PATENT DOCUMENT

Publication Number: US-12161447-B2
Application Number: US-201816124792-A
Country: US
Kind Code: B2

Title: Reflective surfaces for PPG signal detection

Abstract:
Reflective surfaces for the apertures of PPG optical components in PPG systems is disclosed. In a PPG system or device, the addition of reflective surfaces around, under, or near the apertures of the optical components can enhance the amount of light received by the light detector. As a result, the measured PPG signal strength can be higher and more accurate compared to the same PPG device without reflective surfaces. The reflective surfaces can reflect and/or recycle light that is incident upon the reflective surfaces back into the skin for eventual capture of the light by the light detectors. In some examples, the reflective surfaces can be diffuse or specular reflectors and/or can be configured to selectively reflect one or more wavelengths of light. In some examples, the back crystal and/or component mounting plane of the PPG system can be made of the same material as the reflective surfaces.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a plurality of windows; 
 a back crystal defining:
 a plurality of cavities, wherein each window of the plurality of windows is mounted via an adhesive in a corresponding cavity of the plurality of cavities, such that the back crystal surrounds each of the plurality of windows; 
 a plurality of ledges positioned along the plurality of cavities, each window of the plurality of windows mounted to a corresponding ledge of the plurality of ledges; 
 
 a plurality of light emitters for emitting first light through at least one of the plurality of cavities; 
 a light emitting section including:
 a plurality of first cavities of the plurality of cavities through which the first light is emitted, 
 a plurality of first ledges of the plurality of ledges; 
 a plurality of first windows of the plurality of windows, each window of the plurality of first windows is mounted via an adhesive in a corresponding cavity of the plurality of first cavities; and 
 a plurality of first reflectors, each reflector of the plurality of first reflectors circumferentially surrounding a corresponding window of the plurality of first windows and disposed on a side of a corresponding first ledge; 
 
 a plurality of light sensors for receiving second light through at least one of the plurality of cavities; and 
 a light sensing section including:
 a plurality of second cavities of the plurality of cavities through which the second light is received; 
 a plurality of second ledges of the plurality of ledges; 
 a plurality of second windows of the plurality of windows, each window of the plurality of second windows is mounted via an adhesive in a corresponding cavity of the plurality of second cavities; and 
 a plurality of second reflectors, each reflector of the plurality of second reflectors circumferentially surrounding a corresponding window of the plurality of second windows and disposed on a side of a corresponding second ledge of the plurality of second ledges. 
 
 
     
     
       2. The electronic device of  claim 1 , further comprising:
 an optical isolation located between the plurality of first cavities and the plurality of second cavities, 
 wherein the plurality of first reflectors is located between the optical isolation and the plurality of first windows, and 
 wherein the plurality of second reflectors is located between the optical isolation and the plurality of second windows. 
 
     
     
       3. The electronic device of  claim 1 , wherein first portions of the back crystal form the plurality of first ledges and second portions of the back crystal form the plurality of second ledges; and
 the plurality of first windows is attached to or touching the plurality of first ledges, and the plurality of second windows is attached to or touching the plurality of second ledges. 
 
     
     
       4. The electronic device of  claim 3 , further comprising:
 an optical isolation located between the plurality of first cavities and the plurality of second cavities, 
 wherein the plurality of first ledges are located between the optical isolation and the plurality of first windows, and the plurality of second ledges are located between the optical isolation and the plurality of second windows. 
 
     
     
       5. The electronic device of  claim 3 , further comprising:
 adhesive located between the plurality of first ledges and the plurality of first windows and further located between the plurality of second ledges and the plurality of second windows. 
 
     
     
       6. The electronic device of  claim 1 , wherein the plurality of light emitters emits the first light through top and bottom surfaces of the plurality of first windows,
 wherein a portion of the plurality of first reflectors is located along side surfaces of the plurality of first windows. 
 
     
     
       7. The electronic device of  claim 1 , wherein the plurality of light emitters emits the first light through top and bottom surfaces of the plurality of first windows,
 wherein at least a portion of the plurality of first reflectors is located along portions of the top surface of the plurality of first windows. 
 
     
     
       8. The electronic device of  claim 1 , wherein the plurality of light sensors receives the second light through top and bottom surfaces of the plurality of second windows,
 wherein a portion of the plurality of second reflectors is located along side surfaces of the plurality of second windows. 
 
     
     
       9. The electronic device of  claim 1 , wherein the plurality of light sensors receives the first light through top and bottom surfaces of the plurality of second windows. 
     
     
       10. The electronic device of  claim 1 , wherein the plurality of first windows is located between the plurality of first reflectors and the plurality of first cavities, and the plurality of second windows is located between the plurality of second reflectors and the plurality of second cavities. 
     
     
       11. The electronic device of  claim 1 , wherein the plurality of first cavities has first apertures with first sizes, and the plurality of second cavities has second apertures with second sizes, the second sizes being less than the first sizes. 
     
     
       12. The electronic device of  claim 11 ,
 wherein diameters of the plurality of first windows are larger than the first sizes, and diameters of the plurality of second windows are larger than the second sizes. 
 
     
     
       13. The electronic device of  claim 1 , wherein the plurality of second reflectors is configured to selectively return one or more colors of incident light while selectively absorbing one or more other colors of the incident light. 
     
     
       14. The electronic device of  claim 1 , wherein the plurality of first reflectors, the plurality of second reflectors, or both include a pattern or a grating for selectively directing incident light based one or more properties of the incident light. 
     
     
       15. The electronic device of  claim 14 , wherein the selective direction of the incident light includes:
 returning a portion of the incident light having a first wavelength in a first direction, and 
 returning a portion of the incident light having a second wavelength in a second direction, the first wavelength different from the second wavelength, and the first direction different from the second direction. 
 
