I’m building a FTIR LCD multi-touch panel, using this diagram

and i’m wondering how the silicone rubber works?  or can i use sulky solvy and will that work?

i’m basically wondering, are there transparent versions of these materials or something?  how do they work and keep the acrylic completely transparent?

thanks.

ah, so the silicone is clear!  i get it!

ok.

makes sense now.

Yeah that would work. The acrylic alone would give you nice blobs, but with the sillicone it would be much easier to genreate the blobs.

So yeah that would work. Obviously you would need to dismantle the LCD so that camera could see through the LCD screen to the acrylic but other that that, there’s no reason why the setup wouldn’t work.

Hi
From what I’ve heard from people who have built FTIR LCD setups, they haven’t used compliant surfaces and still reported great results - perfect transparency being too much of a hassle and unnecessary for FTIR LCD...not sure why.

But I don’t know about leaving it out...I’m going to build everything except the compliant surface, and see how the blobs are, and then, if necessary, look into compliant surfaces. Is plexiglass the best plastic to go with?
Talking about various plastics (mylar, lexan polycarbonate, acetate, etc.) and their qualities:
http://nuigroup.com/forums/viewthread/2892/

good luck
rbedi100

Hey rbedi100, yeah some people have tried their setups without the compliant surface with success.

Is plexiglass the best plastic to go with?

Do you mean as a protective layer on top of the LCD? If so, I have seen Lexen used as a protection layer (with mixed resuts), also some transparent films such as Mylar etc and also touching the LCD directly( as some LCD monitors have a Rosco type film already applied.)
You can however (and I would encourage) experiment with different types of materials, after all, this is why the forum is so good! Lot’s of people trying different things

Let us know how you go!

Fairlane,
About the plexiglass - I meant is that the best surface to apply silicone to? - because avia’s original diagram said silicone rubber + plexiglass. Same thing about lexan and mylar.

I’m probably going to try out lexan this weekend (home depot didnt have mylar)...I don’t have a working setup, but I’ll still run tests on IR blockage, clarity, flexibility, etc…
How best should I apply the silicone? - I’m a bit confused on applying technique differences between Tinkerman’s textured method and regular(?) methods.

Thx
rbedi100

Oh..Ok, yeah plexiglass (acrylic) would work to apply the silicone to, Mylar would probably be better cause it’s a thinner material.
Tinkerman’s method is using textured screened silicone as non-textured silicone (for this ‘screening’ method) tends to stick to the surface leaving a trail or residule image when you’ve lifted your finger off the silicone.

Tinkerman’s thin Textured silicone would be the way i’d go… but that’s just my opinion.

Ok, so textured silicone even if I’m applying directly to acrylic? That sounds good...stupid Home Depot only sells Xylol in 1 gallon containers...have to find a smaller amount to do Tinkerman’s method.

I’m slightly confused on how an FTIR LCD setup works. Fairlane said that you would need to “dismantle the LCD so that camera could see through the LCD screen to the acrylic,” which makes sense, but if you dismantle the LCD screen, then how does the LCD screen “work.” I know I’m coming off sounding really dumb, and I must be misunderstanding something, but darn it, I just don’t get it. :-p

Hey IsaiahQ, LCD screens are usually LCD panels mounted onto a piece of acrylic.
The LCD screens have an aluminum backing on them, and (in some cases) some film layers which would need to be removed to enable the camera to see ‘through’ the acrylic and LCD panel.

The LCD screen needs the acrylic so that the 2x Fluro lights can illuminate the LCD screen evenly. We just use the FTIR setup to flood the acrylic with IR light as well, and - because we’ve removed the backing of the LCD monitor - our rear mounted IR camera can detect touch inputs through the acrylic/LCD module on to the surface of the screen itself.

There are many examples of these type of setups on various threads throughout the forums.
I’ve added a picture from one example (BlaxWan’s website) showing the camera and dismantled LCD screen.

In the picture below, the aluminum backing (at the top of the picture - with the white layer) has been detached and moved to the side to allow the camera to see ‘through’ the acrylic/LCD module.

Also check out nima’s LCD FTIR thread here

Hope this helps you understand the process a little more…

Ok, but when a pixel is black, it’s blocking light, so the IR light couldn’t travel through it to the camera, right?

i think that ir light can travel through the blackness of pixels. like ir light also flows through the blackness of exposed negatives which else blocks normal light.