Monitoring of CO₂ Laser Cutting of Thick Steel Plates by Means of a NIR Camera Based System

An optical monitoring system has been developed by the authors aiming at real-time monitoring of laser cutting of thick plates of mild steel. This optical system uses photodiodes and a NIR camera as sensors. The concepts and results of the photodiode-based monitoring system have already been reported [1,2]. This paper is dedicated to the development of the optical set-up for camera-based monitoring of the laser cutting process. Firstly, some general aspects concerning the sensing principles and the conceptual design of the physical layout of the camera set-up are discussed. Based on a detailed optical analysis of the proposed conceptual design, some relevant information with regard to the selection of the camera type was obtained. Aspects related to the acquisition and analysis of the images, are highlighted. The initially developed camera set-up is presented. Firstly the design of the corresponding optical path is discussed in detail, including the results of the performed optical analysis. Next the results of the verification tests, performed on this physical set-up, are presented. Finally some preliminary results are included, proving the superior capability of the NIR camera compared to the photodiode-based solution for monitoring purposes.