Influence of lift-off on microwave open-ended waveguide time of flight based tire inspection

The comfort and safety of driving vehicles largely depends on state of the tires. However, inspecting defects within tires is a challenging task. Numerous inspection methods have been proposed such as X-ray, impact-acoustic and machine vision. X-ray is a mature method providing high-resolution images of tire structure but it is costly and requires safety precaution. Impact-acoustic requires impactor and cannot tolerate noisy environments; machine vision is computationally slow and can only obtain information of the tire surface. In this paper, we propose the use of Microwave inspection using open-ended waveguide probe that is fast, low cost and can penetrate to reveal the internal structure of the tire. This is achieved using Time of Flight (ToF) to extract the tire features for the reconstruction. Cumulative side lobe level is used to determine the optimum lift-off scanning range which is used for the tire scanning. Experimental results show that the technique can image the surface and reveal the internal structure of the tire.