn by the user;
• and
• a collimator positioned in an optical path of at least one SMI sensor in the set of one or more SMI sensors;
• and
• a processor configured to:
• operate the optical sensor subsystem to obtain a set of one or more SMI signals from the set of one or more SMI sensors;
• and
• determine a respiration characteristic of the user based at least in part on the set of one or more SMI signals.