Real-Time Inspection of Long Steel Products Using 3-D Sensors: Calibration and Registration

Calibration and registration are two challenging tasks required by a real-time inspection system for long steel products based on multiple three-dimensional sensors. Spatial calibration is required to transform the information acquired by each sensor into a common reference system. Registration is used to align the calculated shape with the model of the product being inspected, which enables the calculation of quality control parameters. This paper proposes efficient solutions for these two problems. Calibration is performed using a specially designed calibration plate that can be used to detect the position and orientation of each sensor. Registration is applied using an analytic alignment between the data and the model. The proposed methods are specially designed to perform accurately in industrial environments where inspection systems are exposed to adverse conditions, such as dust, oil, or water, which provoke noise in the signals. Moreover, vibrations affect the position of the inspected product randomly, which makes accurate measurements much more difficult to achieve. The proposed procedures are validated with extensive tests using real and simulated data showing excellent performance.