I'm not entirely sure if this is on-topic here, since it's about stage lighting rather than audio or video directly, but I'll give it a shot.
I've been looking at various types of laser stage lighting, and I'm trying to work out how they work internally. I figure the scanning lasers (single fast-moving beam) work by firing a single laser onto a rotating mirror, or a mirror controlled by servos for more precise movements.
However, I can't figure out how the cluster lasers work. I'd guess there's some kind of prism in there, or some trickery with a set of mirrors and lenses that somehow "split" the beam, but I can't quite figure it out. My first thought was a fixed prism, but that wouldn't explain how these devices can spread, focus and rotate the beams.
How do these laser effects usually work?