Designing a laser scanning picoprojector. Part 2: laser-safety-related issues

Laser scanning picoprojectors present a new challenge in the field of laser safety with methods of calculating accessible emission limits still in their infancy. We present a laser safety analysis and a calculation of an example picoprojector. We show that, due to its scanning operation, a picoprojector should be considered an extended laser source, and we also show that a picoprojector with two separate one-axis microelectromechanical systems mirrors offers a higher safe power limit than a projector with a single scanning mirror. Finally, a safety analysis is done under conditions of mirror failure. We show that, if the projector fails to scan in just one of the axes, the ocular hazard rises sharply, highlighting the need for a fail-safe system to be built into laser scanning picoprojectors.