Illumination Adaptation in a Multi-Wavelength Opto-Electronic Patch Sensor.pdf (3.38 MB)

Illumination adaptation in a multi-wavelength opto-electronic patch sensor

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journal contribution
posted on 02.09.2020 by Liangwen Yan, Yue Yu, Sijung Hu, David Mulvaney, Panos Blanos, Samah Alharbi, Matthew Hayes
In capturing high-quality photoplethysmographic signals, it is crucial to ensure that appropriate illumination intensities are used. The purpose of the study was to deliver controlled illumination intensities for a multi-wavelength opto-electronic patch sensor that has four separate arrays each consisting of four light-emitting diodes (LEDs), the wavelength of the light generated by each array being different. The study achieved the following: (1) a linear constant current source LED driver incorporating series negative feedback using an integrated operational amplifier circuit; (2) the fitting of a linear regression equation to provide rapid determination of the LEDs driver voltage; and (3) an algorithm for the automatic adjustment of the output voltage to ensure suitable LED illumination. The data from a single centrally-located photo detector, which is capable of capturing all four channels of back-light in a time-multiplexed manner, were used to monitor heart rate and blood oxygen saturation. This paper provides circuitry for driving the LEDs and describes an adaptive algorithm implemented on a microcontroller unit that monitors the quality of the photo detector signals received in order to control each of the individual currents being supplied to the LED arrays. The study demonstrated that the operation of the new circuitry in its ability to adapt LED illumination to the strength of the signal received and the performance of the adaptive system was compared with that of a non-adaptive approach.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Published in

Sensors

Volume

20

Issue

17

Publisher

MDPI AG

Version

VoR (Version of Record)

Rights holder

© The Authors

Publisher statement

This is an Open Access Article. It is published by MDPI under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: https://creativecommons.org/licenses/by/4.0/

Acceptance date

19/08/2020

Publication date

2020-08-21

Copyright date

2020

eISSN

1424-8220

Language

en

Depositor

Dr Sijung Hu. Deposit date: 28 August 2020

Article number

4734

Licence

Exports