Study on Non-contact Heart Beat Measurement Method by Using Depth Sensor

For the purpose of simple observation of the mechanical phenomenon of the heart, we propose a new non-contact heartbeat measurement using a depth sensor. The depth sensor is an image sensor applying infrared light projection, and by using this sensor it is possible to calculate the three dimensional shape of the chest. In addition, it is possible to measure minute displacement appearing on the body surface by heartbeat. By visualizing the distribution of shape change using computer graphics, visualization of the heart beat is realized. Since the method is non-contact measurement, it does not prevent simultaneous measurement with the electrocardiogram. Therefore, it can be expected to be used as a means for simultaneously observing mechanical and electric phenomena of the heart. Simultaneous measurement using the method and electrocardiogram was performed. As a result of the measurement of three subjects (two males in 20 s and one male in 40 s), it was confirmed that the peak interval of the waveforms obtained by the two methods shows high consistency. The difference between the two peak intervals was less than 0.04 s. In the measurement, subjects stopped respiration, by applying the filtering process, it is also possible to detect the heartbeat waveform during breathing. During respiration, fluctuations are included in the measured waveform. In the simultaneous measurement of the two methods, the difference in the peak intervals is less than 0.05 s. This value is slightly larger than when breathing is stopped. In addition, as a result of the visualization of heart beat, the phase of vibrations by the heartbeat is different at each position on the chest surface. Specifically, a phase lag occurred upward direction from the abdominal, and it is visible by animation. This result suggests that the observation of the mechanical phenomenon of the heart may be realized by the method.