I always wondered about that. What do people who need to see the laser beam do when they are required to wear protective goggles that make the beam invisible? I guess they have to rely on phosphor cards & stuff.
After final setup we would record the numbers off the photo-meter and run a scan on Dietz (blueprint) paper, but that was just for the QA records.
When the rule came down to wear goggles, we'd hang them around our neck, just in case a clue-less suit wandered by. Once the machine went into the clean room, nobody would bother you.