Weird Display on LED screen

I happened to be at a restaurant (world-wide chain) with a friend today, and i had my sunglasses on. And, i go inside and check the LED Board, to my surprise i felt that the boards weren't working at all. They seemed to display just blue screens with a minutely visible texts on it. And, I was not able to order the food at one go.

And, suddenly i removed my sunglasses and i could see the LED screen normally. And, it seemed like the sunglasses had filtered out lot of the light that was coming from the LED Screens.

I don't understand why all of it was gone from the screen, which was other wise mostly white and other color texts. What i don't understand is that are these LED screens/TV displaying harmful radiation such that the sunglasses needs to block it.

LED or LCD? A polarizing filter is an integral part of LCD displays and may be added to an LED display to make it more readable in bright light (blocks off-axis light from hitting it).

If you rotate your head 90°, it will be readable.

I believe all of them have shifted now to the LED Backlight ones on LCD screens. So, we can call it either way.
Interesting... How does it work? The bright sunlight/electric light still falls on the display?

So, i think my sunglasses also uses a Polaroid Glass.

Electroenthusiast said:

I believe all of them have shifted now to the LED Backlight ones on LCD screens. So, we can call it either way.
Interesting... How does it work? The bright sunlight/electric light still falls on the display?

So, i think my sunglasses also uses a Polaroid Glass.

Click to expand...

Then turn your head 90 degrees

Electroenthusiast said:

I believe all of them have shifted now to the LED Backlight ones on LCD screens. So, we can call it either way.
Interesting... How does it work? The bright sunlight/electric light still falls on the display?

So, i think my sunglasses also uses a Polaroid Glass.

Click to expand...

I believe you are wrong. The LED is a broad panel of LEDs that pass light through an LCD. Historically, fluorescent tubes were used to backlight LCD panels. So, no, many TVs that have the LED on them means the LCD panels are backlit by LEDs.

Low coast LCD TVs have this highly polarized effect. TVs intended for outdoors and most reasonably good Displays in vehicles have a Depolarizing film - also known by other names (e.g. Super Retardation Film) - Panasonic is the biggest producer of this film. You can look at these displays from any angle.

Electroenthusiast said:

So, i think my sunglasses also uses a Polaroid Glass.

Click to expand...

They must if you notice that effect. Recent studies have shown that polarized sunglasses reduce glare better but remove a persons ability to judge depth/distance in fast moving sports. Athletes are able to perform better with non-polarized glasses in Baseball (when there is actually some action), grand prix racing (but not the left, left, left of NASCAR), and mountain biking - especially when moving from shade to sun repetitively.

ZipZapOuch I didn't understand why this polarizing effect is needed for LCD TVs, whether it is indoor or outdoor. Why do we even require that, since these were not there in CRTs or so?

The next time i go to that restaurant, i will try to have a confirmation whether Polaroid/Polarizing effect is that which caused it.

Electroenthusiast said:

ZipZapOuch I didn't understand why this polarizing effect is needed for LCD TVs, whether it is indoor or outdoor. Why do we even require that, since these were not there in CRTs or so?

The next time i go to that restaurant, i will try to have a confirmation whether Polaroid/Polarizing effect is that which caused it.

Click to expand...

The liquid crystals flow into an alignment or random orientation when power is on/off. To increase contrast (make more opaque areas), light is polarized to align with the aligned crystals. Without polarization, the randomly oriented light will slip through a dark pixels and they will appear gray instead of black. People much prefer dark, dark and true white for the highest possible dynamic range of a display.