Wireless Photoplethysmograph Knuckle Sensor System for Measuring Finger Motions

In this paper, we present the on-going study to explore the use of photoplethysmograph (PPG), and inertial measurement unit (IMU) sensors to sense the movement of the fingers and the orientation of the hand. This paper focuses on an optical sensor system that can detect the movement of the fingers by utilizing the photoplethysmograph (PPG). The optical sensor consists of the light emitting and detecting components, which are two LEDs and a photodiode in our system. The photodiode senses the intensity of the light emitted from each LED after the light passes through the tissue. As a finger moves, the light diffused through the skin of the knuckle, therefore, finger position can be differentiated. In this paper, we discuss the sensitivity and the response time of the knuckle sensor system with respect to the finger motions.