9. September 2009 - 11:07

How to build a low-cost multitouch screen

This instructions will help you getting started building your own low-cost multitouch screen

Material

Mandatory

Price are mentioned as indication, without shipping. Delivery expected within 10 business days.

What you probably need to order:

Material Price Link Remarks
 
Diffuser Foil: LEE-Filter, Nr.225     19.20 CHF moving.ch  
IR Lamp: Night vision 140 LED IR Infrared Illuminator Lamp CCTV about 32CHF ebay.com and others Tape over the built-in light sensor.
High speed Camera: Sony PLAYSTATION Eye Camera   43.50CHF microspot.ch You easily find this camera at your favorite computer store.
IR pass filter with 11.5mm diameter (850 nm, select the same wavelength as for the ordered IR Lamp) 20CHF ebay.com You can also use an over-illuminated, developed black-white film. This filter cut out the visible light but allows the IR light send by the IR lamp to be received by the camera.

What you probably have:

  • (Windows) Computer
  • Projector, from about 450 CHF http://www.toppreise.ch/index.php?k3=2103&manu=&o=pa. It would be better to buy a short throw projector to simplify the setup.
  • A table with glass top, or a picture frame (about 50cm x  67cm or 50cm x 89cm depending on your projector's format)

Facultative

  • To tweak your setup you could buy a high quality IR Cut Filter in your favorite photo store. We used the Baader IR Cut filter to cover the Projector's lens. The performance of this filter is quite adequite. For an LED Projector you will not need an IR cut filter as they do not interference to the IR wavelength.
  • Mirror, which might reduce the size of your setup

Instruction Manual - Hardware

Please be aware that most setups works best in a dark environment.

Camera Modification

A detailed Instruction can be found at: http://alexpopovich.wordpress.com/2008/09/05/sony-ps3eye-b304061-ir-filter-removal/. It is worth to take enough time to do the modification properly. You might need one or two hours.

Setup

For the setup you can use any single layer glass or Plexiglas object you find:  This could be an existing, single layer glass wall in your house. Or a glass table in your living room. Or simply a picture frame.

Multitouch Table

Version Dice

  1. The first step is to build the closed box. We used the cheapest wood-plates we found and build the box following the simple measures mentioned in the sketch. The surface plate we cut a hole. On the top of it we placed a Plexiglas measuring 1.00 by 1.00 meter. On the top of the Plexiglas we stuck the LEE diffuser foil.
  2.  We mount the project and the camera inside the box. It might be helpful to use a mirror when the projector does not support short throw to prolong the required distance between the projector and the diffuser.
  3. Place the IR lamp in the backmost edge of the box. It is important that the lamp shine to the LEE foil, but cannot give a direct reflection via the Plexiglas to the camera.

Standard view:

X-Ray view:

Version IKEA

It is possible to modify the ramvik IKEA coffee table to an interactive multitouch table. Buy the ramvik IKEA coffee table (in the "old" colors you get it from 79 CHF) and start to set it up with the instruction manual. Be aware that it is needed to alter some steps, which we explain here. Use the delivered instruction manual or download it from here: http://www.ikeafans.com/forums/ikea-instructions/9429-ramvik-coffee-table-instructions-annotated.html

Manual modifications:

  • Steps 1 to 7: do exactly as described in the official manual
  • Step 8 to 12: you need to cut a hole in the upper and in the lower large board to pass the light coming from the projector.
  • Steps 13 to 21: do exactly as described in the official manual
  • Steps 22 to 30: do only one drawer exactly as described in the official manual. The other drawer has to be assembled without bottom plate (steps 28 to 30) and the backend plate (step 25). Do not use the small dampers provided for the drawer, as the will let light enter the table.

Additional modifications:

  • Install the projector at the bottom of the table and redirect the beam with a mirror to the top of the table. If you use a short throw projector you will probably not use a mirror.
  • Stick the diffuser filter on top of the glass plate
  • Install IR camera in the table such that it can see the touchable part of the table
  • Install the IR illuminator such that it illuminate the touchable part of the table but cannot shine nor reflect directly to the IR camera
  • Close the lower part of the table with the resting boards.

 

Multitouch Wall

Here we will sketch a very simple setup

The easiest way will be to take a picture frame where you cut out a rectangle out of the wooden back-stabilization. The modified picture frame could be hanged at an open door. In front of the (Plexi-) glass you stick the LEE-filter.

