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Comment by the__alchemist | Hacker News Reader

Thoughts on danger to eyes? Ie lasers capable of killing a mosquito may not be eye safe. (?)

absolutely not safe for eyes in my GitHub the next information "The main limiting factor in the development of this technology is the danger of the laser may damage the eyes. The laser can enter a blood vessel and clog it, it can get into a blind spot where nerves from all over the eye go to the brain, you can burn out a line of "pixels" And then the damaged retina can begin to flake off, and this is the path to complete and irreversible loss of vision. This is dangerous because a person may not notice at the beginning of damage from a laser hit: there are no pain receptors there, the brain completes objects in damaged areas (remapping of dead pixels), and only when the damaged area becomes large enough person starts to notice that some objects not visible. We can develop additional security systems, such as human detection, audio sensors, etc. But in any case, we are not able to make the installation 100% safe, since even a laser can be reflected and damage the eye of a person who is not in the field of view of the device and at a distant distance. Therefore, this technology should not be used at home. My strong recommendation - don't use the power laser! I recommend making a device that will track an object using a safe laser pointer."

Could you use a laser at a frequency that the cornea is opaque to?

Then you injure the cornea. That's why they use UV lasers for laser surgery, because the cornea absorbs it.

Edit: I recently had a small corneal erosion from my eye drying out over night (eyelid was pulled open by sleeping in a weird posture) and I had 30% vision for 2 days on that eye. The cornea contributes about 40% (iirc could be more) to the total refractive power in the eye. If you have a UV-spot that melts moskitos dancing around on that for half a second...

What about an infrared laser? Something where a microburst would melt delicate insect wings, but a direct hit on a human eye would just warm it up a tiny bit. Possible?

You basically can't make laser pulses safe and melt things at the same time, because by nature of having the energy in a short pulse created heat doesn't have time to distribute, so it doesn't matter if you hit a tiny thing or a tiny spot on a larger object, the damage done locally is the same.

I’m confused, are you saying that the minimum amount of energy in an infrared pulse sufficient to melt a fly’s wings (< 1mm) would necessarily also damage a human eye?

I have to believe there is a threshold value of safety, particularly with IR. You can tell me I’m wrong, but please provide a bit of physics to justify it.

Use an array of eye safe lasers that converge on the target.

it is not easy

That is (almost*) the same as focusing a laser on the target with a very large lens - a highly divergent beam is only dangerous near the focus. Some laser processing machine developers make their machines eye-safe that way, if you're half a meter from the focus, the remaining radiance is low enough to not be caught by the laser safety norms anymore (there is a very low limit to which radiance is still considered class 1, after that it's not considered a laser according to the norm). But to make a highly divergent beam, you need large aperture optics.

* you'd need to have very good optics and optomechanics on each laser to make the spot small enough - the smaller optics on each smaller laser would make the spot worse than one created with a single large lens, unless the single lasers are actually from a single coherent source

To fry a mosquito, you don't need an awful lot of energy. That means you don't need awfully big lenses to keep it human safe away from the focus.

That would depend on the distance you want to fry moskitos at, if you want to burn them at meters, you need a larger aperture to get a similar divergence angle as with cm.

Maybe a salt/sand airgun, but it wouldn't be as quiet...

Or carefully targeted squirts/droplets of a pyrethroid. That would add another interesting problem: how to detect and compensate for airflow.

it is not a toy, not for home application

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