Size is a matter of definition. Depending on the industrial sector, some millimeters can be a tolerance or determine the function.
A hundred years ago the idea of cutting material without touching it seemed to be science fiction.
In principle optical designers differ between optical glass and two types of fused quartz glass. On the one hand melted minerals containing silicon oxide are the basic for natural fused quartz.
In many industrial inspection applications, different object heights have to be measured. Therefore, object sided telecentric lenses are recommended to use the entire depth of field with a constant magnification.
Beam focusing has an important role to play in many spheres of technical optics.