Potential for remote TD-NIRS imaging using a TCSPC camera

Advances in the CMOS process enables single-photon detection and timing to occur within an individual pixel. Pixel arrays incorporating this in-pixel timing methodology have been increasing in size, facilitating time of flight (ToF) imaging. This means that a fully parallel approach can be made to the collection of images, dramatically speeding up data collection in relation to sample scanning and allowing imaging based on time-correlated single-photon counting (TCSPC) to be made in real time. In this work we make use of a commercial TCSPC camera, based on an array of 192 x 126 imaging pixels with in-pixel timing applied in the area of time-domain near infrared spectroscopy. The potential of remote imaging using this methodology was demonstrated using two model systems. The effect of increasing scattering coefficient using a liquid based (milk added to water) system to assess real time potential was investigated. Additionally a more complex system consisting of a solid with liquid interior (egg) to verify the potential of remote imaging into the interior of the object with different illumination conditions was studied. Using a time-slicing approach intensity images related to each time bin in the ToF distribution were obtained and contrast between the yolk and albumin within the egg was observed.