Optimal Spatial Resolution in Catadioptric Sensors for Pipe Inspection Applications

Spatial resolution in imaging systems used for pipe inspection plays a crucial role. Catadioptric imaging systems, which normally consist of a perspective camera and a hyperbolic mirror provide a cost-effective solution. Also, they would be the imaging system of choice in confined spaces due to their size factor. In this paper we, (1) define the cylindrical spatial resolution for the pipe inspection purposes, (2) formulate the spatial resolution mathematically based on system´s parameters such as, the focal length of the perspective camera, and the mirror shape, and (3) provide a guideline on having the optimal configuration yielding the highest spatial resolution. Numerical results are provided which are also supported by experimental results. Experimentation was carried out using a Catadioptric imaging system mounted on a motorized linear track moving inside a PVC pipe. Checkerboard calibration patterns were used through experiments to verify on results.