Transdermal Optical Imaging (TOI)

Anon-invasive technology that uses optical sensors and AI to analyse light reflected from the face, measuring changes in facial blood flow.

The skin's translucent nature allows light to reach the face vascular network, interacting with melanin and haemoglobin. TOI will track 17 regions of interest in three colour channels and use AI models to separate haemoglobin-rich signals from melanin-rich ones. The resulting signals undergo digital signal processing to determine plethysmographic (PPG) signals, removing high frequency noise and low frequency signals. This technology therefore enables accurate measurements of facial blood flow oscillations while being protected from variations in light conditions and skin tone. Recent technologies such as TOI typically relies on light being reflected from tissues. Light is affected by both absorption and scattering. Therefore the light reflected from tissues is captured by optical sensors (e.g., the CMOS sensors in the cameras of modern smartphones), which will convert photons of light into charges and ultimately into a series of digital images that constitute the video of the face.