How to understand the principle of AR coating on cover glass?

AR means anti reflection coating, it's thin layer you sometimes can see on glasses, camera lenses or phone screens. Its job is very simple: Cut glare down and let more light pass through.

How does it work in simple?

It puts an ultra thin film on top of the glass. The film designed to make light bounce off to cancel out the light bounce off the glass itself. So less reflection more transmission.

What plain reflect in the first place?

It's because air and glass belong to different materials. When the light hits the boundary, some of it bounces back: That'w why you see your own face in a window or glare on a screen.

What does the coating actually work?

It doesn't soak up reflections like a sponge but it plays a trick with light waves.

Think of light like ripples on water:

Some light bounces off the top of the coating.

The rest goes through, hits the glass underneath and bounces back from there.

If the coating is exactly the right thickness, those two reflected waves end up out of step-one crest meets the other's trough. They interfere and pretty much wipe each other out.

Less reflected light means more light makes it through to your eye. That's why it's also called "anti-reflection" and "transmission-enhancing."

A simple way to picture it:

You can imagine 2 teams of waves showing up to the same spot and canceling each other out like noise canceling headphones, but for light. The coating doesn't block reflections, it tricks them into fighting each other.

So why does AR glass sometimes look colored?

It's because different colors have different wavelengths. The coating can only be perfectly tuned for one color at a time. Others still reflect a little, and that leftover reflection often shows up as purple, green, or blue-ish tint.

So the AR coating on cover glass basically is a precision layer which uses wave interference to kill reflections and boost clarity: Making glass looks almost invisible.