Experimental Characterisation of an Optical Tracking Sensor for Capsule Localisation in the Small Intestine

Abstract

This study reports the first systematic characterization of a miniature laser-based optical tracking sensor for smart capsule odometry in the small intestine in controlled and biologically relevant conditions. Data was collected by attaching the sensor to a CNC milling machine, allowing sensor measurements to be validated against ground-truth displacement data. A series of experiments were performed to probe the effects of biological tissue, interface material, material thickness, and environmental illumination on sensor performance. The findings suggest that the sensor exhibits consistent, repeatable results in identical conditions. Additionally, the effect of intestinal digesta content on the localisation performance of the sensor is investigated for the first time. Results show a 40% underestimation of distance travelled when traversing over high levels of digesta, indicating the importance of patients’ fasting before any in-vitro application. Despite this underestimation, the near-linear performance of the sensor indicates its feasibility for capsule odometry applications given suitable calibration.