     
     
       16. The electronic device of  claim 1 , wherein reflecting surfaces of the plurality of first reflectors face an external housing of the device, and reflecting surfaces of the plurality of first reflectors face the external housing of the device. 
     
     
       17. A method for operating an optical sensing system having a back crystal, the method comprising:
 emitting first light from a plurality of light emitters through a light emitting section, the light emitting section including a plurality of first cavities defined by the back crystal, a plurality of first ledges, a plurality of first reflectors, and a plurality of first windows, the plurality of first windows mounted via an adhesive in corresponding cavities of the plurality of first cavities and surrounded by the back crystal, 
 wherein each first reflector of the plurality of first reflectors circumferentially surrounds a corresponding window of the plurality of first windows, each first reflector disposed on a side of a corresponding ledge; 
 returning at least a portion of the first light using the plurality of first reflectors; 
 receiving second light by a plurality of light sensors through a light receiving section, the light receiving section including a plurality of second cavities defined by the back crystal, a plurality of second reflectors, a plurality of second ledges, and a plurality of second windows, the plurality of second windows mounted via an adhesive in corresponding cavities of the plurality of second cavities and surrounded by the back crystal, 
 wherein each second reflector of the plurality of second reflectors circumferentially surrounds a corresponding window of the plurality of second windows, each second reflector disposed on a side of a corresponding ledge; and 
 returning at least a portion of light incident on the plurality of second reflectors. 
 
     
     
       18. The method of  claim 17 , wherein the portion of light incident on the plurality of second reflectors to a skin of a user. 
     
     
       19. The method of  claim 17 , wherein at least a portion of the received second light includes the portion of the light incident on the plurality of second reflectors.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 14/470,834, filed Aug. 27, 2014 and published as U.S. Patent Publication No. 2016-0058309 on Mar. 3, 2016; the contents of which are herein incorporated by reference in its entirety for all intended purposes. 
    
