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.