Preliminary design of longitudinal chromatic aberration sensor implemented to laser processing head

The problem of process monitoring is one of the most critical aspects of control in laser material processing. Chromatic sensors, which are characterized by high resolution, relatively large measurement range and good repeatability, may be used for measuring and adjusting the distance between laser head and the substrate. In this paper we propose a new solution of chromatic sensor integrated with optical laser head via an available standard monitoring port. Optical components of laser heads are fabricated from materials characterized by high Abbe number (low range of longitudinal chromatic aberration). Therefore, for sensors application, the resulting chromatic aberration of the overall optical system should be enhanced by implementation the sets of lens described by a low value of Abbe. The numerical analysis were carried out in order to design an optical system of proposed solution, which will be described by wide measurement range, low attenuation and narrow characteristic spectral peak. The results obtained by WinLens software solutions were presented. The numerical tool whose principle of operation is based on geometric optics equations, was chosen for rapid prototyping because of its simplicity in implementation of optical components. The results from the numerical analysis were afterwards confirmed by the experiment on real optical system.