Photoplethysmography (PPG) has come to be accepted as a common, non-invasive method for measuring the level of oxygen saturation in arterial blood. This paper describes a variation of the accepted PPG technique, to provide a contact-less and non-invasive method of characterizing dermal perfusion. It employs a 3-CCD, multi-spectral camera, to image the selected area. The acquired images are analysed by making use of the fact that the absorption co-efficient of oxygenated blood is more in the infra-red (IR) region of the spectrum, when compared to the red region. This fact is utilised to characterize the extent of dermal perfusion in the selected area of the skin.
Dr. Madhu Mohan N. and Kumar, V. J., “Contact-less, Multi-Spectral Imaging of Dermal Perfusion”, in 2008 IEEE Instrumentation and Measurement Technology Conference, 2008.