Universal laser offers their HPDFO optics which claim to be able to mark metals directly by making a tighter focus.
Here is a good reference
https://www.engraversjournal.com/articl ... index.htmlHere is a good reference of spot size vs lens:
http://www.engraversnetwork.com/uls/lens_details.htmlI can make a beam expander from say 8mm beam to 12mm then use a 1" (25.4mm) focus lens to get a spot size around .0011". This is 5x smaller than the traditional 55mm lens which gives 25x more power density. So your 40W laser will be the equivalent of 1000W laser in power density.
Both the beam expander and 1" FL lens I can get reasonably inexpensive if there is sufficient interest. Direct metal marking would be interesting. Anyone want to machine the holder for it or at least make the cad drawings? The precision doesn't need to be that high.
I am not sure why the Universal laser system has a beam expander + 3 mirrors + focus lens instead of 1 beam expander + 1 mirror + 1 lens.
It also costs $2650 but I can get all the optics for a fraction of that price.