    
     FIELD 
     This relates generally to a device that measures a photoplethysmographic (PPG) signal, and, more particularly, to reflective surfaces for PPG signal detection. 
     BACKGROUND 
     A photoplethysmographic (PPG) signal can be measured by PPG systems to derive corresponding physiological signals (e.g., pulse rate). In a basic form, PPG systems can employ a light source or light emitter that injects light into the user&#39;s tissue, and a light detector to receive light that reflects and/or scatters and exits the tissue. The received light includes light with amplitude that is modulated as a result of pulsatile blood flow (i.e., “signal”) and parasitic, non-signal light with amplitude that can be modulated (i.e., “noise” or “artifacts”) and/or unmodulated (i.e., DC). However, in some examples, the reflected and/or scattered light received by the light detector may be have a low signal strength, making it difficult to accurately determine the user&#39;s pulse rate. 
     One way to increase the signal intensity or signal strength can be to decrease the distance between the light sensor and light emitter. The minimum distance between the light sensor and light emitter can, however, be limited by mechanical or functional requirements of other components on the PPG system, such as the windows used to cover and protect the light source and light detector. An alternative way to increase the signal strength may be needed. 
     SUMMARY 
     This relates to reflective surfaces around the apertures of PPG optical components in PPG systems. In a PPG system or device, the addition of reflective surfaces around, under, or near the apertures of the optical components can enhance the amount of light received by the light detector. As a result, the measured PPG signal strength can be higher and more accurate compared to the same PPG device without reflective surfaces. The reflective surfaces can reflect and/or recycle light that is incident upon the reflective surfaces back into the skin for eventual capture of the light by the light detectors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 A- 1 C  illustrate systems in which examples of the disclosure can be implemented. 
         FIG.  2    illustrates an exemplary PPG signal according to examples of the disclosure. 
         FIG.  3 A  illustrates a top view of an exemplary electronic device configured to measure a PPG signal according to examples of the disclosure. 
         FIG.  3 B  illustrates a cross-sectional view of an exemplary electronic device configured to measure a PPG signal according to examples of the disclosure. 
         FIG.  4 A  illustrates a top view of an exemplary electronic device with ledges configured to measure a PPG signal according to examples of the disclosure. 
         FIG.  4 B  illustrates a cross-sectional view of an exemplary electronic device with ledges configured to measure a PPG signal according to examples of the disclosure. 
         FIGS.  4 C- 4 F  illustrate bar charts of measured modulated light, unmodulated light, perfusion index and signal-to-noise ratio of an exemplary device without ledges and an exemplary device with ledges according to examples of the disclosure. 
         FIG.  5 A  illustrates a top view of an exemplary electronic device with increased aperture sizes configured to measure a PPG signal according to examples of the disclosure. 
         FIG.  5 B  illustrates a cross-sectional view of an exemplary electronic device with increased aperture sizes configured to measure a PPG signal according to examples of the disclosure. 
         FIGS.  5 C- 5 F  illustrate bar charts of measured modulated light values, unmodulated light values, perfusion index and signal-to-noise ratio values for an exemplary device without ledges, an exemplary device with ledges, and an exemplary device with increased aperture sizes according to examples of the disclosure. 
         FIGS.  6 A- 6 B  illustrate top views of exemplary electronic devices with different aperture sizes configured to measure a PPG signal according to examples of the disclosure. 
         FIGS.  6 C- 6 F  illustrate bar charts of measured modulated light values, unmodulated light values, perfusion index and signal-to-noise ratio values for exemplary devices with different aperture sizes according to examples of the disclosure. 
         FIG.  7 A  illustrates a top view of an exemplary electronic device with reflective surfaces configured to measure a PPG signal according to examples of the disclosure. 
         FIGS.  7 B- 7 E  illustrate cross-sectional views of exemplary electronic devices with reflective surfaces configured to measure a PPG signal according to examples of the disclosure. 
         FIG.  8    illustrates a block diagram of an exemplary computing system comprising light emitters and light sensors for measuring a PPG signal according to examples of the disclosure. 
         FIG.  9    illustrates an exemplary configuration in which a device is connected to a host according to examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the various examples. 
     In the following description, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects and/or features described or referenced herein. It will be apparent, however, to one skilled in the art, that one or more aspects and/or features described or referenced herein may be practiced without some or all of these specific details. 
     A photoplethysmographic (PPG) signal can be measured by PPG systems to derive corresponding physiological signals (e.g., pulse rate). Such PPG systems can be designed to be sensitive to changes in blood in a user&#39;s tissue that can result from fluctuations in the amount or volume of blood or blood oxygen in the vasculature of the user. In a basic form, PPG systems can employ a light source or light emitter that injects light into the user&#39;s tissue, and a light detector to receive light that reflects and/or scatters and exits the tissue. The PPG signal is the amplitude of reflected and/or scattered light that is modulated with volumetric change in blood volume in the tissue. However, in some examples, some of the reflected and/or scattered light can be lost, leading to a PPG signal measured by the light detector having a low signal strength. As a result, it may be difficult to accurately determine the user&#39;s physiological state. 
     This disclosure relates to reflective surfaces around, under, on or near one or more apertures of the PPG optical components. In a PPG device, the addition of reflective surfaces around, under, on or near the apertures of the optical components can enhance signal strength compared to the same PPG device without reflective surfaces. The reflective surfaces can reflect or recycle light that is incident upon the reflective surfaces back into the skin for eventual capture of the light by the light detectors. This incident light may not have been as effectively reflected (if at all) without the reflective surfaces, and could therefore be lost (i.e., not contribute to the signal measured by the light detector). 
     Representative applications of methods and apparatus according to the present disclosure are described in this section. These examples are being provided solely to add context and aid in the understanding of the described examples. It will thus be apparent to one skilled in the art that the described examples may be practiced without some or all of the specific details. Other applications are possible, such that the following examples should not be taken as limiting. 
       FIGS.  1 A- 1 C  illustrate systems in which examples of the disclosure can be implemented.  FIG.  1 A  illustrates an exemplary mobile telephone  136  that can include a touch screen  124 .  FIG.  1 B  illustrates an exemplary media player  140  that can include a touch screen  126 .  FIG.  1 C  illustrates an exemplary wearable device  144  that can include a touch screen  128  and can be attached to a user using a strap  146 . The systems of  FIGS.  1 A- 1 C  can utilize the reflective surfaces as will be disclosed. 
