Abstract

A non-invasive optical measurement system based on a broadband light source and color filters has been developed for determining pulse rate and arterial blood oxygen saturation (SaO₂). In contrast to classical pulse oximetry using red and infrared LEDs to measure the peripheral capillary oxygen saturation (SpO₂), we use color filters in our system. Spectral analysis of human tissue can be easily achieved by combining a tiny color filter matrix and a commercial CMOS/CCD image sensor. During system operation, white LED light illuminates our tissue (e.g., a finger), while a CCD sensor covered by filters detects the light transmitted through that tissue. The CCD sensor is controlled by a Field Programmable Gate Array (FPGA) and a microcontroller. The detected photoplethysmographic (PPG) signal is transferred to a host computer and analyzed with MATLAB. After sensor system calibration, pulse rate and SpO₂ can be simply extracted from the PPG signal. The heart rate and SpO₂ of different volunteers are then measured simultaneously by commercial pulse oximetry and the proposed sensor system, in which results from both devices show good agreement. To integrate more functions into system, nanostructured color filter matrix containing 15 filters for different wavelengths is designed and fabricated. This filter can be designed to provide transmission peaks over the visible and near-infrared range (i.e., the human tissue optical transparent window) and has a high potential to be fabricated directly on top of pixels of an image sensor.

© 2019 SPIE/OSA