It's incredibly important to understand that eyes and glass have different optical properties at these wavelengths. It's hard to conceptualize because to us clear is clear, but that's only at visible light. The same way that x-rays and infrared and other spectra can show things human eyes can't see, or can't see things visible light can see, it's a 2 dimensional problem. The medium and the wavelength are both at play. So, when you have the eye which is known to absorb such light, and artificial optics which are known to pass it without much obstruction, they're going to behave like opposites. Imagine if the glass/plastic they used in the car blocked the light. Wouldn't really work.

There is a flip side to this though. Quick searches show that the safety of being absorbed and then dissipated by the water in the eye also makes that wavelength perform worse in rain and fog. I think a scarier concept is a laser that can penetrate through water (remember humans are mostly bags of salt water) which could, maybe, potentially, cause bad effects.

Depends on the wavelength of lidar. Near IR lidars (850 nm to 940 nm, like Ouster, Waymo, Hesai) will be focused to your retina whereas 1550 nm lidars (like Luminar, Seyond) will not be focused and have trouble penetrating water, but they are a lot more powerful so they instead heat up your cornea. To quote my other comment [1]:

> If you have many lidars around, the beams from each 905 nm lidar will be focused to a different spot on your retina, and you are no worse off than if there was a single lidar. But if there are many 1550 nm lidars around, their beams will have a cumulative effect at heating up your cornea, potentially exceeding the safety threshold.

[1] https://news.ycombinator.com/item?id=46127479

GP is slightly wrong. IIRC those problematic LIDARs are operating at higher power than traditionally allowed, with the justification that the wavelength being used is significantly less efficient at damaging human eyes, therefore it's safe enough at those powers, which is likely true enough. But it turned out that camera lenses are generally more transparent than our eyes and therefore the justification don't apply to them.

Your eyes a much larger sensor area than the opening, they do the opposite of concentrating light in a small area.

I have a Class 1 Makita (green) laser level, wide strong beam, excellent tool for landscaping. I accidentally looked into it from a 10 cm distance. It did not leave permanent damage, but for a few days I had the dot burned on my retina. And yes, I almost immediately closed my eye - within a few hundred ms's.

Don't look into the laser with the remaining eye

Also although that energy longer than 1400nm is generally absorbed by the cornea and lens, it is still energy, and it is not a hard bandpass filter per se. Safety is relative at higher wattages.

NGL I thought sub 1550nm LIDAR had been banned for use in new automotive applications already? I clearly must be mistaken but I had thought that was the case.

Ah. Theirs may be then. In which case they are probably using a different wavelength and a different glass.

I was just speaking in terms of the commonplace LIDAR solutions for road use.

Your body has signs to knock it off when you're staring at the sun, does it do the same thing for Lidar?

I mean, technically the Sun is "above" us and the LIDARs are at...eye level? So not exactly the same, at least to my layman eyes

If it's like everything else, it's "move fast, break things". I'm sure if it turns out to be harmful, we'll find out decades before regulation catches up

> class 2 but basically not shined into your eye (barcode reader)

TIL barcode readers can cause serious eye damage when misused. You'd think they'd have warning labels on these things given how common self-checkout is nowadays and how curious/stupid children can be

>I can't think of any existing lasers which you are intended to look at during daily use

Iphone face unlock users lidar to scan your face when you look at it.

Yes but failure cases are still possible. A stuck mirror or frozen phased array can result in a continuous beam.

Engineers should design in a way where the worst case possible is the assumption not the exception