Clear, black and super bright

GLOBAL – Being able to answer emails and access entertainment while you’re out and about is one of the greatest revolutions in work and leisure of the last 100 years.

But the whole thing’s scuppered if the sun’s shining right on your screen and reflections mean you can’t see anything. In fact, the problem’s become worse in recent years as we’ve largely switched to full screen, touch-driven displays.

Brighter displays are one part of a solution. And so we’ve pumped up the power and moved to improved display solutions in pursuit of a few extra nits.

But making the screen brighter and brighter has a big drawback. Big, modern screens use up a lot more power than the 1.5-inch mono display on your old Nokia 3310. There comes a point where you’d be prepared for the screen to be a little dimmer if it meant you could get a couple more hours’ use out of your phone.

So a second strand to improving outdoor usability needed to be devised. One that focused on reducing the reflectiveness of your screen. Anti-reflective coatings were introduced. But they don’t go quite far enough.

That’s why Nokia created ClearBlack display.

ClearBlack display uses a sequence of polarising layers to eliminate reflections.

You have probably tried polarising sunglasses before now and so have a rough idea of how that works. If you look at a window or the surface of some water using polarising glasses, then they become more transparent – which is why they’re especially good for fishermen. The polariser cuts out reflected light.

Polariser layers used in display solutions are bit more sophisticated than in sunglasses. Light rays actually get “processed” many times on its way in and out of your phones´s screen.

Download the larger image, under the resources tab on the right column.

There’s both a linear polariser and retardation layers between the surface of your phone and the display. When light hits your screen, this is what happens:

1. It hits the linear polariser, this vertically polarises the light. (Polarising means – roughly – aligning the wave vibration in a particular direction).
2. Then it hits the circular polariser retardation layer. This converts the light again, making it right-circularly polarised.
3. Then it hits the screen and bounces off it, switching the rotation of the light to leftist.
4. It goes back through the retardation layer. When this happens, the light becomes horizontally polarised.
5. Finally, it hits the linear polariser, since the light is horizontally polarised at this point it can be blocked entirely by this optical solution.

So why doesn’t the light from your phone’s display get blocked? Because it only goes through the second half of this journey so the light is unpolarised when it hits the final filter and goes through.

image credit: illustration by Jamie Sneddon
featured image: Kevin Dooley