Method and device for detecting blood flow rate

A device for detecting a blood flow rate, comprising

• a device body including a detection area, which is corresponding to a skin of a living body;
• a light source generator disposed inside the device body and exposed to the detection area, the light source generator enabled to generate a light of a detection light source projected onto the skin of the living body, wherein the light of the detection light source passes through the skin of the living body and reaches a blood vessel in the skin of the living body;
• a photo sensor, which includes a plurality of photo sensing unit, disposed inside the device body and exposed to the detection area, the photo sensor enabled to receive a polarized light beam reflected by expanding or contracting the blood vessel, which is illuminated by the light of the detection light source, wherein while the blood vessel is expanding, one of the photo sensing units receives one polarized light beam reflected at a first polarization angle and generates a first photoplethysmographic (PPG) signal, and wherein while the blood vessel is contracting, another one of the photo sensing units receives another polarized light beam reflected at a second polarization angle and generates a second PPG signal;
• and
• a microprocessor disposed inside the device body and connected with the light source generator and the photo sensor, the microprocessor receiving at least one first PPG signal and at least one second PPG signal from the photo sensor, working out an offset of received light beams and a time derivative of the offset according to a sequence of the first PPG signal and the second PPG signal, and according to a distance difference between two of the photo sensing units generated at the first polarization angle and the second polarization angle, the microprocessor calculating and converting the offset of the received light beams and the time derivative of the offset into a blood flow rate.