       FIG.  2    illustrates an exemplary PPG signal absent of artifacts. Signal  210  can be light measured by one or more light detectors and processed such that artifacts are optionally removed or extracted from the signal. Signal  210  can include light information with an amplitude that is modulated as a result of pulsatile blood flow (i.e., “signal”) and parasitic, unmodulated, non-signal light (i.e., DC). From the measured PPG signal  210 , a perfusion index can be determined. The perfusion index can be the ratio of received modulated light (ML) to unmodulated light (UML) (i.e., ratio of blood flow modulated signal to static, parasitic DC signal) and can give extra information regarding the user&#39;s physiological state. The modulated light (ML) can be the peak-to-valley value of signal  210 , and unmodulated light (UML) can be the zero-to-average (using average 212) value of signal  210 . As shown in  FIG.  2   , the perfusion index can be equal to the ratio of ML to UML. 
       FIG.  3 A  illustrates a top view, and  FIG.  3 B  illustrates a cross-sectional view of an exemplary electronic device configured to measure a PPG signal. Device  300  can include light emitters  306  and  316  and light sensors  304  and  314  located on a surface of device  300 . Light emitters  306  and  316  and light sensors  304  and  314  can be facing towards a skin  320  of a user. Between light emitter  306  (or any one or more of light emitter  316  and light sensors  304  and  314 ) and skin  320  can be windows  301  surrounded by back crystal  318 . Windows  301  can have a diameter  312  and can be mounted to device  300  using an adhesive  322  on the sides of windows  301 . Device  300  can optionally include optical isolation  319 . Light emitters  306  and  316  can be any type of light source, including but not limited to, light emitting diodes (LEDs), incandescent lights, fluorescent lights, organic light emitting diodes (OLEDs), and electroluminescent diodes (ELDs). Light sensors  304  and  314  can be any type of optical sensing device such as a photodiode. In some examples, light emitters  306  and  316  and/or light sensors  304  and  314  can be mounted or touching a component mounting plane  346 . In some examples, either light sensors  304  and  314  or light emitters  306  and  314  or both can be symmetrically placed with respect to the center of the back crystal  318 . In some examples, either light sensors  304  and  314  or light emitters  306  and  316  or both can be asymmetrically placed with respect to the center of the back crystal  318 . 
     In some examples, adhesive  322  applied to the sides of the windows  301  can be insufficient for effectively attaching windows  301  to device  300 . For such a case, back crystal  318  can be designed to improve mechanical stability.  FIG.  4 A  illustrates a top view, and  FIG.  4 B  illustrates a cross-sectional view of an exemplary electronic device configured to measure a PPG signal according to examples of the disclosure. Device  400  can include light emitters  406  and light sensors  404  located on a surface of device  400 . Light emitters  406  and light sensors  404  can be facing towards a skin  420  of a user and can be mounted to or touching a component mounting plane  446 . In some examples, light emitters  406  can be y-centered (i.e., symmetrically placed along the horizontal axis). Between light emitters  406  (or light sensors  404 ) and skin  420  can be windows  401  surrounded by back crystal  418 . Back crystal  418  can include ledges  448  for improving the mechanical stability of device  400  by providing a larger surface area for windows  401  to rest on and/or adhere to. Windows  401  can have a diameter  412  and can be mounted to device  400  using an adhesive  422  to attach the sides of windows  401  and at least a portion of one side of windows  401  to ledges  448 . While back crystal  418  can improve the adhesion of windows  401  to back crystal  418 , the ledges  448  may lead to a smaller aperture or diameter  413  than for devices without a ledge (such as illustrated in  FIGS.  3 A- 3 B ). Device  400  can optionally include optical isolation  419 . 
     The smaller diameter  413  can lead to a lower amount of light reaching skin  420  from light emitters  406  and/or a lower amount of light reflecting or scattering back and being sensed by light sensors  404 . As a result, the light intensity and measured signal strength may be reduced.  FIG.  4 C  illustrates a bar chart of measured modulated light of an exemplary device without ledges and an exemplary device with ledges according to examples of the disclosure. A device with ledges (such as device  400  shown in  FIGS.  4 A- 4 B ) can have a lower modulated light signal than a device without ledges (such as device  300  shown in  FIGS.  3 A- 3 B ). As discussed above, the lower modulated light signal can be due to a change in aperture size. For example, diameter  312  or  412  can be 6.1 mm, and diameter  413  can be 3.9 mm. In the present example, ledges  448  in device  400  can lead to an optical aperture that can be reduced by 2.2 mm in diameter or 69.12 mm 2  in area. The device without ledges (device  300 ) can have a modulated light signal value of 392 pA/mA from the shorter path (path  391 ) and a modulated light signal value of 309 pA/mA from the longer path (path  393 ). The device with ledges (device  400 ) can have a modulated light signal value of 197 pA/mA, which is at least 50% lower than the modulated light signal values of the device without ledges (device  300 ). 
     In addition to a lower modulated light signal, ledges  448  in device  400  can result in a lower unmodulated light signal as shown in  FIG.  4 D . For example, the device without ledges (device  300 ) can have an unmodulated light signal value of 22.2 nA/mA from path  391  and an unmodulated light signal value of 17.0 nA/mA from path  393 . The device with ledges (device  400 ) can have an unmodulated light signal value of 7.5 nA/mA, which is at least 55% lower than the unmodulated light signal values of the device without ledges (device  300 ). 
     As discussed above, the perfusion index is equal to the ratio of modulated light to unmodulated light.  FIG.  4 E  illustrates a bar chart of the perfusion index of an exemplary device without ledges and an exemplary device with ledges according to examples of the disclosure. Although the device without ledges (device  300 ) can have a higher modulated light signal and a higher unmodulated light signal than a device with ledges (device  400 ), the perfusion index can be lower. For example, the device without ledges (device  300 ) can have a perfusion index from the shorter path (path  391 ) of 1.7% and a perfusion index from the longer path (path  393 ) of 1.73%, whereas the device with ledges (device  400 ) can have a perfusion index of 2.36%. 
     Additionally, the device with ledges (device  400 ) can have a lower signal-to-noise ratio than the device without ledges (device  300 ), as illustrated in  FIG.  4 F . For example, the shorter path (path  391 ) of the device without ledges (device  300 ) can have a signal-to-noise ratio of 9.6 bits, and the longer path (path  393 ) of the device without ledges (device)  300  can have a signal-to-noise ratio of 9.3 bits. The device with ledges (device  400 ) can have a lower signal-to-noise ratio value of 8.3 bits. 
