Laser welding apparatus and method

A method of controlling a laser welding apparatus, the method comprising:

• providing a laser welding apparatus comprising a laser welding unit, the laser welding unit comprising:
• a laser focusing section arranged to focus a laser beam, the laser focusing section comprising:
• a first lens adapted to focus the laser beam at a focal point,
• a second lens adapted to diffuse the laser beam to the first lens, and
• a third lens adapted to guide the laser beam to the second lens;
• a focus adjusting section comprising a lens-barrel, the lens-barrel being rotatable supported in the laser welding unit such that the lens-barrel is rotatable about a longitudinal axis of the lens-barrel, the lens-barrel including three spiral grooves in an inner peripheral wall of the lens-barrel;
• and
• at least one stopping device arranged to restrict rotation of the first lens, the second lens, and the third lens when the lens-barrel is rotated,
• wherein the first lens, the second lens, and the third lens are engaged with respective ones of the spiral grooves such that the first lens, the second lens, and the third lens move in a direction of the longitudinal axis of the lens-barrel when the lens-barrel is rotated, and
• wherein the focus adjusting section is arranged to adjust at least one of a focal length of the laser beam, and a focal spot size of the laser beam;
• actuating the laser welding unit to travel at a predetermined speed along a predetermined trajectory;
• directing the laser beam at a first welding spot;
• adjusting the focal length to focus the laser beam at the first welding spot;
• holding the laser focal spot size constant;
• and
• directing the laser beam at a second welding spot after completion of welding for the first welding spot,
• wherein the predetermined speed of the laser welding unit is predetermined to be constant during welding for each welding spot.