Research On Automatic Focusing System Of Laser Marking Machine Based On Binocular Vision

With the development of science and technology,great changes have taken place in the requirements of industrial processing and production.As a kind of new technology,laser marking is gradually replacing the traditional marking method.Laser marking machines are now widely used in industries requiring high processing accuracy,such as electronic components,integrated circuits(IC),precision machinery,metal accessories,household appliances,hardware tools,material markers,etc.Laser marking machine realizes a non-contact processing,does not wear the workpiece,have a high processing efficiency and a low pollution rate created.However,the quality of marking is affected by the accuracy of laser focusing on the workpiece.In order to increase the focusing accuracy and improve the marking efficiency,an automatic focusing system of laser marking machine based on binocular stereo vision is designed in this paper,which is implemented by steps in each part of the system.This paper proposes the use of binocular stereo vision ranging method to realize the automatic focusing function of laser marking machine,and analyzes the superiority of binocular stereo vision ranging to other methods for the focusing function of laser marking machine.The principle of binocular stereo vision imaging and the principle of Zhang Zhengyou calibration method are introduced.According to the needs of this topic,a binocular stereo vision system is built.Binocular camera calibration was performed using Zhang Zhengyou's camera calibration method.The internal and external parameters of the camera were obtained,and the captured images were image processed,including image contrast enhancement,image filtering and edge gradient processing.The Bouguet polar line correction algorithm is used to correct the image.The parallax map containing the left and right image disparity information is obtained by the semi-global stereo matching algorithm.Combined with the camera calibration parameters,the three-dimensional position information of the object to be tested is obtained by the optical axis parallel binocular vision model.The distance measurement experiment was carried out on the binocular stereo vision ranging system and the measurement results were analyzed.The accuracy of the obtained measurement results can meet the accuracy requirements of the focusing system.Analyze the factors affecting the measurement results,including the length of the baseline,the relative position of the workpiece to be tested,and propose corresponding improvement methods for different influencing factors.In order to improve the measurement accuracy of the system,the performance comparison experiments of the filtering algorithm,edge detection algorithm and stereo matching algorithm in image preprocessing are carried out,which will be more suitable for the wavelet threshold denoising algorithm and Sobel edge detection operator.A semi-global stereo matching algorithm is applied to the system.The laser marking experiment was designed to compare the different marking effects of the laser head at different positions.The experimental research on the marking situation was carried out within the appropriate range of the laser marking machine,which proved the feasibility of the system.