A beam expander is an optical system consisting of two or more components that changes the size and divergence of the beam. It can:

1. In laser processing applications, the beam expander can transform the laser beam with a certain divergence angle into a collimated (parallel) beam,
thereby using the focusing lens to obtain a small high power density spot;
2. In laser ranging, the beam expander can be used to maximize the collimation of the laser to obtain the ideal long-range measurement effect;

3. Beam expander can change the beam diameter for different optical instruments and equipment;
4. The combination of a spatial filter and a beam expander can make the asymmetric spot energy distribution symmetrical and make it more uniform.