PPG Sensor Having Light Arrival Angle Control at Detector

Abstract

The present disclosure generally relates to wearable devices and methods for measuring a photoplethysmographic (PPG) signal. The wearable devices and methods described herein are capable of obtaining PPG signals by employing a PPG sensor array configured to receive light at angles associated with a high perfusion index. Viewing components may be coupled to the PPG sensor array to effect transmission of light at these preferential angles.

What is claimed is: 
     
         1 . A wearable device for monitoring a physiological parameter of an individual, comprising:
 a housing having a skin-contacting surface;   one or more light emitters located to emit light from the skin-contacting surface;   one or more light sensors, wherein each light sensor is configured to detect light that has interacted with a tissue region of the individual at one or more preselected angles of incidence;   one or more viewing components optically coupled to the one or more light sensors and configured to allow light with the one or more preselected angles to pass through to the one or more light sensors; and   a processor within the housing and in communication with the one or more light sensors, wherein the processor is configured to compute the physiological parameter based on light detected from the one or more light sensors.   
     
     
         2 . The device of  claim 1 , wherein each of the one or more viewing components allow light at a different preselected angle of incidence to pass through. 
     
     
         3 . The device of  claim 1 , wherein a first one or more viewing components is disposed over a first of the one or more light sensors and transmits light at a first preselected angle of incidence, and
 a second of the one or more viewing components is disposed over a second set of the one or more light sensors and transmits light at a second preselected angle of incidence.   
     
     
         4 . The device of  claim 1 , wherein a first of the one or more light sensors is configured to detect light having a first preselected angle of incidence, wherein the first preselected angle of incidence is selected based on a first separation distance between the first of the one or more light sensors and a first of the one or more light emitters configured to emit light of a first wavelength. 
     
     
         5 . The device of  claim 4 , wherein a second of the one or more light sensors is configured to detect light having a second preselected angle of incidence, wherein the second preselected angle of incidence is selected based on a second separation distance between the second of the one or more light sensors and a second of the one or more light emitters configured to emit light of a second wavelength. 
     
     
         6 . The device of  claim 5 , wherein the first preselected angle of incidence is different from the second preselected angle of incidence. 
     
     
         7 . The device of  claim 5 , wherein the first wavelength is the same as the second wavelength, the first separation distance is different from the second separation distance, and the first preselected angle of incidence is different from the second preselected angle of incidence. 
     
     
         8 . The device of  claim 5 , wherein the first wavelength is different from the second wavelength, the first separation distance is the same as the second separation distance, and the first preselected angle of incidence is different from the second preselected angle of incidence. 
     
     
         9 . The device of  claim 5 , wherein the first wavelength is different from the second wavelength, the first separation distance is different from the second separation distance, and the first preselected angle of incidence is different from the second preselected angle of incidence. 
     
     
         10 . The device of  claim 5 , wherein the first wavelength is different from the second wavelength, the first distance is different from the second distance, and the first preselected angle of incidence is the same as the second preselected angle of incidence. 
     
     
         11 . The device of  claim 5 , wherein the processor receives first data from the first of the one or more light sensors and second data from the second of the one or more light sensors,
 wherein the first data and the second data each comprise physiological data pertaining to the same tissue region, and   wherein the processor is configured to compute the physiological parameter based on the physiological data.   
     
     
         12 . The device of  claim 1 , wherein the one or more light sensors include a first set of light sensors configured to measure a first wavelength and a second set of light sensors configured to measure a second wavelength,
 wherein at least one of the first set of light sensors is configured to have the same preselected angle as at least one of the second set of light sensors, and   further wherein at least one of the first set of light sensors is configured to have a different preselected angle than another of the first set of light sensors.   
     
     
         13 . The device of  claim 12 , wherein the first set of light sensors is interleaved with the second set of light sensors. 
     
     
         14 . The device of  claim 1 , wherein the one or more light sensors includes a first set of light sensors configured to measure a first tissue region and a second set of light sensors configured to measure a second tissue region,
 wherein at least one of the first set of light sensors is coupled to a first of the one or more viewing component,   the first of the one or more viewing components having the same preselected angle of incidence as a second of the one or more viewing components,   the second of the one or more viewing components coupled to at least one of the second set of light sensors.   
     
     
         15 . The device of  claim 14 , wherein the first of the one or more viewing components is optically coupled to a first of the one or more light emitters and the second of the one or more viewing components is optically coupled to a second of the one or more light emitters, a separation distance between the first of the one or more viewing components and the first of the one or more light emitters being the same as a separation distance from the second of the one or more viewing components and the second of the one or more light emitters. 
     
     
         16 . The device of  claim 1 , wherein the one or more light sensors are configured as an array of light sensors, each light sensor optically coupled to a different of the one or more viewing components, each of the one or more viewing components having a different preselected angle. 
     
     
         17 . A method of measuring a physiological parameter of an individual, the method comprising:
 selectively allowing light having one or more preselected angles of incidence to pass through one or more viewing components;   detecting the light that has interacted with a tissue region of the individual using one or more light sensors; and   computing the physiological parameter based on the light detected from the one or more light sensors.   
     
     
         18 . The method of  claim 17 , further comprising:
 emitting a first light using a first of the one or more light emitters, a portion of the first light included in the light;   emitting a second light using a second of the one or more light emitters, a portion of the second light included in the light;   optically coupling a first of the one or more light sensors to a first of the one or more viewing components;   optically coupling a second of the one or more light sensors to a second of the one or more viewing components;   locating the first of the one or more light emitters a separation distance from the first of the one or more viewing components; and   locating the second of the one or more light emitters the separation distance from the second of the one or more viewing components.   
     
     
         19 . The method of  claim 18 , wherein computing the physiological parameter includes selecting between a signal associated with the first light and a signal associated with the second light. 
     
     
         20 . The method of  claim 19 , further comprising:
 associating each of the one or more viewing components to one of the one or more preselected angles of incidence;   associating each of the one or more light sensors to one of the one or more viewing components; and   associating each signal from the one or more light sensors to a different layer in a skin of the individual.