[lmilcin]

This is actually more complex than that.

Due to optical aberration wavelengths outside of visible range don't get focused the same way as visible light. This means that the energy is spread over larger area.

Also, both UV and IR light is absorbed in a different way. UV tends to be absorbed much faster than visible light so that little of it reaches the retina while for IR opposite is true, the eye is more translucent to IR and only a portion of it is absorbed at retina and a lot of it tends to pass through it.

What it means is that, while a source of visible light is very well focused on the retina and absorbed in very small volume of retina cells, UV and IR are spread over larger area and then large part of it is absorbed somewhere else.

Still it doesn't mean IR or UV beams aren't dangerous. It is just that you can't directly compare beams by their power.

The way I understand it the main danger is that, since people may not see the IR or UV beam very well, there might be no involuntary response to close the eye.

[DaniFong]

Love these kind of analyses on HN (still where you can find them!) where someone will describe how the details matter.

Thank you to all involved.

If anyone can point me to the generalized best studies for safety margins and laser energy, please post links -- it's pretty relevant to a lot of AR designs to use laser projectors, and it is of course relevant to the lidar self driving cars at question.