My vague recollection is that they could do pretty sharp corners, but it's been decades. IIRC, they were multi-coloured. Probably the trick is to do what old voice-coil actuator drives did for multi-track seeks, which was to evenly accelerate up to maximum velocity, coast at that until you got close to the target track, and then evenly ramp down, so that the head assembly's radial velocity goes to 0 as you get to the target track. (If you're not moving enough tracks to do the whole thing, you only ramp up part-way, then ramp back down.) The RK05 drive did this with fancy analog circuits, but these days one would do it in software. I would assume one would do something similar with the mirror; evenly accelerate up to maximum slew rate, then back down at the end of the move, so that when one gets to the corner, the mirror is mostly stationary, and so not so much force is needed to sharply change directions. Of course, this might make the parts of the line where the mirror is moving slower brighter, but perhaps one could tweak the brightness to compensate. Noel