I looked into that for VR headset eye tracking, which uses IR lights plus cameras to see the eyes inside the dark headset.
Here someone did some calculations [0].
> The International Commission on Non-Ionizing Radiation Protection's Guidelines of limits of exposure to broad-band incoherent optical radiation (0.38 to 3 µm)[1] states:
> "To avoid thermal injury of the cornea and possible delayed effects on the lens of the eye (cataractogenesis), infrared radiation (780nm < > λ < > 3μm) should be limited to 100 W m⁻² (10 mW cm⁻²) for lengthy exposures (> 1000 s)"
Yes. The manual from the manufacturer recommends wearing specific green tinted safety glasses if you are standing closer than a meter to their transmitter while it is on.
- IR is just super red light. It's not significantly more dangerous as looking at a lightbulb can be, except human eyes cannot perceive IR and can't contract pupils or stare away by reflexes.
- UV is baby step towards X-rays. It's technically super blue light, but it's entering region where lights start splitting chemical bonds and bleaching stuffs like pathogens and human eyes.
- LASER is perfectly parallel beams of light. Because it's perfectly parallel and do not diverge, it behaves like sun under magnifying glass at all points in its path, which can be dangerous when the "sun" is high and "glass" focusing it tight.
High power IR lamp illuminating audiences from afar is almost safe as any searchlights. IR lasers can be dangerous. UV lamps are not so safe, UV lasers would be bad.
> LASER is perfectly parallel beams of light. Because it's perfectly parallel and do not diverge, it behaves like sun under magnifying glass at all points in its path
To first approximation, in the typical situations regular people deal with lasers. Inverse square rule still applies; laser light does spread out with distance.
Standard off the shelf, 5W white LED emitters come with a warning against eye damage from staring directly into the beam. Those suckers are bright, and while your pupils will automatically contract to minimize damage from visible light, the same is not true when they're hit with IR.
So is regular light, in that sense. The IR that's used for this kind of application is 'near infrared', which is much closer to light than the IR emitted by most warm objects.
It's light, and some animals can see it, just not us. https://en.wikipedia.org/wiki/Infrared has some pictures from the right kind of cameras and telescopes.
At those distances, yes. I’ve gone through the certification process for even higher power units. IIRC you needed direct exposure of several minutes at much less than 1meter from the source to even begin to have risk.
The sun also emits in the visible wavelengths. Your eyes do not feel pain from bright lights due to the heat or similar. It's a response to brightness, in the visible spectrum. Without the visible component, there's no pain. With unhappy optical circumstances it could cook the retina because the pupil is dilated and there's no instinctive response to look away. Not sure how plausible those circumstances are. But I sure wouldn't put a 10 watt IR LED source right up to my eyeball.
Here someone did some calculations [0].
> The International Commission on Non-Ionizing Radiation Protection's Guidelines of limits of exposure to broad-band incoherent optical radiation (0.38 to 3 µm)[1] states:
> "To avoid thermal injury of the cornea and possible delayed effects on the lens of the eye (cataractogenesis), infrared radiation (780nm < > λ < > 3μm) should be limited to 100 W m⁻² (10 mW cm⁻²) for lengthy exposures (> 1000 s)"
0: https://docs.eyetrackvr.dev/getting_started/led_safety#about...
1 (pdf): https://docs.eyetrackvr.dev/safety/ICNIRP_optical_radiation....