Reflective photoplethysmography sensor with ring-shaped photodiode

This paper reports a fabrication process of pulse wave sensor and detection result of pulse wave using the ring-shaped sensor, which has ring-shaped photodiode. An LED is located at the center of a photodiode. This structure achieved noninvasive detection of the pulse wave and does not have the directivity. Therefore, the ring-shaped sensor is expected to reduce noises of body motion (motion artifacts). We evaluated the characteristics of the photodiode and detected the pulse wave using the fabricated sensor. As a result, the ring-shaped sensor can detect the pulse wave. Furthermore, detection of the pulse wave can be applied to measure the pulse wave velocity (PWV).