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A Transparent Display with Per-Pixel Color and Opacity Control

94 points by fezz 7y ago

ChuckMcM 7y ago
Uh this is broken. Can someone post a link to a5-rhodes.pdf directly? I managed to read it by going here: https://dl.acm.org/citation.cfm?id=3327984 https://dl.acm.org/citation.cfm?id=3327984 and then clicking the PDF link. Apparently it drops a cookie or something.
zeta0134 7y ago
I'm not sure what's going on with the original link, but this shortened link seems to actually work: https://dl.acm.org/citation.cfm?id=3327984 https://dl.acm.org/citation.cfm?id=3327984 The concept seems clever (rapidly alternate between illuminating the front-panel, and illuminating the contents of the enclosure while displaying a transparency negative on the front panel) but the requirement for an enclosure and controllable backlight limits the scope of the approach. Still, those results look pretty good for mostly off the shelf hardware.
- joezydeco 7y ago
  Found a demo video here: https://www.youtube.com/watch?v=NgJJtkb3Fr4 https://www.youtube.com/watch?v=NgJJtkb3Fr4
- cfitz 7y ago
  This is wild! I can already see hotels using this tech as large glass walls that later turn into movie screens or “smart” screens...
  - joezydeco 7y ago
    That might be hard to do if the lighting in the entire room needs to be precisely controlled.
- im3w1l 7y ago
  I read the article and I read your comment but I still don't quite get how all the pieces fit together. To make it concrete, let's say we want to set a pixel to red, with 20% transparency. During the transparent phase we light up the object with white light (always). We set this particular pixel to 20% transparency for red green and blue channels. During the opaque phase we light up the pixel directly (how? I didn't understand this? just a strong spotlight aimed at the display?) and set red to 80% transparency (100% red * 80% opaque) and the green and blue channels we set to block all light.
  - zeta0134 7y ago
    So it's important to call out here that they're using a modified LCD panel. A traditional LCD panel has two components: a backlight that constantly provides solid white light, and the LCD in front of it, which darkens each pixel. This is why on your computer monitor, if you send it a "black" signal, you still see some light. The LCD is as dark as it will go, but some light still bleeds through because the backlight is on all the time. In the paper, they're effectively using two backlight configurations. When displaying the solid object, they shine the backlight on the object, which scatters some of that light back towards the viewer. During this phase, they mask the image the LCD wants to display by having it render a greyscale image, where black pixels should hide the physical object, and white pixels should let the physical object shine through. In this mode, the physical object becomes the backlight, effectively. In the image display mode, they point the backlights towards the LCD panel, and display their super-imposed image. In this mode, the object is not being illuminated, and so its contribution to the image is minimal. This is also why an enclosure is required, because the display needs to be able to throw the physical object into shadow during this second phase. All of this is, of course, happening extremely quickly. The panel alternates between these two modes so fast that the human eye can't perceive the flicker, and persistence of vision simply combines the light contributions from both modes. The result is what you see in the images and video example.
    - fieryskiff1 7y ago
      You are incorrect about the need of an enclosure: they don't shadow the back objects at all, instead they use a "diffuser" which obstructs the image of the back objects (and reflects backlight) during the color phase.
taneq 7y ago
Wow, very impressive effect! How long until something similar to this makes its way into AR glasses for overlaying proper solid-looking rendered objects? The sticking point would seem to be the cutover from masking to backlighting the screen, so maybe a transparent OLED display backed by an LCD screen acting as a shutter?
reaperducer 7y ago
I've seen something similar to this implemented on high end slot machines in Vegas. It looks like several layers of transparent LCD screens and combined they give a 3D look.
fizzledbits 7y ago
I saw this in person yesterday at Siggraph and it works perfectly. No perceptible flickering, fully opaque images (when the alpha mask is on), cap touch, good color fidelity. It’s a simple, terrific idea.

94 points by fezz 7y ago

Uh this is broken. Can someone post a link to a5-rhodes.pdf directly? I managed to read it by going here: https://dl.acm.org/citation.cfm?id=3327984 https://dl.acm.org/citation.cfm?id=3327984 and then clicking the PDF link. Apparently it drops a cookie or something.

zeta0134 7y ago

I'm not sure what's going on with the original link, but this shortened link seems to actually work: https://dl.acm.org/citation.cfm?id=3327984 https://dl.acm.org/citation.cfm?id=3327984 The concept seems clever (rapidly alternate between illuminating the front-panel, and illuminating the contents of the enclosure while displaying a transparency negative on the front panel) but the requirement for an enclosure and controllable backlight limits the scope of the approach. Still, those results look pretty good for mostly off the shelf hardware.

joezydeco 7y ago
Found a demo video here: https://www.youtube.com/watch?v=NgJJtkb3Fr4 https://www.youtube.com/watch?v=NgJJtkb3Fr4
cfitz 7y ago
This is wild! I can already see hotels using this tech as large glass walls that later turn into movie screens or “smart” screens...
- joezydeco 7y ago
  That might be hard to do if the lighting in the entire room needs to be precisely controlled.
im3w1l 7y ago
I read the article and I read your comment but I still don't quite get how all the pieces fit together. To make it concrete, let's say we want to set a pixel to red, with 20% transparency. During the transparent phase we light up the object with white light (always). We set this particular pixel to 20% transparency for red green and blue channels. During the opaque phase we light up the pixel directly (how? I didn't understand this? just a strong spotlight aimed at the display?) and set red to 80% transparency (100% red * 80% opaque) and the green and blue channels we set to block all light.
- zeta0134 7y ago
  So it's important to call out here that they're using a modified LCD panel. A traditional LCD panel has two components: a backlight that constantly provides solid white light, and the LCD in front of it, which darkens each pixel. This is why on your computer monitor, if you send it a "black" signal, you still see some light. The LCD is as dark as it will go, but some light still bleeds through because the backlight is on all the time. In the paper, they're effectively using two backlight configurations. When displaying the solid object, they shine the backlight on the object, which scatters some of that light back towards the viewer. During this phase, they mask the image the LCD wants to display by having it render a greyscale image, where black pixels should hide the physical object, and white pixels should let the physical object shine through. In this mode, the physical object becomes the backlight, effectively. In the image display mode, they point the backlights towards the LCD panel, and display their super-imposed image. In this mode, the object is not being illuminated, and so its contribution to the image is minimal. This is also why an enclosure is required, because the display needs to be able to throw the physical object into shadow during this second phase. All of this is, of course, happening extremely quickly. The panel alternates between these two modes so fast that the human eye can't perceive the flicker, and persistence of vision simply combines the light contributions from both modes. The result is what you see in the images and video example.
  - fieryskiff1 7y ago
    You are incorrect about the need of an enclosure: they don't shadow the back objects at all, instead they use a "diffuser" which obstructs the image of the back objects (and reflects backlight) during the color phase.

taneq 7y ago

Wow, very impressive effect! How long until something similar to this makes its way into AR glasses for overlaying proper solid-looking rendered objects? The sticking point would seem to be the cutover from masking to backlighting the screen, so maybe a transparent OLED display backed by an LCD screen acting as a shutter?

reaperducer 7y ago

I've seen something similar to this implemented on high end slot machines in Vegas. It looks like several layers of transparent LCD screens and combined they give a 3D look.

fizzledbits 7y ago

I saw this in person yesterday at Siggraph and it works perfectly. No perceptible flickering, fully opaque images (when the alpha mask is on), cap touch, good color fidelity. It’s a simple, terrific idea.