Calibration of thickness measurement instruments based on twin laser sensors. Isoline bilinear look up tables

We present a procedure for the calibration of an instrument for noncontact thickness measurement of stainless steel sheets, based on a pair of triangulation laser sensors. Firstly, we carry out a general review of the architecture of this kind of instrument and of the problems associated with noncontact measurement based on commercial laser sensors in an industrial production environment. Secondly, we introduce a method for the calibration and characterization of this instrument based on the piecewise linear approximation of the isoline curves obtained in the calibration process (isoline bilinear look-up tables). We follow with a description of the searching and calculation of thickness in these types of tables.