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Polychromatic Pixels

compoundsemiconductor.net

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Re: Polychromatic Pixels

#21

Post by refulgentis »

Retr0id wrote: post #18

Hm, thinking about this further, this would need dithering to work properly (which probably works fine, but the perceived quality difference would mean pixel density comparisons aren't apples-to-apples) Presumably, you get to control hue and brightness per-pixel. But that only gives you access to a thin slice of the sRGB gamut (i.e. the parts of HSL where saturation is maxed out), but dithering can solve that. Coming…

I'm not sure why saturation couldn't be controlled.

I probably missed something in the article, though I do see ex. desaturated yellow in the photographs so I'm not sure this is accurate.

If you can't control saturation, I'm not sure dithering won't help, I don't see how you'd approximate a less saturated color from a more saturated color.

HSL is extremely misleading, it's a crude approximation for 1970s computing constraints. An analogy I've used previously is think of there being a "pure" pigment, where saturation is at peak, mixing in dark/light (changing the lightness) changes the purity of the pigment, causing it to lose saturation.

Re: Polychromatic Pixels

#22

Post by kurthr »

hobscoop wrote: post #19

Are they able to adjust the color and brightness simultaneously? Or would brightness be controlled with PWM?

Brightness is PWM controlled, but likely at the micro - millisecond level. The required brightness range is about 100k:1.

Black levels would be determined more by reflectivity of the display than illumination.

Re: Polychromatic Pixels

#23

Post by modeless »

yig wrote: post #11
dmitrygr wrote: post #4

These still produce a single [adjustable] wavelength, which means some colors that are displayable on displays of today are not representable using just one of these, and multiples will be required.

Two adjustable wavelength emitters should be sufficient, right? So the picking-and-placing problem gets easier by factor of 3:2 rather than 3:1.

I bet you might run into some interesting problems trying to represent white with two wavelengths. For example, colorblind people (7% of the population) might not perceive your white as white. And I wonder if there is more widespread variation in human eye responses to single wavelengths between primary colors that is not classified as colorblindness but could affect the perception of color balance in a 2-wavelength display.

Re: Polychromatic Pixels

#24

Post by Retr0id »

refulgentis wrote: post #21
Retr0id wrote: post #18

Hm, thinking about this further, this would need dithering to work properly (which probably works fine, but the perceived quality difference would mean pixel density comparisons aren't apples-to-apples) Presumably, you get to control hue and brightness per-pixel. But that only gives you access to a thin slice of the sRGB gamut (i.e. the parts of HSL where saturation is maxed out), but dithering can solve that. Coming…

I'm not sure why saturation couldn't be controlled. I probably missed something in the article, though I do see ex. desaturated yellow in the photographs so I'm not sure this is accurate. If you can't control saturation, I'm not sure dithering won't help, I don't see how you'd approximate a less saturated color from a more saturated color. HSL is extremely misleading, it's a crude approximation for 1970s computing co…

Saturation can't be controlled on a per-pixel basis because, per the article, they're tuned to a specific wavelength at any given time.

You're right though, there appear to be yellows on display. Maybe they're doing temporal dithering.

Edit: Oh wait, yellow doesn't need dithering in any case. Yellow can be represented as a single wavelength. Magenta on the other hand, would (and there does seem to be a lack of magenta on display)

Re: Polychromatic Pixels

#27

Post by k__ »

nfriedly wrote: post #17

> 6,800 pixel-per-inch display (around 1.1 cm by 0.55 cm, and around 3K by 1.5K pixels) That sounds like it's getting close to being a really good screen for a VR headset.

Nice, that's double of what the Vision Pro has.

Re: Polychromatic Pixels

#28

Post by bobmcnamara »

ginko wrote: post #20
jjmarr wrote: post #16

My ultimate hope is that this will allow us to store and display color data as Fourier series. Right now we only represent colour as combinations of red, green, and blue, when a colour signal itself is really a combination of multiple "spectral" (pure) colour waves, which can be anything in the rainbow. Individually controllable microLEDs would change this entirely. We could visualize any color at will by combining t…

With two wavelength-tunable LEDs you should be able to cover the entire CIE colorspace. That's because the points on outer edge of CIE are pure wavelengths and you can get to any point inside by interpolating between two of them.

How do you make white?

Re: Polychromatic Pixels

#29

Post by refulgentis »

Retr0id wrote: post #24
refulgentis wrote: post #21

Earlier quoted context omitted.

I'm not sure why saturation couldn't be controlled. I probably missed something in the article, though I do see ex. desaturated yellow in the photographs so I'm not sure this is accurate. If you can't control saturation, I'm not sure dithering won't help, I don't see how you'd approximate a less saturated color from a more saturated color. HSL is extremely misleading, it's a crude approximation for 1970s computing co…

Saturation can't be controlled on a per-pixel basis because, per the article, they're tuned to a specific wavelength at any given time. You're right though, there appear to be yellows on display. Maybe they're doing temporal dithering. Edit: Oh wait, yellow doesn't need dithering in any case. Yellow can be represented as a single wavelength. Magenta on the other hand, would (and there does seem to be a lack of magent…

Honestly might just be the limits of photography, there's so much contrast between the ~97 L* brightness of pure yellow and black that the sensor might not be able to capture the "actual" range.

I've been called a color scientist in marketing, but sadly never grokked the wavelength view of color. It sounds off to me, that's a *huge* limitation to not mention. But then again, if they had something a year ago, its unlikely ex. Apple folds its microLED division they've been investing in for a decade. Either A) it sucks or B) it doesn't scale in manufacturing or C) no ones noticed yet. (A) seems likely given their central claim is (B) is, at the least, much improved.

Re: Polychromatic Pixels

#30

Post by Joel_Mckay »

k7sune wrote: post #12

Does this need very accurate DAC to cover the entire color spectrum? Maybe even fine-tuning on each pixel?

LED are somewhat temperature sensitive devices, and getting repeatable high-granularity bit-depth may prove a difficult problem in itself.

There are ways to compensate for perceptual drift like modern LCD drivers, but unless the technology addresses the same burn-in issues with OLED it won't matter how great it looks.

You may want to look at how DMD drivers handled the color-wheel shutter timing to increase perceptual color quality. There are always a few tricks people can try to improve the look at the cost of lower frame rates. =)

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