The beam pattern of metal RF tube is close to TEM00, which is round and uniform with small divergence angle. The diameter of the emergent light spot is generally very small, ranging from 2 to 4 mm. According to different lasers, the emergent light spots are 2 to 4 mm, 2.5mm, 3mm and 3.5 mm.. See the laser parameter specification for details. As we all know, 12 light spot is generally selected for the vibrating mirror of CO2 marking machine, so we can choose the beam expander with 3, 3.5, 4, 5 and 6 times. As we all know, the larger the multiple of the beam expander, the better the effect of compressing the divergence angle. ), so that the light coming out is closer to parallel light, so that the spot focused by the field mirror is smaller, and the minimum can be 0.07 mm