Internal surface inspection method under linear structured light illumination based on dual non-coaxial optical paths

Abstract

Abstract The inner space of tubular and hole-like workpieces, such as oil pipes and cylinders, is limited in volume and has no effective means of measuring the inner surface under geometric constraints. This paper proposes a non-coaxial optical path line structured light method for inner surface inspection, which can significantly reduce the device size and working distance. The method constructs two non-coaxial optical paths for light source and imaging, and uses two fixed reflectors to achieve the deflection of the optical axes of the light source and imaging paths. After theoretical derivation and verification, a sample device was designed and fabricated for experiments. The device measures approximately 22 mm by 24 mm in cross-section, the maximum insertion distance is about 200 mm, and the minimum inner diameter of the accessible space is 50 mm. The results show that the optical path design does not destroy the original homography relationship, and can still ensure the measurement capability comparable to the existing methods when reducing the device size to 10% of the original. The method has obvious advantages when applied to the inspection of tubular and hole-like workpieces in fields such as petrochemical industry, military equipment, etc.