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The interrogation of polarisation state of light is a developing technique in biomedical imaging. As polarised light interacts with structural changes in tissue, it has seen use in differentiation between (pre)cancerous and noncancerous tissue, for example. In biomedical imaging rapid diagnostics using minimally invasive techniques is desirable. Endoscopy is already very prevalent in medicine and therefore miniaturisation of polarimetry systems onto endoscopic platforms is a natural development. Flexibility of such a device allows navigation to more complicated parts of the body. All polarimetric systems consist of a polarisation state generator (PSG) and a polarisation state analyser (PSA) which need to be integrated into such a system. A rigid endoscope capable of imaging a full 4×4 Mueller matrix has been developed by Qi et al. This endoscope achieves the polarisation state generation a rigid rotating sheath. Partial polarimetric endoscopy which captures a 3×3 Mueller matrix has also been demonstrated and is easier to achieve since it does not require quarter wave plates in the generator or analyser. Clancy et al and Qi et al both demonstrate a rigid polarimetric endoscopy using a stereo endoscope and a standard rigid endoscopy, respectively. Integration of polarisation state analyser and generator into the tip has been demonstrated using complex mechanical designs. However questions have been raised regarding the electromagnetic compatibility of such a system due to the presence of motors in the tip. Forward et al present a flexible 3×3 fibre based probe that uses diced polarisers orientated at the horizontal, vertical, and -45 degree positions to generate and acquire the necessary polarisation states. This work presents an imaging probe designed to enable in-vivo polarimetry measurements using a micro camera on the tip as a sensor. A 3×3 Mueller matrix image of crossed linear polarisers, captured using a micro camera is demonstrated. This device demonstrates the potential of micro camera sensors in providing 2-dimensional polarimetry data in a flexible endoscopic system. For a device to be used in a clinical setting it needs to be capable of providing data rapidly when it is needed, as well as being navigable to the target location. A fibre optically illuminated endoscope with micro-camera sensor allows for rapid switching of illumination fibres using backend illumination systems as well as rapid acquisition of data. Optical fibres enable the probe to be rigid or flexible depending on application, and the camera at the tip ensures consistent image quality regardless of application area. An idealised system and its potential future of polarimetry in translational biophotonic devices is also discussed.
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