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CBD, Clear Black Display Technology explained by Nokia!!


Nokia conversations has finally provided details of their Display technology, “Clear Black Display” or better known as CBD. This might need a bit of knowledge of Physics to understand , but the result is awesome which we can see on the displays of E7, N9, 701,E6, C6 01, Lumia 800, Lumia 900, Lumia 710. The display of N9 is Amoled, but with CBD it beats display of super Amoled Galaxy S2 hands down in outdoor visibility and colour accentuation.

Please see the following picture for a comparison,

Nokia N9 vs Samsung Galaxy S2 (1)

Now read the details of how it works in providing super visibility under bright sunlight. Nokia says there were only two ways to good outdoor visibility before,

  • 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. So anti-reflective coatings were introduced. But they don’t go quite far enough.
Nokia polarisation

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. Polariser cuts out reflected light.

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

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