Research On Dynamic Focusing Surface Laser Marking System Based On Machine Vision

With the continuous development of laser marking technology,the manual-based production flow adjustment and product information traceability mode are gradually being replaced by informatization and automation.In order to explore a new production mode,an existing coupling company has built a new fully automated coupling production workshop.Combined with the product’s shape characteristics and the testing requirements in actual work,a fully automated curved surface laser is proposed for product information traceability,marking requirements.In this paper,a set of dynamic focus surface laser marking system based on machine vision is designed for this requirement.The main research contents are as follows:Aiming at the problem that the 2D laser marking machine will produce image distortion due to the change of the marking distance when marking the curved surface,by studying the transformation relationship between the cylindrical surface and the plane,the relationship between the points in the space coordinates is established.And the correction method of the distorted QR code image on the cylindrical surface is proposed,and the correction process of the distorted QR code image is realized by HALCON software.In order to solve the problem that the incoming material position of the product is not fixed,a tracking and positioning algorithm of the coupling workpiece based on machine vision is studied.By placing a set of camera lenses above the conveyor belt,the images collected in the field of view are preprocessed,and then the sub-pixel fitting circle method is used to optimize the outer contour of the workpiece to improve the accuracy of the workpiece center coordinate position,and then realize the tracking and positioning function of the workpiece at any position within the field of view,and pave the way for the dynamic initial position compensation of the subsequent laser marking machine.Since the two-dimensional laser marking machine only has the mechanical structure characteristics of the X-Y axis galvanometer,it cannot realize the movement in the Z axis direction,so when the marking depth exceeds the maximum deviation value,the marking virtual focus problem will occur.In this paper,a dynamic focusing point adjustment strategy is proposed to optimize this problem.The realization method is to bind the two-dimensional laser marking machine and the three-axis slide table,and combine the workpiece center coordinates fed back by the visual positioning system to adjust the marking machine.Coordinate compensation is performed at the initial position,and at the same time,by optimizing the original focusing principle,a dynamic focus point optimization algorithm that automatically adjusts according to the radius of the workpiece is realized.The factory has carried out laser marking tests on actual production lines.Experiments show that this system can effectively expand the range of marking depth,so that a single device can meet the marking requirements of products of the specified specifications of the enterprise.