Feasibility of non-contact photoplethysmography

This thesis explores and investigates the feasibility of a non-contact photoplethysmography system operating in both transmission and reflection modes. Several issues are addressed in the implementation of the non-contact system, including the dynamic range of PPG signals, ambient artefacts and effects of direct coupling, which is light that is detected without any interaction with the measured tissue area. Plethysmography has been used in a range of biomedical applications to study blood volume changes. All current applications employ contact probes, where the transducers are positioned directly on the tissue surface. Non-contact measurements, where the transducers have no direct contact with the tissue surface, i.e. skin, are in demand for clinical benefits. Measurements by non-contact photoplethysmography can be obtained from any tissue since it is not probe limited, can be used on patients with bums as the probe does not touch the skin, and can reduce anxiety in patients, as they are not wired to any equipment. [Continues.]