Source: Evil Mad Scientist
"Recently we have seen some fantastic DIY examples of CNC image carving with traditional halftones and alternative versions with regions generated with reaction-diffusion equations. More impressively, all of this is now possible with freely available, homegrown software released by the people behind those projects (Here and here.)
Seeing these examples reminded us of another "classic" method of making halftones: ASCII art. In what follows, we walk through the process of using making CNC halftones for engraving or carving from both vintage and automatically generated ASCII art.
We began with a sheet of 1/4" plywood, and coated the top surface with a black polyurethane finish, to give the "black screen" effect. Carving through this reveals the white (or nearly so) wood underneath."