Behind the door, you install a box, which contains the camera, the projector, the IR-Lamp and potentially the computer. Top in the box there is the IR-light, which needs to be lower than the lowest point of the picture frame (red dotted line). On the bottom of the box you set the projector and top of it the ps3 eye web camera.
sketch of setup

sketch

Photo at our lab-door

Setup at our lab

The light from the IR-Lamp at the bottom you can see only in the photo as the iPhone-Camera has a weak IR-cut filter. Humans cannot see this IR light.

Software Sources

Backend-Software

Settings for the backend-software

These setting are for the CCV 1.3 Version. These setting are a good start when you build your table according to our manual. We used the table in a shaded room during the day. With other environment light the settings might change significantly.

Version Smooth Blur Noise
 Amplify Image Treshold Movement Treshold min. Blob size max. Blob size
DICE off 7 3 40 5 depends on your application: lower value is faster but might appear more nervous 10 15

Front-end Software

You will find good example front-end software in the folder downloaded in the  (Community Core Vision Release) Version 1.2

Name Description Link
MT Google Earth A virtual globe, map and geographic information program. http://nuigroup.com/forums/viewthread/5422
Air Hockey   http://nuigroup.com/forums/viewthread/4121/
Windows 7 Multitouch driver

http://nuigroup.com/forums/viewthread/4087/

http://multitouchvista.codeplex.com/
reactable real-time musical interaction http://www.reactable.com/reactable/technology
Processing is an open source programming language and environment for people who want to program images, animation, and interactions. processing.org/
Orion Various games and a nice multitouch console http://orionmultitouch.blogspot.com/search/label/Download
Sethsandler Games, Music Application http://sethsandler.com
    http://kaiouncharles.free.fr/touch/share/MTVrelease.zip
MT Pack for Windows 7 Introduction http://windowsteamblog.com/blogs/windows7/archive/2009/05/27/introducing-the-microsoft-touch-pack-for-windows-7.aspx

Multitouch Front-end Software

We recommend developing you front-end software in flash.

Introduction

By now, Flash is one of the most powerful tools in a web designer's arsenal, but it no longer stops at the web. Because of new coding platforms, namely Adobe Flex and Adobe AIR, developers can use Actionscript 3.0 to create cross-platform desktop applications. And now, Flash can be used to create multi-touch applica­tions via communication with a computer vision and multi-touch sensing applica­tion, such .. CCV ... (from Multi-Touch Technoligies, NUIgroup Book)

How to develop your own Multitouch Front-end Software

In the multi-touch technology handbook you find detailed instruction how to program with Flash (starting from page 52).

You might also simply follow this short step by step instruction.

Selected Links

Please don't hesitate to ask us any question relating new communication interfaces as for example the multitouch table. We are happy to get your feedback and to help you!

Community

  • open source interactive media community NUI Group

Books

Papers

35 Comments

I tried that way you mentioned above to build my own multi touch screen and  now I am having a problem. The picture is not clear(some zigzag lines appear).Now could you please tell me what can I do?

Abir

Between the Apple iPhone and Microsoft's interactive table, multi-touch displays are all the rage. This instructable will show you how to turn your lcd projector into an interactive multi-touch display table using a few cheap components readily available from the hardware store.

I really like this App, but, wouldnt it be handy to directly start the GPS and localize the position and then show the Hotspots?

That is highly intriguing.i wish i could give it a shot sometime next weekend along with my nerdy friend .And those links for the front end development were also impressive.i never thought DIY was so easy.thanks a ton Jeff

Gut gelungene und eindrückliche Anleitung. Gut geeignet zum Nachbauen! Habe beide Multitouch-Tables (Würfelversion sowie Salontischversion) beim Autor in Aktion gesehen....- Einfach nur Hammer!!!

Impressive! You really did it! I don't even know where to start, your ingeniousness and skill really made something out of nothing, a multitouch screen fully packed with hardware and software. You really have a lot to share to the world, don't you? Dorra

Hello, this is a genuinelyterrific put up. In theory I'd liketo be able to be able to produce like this too - taking time and real work to make a great article.!!!. but what can I say.!!!. I procrastinate alot and never seem to acquire anything done.

C'est l'article de Nice pour des gens qui en a besoin et ne peut pas se permettre un logiciel multi-touch avant. Spécialement pour les étudiants qui en prenant leur document final
term paper leur école. Ce logiciel est vraiment bien pour apprendre cette demande.

