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I’ve posted two Howto’s on compiling touchlib in Windows (XP and Vista) and Linux (Ubuntu).

Howto: Compile Touchlib in Windows
Howto: Compile Touchlib in Linux

Both compile instructions apply to subversion rev.73 of touchlib. If you followed the Howto’s and still have some trouble please post the problem in the comment section.

It works!

After the last blog not much had to be done about the FTIR screen. Actually I only used some tape to hide the wires on the sides.
With all LED’s in place and the frame being placed on two chairs it was time to finally test the FTIR screen.

All LED’s are fully functioning !

Testing with 5 and 2 fingers…

10 finger test:

Video containing a summary of the project and some demo applications

To get the Touch Tracer tool (from the demo video) please click on read more.
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In this final step of building the FTIR prototype I will cover the soldering of LEDs.
In my previous blog post I already calculated that 30 LED’s would be enough to cover the entire plate.

As power source for my LED’s I will be using a 12V DC Adapter (1000 mA).
To calculate the LED array and the amount of needed resistors I used an internet tool the LED Wizard.

According to the wizard I should create 5 array’s of LED’s. Each array should contain 6 LED’s and one resistor of 68 ohms.

Click the link below to continue reading.
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Inspired by other FTIR prototypes I decided to use an aluminum frame. The main reasons for are because its cheap and strong.

Before actually working on the frame, I made a drawing in AutoCAD. Within this drawing I could easily calculate the amount of IR LED’s I would need and at the same time see how the IR light beams would spread.

FTIR Prototype Drawing

The local tool shop was friendly enough to cut the aluminum frame (H shaped) into the sizes of my drawing.
So at home I just needed to remove the edges in 45 degrees.

Click the link below to continue reading.
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The FTIR prototype which I am building will be using an acrylic plate which will be mounted in a frame.

I tried to maintain the aspect ratio of a regular screen (4:3). The size of the plate is 41 x 31 cm and about 8 mm thick. The actual area which will be captured is 40 x 30 cm.

Two days after ordering the acrylic plate I received it in a nice package:

In the image below we can see the plate has been cut roughly.

(The plate looks a bit blue but thats due the colour of the protective layer)

Because we want to beam IR light into the sides of the acrylic plate, it is necersaily to polish the sides.

Click the link below to continue reading about how to treat the acrylic plate.
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For the past several days, I have received parts for constructing my touchscreen prototype which is based on Frustrated Total Internal Reflection (FTIR).

Today I will cover how the lens of the Philips webcam can be dismounted and replaced by one without an infrared (IR) blocking filter.

Most consumer webcams contain an IR filter which will prevent IR light coming through. This is done to prevent image distortion. However in our case we want to capture the IR light. On some webcams it’s possible to remove the IR filter (which is behind the lens and often has a red colour). With our current webcam from Philips this isn’t possible. Therefor a new camera lens has been ordered on eBay.

It was called “4.3MM 4.3 MM CCTV Camera board Lens IR DVR NEW”

Some specifications of the new camera lens:
* Glass Lens
* Focal length: 4.3 mm
* Aperture F/1.8
* Image format 1/3 inch
* Angel of view 68°
* Mount M12 x P0.5
* Size ?14×14.75

Click the link below to continue reading about how to replace the camera lens.
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