Trinocular stereo system with object space oriented correlation for inner pipe inspection

•Trinocular stereo vision for inner geometry pipe inspection.•Cameras symmetrically positioned with respect to the pipe axis for better sensitivity distribution.•Object space oriented point selection for correlation.•Point cloud intrinsically organized in a regular mesh using a cylindrical coordinate system.

Geometric inspection of pipes is a fundamental task in the oil industry. This work shows the development of a system to measure the geometry of a pipe’s inner wall using a trinocular stereo system. Natural pipe texture is used to produce a point cloud intrinsically organized in a regular mesh in a cylindrical coordinate system. The main novelty in the proposed algorithm is the definition of a regular kernel in object space, which is mathematically projected to each image plane using the inverse triangulation approach. The use of a triple correlation coefficient estimator led to simultaneous detection of homologous points. Experiments depict measurements of pipes with real and simulated textures, and results on a calibrated pipe of approximately 150 mm in diameter showed a mean error of 0.3 mm with a standard deviation of 0.2 mm.