Natural interactions for medical image analysis

Interaction-Design Master Thesis

Hardware Prototyping – 3D pen

with 4 comments

I just finished the final version of the LED pen I am using for the 3D tracking. I added a button to the pen that is currently used to change viewmodes in the 3D tracking system. Also I found some nice light diffusers, this will make the color tracking more stable because the cameras can now see the light from all directions.


more details here:

Before and after the assembly. Pen + 1 blue LED + 1 red LED + pushbutton + Arduino


I was asking Camille if he knows any good light diffusers I could use for the pen. He had some good ideas, however while we were talking about it I discovered a abandoned Muji pen on the floor of his office. The caps of the Muji pen were exactly what I was looking for – great, milky, pen sized light diffusers that fit around a LED.


Along the way of my project I’ve built 4 “generations” of pen for the 3D tracking system.

1. The first one had no lights and only one tracking point (the yellow cap of the pen). with only 1 tracking point I couldn’t track the orientation of the pen.

2. So I added two different colored leds attached them to batteries and just taped them around the first pen.

3. For the third generation I removed all the insides of a pen, so I can put the cables inside instead of taping them around the pen. also I added a pushbutton (attached to the computer via arduino).

4. I had some problems with the 3rd pen. it was to small, so it was easy to accidently cover one of the LEDs with your hand. Also the LEDs had different brightness and they had the attribute to shine in one direction. Different brightness and directional light made it difficult to track the LEDs from all angles. I fixed these issues in the 4th generation and hope to be able to track from further away, so there would be more space that you can move the pen in.



Written by Jannes

May 12, 2009 at 20:48

Posted in Phase 03 - Prototyping

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4 Responses

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  1. nice read…i will try myself


    March 9, 2011 at 08:17

  2. Man… I don’t know much about tracking pens… I’m just starting to search about this… I’m an architecture student on my way to graduate with a last project in my hands… But I have this shape in my mind and not enough weapons to create it… so… I thought… “well… maybe a tracking pen might help me”… Could you tell me more about this device, how they work.. or how can I built/get one???


    October 18, 2012 at 19:07

    • Hi Raphaela, i built this device myself so I am not sure if you could buy a similar device anywhere. But there is new gesture tracking devices that could maybe help you, like Xbox kinect. For more information about the device I built i would recommend downloading my thesis report, in the end of the document you will find detailed info about how it works.


      October 25, 2012 at 04:34

      • Thanks Jannes, I really appreciate it. I’ll read everything I can about it as soon as I can.
        I guess that when I figure out how it works I’ll be able to know if I can bring this to the architectural world… I think it would be good thing. Usually we just make the 3D videos and that’s it. But… I think it would be nice if the person could travel thought the project on her own… Is it too mush to ask??? Well… I guess I’ll find out after reading your thesis.


        October 25, 2012 at 17:26

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