Ambient Light Contribution as a Reference for Motion Artefacts Reduction in Photoplethysmography Topics: Biomedical Sensors; Electrocardiography and Heart Monitoring; Health Monitoring Devices; Wearable and Mobile Devices In Proceedings of the 13th International Joint Conference on Biomedical Engineering Systems and Technologies - Volume 1: BIOSTEC, 23-32, 2020 , Valletta, Malta