The Research Of Focal Length Changed In Long Distance Welding

With the progress of science and technology and the growth in the living standard, itis gradually necessary for people to go out by car. The rapid population growth willpromote the rapid development of the car processing industry in which the application oflaser in auto industry became apparent, for example, the laser welding. During the weldingprocess, because of the varieties of auto parts, the surface of the parts will fluctuate,drifting the focus of the system from the parts and affecting the quality of welding process.At the same time, the height change of the works will change the welding light spot whosesize affects the welding quality. This thesis mainly tells that when the surface of workschanges, by moving the lens with small displacement is used to change the focus of thecombined system, analyses the laser spot and optimizes the spot at the same time duringthe long distance welding.First, this thesis analyzes the importance of the laser welding and laser applied to thewelding. At present, with the rapid development of the fiber laser, it becomes more andmore extensive for the application in the laser welding, this thesis does research on thefiber laser whose wavelength is1.06μm.During the process of laser welding, the laserhead lying in the welding joint emits the light which must be collimated and focusedbefore the welding. In order to focus the light, this thesis analyses the differences betweenthe single lens focusing system and the double lens focusing system. It is concluded thatthe double lens system has better focusing characteristic. Second, it’s based on the opticalimaging principle to deduce the formula between the ups and downs of work and thechanged focal length, so it can adjust the distance of the double lens to make the focallength changed. Later, this thesis discusses the change of the spot with the movement ofthe lens and finds the relationship between the displacement of the lens and the change ofthe spot and optimizes it according to the known conditions, and uses the ZEMAXsoftware to analyse the spot.This thesis researches the changes of the spot in detail in the case of the movement ofthe lens and optimizes it eventually with the known conditions. At last, it’s concluded thatthere is only one group of focus system, in other word, the focal length of the two lensesmeets specific relation which can make the spot change smallest.