Whether lenses for machine vision, or lenses and mirrors to direct laser light, the need to keep dust off their surfaces should be obvious.
One likely solution is to surround the lens with a doughnut-shaped (toroidal) trough, with an outer opening at least as large as the lens itself. Compressed, filtered air would be introduced tangentially, through a jet positioned along the trough's widest circumference, causing the air within to spin. The rate of spin would increase as the air climbed the inner wall of the trough toward the opening, and continue to increase approaching the axis of the lens.
There would also be a net movement of air outward through the opening. Once outside the confines of the trough, air would spray outward in an approximate disk shape. Any dust that happened to come close to the opening would be pushed off by this disk-shaped, laminar outflow, with essentially no chance that it would end up inside where it might come in contact with the lens.