REMOTE MONITORING OF VITAL SIGNS
First Claim
1. A method of suppressing ambient light interference in a PPG image signal comprising the steps of:
- imaging a region of interest on a subject'"'"'s skin using a video camera to obtain a PPG image signal comprising periodic intensity variations in ambient light reflected from the region of interest;
imaging a reference region of interest not on the subject'"'"'s skin using the same video camera to obtain a reference signal;
spectrally analysing the reference signal using an auto-regressive (AR) all pole model and identifying poles corresponding to spectral components;
spectrally analysing the PPG image signal using an auto-regressive (AR) all pole model to identify poles corresponding to spectral components therein and ignoring poles corresponding to those identified as spectral components of the reference signal.
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Accused Products
Abstract
A method of remote monitoring of vital signs by detecting the PPG signal in an image of a subject taken by a video camera such as a webcam. The PPG signal is identified by auto-regressive analysis of ambient light reflected from a region of interest on the subject'"'"'s skin. Frequency components of the ambient light and aliasing artefacts resulting from the frame rate of the video camera are cancelled by auto-regressive analysis of ambient light reflected from a region of interest not on the subject'"'"'s skin, e.g. in the background. This reveals the spectral content of the ambient light allowing identification of the subject'"'"'s PPG signal. Heart rate, oxygen saturation and breathing rate are obtained from the PPG signal. The values can be combined into a wellness index based on a statistical analysis of the values.
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Citations
27 Claims
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1. A method of suppressing ambient light interference in a PPG image signal comprising the steps of:
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imaging a region of interest on a subject'"'"'s skin using a video camera to obtain a PPG image signal comprising periodic intensity variations in ambient light reflected from the region of interest; imaging a reference region of interest not on the subject'"'"'s skin using the same video camera to obtain a reference signal; spectrally analysing the reference signal using an auto-regressive (AR) all pole model and identifying poles corresponding to spectral components; spectrally analysing the PPG image signal using an auto-regressive (AR) all pole model to identify poles corresponding to spectral components therein and ignoring poles corresponding to those identified as spectral components of the reference signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 19, 21, 22, 23, 24, 25)
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- 11. A method of obtaining an estimate of heart rate of a human or animal subject comprising the steps of obtaining a PPG signal from the subject, spectrally analysing the PPG signal using a plurality of auto-regressive (AR) all pole models of different order to identify from each model a spectral component representing the heart rate and producing a heart rate estimate corresponding to that spectral component, fusing the estimates of the heart rate from the different models thereby producing a robust heart rate estimate.
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15. A method of obtaining an estimate of breathing rate of a human or animal subject comprising the steps of obtaining a PPG signal from the subject, filtering and downsampling the PPG signal before spectrally analysing it using a plurality of auto-regressive (AR) all pole models of different order to identify from each model a spectral component representing the breathing rate and producing a breathing rate estimate corresponding to that spectral component, fusing the estimates of the breathing rate from the different models thereby producing a robust breathing rate estimate.
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20. A method of measuring one or more of a subject'"'"'s vital signs by PPG imaging of the subject using a video camera and performing a facial recognition process on an image of the subject obtained by the same camera to link the identity of the subject to the vital signs measurement.
Specification