The two larger lenses are held in a tube in front of the laser package. The tube can slide in and out of its holder, and can rotate on its axis, using overconstraint and elastic averaging to hold it semi-kinematically after its adjustment and before it is locked into place with glue. The glue is actually cast into place in facing grooves, so we do not depend upon its adhesion to surfaces. The laser package is adjusted by three screws for proper centering behind the lenses. All these adjustments produce a collimated, astigmatism free, laser beam emerging along the mechanical axis of the lens tube. This subassembly is called an "illuminator". Its outer cylinder diameter is 25.4 mm. 054