Multitouch Zero Force Setup Based on IR Laser Light

Here is the setup that I’ve been working on for a while now. It is based on front IR illumination by IR laser.

Camera

For this project I’ve been using my old Orange Micro iBot firewire camera with great success. This low-cost camera generates 640×480 at 30fps uncompressed images in Y800 format. I found that because of all of this and the IR sensitivity this camera is very suitable for IR multitouch application:

Camera1.jpg

After removing the original lens and mounting the new lens without IR blocking filter, I placed the double-sided tape on top of the lens and cut the opening in it:

Camera2.jpg

IR Bandpass Filter

In the past I used photo negative with some success, but found that using narrow bandpass filter is by far the best in removing any unwanted IR noise and visible light:

BandPassFilter.jpg

Here is the filter mounted on the camera:

CameraWithFilter.jpg

Table Setup

Currently I’m in the process of redesigning the table. Right now it is an open-frame setup:

TestSetup1.jpg

TestSetup2.jpg

IR Laser

And now the most important part. I use the 850nm IR Laser light to illuminate the front of the surface. When finger or any object interfere with the laser light, the camera below picks up the bright spot and runs it through the image processing algo to generate detected blob information. 
Here is the view from the surface:

TestSetup3.jpg

The laser is mounted on a tripod on a tri-point adjustable platform so that it can be positioned is a way that it generates a light beam that is parallel to the glass surface:

IRLaserSetup.jpg

The IR laser is positioned just above the glass surface:

TestSetup4.jpg

Software

Even though I could use touchlib for blob processing/tracking, having a lot of experience in image processing, I found that it was easier for me to write a highly optimized version blob tracking software. Because of this, I achieve very low latency and low CPU usage running my blob tracking software (around 3-4% on my E6600 2.4GHz system). 
Here are some screenshots of my blob tracking app: 

TrackingApp1.jpg

As you can see blobs are very bright and clean:

TrackingApp2.jpg

Here is my iPhone placed on the surface:

TrackingApp3.jpg

Video

Here you can see the system in action. While using FTIR the blobs become dimer during the fast movement, using the laser method the blobs are always bright

Short video of the system:

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~ by Alexander Popovich on May 28, 2008.

3 Responses to “Multitouch Zero Force Setup Based on IR Laser Light”

  1. […] Multitouch Zero Force Setup Take #2 Every since posting the results of my previous setup, I worked on improving some aspects of this setup.  During this time I decided to make a […]

  2. Are you from Romania?

  3. Hi!!

    Where did you buy the Bandpass IR Filter?.

    Regards.

    P.S.: Congratulation for your blog. It’s really cool!

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