Hej, for lazy guys:

you could also buy a MT screen or All-in-one-PC from ALDI and build it in into your favorite furniture.

Please be aware that this technology has some disadvantage compared to the previous mentioned technologies. It can track only two fingers and can have some shadowing issues. Nevertheless, you can hassle free plug-and-play this screen to your windows7 computer and run nice soft with it.

You can download a fun Multitouch packet from Microsoft @: http://www.microsoft.com/downloads/details.aspx?displaylang=de&FamilyID=... have fun taxi

Dear Pete,

cool Idea! Thanks for sharing with us.

Also some hints from our side: we got excellent results using the LEE foil mounting in front of the IR-lights. The IR light will be significantly better distributed. Of course you should still avoid direct reflections. To avoid this in large setups you could use switched IR lights controlled with the PS3eye clock and the arduino board: (http://dshop.ch/osc/product_info.php?cPath=23_25&products_id=39&osCsid=c...).

If the short throw range of the projector is too large, you can shorten it using eyeglasses. We bought a +1 dpt glass for 15 CHF at Fielmann Bern to halve the throw distance!

taxi / Labs Team

Hi taxi

Hehe clever. I think the Sanyo PDG-DWL 100's throw range will be fine, but I'm waiting for my christmas bonus before I buy it =)

The easiest way will be to take a picture frame where you cut out a rectangle out of the wooden back-stabilization. The modified picture frame could be hanged at an open door.

Thanks,

Still waiting to receive the IR Illuminator, but just in case somebody is interested I've found that the LEE filter 225 can be bought in Geneva at Art-Scénique, but they don't ship the product (you have to take it from the shop in Geneva). Might be useful if you live near Geneva and don't want to pay shipment fees.

Hello FAS,

thanks for your useful remark!
For testing how your device interacts with IR light you could also use any halogen light. Halogen light emits most light in the IR but not in the visible spectrum. A 50W halogen table lamp has approximately the same intensity as the 120 LED IR lamp.

taxi / Labs Team

 

Hello again,

Since I received the IR lamp I tried to build a test table, and it works well. The only thing I couldn't get to work correctly is the Windows 7 multitouch driver (it receives the touch events sent by CCV but it seems like they only works in a small portion of the screen (maybe a rectangle of 320x240, since it's the resolution of the camera).

I'll try to update CCV and MultitouchVista to the latest development versions, maybe it can help. Did anybody got it to work ?

For the IR pass filter, a friend just told me that you can use floppy disks for that : the material which forms the disk inside a 3.5'' floppy apparently filters almost completely visible light but not IRs. I will test that as soon as I receive the IR illuminator.

Hello FAS,

that is true. You could also use a developed black/white film. You might already test it right now by filming your flat screen. You nearly cannot differentiate black and white. Please don't forget to remove the IR cut filter.

Nevertheless, it is worth to buy a good filter which cut off the visible light. Otherwise the camera will recognize false bolbs caused by the projector and other light sources.

taxi / Labs Team

Dear Pete,

you might find an overview of projector with low latency  in the paper: Multi-Touch Surfaces: A Technical Guide, Technical Report TUM-I0833 on page 19.

In our setup we use an old, no-name projector. From the technical specifications we recommend the short throw Sanyo PDG-DWL 100.

It should have a low latency projection. Having a distance of 50cm from the projector to the glass you get a screen size of 96cm by 60cm (thus slightly broader than what you can project). You will need a mirror to achieve the 50 cm total distance. Please consider that the projector is quite large and you need to carve some more of the wood. For this ramvik setup it is rather difficult to get a projector with enough short throw distance.

taxi / Labs Team

 

Hello Pete,

I assume with the Sanyo projector you can use one mirror, angled with 45°. It should be possible to put the side of the projector towards the bottom of the table:

You can do the same with the PS3 camera. The camera distance you can calculate with: x = 1.22*h, y = 0.94*h. h is the distance between the camera and the screen, x and y the observation area. It might be interesting to use the multicam driver for the ps3 eye: http://alexpopovich.wordpress.com/2009/09/04/the-ps3eye-multicam-driver-...

Right now you could do the first test without the IR-illumination but just track the shadows generated by the fingers (passive mode). Like this you will see the limitation of your system.

taxi / Labs Team