The method of expanding or adjusting the beam is as follows:

1. Make it propagate far enough and measure the change in spot size. This method is the simplest, but it requires a longer distance. The longer the better.

2. Use a convex lens to focus. Check the focus. The smaller the focus, the better the parallelism of the light. This method requires that the optical quality of the convex lens is good enough.

3 , first use the beam expansion system to expand the beam, and then use the above method to check its parallelism. This method is the most accurate, but it is a bit troublesome.