CPC A61B 5/7214 (2013.01) [A61B 5/0036 (2018.08); A61B 5/02433 (2013.01); A61B 5/1102 (2013.01); A61B 5/1128 (2013.01); A61B 5/14552 (2013.01); A61B 5/7207 (2013.01); H04N 23/11 (2023.01); A61B 5/02427 (2013.01); A61B 2576/00 (2013.01); G06T 7/0012 (2013.01); G06T 2207/10048 (2013.01); G06T 2207/30076 (2013.01)] | 9 Claims |
1. A device for generating a photoplethysmographic image carrying vital sign information of a subject, said device comprising:
an input interface unit that obtains image data of a skin region of a subject in at least two different wavelength channels,
wherein said image data comprises two or more image frames acquired by detecting light transmitted through or reflected from the skin region over time, and
wherein said image data comprise wavelength-dependent reflection or transmission information in said at least two different wavelength channels;
a combination unit that combines, per pixel or group of pixels and per time instant, image data values of said at least two different wavelength channels to obtain a time-variant pulse signal per pixel or group of pixels,
wherein the combination unit is configured to combine the image data values of said at least two different wavelength channels are combined as a weighted combination of one of temporally normalized wavelength channels or of the logarithm of wavelength channels, and
wherein the sum of the weights used for the combination is zero;
an image generating unit that generates a photoplethysmographic image from a property of the respective pulse signals in a time window including at least two image frames,
wherein the image generation unit is configured to compute at least one of an amplitude map and a phase map of the temporal variations of the time-variant pulse signals as the photoplethysmographic image, and
wherein the image generation unit is configured to compute at least one of:
the amplitude map as an inner product of the respective pulse signal with a reference signal, and the phase of the phase map with respect to a reference signal; and
a computation unit that computes weights for determining said weighted averages and/or that computes said reference signal from a skin area covered by a plurality of pixels in said image frames.
|