There are 3 mirrors each situated at approximately 45 degrees to one another that reflect the beam from the laser tube to the lens and the to the material to be cut or engraved. It is necessary to align or "focus" them. I had hope that my unit was aligned well enough to use right out of the box, as many are on delivery, but sadly I was disappointed and needed to learn to do it myself.
Focusing involves putting a piece of masking tape or similar material onto the lens and doing a short test fire and see where the burn mark is. This is the rear mirror as seen through the hole that separates the tube from the rest of the unit. A series of set screws as seen above change the angle to the desired point.
This is the head unit that houses the last mirror and the lens.
Just a few of probably a couple of dozen attempts at alignment.