研究目的
To measure depth-dependent blood volume changes using multi-wavelength photoplethysmography sensors.
研究成果
The developed omnidirectional multi-wavelength optical sensor module successfully measured pulsatile waveforms at all four wavelengths in various measuring sites, confirming the feasibility of measuring PPG using a multi-wavelength circular optical sensor. This research provides insights into future sensor fabrication and potential clinical applications.
研究不足
The study acknowledges that the signal quality at the blue wavelength was poor, possibly due to the sensitivity of the photodetector and the penetration depth of the blue wavelength. Additionally, pulsatile waveforms were not observed in signal acquisition from the outer layer of the sensor, indicating limitations in source-detector distance.
1：Experimental Design and Method Selection:
The study designed an omnidirectional optical sensor module with multiple wavelengths to measure photoplethysmogram. The sensor was manufactured by making a hole in a metal plate and mounting an LED therein, with four wavelength LEDs arranged concentrically around a photodetector.
2：Sample Selection and Data Sources:
The photoplethymogram was measured at various peripheral sites of the human body such as fingertip, earlobe, toe, forehead, and wrist.
3：List of Experimental Equipment and Materials:
The sensor included blue (460 nm), green (530 nm), red (660 nm), and IR (940 nm) LEDs. Photoluminescent tests were conducted to measure irradiation light intensity.
4：Experimental Procedures and Operational Workflow:
The sensor's performance was evaluated by measuring pulsatile waveforms at all four wavelengths in all measuring sites. The signals were acquired at a sampling frequency of 500 Hz for each wavelength through RS232C serial communication.
5：Data Analysis Methods:
The obtained signal was filtered using a finite impulse response (FIR) bandpass filter with a 0.5–5 Hz passband.
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