For my engraving application, I use a standard laser engraver in 1064 nm. The laser system is equipped with galvo scanning head and a f-theta lens with marking range of 100x100 mm Since I need to mark very small objects (like jewelry) I do not need such a large marking area, but an area of 25x25 mm would suffice. On the other side, I would benefit from faster processing time. Right now I need to keep the laser spot for some time in the single pixel I want to engrave, in other to produce a noticeable engraving. This is affecting engraving speed. If I engrave the object at higher speed, the image will not appear. Thus, I am planning of using an additional lens to make the laser working area smaller and increase the spot power at the same time. Which would be the best set-up to use?
- Change the current f-theta lens with another one with smaller working area, however this option is complicated since a need to modify the machine and the f-theta lens is very expensive
- Add another lens in front of the f-theta, such as a plano-convex lens, to focus the laser beam. This could be a good option as I would just need to add an extra element, which does not seem to be very expensive. However, how should I choose this lens? Which size, magnification factor should I choose to achieve a smaller working area? How much would the efficiency of the system decrease? I mean, adding a lens some laser power will for sure be lost and dissipated in some other form of energy. What about the focus distance of the laser? This would decrease the laser focus distance, which is indeed a good thing for my application as I can work closer to the object. Moreover, at which distance from the original f-theta lens should I install the new plano-convex lens?