US 11,944,416 B2
Photoplethysmography (PPG) apparatus and method for determining physiological changes
Estanislao Glenn Bondice, Singapore (SG); Suppasit Chuwatsawat, Singapore (SG); Wiputpong Klinsukon, Singapore (SG); Somchai Baotong, Singapore (SG); and Visit Thaveeprungsriporn, Singapore (SG)
Assigned to Nitto Denko Corporation, (JP)
Appl. No. 16/633,896
Filed by Nitto Denko Corporation, Osaka (JP)
PCT Filed Jul. 26, 2018, PCT No. PCT/SG2018/050375
§ 371(c)(1), (2) Date Jan. 24, 2020,
PCT Pub. No. WO2019/022670, PCT Pub. Date Jan. 31, 2019.
Claims priority of application No. 10201706109Y (SG), filed on Jul. 26, 2017.
Prior Publication US 2020/0329986 A1, Oct. 22, 2020
Int. Cl. A61B 5/00 (2006.01); A61B 5/024 (2006.01)
CPC A61B 5/02427 (2013.01) [A61B 5/02416 (2013.01); A61B 5/7225 (2013.01); A61B 5/725 (2013.01); A61B 2560/0209 (2013.01); A61B 2562/0233 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A photoplethysmography (PPG) apparatus for determining physiological changes, comprising:
a light source configured to emit a light signal of one wavelength towards a user's skin, the light signal controlled by a driving current to have a variable intensity level dependent on a skin characteristic of the user's skin;
a driving circuit including a signal transistor having a base current for controlling the driving current to alternate the light signal between two ON states and one OFF state, at a frequency of greater than 80 Hz, the two ON states corresponding to two different positive intensity levels of the light signal of the same wavelength for two different skin characteristics;
first and second photodetectors connected in parallel and configured to detect a reflection of the light signal from the user's skin to provide a combined current signal; and
a signal processing circuit operable to convert the combined current signal into a PPG signal for determining the physiological changes.
 
16. A photoplethysmography (PPG) method for determining physiological changes, comprising:
emitting, using a light source, a light signal of one wavelength towards a user's skin, the light signal controlled by a driving current to have a variable intensity level dependent on a skin characteristic of the user's skin;
controlling, using a driving circuit including a signal transistor having a base current, the driving current to alternate the light signal between two ON states and one OFF state, at a frequency of greater than 80 Hz, the two ON states corresponding to two different positive intensity levels of the light signal of the same wavelength for two different skin characteristics;
detecting, using first and second photodetectors connected in parallel, a reflection of the light signal from the user's skin to provide a combined current signal; and
converting, using a signal processing circuit, the combined current signal into a PPG signal for determining the physiological changes.