학술논문
적외선을 사용한 반사형 PPG 측정 장치에서의 주변광의 영향에 대한 연구
Document Type
Academic Journal
Author
Source
한국정보전자통신기술학회 논문지. 2023-12 16(6):406-412
Subject
Language
Korean
ISSN
2005-081X
2288-9302
2288-9302
Abstract
본 논문에서는 주변광으로 인한 잡음이 적외선을 사용한 반사형 PPG 측정 장치에 미치는 영향을 고찰하였다. 주변광으로 인한 잡음은 일반적인 상황과 특수한 상황으로 나누어 고찰하였으며, 일반적인 상황은 시간과 주변 광원의 변화로 인한 잡음을 무작위로 관찰하였고, 특수한 상황은 할로겐램프를 사용하여 측정 장치와 광원과의 거리에 따른 잡음 변화를 관찰하였다. 실험은 각각의 상황에 따라 PPG 신호를 실시간으로 측정하고 데이터를 획득하였으며, 측정된 데이터는 시간 영역과 주파수 영역에서 분석하였다. 먼저 일반적인 상황 실험을 통해 주변광의 밝기에 따라 잡음이 커짐을 육안으로 확인하였고, 주파수 분석을 통해 백색잡음, 전력선 잡음, 회로 내부 잡음이 발생함을 확인하였다. 또한 할로겐램프를 사용하여 주변광과의 거리 변화에 따른 잡음의 변화를 실험하고 SNR을 계산하였다, 실험 결과, 278.3W/m²의 복사 조도를 갖는 50cm 거리에서는 3.2dB의 SNR을 나타내었고 그 이하의 SNR에서는 정상적인 측정이 어려움을 확인하였으며, 27.7W/m²의 복사조도를 갖는 2m의 거리에서 18.2dB 값을 나타내었고 그 이상 값에서 필터를 통해 정상적인 PPG 측정이 가능함을 확인하였다.
In this paper, we studied the effect of noise caused by ambient light on a reflective PPG measurement device using infrared light. Noise caused by ambient light was examined by dividing it into general situations and special situations. In the general situation, noise due to changes in time and ambient light sources was randomly observed, and in the special situation, a halogen lamp was used to observe the effect of noise variations. In the experiment, PPG signals were measured and data acquired in real-time depending on each situation, and the measured data was analyzed in the time domain and frequency domain. First, through a general situation experiments, it was visually observed that noise increases with the brightness of ambient light, and through frequency analysis, it was observed that the noise sources were white noise, power line noise, and internal noise of the circuit. Futhermore, using a halogen lamp, we experimented with the change in noise depending on the change in distance from the ambient light and calculated the SNR. As a result of the experiment, an SNR of 3.2 dB was shown at a distance of 50 cm with an irradiance of 278.3 W/m². It was observed that normal measurement was difficult at SNRs below that, and an irradiance of 27.7 W/m² was obtained. It showed a value of 18.2 dB at a distance of 2 m, and it was observed that normal PPG measurement was possible through a filter at values above that.
In this paper, we studied the effect of noise caused by ambient light on a reflective PPG measurement device using infrared light. Noise caused by ambient light was examined by dividing it into general situations and special situations. In the general situation, noise due to changes in time and ambient light sources was randomly observed, and in the special situation, a halogen lamp was used to observe the effect of noise variations. In the experiment, PPG signals were measured and data acquired in real-time depending on each situation, and the measured data was analyzed in the time domain and frequency domain. First, through a general situation experiments, it was visually observed that noise increases with the brightness of ambient light, and through frequency analysis, it was observed that the noise sources were white noise, power line noise, and internal noise of the circuit. Futhermore, using a halogen lamp, we experimented with the change in noise depending on the change in distance from the ambient light and calculated the SNR. As a result of the experiment, an SNR of 3.2 dB was shown at a distance of 50 cm with an irradiance of 278.3 W/m². It was observed that normal measurement was difficult at SNRs below that, and an irradiance of 27.7 W/m² was obtained. It showed a value of 18.2 dB at a distance of 2 m, and it was observed that normal PPG measurement was possible through a filter at values above that.