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As a creative project, I'm trying to project some lines or text onto a window. That is, I have a large window that I still want to see out of, but I want to use an LCD projector from the inside to project onto the window. Someone looking at the window would be able to see through it, but could also read the time or temperature or something projected onto it.

Window Mock-Up

Of course, most of the light from the projector is going to go through the window, but some of it is bouncing back in as glare. I'm going to experiment to see if I can take advantage of this effect, but it might be tricky.

Is there any other sort of window treatment I can apply that might make this work better? Perhaps some sort of stick on window darkening material that might reflect a bit more light from the inside? Or, some sort of stick-on plastic that would react to UV? (The LCD projectors tend to kick out quite a bit of UV, so maybe the visible light plus UV would be fine. Color doesn't matter... this is going to be in monochrome.)

Any other alternatives you can think of to get a similar effect? Open to oddball and creative ideas! Thanks.

  • Anything that reflects projector output will probably reflect everything more readily, drastically reducing your outside view. – isherwood Dec 6 '17 at 23:18
  • @isherwood Agreed, it's going to be a tricky one. I can at least put up something to block lighting from hitting it directly, but light from the room will reflect a bit. I'm hoping to find a reasonable balance. I'm borrowing a projector to experiment with on Friday. What I really need is a way to block light from the outside from coming in for pixels, but I haven't found anything. The LCD windows are either on or off for the whole window. I found some commercial LCD panels that are applied to glass, but they're crazy expensive ($10k+) and not practical for my use case. – Brad Dec 6 '17 at 23:20
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Depending on how much optical interference you can tolerate, you can either use a translucent film like they use for this product: Window Wonderland or if you are only displaying monochromatic images you can use a partially reflective mirror coating like EdmundOpticals.com. Here's one that looks useful: Abrisa Technologies.

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Why do you want to project an image on the glass when you can create it in there?

The window can be large LCD/OLED screen with no backlight.

  • This would be idea, but I haven't been able to find something available for purchase. Any suggestions? – Brad Dec 7 '17 at 16:02
  • Ask at LG or Samsung ;) – Crowley Dec 8 '17 at 7:04
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@Arluin has the same notion that I had.

  • Do you need the entire window space able to accept text? If so, then @Crowley's notion is worth a look.
  • Does it have to be projection? Could it be an LCD display instead?
  • Does it have to be on the window? Can you project onto the window frame instead.

Experiment: Test with a projection onto a piece of onionskin paper, a piece of wax paper, a piece of mylar reflective window coating, and a wrinkled piece of shrink wrap. This will give you a feel for how much reflectivity you need to show up against a daylight scene (which is very bright. There is a reason we turn the lights off when running displays)

You probably don't want to use these but it will give you a better handle on what you need.

While you are at it, project onto a chunk of bond paper taped to the window frame.

All of these are cheap experiments.


A sunlit scene is several hundred watts per square meter. I don't think any projector can compete with that. Indeed, I doubt that even projecting onto a white wall adjacent to the window will give satisfactory results. You might be able to do it if the window is glazed with something like a 90% reflective coating. (Lot of buildings are to reduce cooling costs. 90% barely looks dimmer than sunlight.)

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