Random ponder: Why LEDs aren't used as pixels?

[caphair]

Random curiosity but why can't they make a tv using leds as individual pixels with color filters for rgb like they do in oleds? Is it bc with oleds they can make them really small due to the material?

[stj]

Re: Random ponder: Why LEDs aren't used as pixels?

they tried, too much heat in a small area was killing the organic led material.

you can get them upto 12inch - maybe a bit bigger in japan, but they have limited lifespan.

[eccerr0r]

Re: Random ponder: Why LEDs aren't used as pixels?

If each LED drew 500 microamps, and you had a 1024x768 RGB display, you'd be drawing 1200 amperes when the screen was all white...

[caphair]

Re: Random ponder: Why LEDs aren't used as pixels?

If each LED drew 500 microamps, and you had a 1024x768 RGB display, you'd be drawing 1200 amperes when the screen was all white...

Yikes. So what makes organic LEDs more efficient in terms of current draw?

[ReeceyBurger123]

Re: Random ponder: Why LEDs aren't used as pixels?

Yes lol even still 55" Oled tvs have a 24v 10amp rail going to the display ! Thats 240w right there.

[eccerr0r]

Re: Random ponder: Why LEDs aren't used as pixels?

I'm probably being very pessimistic at 500microamps however, as the LED pixels probably would be smaller than 1mm x 1mm (then again, not for the large OLED display...)

I think it's more of the manufacturing costs needed to make regular LEDs compared to OLEDs that makes the latter feasible.

[stj]

Re: Random ponder: Why LEDs aren't used as pixels?

oleds are killed by heat.

current for a panel wont be too bad though because it will be a scanned matrix not a direct-drive scenario.

[ReeceyBurger123]

Re: Random ponder: Why LEDs aren't used as pixels?

oleds are killed by heat.

current for a panel wont be too bad though because it will be a scanned matrix not a direct-drive scenario.

Yep like Lcd basically, not like good old Plasma. I expected it to be similar to Plasma in the drive method however just like Lcd so I expect panel failures to be quite high after a few years tbh.

[stj]

Re: Random ponder: Why LEDs aren't used as pixels?

you can screenburn OLED, i'v seen it on a galaxy tab fone!

[ReeceyBurger123]

Re: Random ponder: Why LEDs aren't used as pixels?

I have as well check this out:

https://www.badcaps.net/forum/showthread.php?t=43951

[ReeceyBurger123]

Re: Random ponder: Why LEDs aren't used as pixels?

They are nice displays very good image best ive ever seen ! The reliability of them is questionable though.

[caphair]

Re: Random ponder: Why LEDs aren't used as pixels?

How is it they can "print" oleds? Read that somewhere. Is it because of the "organic" materials used as oppose to solid minerals in LEDs?

[ReeceyBurger123]

Re: Random ponder: Why LEDs aren't used as pixels?

How is it they can "print" oleds? Read that somewhere. Is it because of the "organic" materials used as oppose to solid minerals in LEDs?

Possibly even im not too sure better get researching :L

[mariushm]

Re: Random ponder: Why LEDs aren't used as pixels?

To answer the random ponder...
Some displays have a larger red compared to green and blue because eyes have different sensitivity, see for example the superAMOLED from Samsung: http://zeptobars.ru/en/read/Samsung-...Galaxy-S4-mini
Just the same, with LED displays you'd have two different led sizes

Then, there's an issue with grayscale and brightness in general. To get a reasonable contrast and brightness, you'd need about 12 bits at least, so that's some pwm'ing of each led, a lot of fluctuations in the power consumption..

Then, you have the issue of binning all leds in the panel, you'd have to measure the light output of each led and measure the candela rating (or whatever is the proper unit of measurement), then age the leds for a few hours and measure them again and throw away the ones with too much difference.
It's not practical. For example, people making advertising panels just split everything in chunks of 32x32 or something like that, measure the brightness and store some data in an eeprom .. then a few of those are connected to a board with a big fpga which reads the eeproms of each small unit and then converts each pixel to a new value based on the information in those eeproms.

Here's a very informative video about this : https://www.youtube.com/watch?v=6iHTbGsnI8Q - imagine all the electronics and all that high speed data in the back of the monitor, and imagine the heat generated and the heatsinks required.

[caphair]

Re: Random ponder: Why LEDs aren't used as pixels?

So what makes oleds different for use in tvs if they work the same as LEDs, is it because the material makes it more practical for screens?

I'm also curious how burn occurs with oleds, do they glow that intense that the phosphor used for rgb burns in?

[eccerr0r]

Re: Random ponder: Why LEDs aren't used as pixels?

Burnin works the same as LEDs, LEDs will also dim with age. Same with all displays, the light emitting source will go down.

Except that with backlight displays, the backlight/frontlight can be replaced. Also you don't notice as much because the backlights/frontlight dim everything at the same rate.

[caphair]

Re: Random ponder: Why LEDs aren't used as pixels?

Ok but I'm still confused how burn in occurs with LEDs/oleds if phosphor isn't used?

[stj]

Re: Random ponder: Why LEDs aren't used as pixels?

heat breaks down the chemical that emits the light.

[ReeceyBurger123]

Re: Random ponder: Why LEDs aren't used as pixels?

Ok but I'm still confused how burn in occurs with LEDs/oleds if phosphor isn't used?

Its an organic material not Phosphor ! Being organic the heat and energy will cause it to fatigue over time.

[caphair]

Re: Random ponder: Why LEDs aren't used as pixels?

Ok so heat breaks it down to where it doesn't emit as much light as it did and this causes shadows of previous images to show?