Instructables

Step 6: Screen sandwich assembly

Once the frame, rails and acrylic are prepared you are ready for the final assembly. Clamp the layers together for easy drilling and bolt them in place. Once the sandwich is assembled, it is necessary to caulk along the edge of the aluminum in order to block any light that might spill out thru the crack. We want it all nicely ducting along the inside of the acrylic instead.

In order for the projector to display on the surface it is necessary to also introduce a diffuser (not shown here). A sheet of thin drafting paper was included in the sandwich supported by a second thin layer of plexiglass.
 
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dancmarsh3 years ago
I know someone asked before, but there was no answer, so i wonder if anyone has tried it.

Has anyone tried mounting the projector under the table yet and setting the screen to rear projection?

I'd like to know if it works, would make for a neater and more portable install.
Hypernoob5 years ago
did you drill through the acrylic? or are there gaps provided by the spacer blocks so you are actually drilling through an empty space.
turkey tek (author)  Hypernoob5 years ago
i didn't drill thru the acrylic. it is just floated inside the frame.
i don't know if this is a dumb question or not but how well dose the IR pass though the paper? i mean i would think that it would be blocked by the paper.
well technically the paper is underneath the acrylic sheet or Plexiglass it is used as a projection surface so the image ur putting on the screen wont pass right through Note: drafting vellum and three+ coats of silicon sealant will work equally well if not better b/c it could possibly be more durable (and you can always add more sealant using a dense foam paint roller to spread the silicon evenly across the vellum and when you mount the vellum, make sure the side with the sealant touches the acrylic sheet or Plexiglass)
cba20k6 years ago
This instructable is great! Quick question though. I am not sure how you are attaching the channel to the acrylic. I see that the wood frame sections are bolted to channel, but that would not keep the four pieces attached to one another....would it? Sorry if I'm missing something obvious here.
Zero-Vision6 years ago
You used drafting paper in your setup, and this part is not critism...the image quality would be super low when compared to say a rigid rear projection screen. Of course no one wants to spend 500 on a rigid frame, in adition to the possibility that it would effect the ir refraction. So my question is, this. I have, for my company a transluscent material. Under normal lighting a person can SEE fingers shapes ect. It is meant for rear projection. So it works for that. When I take my IR cam, and loook at the material and put a remote control behind it, the ir is very clear, meaning it doesn't block ir at all or disperse it like it does lower band visible light. In theory would this effect "bouncing" of ir waves inside? or does it take actual Preasure to do so? I'm asking this now so i can better design the final product in advance.
turkey tek (author)  Zero-Vision6 years ago
If you put the diffuser behind a sheet of acrylic, then i don't think there would be any problem. If you want to use the diffuser as both diffuser and the touch surface, you'll definitely want to experiment to see how well the internal reflection works in the diffuser.
eagleapex7 years ago
A tip for caulking: If you wet your finger with soap and water, you can smooth out the bead and make it all pretty like. It also helps you use less.