New Apple and Samsung phones use infrared light to verify your identity. It’s like a hands-free version of the fingerprint scanner. But can the infrared lights used for Face ID and Iris Scanner hurt your eyes?
It’s a fair question. People don’t know much about infrared light, and it’s hard to find information that explains the potential risks of infrared in layman’s terms. Not to mention, Samsung’s safety disclaimer for the Iris Scanner makes infrared sound kind of scary. But what is infrared, and should we be worried about it?
What is Infrared?
Infrared (IR) is a form of invisible radiation, and it occupies the lower end of the electromagnetic spectrum. Like visible light, microwaves, and radio waves, IR is a form of non-ionizing radiation. It doesn’t strip molecules of their electrons, and it doesn’t cause cancer.
It’s important to know that IR radiation can come from a lot of places. In some ways, you could consider IR a natural byproduct of heat production. Your toaster emits IR light, the sun emits IR light, and campfires emit IR light. Interestingly enough, 95% of the energy produced by fluorescent bulbs is translated into IR. Even your fleshy, disgusting body emits IR light, and that’s how the heat-tracking cameras in spy movies work.
The IR-LED that’s built into your phone is classified as near IR (700–900 nm). It straddles the line between the visible light spectrum and the IR spectrum. Near IR is very similar to visible light, it’s just a lot more difficult for you to see.
The radiation from both visible light and near IR light can heat objects, depending on light intensity and exposure time. Prolonged exposure to high-intensity IR and visible light (staring at the sun or a bright lightbulb) can cause your photoreceptors to bleach and your lens to develop cataracts. To experience vision loss with a low intensity visible or IR light, you would need to keep your eyes open within a millimeter of the light source for almost 20 minutes. This could happen with a light bulb or an IR-LED.
The main concern with near IR is simply the concentration of your exposure. With visible light, it’s easy to tell when you’re being exposed to a blinding amount, and your reflexes cause you to squint or look away. But your eyes aren’t built to see IR light, so it’s impossible to tell when you’re being exposed to a dangerous amount. You know how you’re not supposed to stare at an eclipse, even though it doesn’t seem that bright? It’s kind of like that.
Far IR radiation (25 – 350 µm) is invisible, and it isn’t used in your phone. Far IR radiation overlaps with microwaves on the electromagnetic spectrum, and like microwaves, far IR radiation causes water molecules to heat up. As you can imagine, prolonged exposure to far IR radiation can cause burns to the eyes and skin, but we don’t need to worry about that, because your phone only uses near IR radiation.