Lens assembly and laser welding head

A lens assembly configured to regulate a size of a focus of a laser beam, comprising:

• a rack,
• a first optical path offset assembly and a second optical path offset assembly, wherein an optical path of the first optical path offset assembly and an optical path of the second optical path offset assembly communicate with each other, and the first optical path offset assembly and the second optical path offset assembly are each rotatable about a central axis of the lens assembly;
• a drive mechanism comprises a coil and a magnet, wherein the coil is arranged at a center of the magnet and fixed to a first positioning member of the rack, the drive mechanism is configured to drive the first optical path offset assembly to rotate about the central axis;
• an elastic seal ring pressed between the first optical path offset assembly and the second optical path offset assembly and configured to drive the second optical path offset assembly to rotate together with the first optical path offset assembly when the first optical path offset assembly rotates;
• and
• a locking mechanism comprises a pushing body and an elastic member, wherein the pushing body is configured to press against the first optical path offset assembly to enable the first optical path offset assembly and the second optical path offset assembly to rotate relative to each other, and the elastic member is configured to hold the pushing body out of contact with the first optical path offset assembly.