     As illustrated in  FIGS.  4 C- 4 F , the device with ledges can lead to a reduced signal intensity. However, removing the ledges or manufacturing a device without ledges can result in a device with poor mechanical stability to secure or attach the windows. A different method to increasing the signal intensity may be needed.  FIG.  5 A  illustrates a top view, and  FIG.  5 B  illustrates a cross-sectional view of an exemplary electronic device configured to measure a PPG signal according to examples of the disclosure. Device  500  can include light emitters  506  and light sensors  504  attached to or touching component mounting plane  546 . Device  500  can optionally include optical isolation  519 . Windows  501  with a diameter  512  can be included for covering and/or protecting light emitters  506  and light sensors  504 . Back crystal  518  can be disposed around windows  501 . Windows  501  can be touching or attached (using adhesive  522 ) to ledges  548 . Light can be emitted from light emitters  506  towards a skin  520  of a user. Light can reflect and/or scatter off skin  520 , vasculature, and blood of the user and reflect back towards light sensor  504 . To increase the signal intensity, a diameter  515  of the apertures can be made larger than diameter  413  of  FIGS.  4 A- 4 B . 
       FIGS.  5 C- 5 F  illustrate bar charts of measured modulated light values, unmodulated light values, perfusion index, and signal-to-noise ratio values for an exemplary device without ledges (device  300  of  FIGS.  3 A- 3 B ), an exemplary device with ledges (device  400  of  FIGS.  4 A- 4 B ), and an exemplary device with increased aperture size (device  500  of  FIGS.  5 A- 5 B ) according to examples of the disclosure. For example, a diameter  515  of the device with increase aperture size (device  500 ) can be 4.9 mm, whereas a diameter  413  of the device with ledges (device  400 ) can be 3.9 mm. In some examples, the device with increased aperture size (device  500 ) can include ledges. The increased aperture size (device  500 ) can lead to an increase in measured modulated light values. As shown in  FIG.  5 C , the device without ledges (device  300 ) can have a modulated light signal value of 257 pA/mA from the shorter path (path  391 ) and a modulated light signal value of 181 pA/mA from longer path (path  393 ). The addition of ledges  448  (device  400 ) can lead to a lower modulated light signal value of 94 pA/mA. However, the reduced intensity can be compensated by increasing the aperture size (device  500 ). The device with increased aperture size (device  500 ) can have a modulated light signal value of 262 pA/mA, which is comparable to device  300  (the device without ledges). As shown in  FIG.  5 D , increasing the aperture size can also result in measured unmodulated light values for the device with increased aperture size (device  500 ) higher than measured unmodulated light values for the device without ledges (device  300 ). For example, the unmodulated light values for the device without ledges (device  300 ) can be 23.6 nA/mA for the shorter path (path  391 ) or 16.2 nA/mA for the longer path (path  393 ), 7.9 nA/mA for the device with ledges (device  400 ), and 29.7 nA/mA for the device with increase aperture size (device  500 ). Although increasing the aperture size can lead to a higher signal strength for measured modulated light, the measured unmodulated light (or noise) can increase as well. 
       FIG.  5 E  illustrates an exemplary bar chart for perfusion index. The device without ledges (device  300 ) can have a perfusion index of 1.16-1.17%, the device with ledges (device  400 ) can have a perfusion index of 1.29%, and the device with increased aperture size (device  500 ) can have a perfusion index of 1.01%. Although the signal strength for modulated light increases, the perfusion index can be lower for the device with increase aperture size (device  500 ) due to the measured unmodulated light value also increasing.  FIG.  5 F  illustrates comparable signal-to-noise ratio values for the device without ledges (device  300 ) and the device with ledges (device  500 ). The device without ledges (device  300 ) can have a signal-to-noise ratio value of between 8.9-9.4 bits. The device with ledges (device  400 ) can have a lower signal-to-noise ratio of 7.9 bits, while the device with increased aperture size (device  500 ) can have a signal-to-noise ratio of 9.2 bits. 
       FIGS.  6 A- 6 B  illustrate top views of exemplary electronic devices with different aperture sizes configured to measure a PPG signal according to examples of the disclosure. Device  600  of  FIG.  6 A  can include light sensors  604  and windows  601  covering and/or protecting light sensors  604 . Windows  601  can be attached to or touching ledges  646 . The apertures associated with light sensors  604  and windows  601  can have a diameter  613 . Device  600  can also include light emitters  606  and windows  603  covering and/or protecting light emitters  606 . Windows  603  can be attached to or touching ledges  648 . The apertures associated with light emitters  606  and windows  603  can have a diameter  615 . In some examples, diameter  613  can be smaller than diameter  615  due to a size difference between ledges  646  and  648 . That is, light sensors  604  can receive light through smaller sized apertures than light emitters  606  emit light. 
     Device  650  of  FIG.  6 B  can include light sensors  654  and windows  653  covering and/or protecting light sensors  654 . Windows  653  can be attached to or touching ledges  698 . The apertures associated with light sensors  654  and windows  653  can have a diameter  665 . Device  650  can also include light emitters  656  and windows  651  covering and/or protecting light emitters  656 . Windows  651  can be attached to or touching ledges  696 . The apertures associated with light emitters  656  and windows  651  can have a diameter  663 . In some examples, diameter  663  can be smaller than diameter  665  due to a size difference between ledges  696  and  698 . That is, light sensors  654  can receive light through larger sized apertures than light emitters  656  can emit light. 
       FIGS.  6 C- 6 F  illustrate bar charts of measured modulated light values, unmodulated light values, perfusion index and signal-to-noise ratio values for exemplary devices with different aperture sizes according to examples of the disclosure. For example, diameters  613  and  663  can be 3.9 mm, diameters  615  and  665  can be 4.9 mm, and diameters  612  and  662  of windows  612  can be 6.12 mm. As shown in  FIG.  6 C , the modulated light value is comparable for device  600  and  650 . That is, selectively choosing which one of the light emitters  606  and  656  or light sensors  604  and  654  is associated with the larger sized aperture may not have a significant effect on the modulated light value. Similarly, as shown in  FIG.  6 D , the unmodulated light value is comparable for the device with larger aperture size associated with the light emitters (device  600 ) and for the device with larger aperture size associated with the light sensors (device  650 ).  FIG.  6 E  shows comparable perfusion indices for the device with larger aperture size associated with the light emitters (device  600 ) and the device with larger aperture size associated with the light sensors (device  650 ), and  FIG.  6 F  shows comparable signal-to-noise ratio values. The highest modulated light value and unmodulated light value can be achieved with device  500  (i.e., the device with largest aperture sizes for both light emitters and light sensors). However, device  500  can also have the lowest perfusion index and highest signal-to-noise ratio. 
     While increasing the aperture size may effectively increase the modulated signal strength and the unmodulated signal strength, the perfusion decreases and the signal-to-noise ratio increases. An alternative solution to increasing the signal intensity may be desired.  FIG.  7 A  illustrates a top view, and  FIG.  7 B  illustrates a cross-sectional view of an exemplary electronic device with reflective surfaces configured to measure a PPG signal according to examples of the disclosure. Device  700  can include one or more light emitters  706 , one or more light sensors  704 , and a plurality of windows  701  protecting and/or covering the light emitters  706  and light sensors  704 . The light emitters  706  and light sensors  704  can be mounted on or touching a component mounting plane  746 , and windows  701  can be mounted, adhered to, or touching a back crystal  718 . Back crystal  718  can include ledges  748  for attaching windows  701  using adhesive  722 . Light emitted from light emitters  706  can be directed towards a skin  720  of a user to penetrate through the skin  720 , vasculature, and/or blood and reflect and/or scatter back to device  700  to be sensed by light sensors  704 . In some examples, the light reflected back can be lost and absorbed by back crystal  718 . As a result, the signal strength of the light sensed by light sensors  704  may be reduced in intensity. 
