Research Of Height Trace System Based On CCD In Laser Cutting Machine

Height adjusting system for laser cutting is got used to detect the height change of workpiece timely during the cutting process, so the focus can be in the ideal position all the time according to the adjusting system. So far, laser cutting with height adjusting system has been developed successfully abroad, but it's quite expensive, and there are not any related products on sale at home.A method using CCD camera and the laser triangulation principle to design a height adjusting system for laser cutting is presented in this thesis. In the hardware part, CCD camera, laser-diode and narrowband-pass-filter are used to capture the image. In the image processing part, expectation of first-order differential algorithm is used instead of the direct interception of gray threshold algorithm to fix the edge of the spot; grey mass center is used to calculate the centre of the circle, and bilinear interpolation algorithm is adopted to improve the precision by adding more sampled points, so the precision in calculation can reach sub-pixel level. In the calculate part, a relationship table is built first. The height change of the workpiece can be calculated by searching the table instead of stereotyping the traditional laser triangulation formula. In the video capture part, images are captured by a 32 bit dynamic link library provided by the sampling card.This method is entirely feasible and has been validated on digital control system.