Pixel Size of TVs: OLED & LCD Explained

[artis]

Just a wild idea while watching a documentary about TV history and CRT sets etc. Just curious to know the physics.

What's the smallest pixel size available today in a modern OLED or even more classical LCD (CCFL backlight) panel?
Then I though about how we now can manufacture CPU's with a single transistor size down to nm range approaching the limits of quantum mechanics and tunneling. These individual transistors are smaller than the individual pixels used in the screens, so why go and make a separate backlight and then a pixel array that varies how much light goes through as in LCD couldn't we simply make a "silicon wafer" the size of a typical tv panel with individual transistors serving as the pixels.?

I did a quick google search and looks like something similar is already proposed ?
https://en.wikipedia.org/wiki/Organic_light-emitting_transistor

 

[f95toli]

Didn't you just describe a LED TV?

Note that size of a pixel is just one -of many- considerations. There are also other factors related to luminosity, viewing angle, colours (blue LEDs haven't been around for very long, black can be difficult etc) and how long each pixel will last before it fails (MTBF).

But yes, LCD TVs are probably on their way out.

 

[russ_watters]

I'd be willing to bet smart phones (or watches) have the smallest pixels...

 

[artis]

sure small screens having the same resolution will have sharper image than larger screens as each pixel is physically smaller.

after some googling refreshed memory and seems like OLED display technology is basically the same as what I thought here, then it's just a matter of how small each individual LED or pixel can be made.
Seeing how we have managed to shrink transistors on a wafer I would guess? that in the future the resolution of a screen will go beyond the current 4K or even higher?
I google and it seems that current pixel sizes are in the um range , would it be reasonable to think they would get in the nm range? Or would that outperform the "resolution" of our eyes and perception and so be needless?

 

[russ_watters]

Seeing how we have managed to shrink transistors on a wafer I would guess? that in the future the resolution of a screen will go beyond the current 4K or even higher?
I google and it seems that current pixel sizes are in the um range , would it be reasonable to think they would get in the nm range? Or would that outperform the "resolution" of our eyes and perception and so be needless?

It will depend on the application of course, but we're basically already at the point where additional resolution will be needless.

 

[sophiecentaur]

It will depend on the application of course, but we're basically already at the point where additional resolution will be needless.

h
That could well be right.
Many factors are at work.
There used to be a rule about the ideal viewing distance was "five times picture height'. This was with 525/625 line TV displays. It was pretty good, actually and it meant that your average family could all sit and watch the same screen comfortably. With 4k pictures, your screen can be four of five times the size and the picture will look just s sharp. But, in your average size room (and they are getting smaller and smaller), there's a limit to how many people can get a good view that's sharp enough - no one wants to be in the equivalent to the cinema 'cheap seat' at the side.
You can bet your life that the manufacturers will keep increasing size/ resolution beyond what's sensible and people will believe its' better. Remember 3DTV? Many people went out and bought a set and never had more than a few 3D movies in their Blue Ray rack.
Mobile phone viewing of HD films has got ridiculous for normal adult viewers because the near-point of vision makes it hard work to watch. Again, it's being sold hard. I am now finally out of the iPhone market at £1k a pop.

 

[gmax137]

I have noticed that, the older I get, the more I think improvements in "everyday" items is a waste of time. I'm pretty sure that says more about aging than it does about the items.

 

[A.T.]

It will depend on the application of course, but we're basically already at the point where additional resolution will be needless.

For VR and AR applications there is still room for improvement in terms of resolution on tiny screens.

 

[sophiecentaur]

For VR and AR applications there is still room for improvement in terms of resolution on tiny screens.

Agreed - when an image is going to be projected and magnified then the pixel size will scale up too. Bearing in mind that chips are already 'inconveniently' small though, I wonder if there will be any advantage in making the display chips / pixels smaller and smaller. There is the interconnection problem and also heat dissipation; neither of which scale down easily. But I guess it's unrealistic for me to imply a minimum size. For bionic applications, there could be advantages in going smaller and smaller.
I think that projection TV is unlikely to be used for the home because the contrast ratio will always affect the performance of projection TV when you really want 'quality'.

 

[artis]

I doubt that such a individual transistor/pixel high resolution screen would have heat sinking problems because if we look at our current CPU'S they have millions to billions of transistors packet into "floors" above one another and we still manage to get decent cooling, a screen is essentially a large matrix with big surface area and instead of being packed transistors would be standing on a single plane next to each other.

I'm sure there are other problems though. Just saying that for larger screens small individual pixel size would make the picture much more sharper and the whole idea of a "wall sized TV" more realistic.

 

[sophiecentaur]

I doubt that such a individual transistor/pixel high resolution screen would have heat sinking problems because if we look at our current CPU'S they have millions to billions of transistors packet into "floors" above one another and we still manage to get decent cooling, a screen is essentially a large matrix with big surface area and instead of being packed transistors would be standing on a single plane next to each other.

I'm sure there are other problems though. Just saying that for larger screens small individual pixel size would make the picture much more sharper and the whole idea of a "wall sized TV" more realistic.

That's a good point. Total luminous power doesn't actually need to be greater when pixel size is reduced - all other things being equal. But power dissipation is still an issue in large scale integration. That's one of the advantages of going to lower and lower logic voltages.
But who knows what the boffins are at this minute planning to sell us in 2019?