     One way to minimize the loss of reflected light can be to utilize reflective surfaces as illustrated in  FIGS.  7 B- 7 E . Device  700  can be formed by at least forming component mounting plane  746 , attaching light emitters  706  and light sensors  704  to component mounting plane  746 , and forming back crystal  718  and ledges  748 . Device  700  can optionally include optical isolation  719 . As illustrated in  FIG.  7 B , reflective surfaces  747  can be disposed on one or more sides of ledges  748  facing skin  720 . Reflective surfaces  747  can be disposed using any number of deposition techniques including chemical vapor deposition, physical vapor deposition, plating, printing, or spray processes. In some examples, reflective surfaces  747  can be formed separately and can be attached to or touching ledges  748 . With reflective surfaces  747 , reflected light incident on ledges  748  can be reflected and/or scattered back to skin  720  and can be recycled instead of being lost. Reflective surfaces  747  can be made of any type of reflective material including, but not limited to, white ink, silver ink, and silver foil. In some examples, adhesive  722  can be made of a transparent material. 
     In some examples, reflective surfaces  747  can be disposed on or attached to adhesive  722 , where adhesive  722  can be applied to ledges  748 , as illustrated in  FIG.  7 C . Adhesive  722  can be a transparent material or can be an opaque material. In some examples, reflective surfaces  747  can be located between adhesive  722  and windows  701 , but disposed on windows  701  instead of being disposed on adhesive  722 . In some examples, reflective surfaces  747  can be disposed on windows  701  between windows  701  and skin  720 . That is, neither adhesive  722  nor windows  701  are between reflective surfaces  747  and skin  720 , as illustrated in  FIG.  7 D . In some examples, reflective surfaces  747  can be disposed on the inner sides of back crystal  718  cavity or orthogonal to a surface of skin  720 , as illustrated in  FIG.  7 E . With reflective surfaces  747  disposed on the inner sides of back crystal  718  cavity, reflected light incident on the inner sides can reflect and/or scatter back towards skin  720  and can be recycled to minimize any lost or absorbed light signal. 
     In some examples, the reflective surfaces  747  can be specular reflectors. Light with a single incoming direction can be reflected with a single outgoing direction (as shown in  FIGS.  7 B and  7 E ). An exemplary specular reflector can be silver foil. In some examples, the reflective surfaces  747  can be diffuse reflectors. Light with a single incoming direction can be reflected in a broad range of directions. An exemplary diffuse reflector can be white ink. In some examples, reflective surfaces  747  can be a combination of a specular reflector and a diffuse reflector. In some examples, one or more reflective surfaces  747  can be specular reflectors, while the other reflective surfaces  747  can be diffuse reflectors. 
     In some examples, reflective surfaces  747  can selectively reflect and/or scatter one or more colors, while absorbing all other colors. For example, reflective surfaces  747  can be configured to reflect and/or scatter green light, while absorbing all other colors and wavelengths of light. To selectively reflect and/or scatter green light, reflective surfaces  747  can be made of a green-colored coating or foil, for example. 
     In some examples, reflective surfaces  747  can be made of a pattern or grating to control the optical paths or light angles or preferentially direct the light to travel along specific paths. In some examples, reflective surfaces  747  can be configured to reflect and/or scatter one wavelength of light in one direction and reflect and/or scatter another wavelength of light in another direction. For example, red light can enter the skin  720  of a user with shallow angles. As a result, red light may not penetrate deep enough to reach pulsatile blood. Reflective surfaces  747  can be configured to direct red light with an angle such that the red light is head-on or near head-on with skin  720  instead of at a glancing angle. 
     In some examples, one or more of back crystal  718  and component mounting plane  746  can be made of a reflective material. In some examples, back crystal  718  and component mounting plane  746  can be made of the same material. In some examples, back crystal  718  or component mounting plane  746  or both can be the same material as reflective surfaces  747 . In some examples, adhesive  722  can be made of a reflective material. 
       FIG.  8    illustrates an exemplary block diagram of a computing system comprising light emitters and light sensors for measuring a PPG signal according to examples of the disclosure. Computing system  800  can correspond to any of the computing devices illustrated in  FIGS.  1 A- 1 C . Computing system  800  can include a processor  810  configured to execute instructions and to carry out operations associated with computing system  800 . For example, using instructions retrieved from memory, processor  810  can control the reception and manipulation of input and output data between components of computing system  800 . Processor  810  can be a single-chip processor or can be implemented with multiple components. 
     In some examples, processor  810  together with an operating system can operate to execute computer code and produce and use data. The computer code and data can reside within a program storage block  802  that can be operatively coupled to processor  810 . Program storage block  802  can generally provide a place to hold data that is being used by computing system  800 . Program storage block  802  can be any non-transitory computer-readable storage medium, and can store, for example, history and/or pattern data relating to PPG signal and perfusion index values measured by one or more light sensors such as light sensors  804 . By way of example, program storage block  802  can include Read-Only Memory (ROM)  818 , Random-Access Memory (RAM)  822 , hard disk drive  808  and/or the like. The computer code and data could also reside on a removable storage medium and loaded or installed onto the computing system  800  when needed. Removable storage mediums include, for example, CD-ROM, DVD-ROM, Universal Serial Bus (USB), Secure Digital (SD), Compact Flash (CF), Memory Stick, Multi-Media Card (MMC) and a network component. 
     Computing system  800  can also include an input/output (I/O) controller  812  that can be operatively coupled to processor  810 , or it can be a separate component as shown. I/O controller  812  can be configured to control interactions with one or more I/O devices. I/O controller  812  can operate by exchanging data between processor  810  and the I/O devices that desire to communicate with processor  810 . The I/O devices and I/O controller  812  can communicate through a data link. The data link can be a one-way link or a two-way link. In some cases, I/O devices can be connected to I/O controller  812  through wireless connections. By way of example, a data link can correspond to PS/2, USB, Firewire, IR, RF, Bluetooth or the like. 
