Laser Line Triangulation Sensor with Wide Measurement Range: a Steel Industry Use Case

Laser line triangulation is a key measurement technology that can be applied in quality control processes to inspect product geometry without contact. This paper presents the design of a Laser Line Triangulation (LLT) sensor developed in the context of the Horizon Europe (HE) project openZDM and tested inline in a steel industry use case.The LLT sensor has been developed focusing on two main target objectives: wide measurement range along transversal (X) and axial (Z) directions and small resolution along the Z axis. These have been achieved thanks to the optimization of the design parameters of the system which has been implemented with a triangulation angle of 45° reaching over a stand-off distance of 1000 mm and a 1000 mm camera-laser distance. The overall measurement range results in a transversal Field-OfView (X-FOV) from 800 mm to 2000 mm and a minimum Z distance of 630 mm in the near field up to 1580 mm in the far field.The resolution along the Z axis has been enhanced thanks to the introduction of subpixel accuracy reaching 0.026 mm at the stand-off distance which is 1000 mm. In this paper, these values are compared to other Laser Line Triangulation sensors available on the market showing that the system developed by UNIVPM is innovative.The Laser Line Triangulation sensor has been also tested inline and this paper presents some results of the laser profiles acquired on a steel bar held by a robot. These laser profiles are then processed in order to detect geometric defects, in particular the non-straightness of the bar, using an algorithm properly developed for the use case. From the results of these feasibility tests, the application has proven effective and opens the path to a full-inline installation, in order to measure non-straightness on 100% of the products.