Optical device for determining pulse rate
AssigneeFitbit, Inc.
InventorsJung Ook Hong, Shelten Gee Jao Yuen
Life of this patent
Estimating the term…
Abstract
Some embodiments provide a wearable monitoring device including a motion sensor and a photo (PPG) sensor. The PPG sensor includes (i) a periodic light source, (ii) a photo detector, and (iii) circuitry determining a user's heart rate from an output of the photo detector. Some embodiments provide methods for operating a heart rate monitor of a wearable monitoring device to measure one or more characteristics of a heartbeat waveform. Some embodiments provide methods for operating the wearable monitoring device in a low power state when the device determines that the device is not worn by a user.
Claims13
A wearable monitoring device, comprising:
- a housing having a physical size and shape that is adapted to couple to a body of a user, wherein the housing comprises a photo sensor housing that protrudes above a base surface of the wearable monitoring device so as to press against skin of the user when worn;
- a periodic light source and a photo detector positioned to receive periodic light emitted by the periodic light source;
- a first light pipe, disposed in the housing and optically coupled to the periodic light source, to direct or transmit light from the periodic light source along a predetermined path to an outer surface of the housing;
- and
- processing circuitry configured to calculate a heart rate of the user using data generated by the periodic light source, wherein the processing circuitry is configured to:
- (i) emit a first set of one or more light pulses in a wavelength using the periodic light source;
- (ii) determine a slope of a detected light value versus an emitted light value for the first set of the one or more pulses;
- (iii) choose a new emitted light value based on the determined slope;
- (iv) when the first set of one or more light pulses interacts with the user's skin or tissue and the first set of one or more light pulses is detected by the photo detector, initiate operation of the wearable monitoring device in a first mode at the new emitted light value;
- and
- (v) when the first set of one or more light pulses is not detected by the photo detector or when the first set of one or more light pulses has a different intensity or pattern from a baseline intensity or pattern, initiate operation of the wearable monitoring device in a second mode, the second mode having a lower power state than the first mode.
Dependencies are inferred from the claim text.