     Computing system  800  can include a display device  824  that can be operatively coupled to processor  810 . Display device  824  can be a separate component (peripheral device) or can be integrated with processor  810  and program storage block  802  to form a desktop computer (e.g., all-in-one machine), a laptop, handheld or tablet computing device of the like. Display device  824  can be configured to display a graphical user interface (GUI) including perhaps a pointer or cursor as well as other information to the user. By way of example, display device  824  can be any type of display including a liquid crystal display (LCD), an electroluminescent display (ELD), a field emission display (FED), a light emitting diode display (LED), an organic light emitting diode display (OLED) or the like. 
     Display device  824  can be coupled to display controller  826  that can be coupled to processor  810 . Processor  810  can send raw data to display controller  826 , and display controller  826  can send signals to display device  824 . Data can include voltage levels for a plurality of pixels in display device  824  to project an image. In some examples, processor  810  can be configured to process the raw data. 
     Computing system  800  can also include a touch screen  830  that can be operatively coupled to processor  810 . Touch screen  830  can be a combination of sensing device  832  and display device  824 , where the sensing device  832  can be a transparent panel that is positioned in front of display device  824  or integrated with display device  824 . In some cases, touch screen  830  can recognize touches and the position and magnitude of touches on its surface. Touch screen  830  can report the touches to processor  810 , and processor  810  can interpret the touches in accordance with its programming. For example, processor  810  can perform tap and event gesture parsing and can initiate a wake of the device or powering on one or more components in accordance with a particular touch. 
     Touch screen  830  can be coupled to a touch controller  840  that can acquire data from touch screen  830  and can supply the acquired data to processor  810 . In some cases, touch controller  840  can be configured to send raw data to processor  810 , and processor  810  can process the raw data. For example, processor  810  can receive data from touch controller  840  and can determine how to interpret the data. The data can include the coordinates of a touch as well as pressure exerted. In some examples, touch controller  840  can be configured to process raw data itself. That is, touch controller  840  can read signals from sensing points  834  located on sensing device  832  and can turn the signals into data that the processor  810  can understand. 
     Touch controller  840  can include one or more microcontrollers such as microcontroller  842 , each of which can monitor one or more sensing points  834 . Microcontroller  842  can, for example, correspond to an application specific integrated circuit (ASIC), which works with firmware to monitor the signals from sensing device  832 , process the monitored signals, and report this information to processor  810 . 
     One or both display controller  826  and touch controller  840  can perform filtering and/or conversion processes. Filtering processes can be implemented to reduce a busy data stream to prevent processor  810  from being overloaded with redundant or non-essential data. The conversion processes can be implemented to adjust the raw data before sending or reporting them to processor  810 . 
     In some examples, sensing device  832  can be based on capacitance. When two electrically conductive members come close to one another without actually touching, their electric fields can interact to form a capacitance. The first electrically conductive member can be one or more of the sensing points  834 , and the second electrically conductive member can be an object  890  such as a finger. As object  890  approaches the surface of touch screen  830 , a capacitance can form between object  890  and one or more sensing points  834  in close proximity to object  890 . By detecting changes in capacitance at each of the sensing points  834  and noting the position of sensing points  834 , touch controller  840  can recognize multiple objects, and determine the location, pressure, direction, speed and acceleration of object  890  as it moves across the touch screen  830 . For example, touch controller  890  can determine whether the sensed touch is a finger, tap, or an object covering the surface. 
     Sensing device  832  can be based on self-capacitance or mutual capacitance. In self-capacitance, each of the sensing points  834  can be provided by an individually charged electrode. As object  890  approaches the surface of the touch screen  830 , the object can capacitively couple to those electrodes in close proximity to object  890 , thereby stealing charge away from the electrodes. The amount of charge in each of the electrodes can be measured by the touch controller  840  to determine the position of one or more objects when they touch or hover over the touch screen  830 . In mutual capacitance, sensing device  832  can include a two layer grid of spatially separated lines or wires (not shown), although other configurations are possible. The upper layer can include lines in rows, while the lower layer can include lines in columns (e.g., orthogonal). Sensing points  834  can be provided at the intersections of the rows and columns. During operation, the rows can be charged, and the charge can capacitively couple from the rows to the columns. As object  890  approaches the surface of the touch screen  830 , object  890  can capacitively couple to the rows in close proximity to object  890 , thereby reducing the charge coupling between the rows and columns. The amount of charge in each of the columns can be measured by touch controller  840  to determine the position of multiple objects when they touch the touch screen  830 . 
     Computing system  800  can also include one or more light emitters such as light emitters  806  and one or more light sensors such as light sensors  804  proximate to skin  820  of a user. Light emitters  806  can be configured to generate light, and light sensors  804  can be configured to measure a light reflected or absorbed by skin  820 , vasculature, and/or blood of the user. Device  800  can include reflective surfaces  847  coupled to light emitters  806  and light sensors  804 . Reflective surfaces  847  can be configured to reflected light incident on ledges or the back crystal (not shown) towards skin  820  to be recycled instead of being lost. Light sensor  804  can send measured raw data to processor  810 , and processor  810  can perform noise and/or artifact cancellation to determine the PPG signal and/or perfusion index. Processor  810  can dynamically activate light emitters and/or light sensors based on an application, user skin type, and usage conditions. In some examples, some light emitters and/or light sensors can be activated, while other light emitters and/or light sensors can be deactivated to conserve power, for example. In some examples, processor  810  can store the raw data and/or processed information in a ROM  818  or RAM  822  for historical tracking or for future diagnostic purposes. 
     In some examples, the light sensors can measure light information and a processor can determine a PPG signal and/or perfusion index from the reflected or absorbed light. Processing of the light information can be performed on the device as well. In some examples, processing of light information need not be performed on the device itself.  FIG.  9    illustrates an exemplary configuration in which a device is connected to a host according to examples of the disclosure. Host  910  can be any device external to device  900  including, but not limited to, any of the systems illustrated in  FIGS.  1 A- 1 C  or a server. Device  900  can be connected to host  910  through communications link  920 . Communications link  920  can be any connection including, but not limited to, a wireless connection and a wired connection. Exemplary wireless connections include Wi-Fi, Bluetooth, Wireless Direct and Infrared. Exemplary wired connections include Universal Serial Bus (USB), FireWire, Thunderbolt, or any connection requiring a physical cable. 
