Method and system for carrying out photoplethysmography

• US 10,271,746 B2
• Filed: 10/04/2010
• Issued: 04/30/2019
• Est. Priority Date: 10/06/2009
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Jeanne, Vincent, Cennini, Giovanni, Kirenko, Ihor Olehovych
• Primary Examiner(s): Dieterle, Jennifer
• Assistant Examiner(s): Bor, Helene
• Application Number:
  US13/500,336
• Publication Number:
  US 20120197137A1
• Time in Patent Office: 3,130 Days
• Field of Search: 600300, 600322, 600476, 600425, 128653
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths

Abstract

A method of photoplethysmography includes processing a signal based on at least one signal from at least one sensor arranged to capture light from a living subject to extract information on a characteristic of a periodic biological phenomenon. At least one of the signals from at least one sensor is obtained via sensing radiation as to a peak in an absorption spectrum of water.

Claims

1. A method of remote photoplethysmography, as to a living subject comprising:

directing polarized light from at least one light source onto an area of exposed skin of the living subject;

generating a plurality of signals corresponding to light reflected from the living subject captured by a respective at least one of a plurality of sensors sensitive to electromagnetic radiation in a respective one of different ranges of a spectrum including

a first range having a peak in an absorption spectrum of water, the first range being a subset of the spectrum,

a second range corresponding to green light for sensing variations in an amount of oxyhemoglobin in a skin of the living subject, the second range being a subset of the spectrum, and

a third range for sensing changes in light intensity across the entire spectrum;

generating an analysis signal corresponding to a periodic biological phenomenon by decorrelating signals of the plurality of signals produced from light captured in the third range from the plurality of signals; and

analyzing the analysis signal to determine at least one characteristic relating to a biological phenomenon of the living subject.

2. The method according to claim 1, wherein the peak is in a range corresponding to a range of wavelengths of electromagnetic radiation in air of above 750 nm.

3. The method according to claim 2, wherein the peak is in a range corresponding to a range of wavelengths of electromagnetic radiation in air smaller than 1100 nm.

4. The method according to claim 1, further comprising:

directing polarized light to the living subject, and wherein the captured light is filtered via a polarization dependent filter.

5. The method according to claim 1, wherein the second range is 500 nm to 600 nm.

6. The method according to claim 1, further comprising:

using a beam splitting arrangement to split light reflected from the living subject into a plurality of beams directed onto the plurality of sensors sensitive to electromagnetic radiation in the first and second ranges.

7. The method according to claim 6, wherein

splitting using a beam splitting arrangement is performed in at least one of the wavelength domain or in the polarization domain.

8. The method according to claim 7, further comprising:

directing polarized light to the living subject, wherein the generating includes filtering light reflected by the living subject via a polarization dependent filter.

9. The method according to claim 1, further comprising:

subtracting the signal in the second range from the signal in the first range.

10. The method according to claim 9, further comprising, prior to capturing light reflected by the living subject, capturing light from a calibration surface and adjusting parameters affecting at least one of the capture of light and a provision of at least one of the signals in the first and second ranges.

11. The method according to claim 1, wherein a sensor of the plurality of sensors that senses radiation in the third range detects changes in light intensity.

12. The method according to claim 1, wherein the peak in absorption spectrum of water is one of the group consisting of:

514 nm, 606 nm, 660 nm, 739 nm, 836 nm, or 970 nm.

13. The system according to claim 1, wherein the entire spectrum is greater than the combination of the first range and the second range.

14. A system for carrying out photoplethysmography as to a living subject, comprising:

at least one light source for directing polarized light onto an area of exposed skin of the living subject;

at least one filter for filtering light reflected from the living subject;

a plurality of sensors sensitive to electromagnetic radiation in different ranges of the spectrum including at least a respective sensor for each of;

a first range having a peak in an absorption spectrum of water,

a second range corresponding to green light for sensing variations in an amount of oxyhemoglobin in the skin, and

a third range for sensing changes in light intensity across the entire spectrum,

wherein, each of the plurality of sensors is configured to capture light reflected by the living subject and produce a plurality of signals corresponding to the captured light; and

a processing system configured to extract a signal of a periodic biological phenomenon by decorrelating signals of the plurality of signals produced from light captured in the third range from the plurality of signals.

15. A system for carrying out photoplethysmography as to a living subject, comprising:

a plurality of sensors configured to capture light sensitive to electromagnetic radiation that is reflected by a living subject, and to produce a plurality of corresponding signals, the light is captured in at least three ranges of the spectrum including;

a first range having a peak in an absorption spectrum of water,

a second range corresponding to green light for sensing variations in an amount of oxyhemoglobin in a skin of the living subject, wherein at least one of the plurality of sensors tuned to the second range is sensitive to variations in an amount of oxyhemoglobin in the skin, and

a third range including an entire spectrum for sensing changes in light intensity across the entire spectrum,

wherein light in each of the ranges is captured by at least one respective corresponding sensor of the plurality of sensors; and

a processing system configured to extract a signal of a periodic biological phenomenon by decorrelating signals of the plurality of signals produced from light captured in the third range from the plurality of signals.

16. The system of claim 15, wherein the peak is in a range corresponding to a range of wavelengths of electromagnetic radiation in air of above 750 nm.

17. The system of claim 16, wherein the peak is in a range corresponding to a range of wavelengths of electromagnetic radiation in air smaller than 1100 nm.

18. A system for carrying out photoplethysmography as to a living subject, comprising:

at least three sensors configured to capture light sensitive to electromagnetic radiation that is reflected by a living subject, and to produce a plurality of corresponding signals, wherein

a first of the at least three sensors captures light in a range of the spectrum having a peak in an absorption spectrum of water,

a second of the at least three sensors captures light in a range corresponding to green light, senses variations in an amount of oxyhemoglobin in the skin, and

a third of the at least three sensors captures light in a range including an entire spectrum for sensing changes in light intensity across the entire spectrum, and is less sensitive to variations in the reflectance of the skin than other sensors of the at least three sensors; and

a processing system configured to extract information characteristic of a periodic biological phenomenon by decorrelating signals of the plurality of signals produced from light captured in the third range from the plurality of signals.

19. The system of claim 18, wherein the peak is in a range corresponding to a range of wavelengths of electromagnetic radiation in air of above 750 nm.

20. The system of claim 19, wherein the peak is in a range corresponding to a range of wavelengths of electromagnetic radiation in air smaller than 1100 nm.