Hi, I’m french and I want to make my own multitouchscreen.
I think i’ve all understand how it’s work, but i made a draw of my future setup to be sure of my work.
I want to know what can I use to project IR on the surface of my table, simple LED setup works or not??
That setup looks okay, except for a few issues. First, use arcrylic (plexiglass) as I believe glass filters IR light naturally. Your going to want to give your lighting situation a little more thought than just a yellow sqaure. In my DI table, (which uses a projector, not LCD) I have an IR led array from amazon meant for nightime survailance, and it works great (about $20). Concentrate on efficiently lighting up your surface as this is really important. Good luck!
yes but there is no probleme with the camera too??
If the camera can read the blobs from an FTIR Screen, through a screen, the IR can pass from behind, no??
i was thinking about such a setup, wonder if it’s going to work fine:
----------------------
Acrylic |--| IR Leds
----------------------
TFT
----------------------
Diffuser
----------------------
-------
| | Camera
-------
Backlight
________________
When stripping some LCDs i found that the TFT alone won’t filter IR...so the main idea is mixing a FTIR with a TFT screen.
If the diffuser layer is transparent enough to let IR pass through and do its own job (diffusing backlight for the TFT), then the camera should be able to see blobs on the acrylic given by the IR array along the framework.
Actually, the backlight should (must?) be placed between TFT and diffuser, but that’s not a problem as far as i know...so just consider the above scheme both ways.
This won’t fix the “black screen = IR filter” problem though, if that really works that way.
If (and i’m sure of it) someone else already posted such an idea and you already discussed this with no success, just sorry me, i didn’t come across it!
When stripping my LCD down to its bare parts, I have found that I can get IR to pass through from both directions on my screen, so that is a good start. However in regards to backlight, etc I was going to go a more (from what I think) better approach, where I do this for DI..
------------------------------------------------
Acrylic
------------------------------------------------
LCD TFT
------------------------------------------------
Endlighten Acrylic with white LED ribbon surrounding
------------------------------------------------
----------
Camera
----------
------------------------------------------------
IR LED array
------------------------------------------------
That should work, since it looks like a nearly normal DI setup...what i was talking about is swapping the IR leds position from bottom (using diffusers) to up (using leds array or whatever along the acrylic edges).
And anyway, anyone knows about the black screen being an IR filter?
That looks more like an FTIR setup (yours).... and yeah as for my experiments, the black screen did dull IR a little bit not not enough to filter it out completely.
p.s. i just looked around the forum for such a “lcd ftir” setup and....wow i found tons of ppl using this! so i’m definitely NOT saying something new haha...sorry!
Ok, first question would be if the LCD blocks IR light.
It certainly blocks visible light, but since people are using it for FTIR setups I guess there would be no problem with IR. The fact that it could block IR in only one direction doesn’t make much sense to me. But I’m not an expert.
The second possible problem I see is that the diffuser could be too far from your fingers to be effective, but I don’t know.
Your diagram seems ok, NoMa[R]o!, but I would put the diffuser/frosted surface on top of the bottom layer, and not under it (it has to be the closest to your fingers as possible).
shockdesign, your diagram lacks the diffuser.
xelapond - 07 September 2008 11:30 AM
Has anyone gotten DI to work with an LCD? I heard it doesn’t work because when an LCD displays black is blocks IR light.
i think i will use the backlight of my LCD screen directly.
