Pressing position and pressure measurement method based on photoplethysmographic imaging

A pressing position and pressure measurement method based on PPG (photoplethysmographic) imaging, comprising:

• step (1):
• placing a camera that covers a pressing area to be detected, collecting video by the camera, and measuring a blood perfusion change from a change of a PPG signal intensity of the pressing area to be detected in an image channel of each video frame, so as to measure a change of a blood perfusion in a tissue blood vessel in the pressing area of a human limb;
• step (2):
• carrying out calibration before the measurement starts;
• touching the pressing area with a finger and gradually increasing a pressure;
• with the increase of the pressing pressure, obtaining PPG signal intensities under different pressures, so that the PPG signal characteristics of a diastolic pressure and a systolic pressure disappear sequentially;
• firstly, recording a corresponding PPG signal intensity v1 and a diastolic pressure p1 as the PPG signal characteristics of the diastolic pressure disappear;
• with the increase of the pressing pressure, recording a corresponding PPG signal intensity v2 and a systolic pressure p2 as the PPG signal characteristics of the systolic pressure disappear;
• obtaining a waveform change diagram of the PPG signal intensity in the pressing area, wherein when the characteristics of the PPG signal intensities of the systolic pressure and the diastolic pressure disappear, respectively, the corresponding diastolic pressure p1 and systolic pressure p2 are applied pressure values;
• completing the calibration;
• step (3):
• fitting an approximate relation curve of the pressure versus the blood perfusion change:
• according to the waveform change diagram of the PPG signal intensity in the pressing area obtained in step (2), determining a moment when different applied pressures are equivalent to the diastolic pressure and the systolic pressure;
• according to the corresponding relation between the two groups of PPG signals obtained in step (2) and the applied pressures, obtaining by fitting the approximate relation curve of the change of the PPG signals versus the applied pressure;
• and
• step (4):
• locating the pressing position and measuring the pressure, and obtaining the pressing position and the applied pressure values according to the approximate relation curve of the change of the PPG signals versus the applied pressure obtained in step (3).