Polymer 'Muscle' Changes How we Look at Color 74
New Scientist is reporting that in the not-so-distant future computer monitors, and televisions may utilize a color changing polymer that responds to a current instead of existing techniques. From the article: "Aschwanden and colleagues built arrays of 10 pixels, each 80 micrometers across. The pixels consist of a piece of polymer covered with ridges tipped with gold. When white light is shone at the polymer from one side it reflects out of the screen and is also split into different wavelengths by this 'diffraction grating'. However, a slit above the polymer ensures that only one wavelength of light escapes, giving the pixel its color. The pieces of polymer also contract in response to current, like simple muscles. As they do so, the fan of light-waves is moved, changing the color that is fed through the slits above and out of the screen. Cutting the current causes the muscle to return to its original state."
Re:Application in fiber optics? (Score:5, Informative)
This is not true.
Different colours are simply different frequencies of light. You can also send different streams of data on different carrier frequencies over a copper transmission line.
This is used all the time, eg. in cable television: you get several television signals in parallel through a single coaxial cable. This is possible because each channel has it's own carrier frequency.
It however is true that the bandwidth of an optical fibre (of course at the frequencies used there) is much much larger.
Re:Application in fiber optics? (Score:3, Informative)
Maybe, but the problem in high-speed fibre optics isn't creating all the different wavelenghts, it's modulating them fast enough that's the real challenge.
In order to get to a useful system, each of these 'colours' have to be modulated, ie. switched on and off according to the bits you want to transfer. So you need to be able to switch on and off at a rate of at least a few gigahertz.
Moving polymer molecules are a bit similar to current LCD technology, in which liquid crystal molecules also physically move. Such processes are inherently slow. You can't find LCD's whose pixels can switch faster than a few milliseconds. That's far too slow for fibre optics.
Re:Requires lots of bandwidth for (uncompressed) d (Score:2, Informative)
It's just a tunable filter with a default value. That default value could be. .
The filter is "tweaked" by sending it another value, say, one between 1 and 255.
KFG
Re:Application in fiber optics? (Score:4, Informative)
Yep. Red, green and blue are not divinely chosen as primary colors, they're based the peak sensitivities of human eyes. Human color vision is based on three different types of light sensitive cells, each with overlapping bell curves of sensitivity. A color within the human range will excite these different kinds of cells to different degrees. Yellow light will trigger red-sensitive and green-sensitive cells, basically decomposing the color. However, red light and green light will obviously also trigger the red-sensitive and green-sensitive cells, and the brain is incapable of telling the difference (other animals with different primary colors might, though).
Now the problem with this approach is that RGB display equipment usually works by emitting the primary colors side by side, as becomes apparent if one spills a drop of water on a screen (or use a magnifying glass). This results in some inherent color bleeding that this new technique will resolve.
It's hard to tell how significant the change is, at least for us humans, since all of our current full color display techniques are RGB based (with the possible exception of non-cmyk paints), but isn't it worth it just to let our dogs watch Lassie in their own color spectrum?
Re:Requires lots of bandwidth for (uncompressed) d (Score:2, Informative)
I'm *assuming* you've experienced a prism. White light into an infinite gradient of spectrum.* Keeping your position still and moving the prism sweeps the colors across your vision. The "muscle" in their prototype is doing essentially the same thing. The "slits" act like filters. Kind of like what's in present displays. Each filter is essentially going to see the gradient for it's particular color (the intensity should be equal for all pixels). A color LCD essentially sees variable intensity (controlled by the twist) which adds up to a particular color.
Wikipedia has a good section on color.
*Not strictly true for some kinds of light sources, but let's keep this simple.
Been there, done it.... (Score:3, Informative)
You probably do not need a continuously variable spectrum for each pixel. A simple set of red, green, and blue primaries cannot reproduce the stimulus of all the spectral colours, yet they give a good enough representation of most scenes. This works because the eye-brain system transmits brightness, colour, motion detection, and other signals as firing rates in nerves. The nerves will typically have a significant background firing rate even for zero signal, so the system has to continuously try to calibrate itself, and work out what the zero and scale signals are. This is why we can look at printed images with a typical contrast ratio of 100:1 and a white point as set by the ambient light, and recognize a scene without worrying that the blacks look grey or the whites look coloured. Many illusions depend on fooling this feedback process. For example, if you look at a slowly moving object for some time and the look at a still scene, it may seem to rotate in the opposide direction because your motion sensors have adapted. Well, the same happens with your sense of colour contrast - that will adapt to compensate for the variations due to intensity. If you look at a dimmer version of an image, the colour difference signals are weaker but colours you see will look much the same (until you get down to mesopic light levels, and the adaption system begins to pack up altogether). If you are looking at an image in a darkened room, and the colours are 10% desaturated, you will probably not notice unless there is some other stimulus (such as a red power LED on your monitor) to act as an independent reference. It many seem that a three-component display can only get at about half the colour space within the spectral locus, but under typical viewing conditions, we are poor judges of colour contrast. If you want to make an image look more colourful, make it brighter. Get a slide projector and move it close to the screen so the image is small but really bright - you know the colours have stayed the same and only the intensity has changed, but you will probably find the colours a lot more satisfying.
There are other reasons for wanting to go for more primaries. You eye does not have uniform colour sensitivity: it will detect colours differently in the centre and in the periphery. The brain tries to remove this variation, as it is part of the eye not part of the image. You do not see this variation directly, but you can get to see it if you look at a large white patch on a screen where the left and right halves have different spectra. If you have an RGB projector with broad spectral primaries, this will give you a similar stimulus to a general reflection scene in the central and the peripheral vision, but you will not be able to get the saturated colors. If you have narrow band primaries, you will be able to get the deep reds, peacock blues, and violets you cannot get with the broad primaries, but you may have strange side-effects because your central and peripheral vision no longer match. make a projector with six primaries, and you could get the best of both.
But, is the extra effort really worth it? It is a bit like 3D - twice as much technology giving you a bit of extra stimulus that can startle, but can also detract from the nett visual experience. I would love one of these variable filters as a research tool, but I don't expect fully spectral displays any time soon.
Re:Application in fiber optics? (Score:3, Informative)
http://www.sciam.com/print_version.cfm?articleID=
There are nifty diagrams showing the different pigments present in the different eyes and their sensitivities. Another interesting factoid, birds have oil droplets associated with their color sensing cells; the droplets narrow the spectrum that the cell is sensitive too, increasing the birds ability to see color. The relatively poor color vision of humans is ascribed to mammal's rather nocturnal evolutionary history.
A somewhat related posting by the author of the article:
http://listserv.arizona.edu/cgi-bin/wa?A2=ind9512