Using this calculator and a 5mm beam size, a 2" lens has a spot size of 0.205mm… 2.7mm depth of focus.
A 6mm beam size makes a smaller spot of 0.171mm… but a corresponding loss of depth of focus to 1.9mm. You’d have to know, more accurately the beam size and beam quality (M2) to be more accurate.
I had run these a few years … then I watched the Laser Everything video on photo engraving. This was very good a describing how to determine a good interval. It’s done on a fiber, but the it will work with any laser and any material, so I suggest to anyone dealing with, not only photo engraving but with interval determination.
It’s worth the watch…
Good luck
