While working for a company making an anti-counterfeiting device, I had to design a positioning and scanning mechanism.  The device used laser speckle (pictured below) to scan microscopic, naturally occurring, random surface features (even on surfaces that look smooth to a person).  It could best be compared to a fingerprint for objects.  By scanning the same area of a surface during production and then again sometime later we could compare the scans to determine if an object was the same one as from the factory scan.

To do this the scan head needed to be positioned in X and Y with a tolerance of +/- 0.1 mm and to have the proper angle within 0.5 degrees.  All of this needed to be done in less than a second.  This system also needed to be reliable, compact and of course within cost targets.