Posted on Mar 9, 2009

Multi-Touch Display (LLP Method)

For several months I have been closely following development of diy multi-touch displays on the internet. A few weeks ago I decided not to spend the $15,000 for the Microsoft Surface and build my own. From months of lurking on the Natural User Interface Forums, I decided to use the Laser Light Pane method of illumination with infrared lasers aimed just above acrylic surface. As you can see from the video on the right, the results were fantastic. Here are some build notes (see photo captions for more info):

– Frame was constructed out of aluminum stock.
– Light guards were constructed out of aluminum L-frame and black foam.
– Rosco Grey rear projection material was attached to the back of the acrylic.
– 850nm 25mw Laser Modules with Cylindrical Lens.
– Modified PS3 Eyecam with infrared 850nm BandPass Filter and custom tripod mount.
– Software: TBeta from nuigroup.com
– Hardware: Macbook Pro 2.4 GHz Intel Core 2 Duo with 4GB SDRAM running OSX 10.5.6

16 Comments

  • jayther says:

    Sweet. It was fun messing around with the thing. -]

  • daniel says:

    i just wanted to say that what you have done is amazing, and blows my mind, and im really jealous to be frank HaHa.
    i have been searching for a method of building this system that would deliver the best results. i feel that the method you have done is the one that delivers the best result, i would like to know where i should start. Im in college but ive got a large sheed of plexi-glass that i can cut down to any size really, and i have many computers at my disposal and maybe 3-4 webcams. so i feel like ive got alot of things i need to get going. but i want to build something that is going to work really well, any help and guidance you could give me it will be vary much appreciated.

    • digitaljoven says:

      Hi Daniel,

      Thanks for the kind comment. Great to hear that your interested in creating your own setup. If you haven’t already, a tremendous resource is the natural user interface forums. Here’s a few links:

      Wiki
      http://wiki.nuigroup.com/Main_Page
      Forums
      http://nuigroup.com/forums/

      The members on that site are extremely nice and helpful (My board name is Goju). You’ll find there many similar projects for inspiration. For me, I spent a lot of time on the site reading and searching about other people’s setups. Once I had a solid understanding of how everything works, I started planning my own.

      This is a good start, but please, if you have any more questions, just contact me on the forums or here on my site.

      Good luck!!!

  • David Ehlers says:

    Wicked cool! I so need that in my office! How bout Multi-Touch Display 2.0 ? =)

  • Chris "D" says:

    Can you tell me how you attached the rosco to the acrylic? I have been loking for a solid setup for this part as it will be sitting at a 45 degree slope to avoid gorilla arm fatigue. (we aren’t made to operate in lengthy sessions with a vertical screen.. so I am trying like a drafting desk..)

    thanks for any feedback or info,

    Chris

  • digitaljoven says:

    Hi Chris,

    I used extra strength double sided tape used for scrap books and framing. I ran it along all four edges of the acrylic surface. I then cut a slightly larger piece of roscro grey than the acrylic. While holding all four corners with a friend, we carefully secured it to the tape. It came out really nice.

    I’ve seen several drafting style setups work really well and I agree about extended usage of a vertical screen. My next build will actually be a coffee table to facilitate some tabletop multiplayer games 😉

    Good luck and thanks for commenting!

  • John S says:

    I would like u to comment on the size of surface as well as how you got 2 lasers to work so well rather than 4.
    Thanks

  • Larry says:

    Very nice work and great demonstration. A couple questions. Using the basic components you used, what is the practical size limitations of the screen? Also, can you give an estimate of the cost to construct your project?

  • digitaljoven says:

    Hi John S,

    Thanks for the comment! I cut the 1/4″ acrylic screen to 36″x24″. In regards to 2 vs 4 lasers it just comes down to the size of the screen. There is some fade in the upper corners due to the angle of the laser line is not wide enough and only one laser will illuminate fingers. This is in the extreme corners. I’ve never had more than a few people interacting with my setup, but in theory I would have some problems with illumination with a high number of fingers on the screen at once (more than 3 people). My advice is if you plan on a larger screen than mine or plan on high number of users, go with 4 lasers. Hope this helps! 🙂

  • digitaljoven says:

    Hi Larry,

    Thanks for the comment! I would say that the main advantage of using lasers is that they scale up easily. The lack of a necessary compliant layer used in FTIR setups allows for a quick build time and larger scalable surfaces. With two lasers I would stick to a size near my setup of 36″x24″ to avoid shadows, but if you bump up to 4 or even 6 lasers, I’ve seen clean setups of around an 100″ diagonal.

    In regards to cost, excluding the computer and the projector, overall it was around $450. The availability of the lasers is much easier with the growth of the DIY multi-touch community so I would estimate a savings of about $150 if I where to build the table again today.

    Hope this helps!

  • Tom says:

    Very sweet setup! Can you tell me where you purchased your lasers from and the power supply used?

  • digitaljoven says:

    Hello Tom,

    I purchased my lasers from another forum member on nuigroup.com. It’s been almost a year since I bought them, but you can message him if you like:

    http://nuigroup.com/forums/member/1652/

    eBay is also a great source for laser modules, just remember to get one with the line generating lens. In regards to powering the laser, my modules were rated at 5v, so I powered them off a usb port for testing. For my final install, I bought a 5v dc power supply from radio shack and built a custom switch.

    Thanks!

  • Torin says:

    Can you comment about the thickness of the acrylic sheet you used? Does it bend when you press hard at the middle of the screen?
    What is the angle of the lens on your laser modules?
    Does the system perform well in a room with bright sunlight (not facing directly then window though)?

    • digitaljoven says:

      Hi Torin,

      Can you comment about the thickness of the acrylic sheet you used? Does it bend when you press hard at the middle of the screen?
      I used 1/4 inch acrylic and yes it does bend slightly in the middle, but never enough that drastically effected performance. For later builds, I did use thicker acrylic and built a frame on all four sides.

      What is the angle of the lens on your laser modules?
      Unfortunately it wasn’t an exact science for this particular build, hence the use of the putty. What I did to tune it, was place a white sheet of paper off all the edges of the screen and using the web camera adjust the lasers to shoot directly into the light guard to ensure that it was as close to the acyclic surface as possible.

      Does the system perform well in a room with bright sunlight (not facing directly then window though)?
      I’ve had success running the system in conference room with mid day sun light. If sun light does become a problem, I suggest enclosing the space between the camera and the screen. In later builds, I a completely enclosed the system similar to the Microsoft surface which worked better in daytime situations.

      Thanks for the comment!

  • rob says:

    Hi Mate,

    Do you recon this method would be sufficient to make something similiar to the unit in this video.

    http://www.youtube.com/watch?v=OVD_Lvv4UOI

  • Mike says:

    “For my final install, I bought a 5v dc power supply from radio shack and built a custom switch.”

    Did you have to use resistors for the lasers? The ones I’ve ordered are rated at 3.7v I think, and I don’t want to overdrive them.