Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Polychromatic Pixels

compoundsemiconductor.net

Post reply on HN
Print view View original

131–140 of 149 posts

Re: Polychromatic Pixels

#131

Post by mastax »

Etherlord87 wrote: post #121
mensetmanusman wrote: post #75

Earlier quoted context omitted.

The human eye will see white when a pixel flashes through all of the colors quickly in time.

How quickly? Surely well above 1 kHz (1000 FPS). Otherwise you will see flickering.

Single chip DLP projectors strobe red, green, blue, white sequentially. Modern DLPs use separate light sources (LED/Laser) and pulse them at a high frequency - kilohertz I assume. Before we had high-power LEDs DLP projectors used a xenon lamp and a color wheel (https://www.projectorjunkies.com/color-wheel-dlp/) spinning at as little as 60 revolutions per second. This caused a "rainbow effect" which was very annoying to some people, but apparently enough people didn't notice it that those products got sold anyway. So somewhere around 180Hz is the bare minimum.

Re: Polychromatic Pixels

#132

Post by cubefox »

incrudible wrote: post #124
cubefox wrote: post #115

Earlier quoted context omitted.

That's not true. Dithering can be used in emissive screens, but dithering is not additive. If you mix red and green with color blending (e.g. by dithering), you get less red and less green in your mix, and therefore the resulting mix (a sort of ochre) is different from additive color mixing (yellow), where the amount of red and green stays the same. Or when you mix black and white, you get white with additive color m…

I am not saying you can use the exact same math as in an image manipulation program, these work with different assumptions. Mixing colors in those is usually not correct anyway. https://www.youtube.com/watch?v=LKnqECcg6Gw I am saying you can think of subpixels, which already exist, as a form of dithering. Most displays use just three primaries for subpixels - red, green and blue. Their arrangement is fixed, but that…

Well I disagree with that. It's two different ways of mixing colors (additive vs blending), with different results and different requirements.

Re: Polychromatic Pixels

#133

Post by wmertens »

ajuc wrote: post #108
mensetmanusman wrote: post #75

Earlier quoted context omitted.

The human eye will see white when a pixel flashes through all of the colors quickly in time.

But that means it has reduced refresh rate.

The two are not related at all. Refresh rate is how fast it can accept input, whereas this is how fast it can do TDM of colors and intensities

Re: Polychromatic Pixels

#134

Post by wmertens »

knotimpressed wrote: post #68

I think a lot of these comments are missing the point-even if you have to reduce their reported density numbers by half, they made a display with dimensions of "around 1.1 cm by 0.55 cm, and around 3K by 1.5K pixels", which is insane ! All without having to dice and mass-transfer wafer pieces, since every pixel is the same. A lot of the article is focused on how this matters for the production side of things, since c…

I'm really curious about the reproducibility. The color is decided by the bandgap and the bandgap is tunable by voltage, but how temperature dependent is it, and how much does production variability impact it?

I image these displays could have color sensors attached to self-calibrate.

Or the variability is low and all you need is very precise voltages.

I think the first versions will be RGB displays with fixed colors, just no longer needing mass transfer. You could use tens of subpixels per pixel, reducing all worries about color resolution.

Make these into e.g. 1x1cm mini displays and mass transfer those into any desired display size.

Re: Polychromatic Pixels

#137

Post by mark-r »

jessriedel wrote: post #54
GrantMoyer wrote: post #45

A single wavelength can't reproduce all visible colors. These pixels are variable wavelength, but can only produce one at a time, so you'd still need at least 2 of these pixels to reproduce any visible color. The fundamental problem is that color space is 2D[1] (color + brightness is 3D, hence 3 subpixel on traditional displays), but monochromatic light has only 1 dimension to vary for color. [1]: https://en.wikipedi…

Ha, yea, in particular these monochromatic pixels can't simply be white. Notably ctrl-f'ing for "white" gives zero results on this page. Relatedly, the page talks a lot about pixel density, but this confused me: if you swap each R, G, or B LED with an adjustable LED, you naively get a one-time 3x boost in pixel area density, which is a one-time sqrt(3)=1.73x boost in linear resolution. So I think density is really a…

The key to this is using the same process to get all the colors. For separate R,G,B pixels you need 3 different processes and can't build them on the same chip, you need to assemble them - that's what allows the vast improvement in pixel density.

Re: Polychromatic Pixels

#138

Post by mark-r »

creshal wrote: post #113
ricardobeat wrote: post #89

Earlier quoted context omitted.

Doesn't the fact they have successfully demonstrated displays at 2000, 5000 and 10000 DPI alleviate those concerns a little bit?

It's not really meant as a concern, more a supporting argument: If every subpixel is identical, you can use simpler wiring patterns.

The subpixels don't need bonding wires, they have dedicated connections just like any transistor on a regular IC.

Re: Polychromatic Pixels

#139

Post by mark-r »

mensetmanusman wrote: post #75
jessriedel wrote: post #58

Earlier quoted context omitted.

It also can't produce white or anything else in the interior of this diagram (as well as, as you mention, shades of magenta and purple that lie on the flat lower edge): https://upload.wikimedia.org/wikipedia/commons/b/ba/Planckia...

The human eye will see white when a pixel flashes through all of the colors quickly in time.

You don't need all the colors. As every household white LED bulb proves, you can get it with just a combination of blue and yellow.

Re: Polychromatic Pixels

#140

Post by mark-r »

ajuc wrote: post #109
pfg_ wrote: post #93

Earlier quoted context omitted.

This seems like a non-problem, cut the display resolution in half on one axis and reserve two 'subpixels' for each pixel. Then you have a full color display with only one physical pixel type and that needs one less subpixel. These displays could even produce some saturated colors with specific wavelengths that can't be represented on regular rgb displays.

You'd still be unable to produce different brightness pixels. You'd get white but no grayscale. I guess you could cheat it by moving the wavelength outside the visible spectrum?

I hate to think of the damage large amounts of IR or especially UV would do to the eye.
Post reply on HN