disp2ppg: Pulse Wave Generation to PPG Sensor using Display

Wearable devices are often used to record the user's biometric information. Among biometric data, pulse data has been used in methods such as heart rate monitoring and emotion estimation. The most common type of pulse sensor is the photoplethysmogram (PPG), which irradiates a green LED on the skin and measures pulse data from changes in the light reflected through the blood vessels. PPG sensors have been implemented in commercially available wearable devices such as smartwatches. When a smartwatch is worn on an artificial body such as a prosthetic hand or a robotic arm, correct data cannot be acquired because there is no blood flow. In this study, we propose a method that enables the PPG sensor to measure arbitrary pulse data using a display. If this method is successful, it will be possible to input pulse data measured at the junction of the live body and the prosthetic hand to the display, and have the smartwatch attached to the prosthetic hand read the same pulse data. In this paper, we focus on the heart rate and report the results of an experiment in which a target heart rate was input and the display was controlled to determine whether the target heart rate could be obtained by a smartwatch. We implemented a display drawing program and conducted the evaluation using five kinds of smartwatches and four kinds of displays. Results showed that the error between the target heart rate and the heart rate acquired by the smartwatch was within +/- 3 beats per minute in many cases.