MobileRead Forums - View Single Post - "Stretching crystals promises flexible colour displays"

jharker · 08-24-2007, 03:49 PM

Thanks, NatCh! I don't mind at all, thanks!

Alex_d, you raised a few interesting points that I'd like to go into a little more deeply...

First, I should clarify that I said that their display should be capable of real true color rendering. I inferred that based on the capabilities of their display. As far as I know, the researchers themselves haven't claimed this (although it seems fairly obvious).

In fact, their display will probably only be capable of close to true color, since from what I've read in their journal paper (available for free download from here), it doesn't actually produce pure monochromatic colors. It does produce fairly narrow slices of the spectrum, however.

The researchers do claim that it's capable of producing a flexible display: "7. Applicable on rigid or flexible substrates", from the list of features on this page.

The concept of colors and color gamut can be fairly confusing and it took me a week to figure it out, back when I first learned about it a few years ago. Without going into the details, though, I think a reasonable illustration would be this picture of the color gamut:

The original of this image may be found at the excellent site Where's Purple?, which has several pages giving a lengthy discussion of color and the conversion of real colors into video display colors, as well as what makes a color out-of-gamut and how to bring it into gamut most accurately. I've mirrored the picture at my googlepages site so as not to impose on their bandwidth.

Anyway, in that picture, you can see several features. The whole area of color, which is tongue-shaped, is the range of colors that the human eye is able to see. The round border edge of the "tongue" represents monochromatic colors, i.e. very pure colors of visible light. If you were to shine white light through a prism, and take a very narrow slice of one color of that rainbow, that would be a monochromatic color. The numbers represent the wavelength of the light in nanometers (nm), ranging from the extreme red (650 nm) to the extreme blue, sometimes called indigo (450 nm).

Lasers produce almost perfectly monochromatic colors. Red laser pointers usually operate at 650 nm or 670 nm.

All the colors in the world that we can see are combinations of the pure monochromatic colors. To represent combining those colors on the color gamut, you would have to move from the edge into the interior of the tongue. For example, to illustrate combining a red laser pointer at 650 nm, and a blue laser pointer at 470nm, you would draw a line from the 650 nm point to the 470 nm point. Any possible combination of those colors would lie along that line. Which color you get depends on the relative brightness of the two lasers: more red brings you closer to red, more blue brings you closer to blue. Here's an illustration:

Similarly, you can combine any two colors simply by drawing a line between them.

This brings us to the question of computer screens. Most computer screens (and TV screens, etc.) use three colors of pixels: Red, Green, and Blue. Unfortunately, the Red pixels aren't monochromatic red, they're a blend of red, so they're away from the edge of the "tongue". Similarly, the Green and Blue are also blends. Now, when you combine two colors, all the colors you can get are on a line between those two colors. To get all the colors a computer or TV screen can make, we just need to draw the Red, Green, and Blue points in the color gamut and connect them, making a triangle like this:

Every color a computer screen can make lies within this triangle. As you can see, there are plenty of colors outside it! Those are all colors that we can see, but that the computer (or TV) screen can't make. Newer HD televisions have slightly different colors of R, G, and B, and they can make a slightly larger triangle. But they are still pretty limited compared to what the human eye can see.

The interesting potential of this new display technology is that it might allow us to create pixels colors that are truly monochromatic, and not limited only to Red, Green, and Blue! We could make pixels of any monochromatic color. And by combining those colors, we might really make pictures with almost every color the human eye can see!

Some interesting links:

The Where's Purple? page explains why purple is a creation of your brain. (So is brown!)
The related Primary Colors page discusses why the primary colors of the eye are not red, green, and blue.
Wikipedia has some excellent pages on the subject. The most relevant are the entry on the color space, and the entry on the RGB color model.
Better color gamut illustrations from Wikipedia: the visible color gamut, and the RGB color gamut.

