As I mentioned in my introduction post, I am interested in building an FTIR based LCD multi-touch table. I’m still in the planning phases, however I would like to understand more about the prep work needed to achieve an LCD based design. To me, the most daunting part of the process is selecting and dismantling an LCD monitor for the project. The biggest design hurdle in my mind is figuring out a good way to illuminate the LCD panel and not wash out my FTIR blobs. Also mentioned in my post, I plan to start small over the coming weeks and build a MTmini to play with just to verify that the camera (also yet to be purchased) works properly. For the opening phases, I will probably have one of my spare laptops powering the setup. It’s a pretty capable Core 2 Duo with 1 Gb of RAM in it and plenty of USB ports.
Does anyone have a good recommendation for a suitable camera to do both the MTmini and the FTIR setup? Ideally, any webcam selected would have an easily removed IR filter. Does webcam resolution matter?
Regarding the LCD, I am looking for a reasonably large display (over 19") that is easily dismantled. I have read many resources that list LCDs that are more suitable than others, however I haven’t found many good resources that list larger LCD screens and I don’t know what to look for in the specs to tell if one would be more suitable than another.
In addition to this (yes, there’s more!) I would appreciate any backlight design ideas.
I apologize in advance if these questions seem rudimentary or ill-informed. I’ve read everything I can find on this topic, however I am certain that I am unaware of better resources that may exist. Once I get a rig (even a simple one) configured, I fully intend to contribute back to the community by flexing my software development muscles!
I did the same project. It has been a while since I’ve been on the NUI forum because of some work for my university. I can help you with a few things.
First, reconsider the plan for your LCD multitouch. I did it, dismantled the complete LCD it worked until someone was not to careful when placing my box (it can be moved on wheels). I think it hit a wall with one of the corners and had a good hit. Result: LCD is “broken” or the image is broken. So that was a wast of 160 euros. If I would do it again, I’m sure i won’t use an LCD.
If you want to enlight the complete LCD, the best thing to do is to mount a TL-bar at the bottom of your box. It gives enough light to illuminate for the complete box and doesn’t remove your blobs. I used it, it worked fine (until my lcd broke).
A sweex webcam has an easy to remove filter. But it’s cheap and not as good as others. It comes with bad drivers. Consider a better can if you want to put out the most of your project.
Thanks for the feedback! If you had it to do again, would you go with a right angle box, or some other configuration?
The Sweex was one of the first HOW-TO’s that I came across when starting to search on FTIR stuff, I was considering picking one up before you mentioned it.
If I would do it again I would use a beamer. LCD is good for the resolution, but small. You have to find out things about the backlight (which many people didn’t know before I went of. I kinda had to sort it out myself that an LCD was the best option. But use some tracing paper under your LCD otherwise you can see the complete inside of the box)
I will start the project again after I build my Java Libraries for blob tracking. Just libraries so I can include them in other projects. After that I will search for some money to make a bigger table.
I’d recomend you use an Xbox 360 Live Vision cam , it’s about 30$ , it’s maximum resolution is VGA , the IR Filter isn’t that hard to remove , and it’s framerate is preaty high.
Alot of users on this forums have used it with great succes.
@SoniX: Once I get my MTmini sorted out, let me know if I can help with the Java for the blob tracking. I do Java for a living and might be able to lend a hand.
@Vlado: I never thought of using one of those! Sounds like a very cost-effective solution. Those attach via USB I assume, yes?
I may pull the trigger on the webcam part using what remains of my discretionary money from this month’s budget, I have to sit down with the Mrs. to see how things are shaping up.
Hi,
I am new here and I am interested in this kind of projects.
I would like to build a multitouch table, like yours (Sonix)… and just like you (I think). I do not want to use a projector (too expensive) but rather a LCD display that I have (17") I know it’s going to be a little table (lol, more of a night table I would say ) but I just want to test it in a small scale.
The thing is that I can not see how to put the camera and everything in order to track the blobs if I am using a LCD screen… how do you do it? You project somehow the image of the LCD into the plexyglass?
Could you, or anyone confirm if this is possible (using a LCD instead of a projector) to do a multitouch table?
Thank you in advance,
PS: And Sonix, you say we must put a tracing paper in the LCD… is it really that translucid? So you put the LCD just behind the plexyglass and the camera in the bottom of the box?? You were able to capture the blobs that way? I dismantled some laptop LCD -s and they are far from translucid… can you explain this a little further?
From top to bottom you have: plexi with ftir, lcd matrix, tracing paper (, maybe an extra plexi), EMPTY space just enough height so the camera at the bottom of the box can view te complete screen.
If you dismantle the lcd properly you will have only the lcd matrix, no backlight, no reflextion papers, ... It about 2 mm thick.
It is not translucent when not powered but when powered white dots on your image are represented by a translucent pixel. So you need something to make those look white. Thats why i use trancing paper. I lets ir light perfectly through.
Oh and about your lcd vs projector. I spent a lot of money on my lcd and it broke due to misuse of the box (i tjink someone kinda smashed it to the wall because its on wheels). With all the things i know now i would rather invest in a projector.
I find value in your experience, SoniX. If we’re talking about projectors, I have been aware of some smaller ones that you can get within the $300-$500 range.
Since its reflected light, I’m guessing you’re not really going to need an ultra-high lumen projector (although it would help) to make a passable MT table… have you done any research on what attributes make for a better projector based table?
Thanks for answering all of the questions, this has been an extremely valuable discussion for me.
If you dismantle the lcd properly you will have only the lcd matrix, no backlight, no reflextion papers, ... It about 2 mm thick.
It is not translucent when not powered but when powered white dots on your image are represented by a translucent pixel. So you need something to make those look white. Thats why i use trancing paper. I lets ir light perfectly through.
Hi and thank’s for your answer…
I have another bunch of questions, so then…
1. how do you iluminate the screen if the back light has been removed?
2. If you put the tracing paper the quality of the image will be neat and perfect just like in a normal LCD?
3. The leds for the blobs will do the job for the proper illumination? what is a TL-bar?
Thank you very much, your experience is being a great help for me
TL
PS: I’ll take care of the screen… lol. I can not afford a projector right now… and I only want to build a mini mini MT.
I haven’t done much research with projectors. But i know that when they are in a closed box they give enough light. To enlarge the distance you could use a mirror because cheap projectors need a longer throw distance.
About the 3 questions:
1. Tl-bar
2. Yes
3. Leds are perfect. Tl-bar is a lamp made of a tube with special gas in it. Unlike normal lamps it does not dispose ir light so it will no interfere with the blobs.
3. Leds are perfect. Tl-bar is a lamp made of a tube with special gas in it. Unlike normal lamps it does not dispose ir light so it will no interfere with the blobs.
Sorry to insist...again.
The leds you are speaking about are additional leds, right? (not the one used to iluminate the plexyglass and that placed in the borders right?)
No problem , glad i could be of help , you should search the forum a little , there are a few threads with build logs of LCD based Multitouch displays.
I’m curently considering one myself , will see if I’m up to the task or not.
) but I just want to test it in a small scale.
