Estimation of Vital Signs from Ambient-Light Non-Contact Photoplethysmography
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Abstract In this thesis we have investigated different aspects of non-contact photoplethysmography (PPG) using only ambient lighting. We have investigated how to develop a functional, automatic system based on this to detect heart rate. We have also investigated how to use the concept of non-contact PPG to acquire further relevant medical information from a human subject. Abstract We have investigated different color spaces and found that the Hue and Saturation channels from HSL and HSV color spaces are far superior to the Green channel of the RGB color space, which has previously been used. Especially under circumstances with much noise, are these channels superior and more robust against noise. Abstract The concept of independent component analysis (ICA) has been investigated as a method of improving results. It is found to improve some channels and color spaces, but the best ICA channel does not have better performance than the best non-ICA channel. Abstract The phase of, and difference between, PPG signals has been investigated as a means of acquiring medical information. The phase measurements are highly vulnerable to noise, but there are indications that occlusion can induce a phase difference between different limbs. This difference can be used to calculate change in blood pressure. Abstract We have synchronized ECG and PPG data, and found that there is a high correlation between the two. Pulse transit time (PTT) from the heart to the measurement site can be calculated using this synchronized information. Abstract Further have different motion compensation algorithms and signal processing techniques been investigated with the goal of improving the PPG signal and a programs ability to automatically detect heart rate.