I have this headlamp: http://dx.com/p/lzz-186-600lm-1-cree-xm-l-u2-3-mode-cool-white-light-zooming-headlamp-black-1-x-18650-221722 and I have decided to build a diffuser for it, in order to be able to obtain even wider beam. It is useful for looking into the map, hanging the headlamp w/diffuser from the tree branch in order to illuminate a wider area, etc. The diffuser has a clip so that it can be carried near the hedlamp itself even when not in use.Since the "membrane" is relatively thin and it is printed as a bridge, I recommend printing with support material. I have used slic3r autogenerated support material (5 mm spaced), and it worked well. The remains of the support material create a nice pattern on the membrane. The membrane itself has about three layers (I have printed at 0.25 mm/layer), which is enough to diffuse the light, and to have all the holes from the imprecise lower layers covered. The OpenSCAD source is customizable a bit, so for example the membrane thickness can be modified. Print it using white filament.