Wearable sensor for acquisition of biometrics data

A method for photoplethysmography acquisition comprising:

• a) coupling a color camera in optical contact against a skin surface of a subject;
• b) coupling a first solid-state light source and a second solid-state light source in optical contact against the skin surface, wherein the first solid-state light source has a first wavelength range and the second light source has a second wavelength range,
• wherein the first and second wavelength ranges are non-overlapping,
• and wherein, over both the first and second wavelength ranges, values for extinction coefficients of hemoglobin Hb and oxygenated hemoglobin HbO2 at the skin surface are unequal at each wavelength;
• c) alternately energizing the first light source and second light source over a predetermined time interval;
• d) acquiring, at the color camera, a first sequence of images from the skin surface using light of the first wavelength range and a second sequence of images from the skin surface using light of the second wavelength range;
• e) for the first sequence of images, computing periodic changes in hue over the predetermined time interval and generating a first set of photoplethysmography data according to the hue computation;
• f) for the second sequence of images, computing periodic changes in hue over the predetermined time interval and generating a second set of photoplethysmography data according to the hue computation;
• g) computing a heart rate and a respiratory rate from either the first or second set of photoplethysmography data;
• and
• h) computing a hemoglobin saturation value SpO2 according to ratios computed using the first and second sets of photoplethysmography data.