IEEE Trans Biomed Circuits Syst. 2007 Dec;1(4):235-41. doi: 10.1109/TBCAS.2007.910900.
This paper addresses the design considerations of a novel earpiece photoplethymograph (PPG) sensor and its in-situ evaluation results. The device is encapsulated with multiple LEDs and photodiodes based on a reflective PPG design. A compact and low power circuitry was developed for signal control and conditioning. PPG signals with an averaged ac/dc ratio of 0.001-0.01 and 10% relative strength (compared to finger-based approach) were recorded from the superior and posterior auricular skins. The integrity of PPG signal and accuracy of heart rate detection were evaluated and the results showed that with adequate optical shielding and the proposed passive motion cancellation, the device was able to reliably detect heart rate both during rest and moderate exercise. The proposed sensor design is low power, easy to wear compared to conventional earlobe PPG devices.
本文介绍了一种新型耳塞式光电容积脉搏波（PPG）传感器的设计考虑因素及其现场评估结果。该设备基于反射式 PPG 设计，封装了多个 LED 和光电二极管。为了进行信号控制和调节，开发了一种紧凑且低功耗的电路。从耳上和耳后皮肤记录到的 PPG 信号的平均交流/直流比为 0.001-0.01，相对强度为 10%（与手指方法相比）。评估了 PPG 信号的完整性和心率检测的准确性，结果表明，通过充分的光学屏蔽和所提出的被动运动消除，该设备能够在休息和适度运动期间可靠地检测心率。与传统的耳垂 PPG 设备相比，所提出的传感器设计功耗低，佩戴方便。