08-24-2007, 03:49 PM	#5
jharker Developer Posts: 345 Karma: 3473 Join Date: Apr 2007 Location: Brooklyn, NY, USA Device: iRex iLiad v1, Blackberry Tour, Kindle DX, iPad.	Thanks, NatCh! I don't mind at all, thanks! Alex_d, you raised a few interesting points that I'd like to go into a little more deeply... First, I should clarify that I said that their display should be capable of real true color rendering. I inferred that based on the capabilities of their display. As far as I know, the researchers themselves haven't claimed this (although it seems fairly obvious). In fact, their display will probably only be capable of close to true color, since from what I've read in their journal paper (available for free download from here), it doesn't actually produce pure monochromatic colors. It does produce fairly narrow slices of the spectrum, however. The researchers do claim that it's capable of producing a flexible display: "7. Applicable on rigid or flexible substrates", from the list of features on this page. The concept of colors and color gamut can be fairly confusing and it took me a week to figure it out, back when I first learned about it a few years ago. Without going into the details, though, I think a reasonable illustration would be this picture of the color gamut: The original of this image may be found at the excellent site Where's Purple?, which has several pages giving a lengthy discussion of color and the conversion of real colors into video display colors, as well as what makes a color out-of-gamut and how to bring it into gamut most accurately. I've mirrored the picture at my googlepages site so as not to impose on their bandwidth. Anyway, in that picture, you can see several features. The whole area of color, which is tongue-shaped, is the range of colors that the human eye is able to see. The round border edge of the "tongue" represents monochromatic colors, i.e. very pure colors of visible light. If you were to shine white light through a prism, and take a very narrow slice of one color of that rainbow, that would be a monochromatic color. The numbers represent the wavelength of the light in nanometers (nm), ranging from the extreme red (650 nm) to the extreme blue, sometimes called indigo (450 nm). Lasers produce almost perfectly monochromatic colors. Red laser pointers usually operate at 650 nm or 670 nm. All the colors in the world that we can see are combinations of the pure monochromatic colors. To represent combining those colors on the color gamut, you would have to move from the edge into the interior of the tongue. For example, to illustrate combining a red laser pointer at 650 nm, and a blue laser pointer at 470nm, you would draw a line from the 650 nm point to the 470 nm point. Any possible combination of those colors would lie along that line. Which color you get depends on the relative brightness of the two lasers: more red brings you closer to red, more blue brings you closer to blue. Here's an illustration: Similarly, you can combine any two colors simply by drawing a line between them. This brings us to the question of computer screens. Most computer screens (and TV screens, etc.) use three colors of pixels: Red, Green, and Blue. Unfortunately, the Red pixels aren't monochromatic red, they're a blend of red, so they're away from the edge of the "tongue". Similarly, the Green and Blue are also blends. Now, when you combine two colors, all the colors you can get are on a line between those two colors. To get all the colors a computer or TV screen can make, we just need to draw the Red, Green, and Blue points in the color gamut and connect them, making a triangle like this: Every color a computer screen can make lies within this triangle. As you can see, there are plenty of colors outside it! Those are all colors that we can see, but that the computer (or TV) screen can't make. Newer HD televisions have slightly different colors of R, G, and B, and they can make a slightly larger triangle. But they are still pretty limited compared to what the human eye can see. The interesting potential of this new display technology is that it might allow us to create pixels colors that are truly monochromatic, and not limited only to Red, Green, and Blue! We could make pixels of any monochromatic color. And by combining those colors, we might really make pictures with almost every color the human eye can see! Some interesting links: The Where's Purple? page explains why purple is a creation of your brain. (So is brown!) The related Primary Colors page discusses why the primary colors of the eye are not red, green, and blue. Wikipedia has some excellent pages on the subject. The most relevant are the entry on the color space, and the entry on the RGB color model. Better color gamut illustrations from Wikipedia: the visible color gamut, and the RGB color gamut. Last edited by jharker; 08-24-2007 at 03:52 PM.