DIY Retinal Projection

Granted, the author addresses safety issues.

The cool thing about a laser projector is that unlike with a lens-based projector, there is infinite depth of field: http://www.amazon.com/review/R1S9P57VXN5LSH/

But I think there should be some regulation on legal maximum instantaneous brightness. Per the review I linked, the projector used in this project has a 848 x 480 pixel framebuffer. But the laser bounces off a scanning mirror, so at any given time, only one pixel is bright as day and the rest of the pixels are black. This means that the actual power being zapped into your retina is about 400 thousand times brighter than what you perceive. Have there been experiments over the long term to make sure these don't cause retinal sunburn?

The problem with a setup like this is that in case of deflection failure if you're not projecting into someone's eye that results in an annoyingly bright line but not much else. If you are projecting into the eye then you could quite possibly do a lot of damage, in an eyeblink (to use a bad pun) at that.

So it's not just enough to deal with reducing the amount of light put out on average to be safe. You also need to deal with failure modes to get the laser to shut down immediately if anything puts the actuators out of order.