The
Multi-Junction VCSELs from Lumentum used in the iPP emit at 905 and 940 nm.
At 400–1100 nm, most of the light is transmitted all the way to the retina.
There is evidence that IR can be perceived by humans as light. The eye can withstand collimated light at about 10 milliwatts per square centimeter (at the cornea) in this band (there is lot published about all this, go visit e.g. Google scholar or pubmed; ).
here is the visible human spectrum within a broader electromagnetic radiation range:
View attachment 1774504
so here you have a chart of transmittance for the human eye:
View attachment 1774500
First, in general, watt for watt, UV is generally worse (almost fully absorpted by vitreous and retina in the eye) than visible and visible is worse than infrared.
You can see that there is a large amount of absorption in the near and infrared band. This makes e.g. the lens susceptible to cataract damage. Historically glas work blowers are affected by this due to the fact that some glasses will radiate a lot of energy in this band when heated.
When you sit in front of a fire, you may get tons of infrared and very little visible. If you feel heat on your skin, you are getting a few dozen milliwatts per square centimeter on you skin. That is equivalent to full direct sunlight at noon.
So, although a campfire may not look that intense, it may actually be brighter than the Sun in the infrared.
There are various standards like ANSI Z136.1-2000 standard for protection of the human eye from laser exposure etc -
here are some bits of it on Wikipedia.
So yes, NIR can technically damage the eye. Firstly by heat and when focused by a lense onto e.g. the retina (as opposed to say UV, which can directly disrupt individual molecules). However as written there are standards for these things, it's easily possible to develop emitters or applications while remaining well within them, and manufacturers seem to be doing it (
NIR is applied for quite some time in e.g. eye tracking, so there is a lot of data and knowledge available).
If you buy the largest IR floodlight available on Amazon and you stare at it 200 mm (~7") from your face for more than 1000 seconds (~ 16 minutes) there is a possibility you might damage your cornea.
So don’t do that.
In general, you should avoid staring at hot or bright light sources, IR or visible, whether they are designated “safe” or not.
