I talked to Matthew Brand and he offered me some tips. Let me know if your interested I'll send you what he told me.
Viewing post in Holocraft comments
Sure, that would be great. I sent him an email twice, about 6 months apart, but never got any reply.
He told me "
* I use a fairly massive CNC machine to drag a diamond stylus through aluminum alloy at a depths of 20-50 micron. Had to customize some machine parts and programming to get optically smooth motion.
* It helps to tilt the stylus slightly in the direction of motion and to use a very light-gauge lubricant. I grind & polish the stylus to a Rouleax-like shape to promote reflectivity.
* Everybody gets the geometry of the stylus motion curves wrong — they're not conic. You need to solve an ODE that asks for rigid 3D image motion when some part of the optical path (e.g. the plate) moves.
* Lighting should be consistent with whatever assumptions you make in your ODE. Point-like sources work best; broad-spectrum sources allow diffractive color effects."
Hope this helps