how to build a multi-touch surface - touch screen gestures

Multi-
Touch gestures are the latest and greatest way to interact with computers.
However, the commercial system is not popular and expensive.
Fortunately, you can do better yourself at a lower cost.
Main components (
Click on the link for product information)
: $35 PS3 eye camera (
Recommended, but can work with any decent webcam)
$20 IR band filter $200 5-
Any recent/decent computer ($1000)PC/MAC)
Any projector> 1000 lumens ($2000)NEC NP410W)
Wear-resistant acrylic board $80 front mirror $40 (23" x 35" x 0. 236")
Acrylic sheets after projection $130 (23" x 35" x 0. 118")
EndLighten acrylic sheet ($145)23" x 35" x 0. 394")
Total Software :~ $2500 (
Click on the link to download):$free CCV (
Used to turn an image into a spot)$free CL-
Platform-driven (
Eye camera for PS3)$free Multi-Touch Vista (Optional Multi-
Windows integrated touch TUIO driver)$? Windows 7 (Recommended)
Justin Clarkson, Duke University B. S. E.
More than 2012 by theDuke LibraryA
The touch surface is essentially a huge touch screen that can handle multiple touches at the same time.
In our case, the number of touches is almost infinite.
By allowing multiple touches, gestures can be performed on the surface.
These gestures are often simple things like pinch and pull images to zoom in and out.
It becomes more intuitive and interesting to interface with a computer by supporting gestures like this.
In public places, more than one
Touching the surface can be a real attention grab.
There are a variety of different technologies that can be used to create more than oneTouch surface.
All or most of the surfaces depend on optical techniques that work with infrared (IR).
The technology used in this guide is direct surface lighting (DSI)
The cartoon below explains this.
Compared to other similar technologies, the basis for using DSI is that it allows for a protective wear-resistant layer on the top that protects the delicate nature of the bottom layer from the user's touch.
The arrangement order of the surface acrylic layer is as follows: 1)Touch surface (
Wear-resistant acrylic)2)
Diffuser/projection layer (
Acrylic back projection)3)
EndLighten acrylicYou don't need to build a computer specifically for this project.
As a matter of fact, any processor and graphics card should be running well recently.
However, if you plan to put the surface into the housing after completion, then make sure the computer has enough cooling and minimal heat dissipation.
Another important factor is the size of the computer because you want to make sure that the computer does not interfere with the camera or the projection system.
Example components used in our devices: Intel Core i5-660 Clarkdale 3.
33 GHzASUS P7H55D-M EVO Micro-
ATX --DATA 4GB (2 x 2GB)
X3 12800 memory xfx hd-567X-
In order to pick up the infrared, the PS3's eye camera needs to be turned on and modified.
Use the PS3 eye camera because it is)cheap and b)
High resolution support (640x480)at 60 fps.
This speed and resolution for many
Touch the surfaces as they provide the details needed to pick up small spots and the speed at which the gestures look smooth.
In order for the PS3 eye camera to work, an infrared filter needs to be removed and an infrared band filter is placed in its position.
The infrared band pass filter ensures that only infrared light of the wavelength is used to enter the system.
Therefore, it is important that the center wavelength of the infrared pass band filter matches the center wavelength of the infrared LEDs present in the infrared strip used to illuminate the surface.
Below you can find the video guide created by Peau Productions to modify the PS3 Eye camera.
The most important acrylic layer is EndLighten acrylic.
The layer is responsible for redirecting the IR light from its side from the top and bottom surfaces of acrylic.
Therefore, it is necessary to polish the edges of the layer to maximize the amount of IR light that can be injected into the layer.
I would recommend laser cutting the EndLighten layer if possible as this will automatically polish the edges perfectly.
If the laser cutting machine is not an option then the car sandpaper can do that.
Starting with 600 sand (
Lower if sawing is rough)
Polish each side until it is completely smooth.
Complete each side with 1000 sand.
Finally, polished with plastic (
Brasso will also work).
Note that milk White will still appear on the edge at this point, which is normal for EndLighten acrylic.
You don't need to polish the other two layers, and I actually recommend that they stay rough so that the infrared light doesn't hit them.
The backing layer should be placed directly on the top of the tail light layer.
This layer will act as a diffuser for the projector so that the projector will not shine directly on the user's surface.
The wear-resistant layer should be placed on the top of the back projection layer.
This layer is important because it protects other more expensive layers and is also the layer that the actual user is going to touch.
Infrared strip lighting should be wound around the edge of the acrylic layer of EndLighten.
Once you move around, you should cut off the IR band because it gets very hot when it stays in the coil at the end.
If you are just building a test device, the tape can stick the IR tape well to the acrylic layer.
Otherwise I would suggest buying/Building a u-
Channel frame and stick the IR bar to the frame.
In this way, your acrylic layer will be permanently aligned and in a simple unit you can put in your shell.
The surface at this time is almost complete.
All that is left to do is set up the projectors and cameras and align them so that they cover the same area and do not deform.
First place the projector under the surface with a slight pitch so it doesn't project directly onto anything
Front/bottom.
Next, set the front mirror to reflect the projector onto the acrylic layer above.
The front mirror is necessary because the ordinary mirror will distort the image and reduce the image clarity projected onto the acrylic surface.
At this point, the image may look more like a ladder, adjusting the ladder on the projector until the perfect rectangle is reached.
In order to reach the image size you want, you may also need to move the projector forward or backward, or the acrylic layer up and down.
Finally, position the camera so that it faces the acrylic layer directly up.
The camera should be placed directly in front of the projector and under the center of the surface so that it can pick up the entire desired area.
Now that you 've aligned everything, it's time to test the settings.
First connect the projector and PS3 camera to the computer and connect all the devices to the power supply.
After the computer is started, install CL-
Eye stand Driverand CCV. CCV is an open-
Process the source code of the infrared image picked by the camera and turn it into a spot (TUIO events).
The program can then use these events to allow user interaction.
Once the CCV is up and running, click the use camera option to start receiving input from the PS3 Eye camera.
Now experiment by touching the surface and observing what spots are picked up in the tracking view.
Play the "image threshold" and other settings until the desired spots are reached.
Once completed, complete the "calibration" mode in order to map the pixels on the projected image to the point picked by the camera.
A complete guide to calibration and test tables can be found here.
At this point, you should have a fully working lot nowTouch surface.
If you're just building a development environment then you can stop here.
However, if you plan to deploy your surface to a production environment, then you need some kind of shell.
The enclosure can be designed no matter what you want, but you have to make sure you have the right angle and space to project the image and pick up the entire surface on the camera.
In addition, proper ventilation is essential because projectors and computers become hot in enclosed spaces.
Once I have completed the build, I will add additional steps and attach a detailed plan for my shell. Good luck!