     In operation, instead of processing light information from the light sensors on the device  900  itself, device  900  can send raw data  930  measured from the light sensors over communications link  920  to host  910 . Host  910  can receive raw data  930 , and host  910  can process the light information. Processing the light information can include canceling or reducing any noise due to artifacts and determining psychological signals such as a user&#39;s heart rate. Host  910  can include algorithms or calibration procedures to account for differences in a user&#39;s characteristics affecting PPG signal and perfusion index. Additionally, host  910  can include storage or memory for tracking a PPG signal and perfusion index history for diagnostic purposes. Host  910  can send the processed result  940  or related information back to device  900 . Based on the processed result  940 , device  900  can notify the user or adjust its operation accordingly. By offloading the processing and/or storage of the light information, device  900  can conserve space and power enabling device  900  to remain small and portable, as space that could otherwise be required for processing logic can be freed up on the device. 
     In some examples, an electronic device is disclosed. The electronic device may comprise: one or more light emitters configured to generate one or more light paths through one or more apertures; one or more sensors configured to detect a reflection of the one or more light paths; one or more reflective surfaces in contact with the one or more apertures; and logic coupled to the one or more sensors and configured to detect a signal from the one or more reflected light paths. Additionally or alternatively to one or more examples disclosed above, in other examples, at least one of the one or more reflective surfaces is a diffuse reflector. Additionally or alternatively to one or more examples disclosed above, in other examples, the diffuse reflector is a white ink. Additionally or alternatively to one or more examples disclosed above, in other examples, at least one of the one or more reflective surfaces is a specular reflector. Additionally or alternatively to one or more examples disclosed above, in other examples, the specular reflector is a silver foil. Additionally or alternatively to one or more examples disclosed above, in other examples, at least one of the one or more reflective surfaces includes a grating or pattern. Additionally or alternatively to one or more examples disclosed above, in other examples, the grating or pattern is configured to change an angle of at least one of the one or more reflected light paths. Additionally or alternatively to one or more examples disclosed above, in other examples, at least one of the one or more reflective surfaces is a combination of diffuse and specular reflectors. Additionally or alternatively to one or more examples disclosed above, in other examples, at least one of the one or more reflective surfaces is configured to selectively reflect one or more wavelengths. Additionally or alternatively to one or more examples disclosed above, in other examples, a color of the at least one of the one or more reflective surfaces is associated with the selectively reflected one or more wavelengths. Additionally or alternatively to one or more examples disclosed above, in other examples, at least one of the one or more apertures is a different size than another of the one or more apertures. Additionally or alternatively to one or more examples disclosed above, in other examples, the device further comprises: a back crystal in contact with the one or more apertures; and a component mounting plane configured for attaching to the one or more light emitters and the one or more sensors, wherein at least one of the back crystal and the component mounting plane is reflective. Additionally or alternatively to one or more examples disclosed above, in other examples, at least one of the back crystal and the component mounting plane is a same material as at least one of the one or more reflective surfaces. Additionally or alternatively to one or more examples disclosed above, in other examples, the device further comprises: one or more windows configured to cover the one or more light emitters and the one or more sensors; and a reflective adhesive configured to attach the one or more windows to the electronic device. Additionally or alternatively to one or more examples disclosed above, in other examples, at least one of the one or more apertures has a diameter between 3.9 mm-4.9 mm. 
     In some examples, a method for determining a physiological signal from an electronic device is disclosed. The method may comprise: emitting light through one or more apertures to generate one or more light paths; receiving light from a reflection of the one or more light paths off at least one or more reflective surfaces in contact with the one or more apertures; and determining the physiological signal from the received light. Additionally or alternatively to one or more examples disclosed above, in other examples, the electronic device further includes a back crystal in contact with the one or more apertures, a component mounting plane in contact with the one or more light emitters and the one or more sensors, one or more windows, and an adhesive configured to attach the one or more windows to the electronic device, the method further comprising receiving light from a reflection off at least one of the back crystal, the component mounting plane, and the adhesive. Additionally or alternatively to one or more examples disclosed above, in other examples, the method further comprises changing an angle of at least one of the one or more reflected light paths. Additionally or alternatively to one or more examples disclosed above, in other examples, the method further comprises selectively reflecting one or more wavelengths of the light. 
     In some examples, a method of a first device communicating with a second device is disclosed. The method may comprise: sending, to a second device, a measured reflected signal from one or more reflective surfaces in contact with one or more apertures of the first device; and receiving, from the second device, a physiological signal. 
     Although the disclosed examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosed examples as defined by the appended claims.

Metadata:
Filing Date: 20180907
Publication Date: 20241210
Grant Date: 20241210
Priority Date: 20140827
Inventors: HAN, Chin San
Assignee: APPLE INC
CPC Classifications: [{"code": "A61B2562/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/7264", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/6898", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/681", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/14551", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/0295", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/0261", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/02438", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/0013", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/02427", "inventive": true, "first": true, "tree": "[]"}, {"code": "A61B5/02427", "inventive": true, "first": true, "tree": "[]"}, {"code": "A61B2562/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/7264", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/6898", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/681", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/14551", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/0295", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/0261", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/02438", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/0013", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/02427", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 53801235